Permanent magnet focused X-band photoinjector

DOEpatents

Yu, David U. L.; Rosenzweig, James

2002-09-10

A compact high energy photoelectron injector integrates the photocathode directly into a multicell linear accelerator with no drift space between the injection and the linac. High electron beam brightness is achieved by accelerating a tightly focused electron beam in an integrated, multi-cell, X-band rf linear accelerator (linac). The photoelectron linac employs a Plane-Wave-Transformer (PWT) design which provides strong cell-to-cell coupling, easing manufacturing tolerances and costs.

PIP-II Cryogenic System and the evolution of Superfluid Helium Cryogenic Plant Specifications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakravarty, Anindya; Rane, Tejas; Klebaner, Arkadiy

2017-07-06

The PIP-II cryogenic system consists of a Superfluid Helium Cryogenic Plant (SHCP) and a Cryogenic Distribution System (CDS) connecting the SHCP to the Superconducting (SC) Linac consisting of 25 cryomodules. The dynamic heat load of the SC cavities for continuous wave (CW) as well as pulsed mode of operation has been listed out. The static heat loads of the cavities along with the CDS have also been discussed. Simulation study has been carried out to compute the supercritical helium (SHe) flow requirements for each cryomodule. Comparison between the flow requirements of the cryomodules for the CW and pulsed modes ofmore » operation have also been made. From the total computed heat load and pressure drop values in the CDS, the basic specifications for the SHCP, required for cooling the SC Linac, have evolved.« less

LIGHT SOURCE: Physical design of a 10 MeV LINAC for polymer radiation processing

NASA Astrophysics Data System (ADS)

Feng, Guang-Yao; Pei, Yuan-Ji; Wang, Lin; Zhang, Shan-Cai; Wu, Cong-Feng; Jin, Kai; Li, Wei-Min

2009-06-01

In China, polymer radiation processing has become one of the most important processing industries. The radiation processing source may be an electron beam accelerator or a radioactive source. Physical design of an electron beam facility applied for radiation crosslinking is introduced in this paper because of it's much higher dose rate and efficiency. Main part of this facility is a 10 MeV travelling wave electron linac with constant impedance accelerating structure. A start to end simulation concerning the linac is reported in this paper. The codes Opera-3d, Poisson-superfish and Parmela are used to describe electromagnetic elements of the accelerator and track particle distribution from the cathode to the end of the linac. After beam dynamic optimization, wave phase velocities in the structure have been chosen to be 0.56, 0.9 and 0.999 respectively. Physical parameters about the main elements such as DC electron gun, iris-loaded periodic structure, solenoids, etc, are presented. Simulation results proves that it can satisfy the industrial requirement. The linac is under construction. Some components have been finished. Measurements proved that they are in a good agreement with the design values.

Design of a CW high charge state heavy ion RFQ for SSC-LINAC

NASA Astrophysics Data System (ADS)

Liu, G.; Lu, Y. R.; He, Y.; Wang, Z.; Xiao, C.; Gao, S. L.; Yang, Y. Q.; Zhu, K.; Yan, X. Q.; Chen, J. E.; Yuan, Y. J.; Zhao, H. W.

2013-02-01

The new linac injector SSC-LINAC has been proposed to replace the existing Separator Sector Cyclotron (SSC). This effort is to improve the beam efficiency of the Heavy Ion Research Facility of Lanzhou (HIRFL). As a key component of the linac, a continuous-wave (CW) mode high charge state heavy ion radio-frequency quadrupole (RFQ) accelerator has been designed. It accelerates ions with the ratio of mass to charge up to 7 from 3.728 keV/u to 143 keV/u. The requirements of CW mode operation and the transportation of intense beam have been considered as the greatest challenges. The design is based on 238U34+ beams, whose current is 0.5 pmA (0.5 particle mili-ampere, which is the measured 17 emA electric current divided by charge state of heavy ions). It achieves the transmission efficiency of 94% with 2508.46 mm long vanes in simulation. To improve the transmission efficiency and quality of the beams, the phase advance has been taken into account to analyze the reasons of beam loss and emittance growth. Parametric resonance and beam mismatch have been carefully avoided by adjusting the structure parameters. The parameter-sensitivity of the design is checked by transportation simulations of various input beams. To verify the applicability of machining, the effects of different vane manufacturing methods on beam dynamics are presented in this paper.

rf conditioning and breakdown analysis of a traveling wave linac with collinear load cells

NASA Astrophysics Data System (ADS)

Chen, Qushan; Hu, Tongning; Qin, Bin; Xiong, Yongqian; Fan, Kuanjun; Pei, Yuanji

2018-04-01

Huazhong University of Science and Technology (HUST) has built a compact linac-based terahertz free electron laser (THz-FEL) prototype. In order to achieve compact structure, the linac uses collinear load cells instead of conventional output coupler to absorb remanent power at the end of linac. The new designed structure is confronted with rf breakdown problem after a long time conditioning process, so we tried to figure out the breakdown site in the linac. Without transmitted signal, we propose two methods to analyze the breakdown site mainly based on the forward and the reflected power signals. One method focuses on the time relationship of the two signals while the other focuses on the amplitude. Both the two methods indicate the breakdown events happened at the end of the linac and more likely in the first or the second load cell.

ARIEL E-linac Cryogenic System: Commissioning and First Operational Experience

NASA Astrophysics Data System (ADS)

Koveshnikov, A.; Bylinskii, I.; Hodgson, G.; Kishi, D.; Laxdal, R.; Ma, Y.; Nagimov, R.; Yosifov, D.

2015-12-01

The Advanced Rare IsotopE Laboratory (ARIEL) is a major expansion of the Isotope Separator and Accelerator (ISAC) facility at TRIUMF. A key part of the ARIEL project is a 10 mA 50 MeV continuous-wave superconducting radiofrequency (SRF) electron linear accelerator (e-linac). The 1.3 GHz SRF cavities are operated at 2 K. HELIAL LL helium liquefier by Air Liquide Advanced Technologies (ALAT) with a tuneable liquid helium (LHe) production was installed and commissioned in Q4’2013 [1]. It provides 4 K liquid helium to one injector and one accelerator cryomodules that were installed and tested in 2014. The 4 K to 2 K liquid helium transition is achieved on-board of each cryomodule. The cryoplant, LHe and LN2 distributions, sub-atmospheric (S/A) system and cryomodules were successfully commissioned and integrated into the e-linac cryogenic system. Required pressure regulation for both 4 K cryoplant in the Dewar and 2 K with the S/A system was achieved under simulated load. Final integration tests confirmed overall stable performance of the cryogenic system with two cryomodules installed. The paper presents details of the cryogenic system commissioning tests as well as highlights of the initial operational experience.

Simultaneous optimization of the cavity heat load and trip rates in linacs using a genetic algorithm

DOE PAGES

Terzić, Balša; Hofler, Alicia S.; Reeves, Cody J.; ...

2014-10-15

In this paper, a genetic algorithm-based optimization is used to simultaneously minimize two competing objectives guiding the operation of the Jefferson Lab's Continuous Electron Beam Accelerator Facility linacs: cavity heat load and radio frequency cavity trip rates. The results represent a significant improvement to the standard linac energy management tool and thereby could lead to a more efficient Continuous Electron Beam Accelerator Facility configuration. This study also serves as a proof of principle of how a genetic algorithm can be used for optimizing other linac-based machines.

Ion tracking in photocathode rf guns

NASA Astrophysics Data System (ADS)

Lewellen, John W.

2002-02-01

Projected next-generation linac-based light sources, such as PERL or the TESLA free-electron laser, generally assume, as essential components of their injector complexes, long-pulse photocathode rf electron guns. These guns, due to their design rf pulse durations of many milliseconds to continuous wave, may be more susceptible to ion bombardment damage of their cathodes than conventional rf guns, which typically use rf pulses of microsecond duration. This paper explores this possibility in terms of ion propagation within the gun, and presents a basis for future study of the subject.

Fluorescent screens and image processing for the APS linac test stand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berg, W.; Ko, K.

A fluorescent screen was used to monitor relative beam position and spot size of a 56-MeV electron beam in the linac test stand. A chromium doped alumina ceramic screen inserted into the beam was monitored by a video camera. The resulting image was captured using a frame grabber and stored into memory. Reconstruction and analysis of the stored image was performed using PV-WAVE. This paper will discuss the hardware and software implementation of the fluorescent screen and imaging system. Proposed improvements for the APS linac fluorescent screens and image processing will also be discussed.

Beam dynamics design of the muon linac high-beta section

NASA Astrophysics Data System (ADS)

Kondo, Y.; Hasegawa, K.; Otani, M.; Mibe, T.; Yoshida, M.; Kitamura, R.

2017-07-01

A muon linac development for a new muon g-2 experiment is now going on at J-PARC. Muons from the muon beam line (H line) at the J-PARC muon science facility are once stopped in a silica-aerogel target, and room temperature muoniums are evaporated from the aerogel. They are dissociated with lasers, then accelerated up to 212 MeV using a linear accelerator. For the accelerating structure from 40 MeV, disk-loaded traveling-wave structure is applicable because the particle beta is more than 0.7. The structure itself is similar to that for electron linacs, however, the cell length should be harmonic to the increase of the particle velocity. In this paper, the beam dynamics design of this muon linac using the disk-loaded structure (DLS) is described.

Design study of low-energy beam transport for multi-charge beams at RAON

NASA Astrophysics Data System (ADS)

Bahng, Jungbae; Qiang, Ji; Kim, Eun-San

2015-12-01

The Rare isotope Accelerator Of Newness (RAON) at the Rare Isotope Science Project (RISP) is being designed to simultaneously accelerate beams with multiple charge states. It includes a driver superconducting (SC) linac for producing 200 MeV/u and 400 kW continuous wave (CW) heavy ion beams from protons to uranium. The RAON consists of a few electron cyclotron resonance ion sources, a low-energy beam transport (LEBT) system, a CW 81.25 MHz, 500 keV/u radio frequency quadrupole (RFQ) accelerator, a medium-energy beam transport system, the SC linac, and a charge-stripper system. The LEBT system for the RISP accelerator facility consists of a high-voltage platform, two 90° dipoles, a multi-harmonic buncher (MHB), solenoids, electrostatic quadrupoles, a velocity equalizer, and a diagnostic system. The ECR ion sources are located on a high-voltage platform to reach an initial beam energy of 10 keV/u. After extraction, the ion beam is transported through the LEBT system to the RFQ accelerator. The generated charge states are selected by an achromatic bending system and then bunched by the MHB in the LEBT system. The MHB is used to achieve a small longitudinal emittance in the RFQ by generating a sawtooth wave with three harmonics. In this paper, we present the results and issues of the beam dynamics of the LEBT system.

Design of 6 MeV X-band electron linac for dual-head gantry radiotherapy system

NASA Astrophysics Data System (ADS)

Shin, Seung-wook; Lee, Seung-Hyun; Lee, Jong-Chul; Kim, Huisu; Ha, Donghyup; Ghergherehchi, Mitra; Chai, Jongseo; Lee, Byung-no; Chae, Moonsik

2017-12-01

A compact 6 MeV electron linac is being developed at Sungkyunkwan University, in collaboration with the Korea atomic energy research institute (KAERI). The linac will be used as an X-ray source for a dual-head gantry radiotherapy system. X-band technology has been employed to satisfy the size requirement of the dual-head gantry radiotherapy machine. Among the several options available, we selected a pi/2-mode, standing-wave, side-coupled cavity. This choice of radiofrequency (RF) cavity design is intended to enhance the shunt impedance of each cavity in the linac. An optimum structure of the RF cavity with a high-performance design was determined by applying a genetic algorithm during the optimization procedure. This paper describes the detailed design process for a single normal RF cavity and the entire structure, including the RF power coupler and coupling cavity, as well as the beam dynamics results.

Free Electron Lasers

DTIC Science & Technology

1991-01-09

Linacs Duke a NIST/NRL UCSB Accelerator Storage ring race - track Electrostatic microtron Van de Graaf Status 1993 19 9 2 h 1990 Electron Energy 0.5-1... phase velocity slightly less than the electrons. This wave is called the "ponderomotive potential wave", which is generated by the beating of the...c is the speed of light. The beat wave has the same frequency as the radiation, but its wavenumber is k + k,. The phase velocity of the beat wave Vph

Sawtooth-wave prebuncher with dual-gaps in Linac injector for HIRFL-SSC

NASA Astrophysics Data System (ADS)

Zhang, Xiaohu; Yuan, Youjin; Xia, Jiawen; Yin, Xuejun; Jin, Peng; Xu, Zhe; Du, Heng; Li, Zhongshan; Qiao, Jian; Wang, Kedong

2018-01-01

An RFQ structure is normally composed of radial matcher, shaper, gentle buncher and accelerator section with changing cell geometry. Bunching is started in the shaper, and adiabatic bunching is done in gentle buncher section. The beam preforms from DC beam to bunch beam through the RFQ and the longitudinal emittance for the ions linacs is defined initially in the RFQ, in which the beam bunch has been shaped. In the present SSC-Linac injector, an RFQ has been designed to accelerate the continuous beam from 3.728 keV/u to 143 keV/u. The heavy ions beam is injected into the SSC (Separated Sector Cyclotron) with the kinetic energy of 1.025 MeV/u after four IH DTLs. The rf frequency of the SSC is 13.417 MHz, and the frequency of the heavy ions RFQ is set to four times of the rf frequency of the SSC. In order to increase the longitudinal capture efficiency of the SSC and suppress the longitudinal emittance at the exit of RFQ, an external MHB (Multi-Harmonics Buncher) is proposed in front of the RFQ. The fundamental frequency of the MHB is the same as the rf frequency of the cyclotron. The scheme of dual-gaps prebuncher with the sawtooth waveform is firstly carried out through multi-harmonics synthetic technology. The multi-particle beam dynamic simulations of the MHB have been done by the BEAMPATH code.

Performance and applications of the 14 MEV electron radiation linac at CIAE

NASA Astrophysics Data System (ADS)

Zhai, X. L.; Chen, G. C.; Qi, B. M.; Xu, F. J.; Pan, L. H.; Zhang, Z. M.; Shi, X. Z.; Chen, J. K.; Wang, F. Y.

1993-07-01

A 14 MeV electron linear accelerator which was designed and manufactured by the China Institute of Atomic Energy (CIAE) has been modified into an radiation processing accelerator in 1987. It consists of an electron gun, two prebunchers, one buncher, a three meter long accelerating section, and a 90 degree bending magnet. The linac is S-band (2856 MHz), travelling wave accelerator driven by a Chinese-made klystron. The energy of electrons can be adjusted from 8 MeV to 18 MeV and the average beam power is about 2 kW. The beam width is 600 mm and the uniformity of scanning beam is better than 10%. The linac is used to irradiate power semiconductor devices for controlling the minority carrier lifetime (MCL). More than twenty factories and scientific institutions use this linac to irradiate silicon controlled rectifiers (SCR) and the fast recovery diodes (FRD), and more than 0.2 million pieces of SCR have been irradiated. Tests have also been carried out for colour-change of topaz.

Studies on the S-band bunching system with the Hybrid Bunching-accelerating Structure

NASA Astrophysics Data System (ADS)

Pei, Shi-Lun; Gao, Bin

2018-04-01

Generally, a standard bunching system is composed of a standing-wave (SW) pre-buncher (PB), a traveling-wave (TW) buncher (B) and a standard accelerating structure. In the industrial area, the bunching system is usually simplified by eliminating the PB and integrating the B and the standard accelerating structure together to form a β-varied accelerating structure. The beam capturing efficiency for this kind of simplified system is often worse than that for the standard one. The hybrid buncher (HB) has been proved to be a successful attempt to reduce the cost but preserve the beam quality as much as possible. Here we propose to exclusively simplify the standard bunching system by integrating the PB, the B and the standard accelerating structure together to form a Hybrid Bunching-accelerating Structure (HBaS). Compared to the standard bunching system, the one based on the HBaS is more compact, and the cost is lowered to the largest extent. With almost the same beam transportation efficiency (∼70%) from the electron gun to the linac exit, the peak-to-peak (p-to-p) beam energy spread and the 1 σ emittance of the linac with the HBaS are ∼20% and ∼60% bigger than those of the linac based on the split PB/B/standard accelerating structure system. Nonetheless, the proposed HBaS can be widely applied in the industrial linacs to greatly increase the beam capturing efficiency without fairly increasing the construction cost.

Stereotactic radiosurgery for intracranial metastases: linac-based and gamma-dedicated unit approach.

PubMed

Alongi, Filippo; Fiorentino, Alba; Mancosu, Pietro; Navarria, Pierina; Giaj Levra, Niccolò; Mazzola, Rosario; Scorsetti, Marta

2016-07-01

For intracranial metastases, the role of stereotactic radiosurgery (SRS) or fractionated stereotactic radiotherapy is well recognized. Historically, the first technology, for stereotactic device able to irradiate a brain tumor volume, was Gamma Knife® (GK). Due to the technological advancement of linear accelerator (Linac), there was a continuous increasing interest in SRS Linac-based applications. In those decades, it was assumed a superiority of GK compared to SRS Linac-based for brain tumor in terms of dose conformity and rapid fall-off dose close to the target. Expert commentary: Recently, due to the Linac technologic advancement, the choice of SRS GK-based is not necessarily so exclusive. The current review discussed in details the technical and clinical aspects comparing the two approaches for brain metastases.

Event-synchronized data acquisition system for the SPring-8 linac beam position monitors

NASA Astrophysics Data System (ADS)

Masuda, T.; Fukui, T.; Tanaka, R.; Taniuchi, T.; Yamashita, A.; Yanagida, K.

2005-05-01

By the summer of 2003, we had completed the installation of a new non-destructive beam position monitor (BPM) system to facilitate beam trajectory and energy correction for the SPring-8 linac. In all, 47 BPM sets were installed on the 1-GeV linac and three beam-transport lines. All of the BPM data acquisition system was required to operate synchronously with the electron beam acceleration cycle. We have developed an event-synchronized data acquisition system for the BPM data readout. We have succeeded in continuously taking all the BPMs data from six VME computers synchronized with the 10 pps operation of the linac to continuously acquire data. For each beam shot, the data points are indexed by event number and stored in a database. Using the real-time features of the Solaris operating system and distributed database technology, we currently have achieved about 99.9% efficiency in capturing and archiving all of the 10 Hz data. The linac BPM data is available for off-line analysis of the beam trajectory, but also for real-time control and automatic correction of the beam trajectory and energy.

Design of robust microlinacs for wide replacement of radioisotope sources

NASA Astrophysics Data System (ADS)

Smirnov, A. V.; Agustsson, R. A.; Boucher, S.; Harrison, M.; Junge, K.; Savin, E.; Smirnov, A. Yu

2017-12-01

To improve public security and prevent the diversion of radioactive material for Radiation Dispersion Devices, development of an inexpensive, portable, easy-to-manufacture linac system is very important. The bremsstrahlung X-rays produced by relativistic electron beam on a high-Z converter can mimic X-rays radiated from various radioactive sources. Here we consider development of two designs: one matching a Ir-192 source used in radiography with ∼1-1.3 MeV electrons, and another one Cs137 source using 3.5-4 MeV electrons that can be considered for borehole logging. Both designs use standing wave, high group velocity, cm- wave, accelerating structure. The logging tool conceptual design is based on KlyLac concept combining a klystron and linac operating in self-oscillating mode and sharing the same vacuum envelop, and electron beam.

Field Emission in Superconducting Accelerators: Instrumented Measurements for Its Understanding and Mitigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geng, Rongli; Freyberger, Arne P.; Legg, Robert A.

Several new accelerator projects are adopting superconducting accelerator technology. When accelerating cavities maintain high RF gradients, field emission, the emission of electrons from cavity walls, can occur and may impact operational cavity gradient, radiological environment via activated components, and reliability. In this talk, we will discuss instrumented measurements of field emission from the two 1.1 GeV superconducting continuous wave (CW) linacs in CEBAF. The goal is to improve the understanding of field emission sources originating from cryomodule production, installation and operation. Such basic knowledge is needed in guiding field emission control, mitigation, and reduction toward high gradient and reliable operationmore » of superconducting accelerators.« less

The ATLAS multi-user upgrade and potential applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mustapha, B.; Nolen, J. A.; Savard, G.

With the recent integration of the CARIBU-EBIS charge breeder into the ATLAS accelerator system to provide for more pure and efficient charge breeding of radioactive beams, a multi-user upgrade of the ATLAS facility is being proposed to serve multiple users simultaneously. ATLAS was the first superconducting ion linac in the world and is the US DOE low-energy Nuclear Physics National User Facility. The proposed upgrade will take advantage of the continuous-wave nature of ATLAS and the pulsed nature of the EBIS charge breeder in order to simultaneously accelerate two beams with very close mass-to-charge ratios; one stable from the existingmore » ECR ion source and one radioactive from the newly commissioned EBIS charge breeder. In addition to enhancing the nuclear physics program, beam extraction at different points along the linac will open up the opportunity for other potential applications; for instance, material irradiation studies at ~ 1 MeV/u and isotope production at ~ 6 MeV/u or at the full ATLAS energy of ~ 15 MeV/u. The concept and proposed implementation of the ATLAS multi-user upgrade will be presented. Future plans to enhance the flexibility of this upgrade will also be presented.« less

The ATLAS multi-user upgrade and potential applications

NASA Astrophysics Data System (ADS)

Mustapha, B.; Nolen, J. A.; Savard, G.; Ostroumov, P. N.

2017-12-01

With the recent integration of the CARIBU-EBIS charge breeder into the ATLAS accelerator system to provide for more pure and efficient charge breeding of radioactive beams, a multi-user upgrade of the ATLAS facility is being proposed to serve multiple users simultaneously. ATLAS was the first superconducting ion linac in the world and is the US DOE low-energy Nuclear Physics National User Facility. The proposed upgrade will take advantage of the continuous-wave nature of ATLAS and the pulsed nature of the EBIS charge breeder in order to simultaneously accelerate two beams with very close mass-to-charge ratios; one stable from the existing ECR ion source and one radioactive from the newly commissioned EBIS charge breeder. In addition to enhancing the nuclear physics program, beam extraction at different points along the linac will open up the opportunity for other potential applications; for instance, material irradiation studies at ~1 MeV/u, isotope production and radiobiological studies at ~6 MeV/u and at the full ATLAS energy of ~15 MeV/u. The concept and proposed implementation of the ATLAS multi-user upgrade will be discussed. Future plans to enhance the flexibility of this upgrade will be presented.

TH-CD-201-06: Experimental Characterization of Acoustic Signals Generated in Water Following Clinical Photon and Electron Beam Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hickling, S; El Naqa, I

Purpose: Previous work has demonstrated the detectability of acoustic waves induced following the irradiation of high density metals with radiotherapy linac photon beams. This work demonstrates the ability to experimentally detect such acoustic signals following both photon and electron irradiation in a more radiotherapy relevant material. The relationship between induced acoustic signal properties in water and the deposited dose distribution is explored, and the feasibility of exploiting such signals for radiotherapy dosimetry is demonstrated. Methods: Acoustic waves were experimentally induced in a water tank via the thermoacoustic effect following a single pulse of photon or electron irradiation produced by amore » clinical linac. An immersion ultrasound transducer was used to detect these acoustic waves in water and signals were read out on an oscilloscope. Results: Peaks and troughs in the detected acoustic signals were found to correspond to the location of gradients in the deposited dose distribution following both photon and electron irradiation. Signal amplitude was linearly related to the dose per pulse deposited by photon or electron beams at the depth of detection. Flattening filter free beams induced large acoustic signals, and signal amplitude decreased with depth after the depth of maximum dose. Varying the field size resulted in a temporal shift of the acoustic signal peaks and a change in the detected signal frequency. Conclusion: Acoustic waves can be detected in a water tank following irradiation by linac photon and electron beams with basic electronics, and have characteristics related to the deposited dose distribution. The physical location of dose gradients and the amount of dose deposited can be inferred from the location and magnitude of acoustic signal peaks. Thus, the detection of induced acoustic waves could be applied to photon and electron water tank and in vivo dosimetry. This work was supported in part by CIHR grants MOP-114910 and MOP-136774. S.H. acknowledges support by the NSERC CREATE Medical Physics Research Training Network grant 432290.« less

Design study of high gradient, low impedance accelerating structures for the FERMI free electron laser linac upgrade

NASA Astrophysics Data System (ADS)

Shafqat, N.; Di Mitri, S.; Serpico, C.; Nicastro, S.

2017-09-01

The FERMI free-electron laser (FEL) of Elettra Sincrotrone Trieste, Italy, is a user facility driven by a 1.5 GeV 10-50 Hz S-band radiofrequency linear accelerator (linac), and it is based on an external laser seeding scheme that allows lasing at the shortest fundamental wavelength of 4 nm. An increase of the beam energy to 1.8 GeV at a tolerable breakdown rate, and an improvement of the final beam quality is desired in order to allow either lasing at 4 nm with a higher flux, or lasing at shorter wavelengths. This article presents the impedance analysis of newly designed S-band accelerating structures, for replacement of the existing backward travelling wave structures (BTWS) in the last portion of the FERMI linac. The new structure design promises higher accelerating gradient and lower impedance than those of the existing BTWS. Particle tracking simulations show that, with the linac upgrade, the beam relative energy spread, its linear and nonlinear z-correlation internal to the bunch, and the beam transverse emittances can be made smaller than the ones in the present configuration, with expected advantage to the FEL performance. The repercussion of the upgrade on the linac quadrupole magnets setting, for a pre-determined electron beam optics, is also considered.

Final Commissioning of the Superconducting Heavy Ion Linear Accelerator at IUAC, Delhi

NASA Astrophysics Data System (ADS)

Datta, Tripti Sekhar; Choudhury, Anup; Chacko, Jacob; Kar, Soumen; Antony, Joby; Babu, Suresh; Kumar, Manoj; Mathuria, D. S.; Sahu, Santosh; Kanjilal, Dinakar

The superconducting linac as a booster of the 15UD Pelletron accelerator was partly commissioned with one linac module housing eight quarter wave bulk niobium cavities along with the superbuncher and rebuncher cryomodules. Subsequently two more linac cryomodules were added to have in total 24 cavities for acceleration. In addition, a new Linde helium refrigerator of capacity 750 W @ 4.2 K was installed in parallel to the earlier CCI refrigerator. The new refrigerator was integrated with the earlier cryogenics network system through a specially designed liquid helium distribution line without any valve box. The cooling philosophy with this new system is modified to have a faster cool down rate in the critical zone (150 - 70 K) to avoid Q disease. The helium gas pressure fluctuation in the cavities is reduced significantly to have stable RF locking. The full linac is being operated and beams with higher energy are being delivered to the users. The present paper will highlight the performance of the new cryogenic system with respect to cool down rate, and helium pressure fluctuation.

The issues in the development of a f = 162 . 5 MHz, β = 0 . 12 superconducting half-wave resonator for the Rare Isotope Science Project (RISP)

NASA Astrophysics Data System (ADS)

Park, Gunn Tae; Joo, Jongdae; Yao, Zhongyuan

2017-10-01

A f = 162 . 5 MHz superconducting half-wave resonator (HWR) with β = 0 . 12 is one of the four superconducting cavities being developed for the heavy ion linac of the Rare Isotope Science Project (RISP). The linac will accelerate various ions ranging from proton to uranium with beam power of about 400 kW. In particular, the HWR's will accelerate the ion beam in low-medium energy range, i.e., from 1.6 to 18 MeV for the case of uranium. In this paper, we describe design, fabrication, surface treatment, and vertical test of the 1st prototype of the cavity in detail. We also discuss some issues on the performance enhancement of the cavity. The Q0 values at 2 K surpassed the target performance, Q0 = 1 . 1 × 109 at Eacc = 6 . 3 MV / m.

Superconducting Resonators Development for the FRIB and ReA Linacs at MSU: Recent Achievements and Future Goals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Facco, A; Binkowski, J; Compton, C

2012-07-01

The superconducting driver and post-accelerator linacs of the FRIB project, the large scale radioactive beam facility under construction at MSU, require the construction of about 400 low-{beta} Quarter-wave (QWR) and Half-wave resonators (HWR) with four different optimum velocities. 1st and 2nd generation prototypes of {beta}{sub 0} = 0.041 and 0.085 QWRs and {beta}{sub 0} = 0.53 HWRs have been built and tested, and have more than fulfilled the FRIB and ReA design goals. The present cavity surface preparation at MSU allowed production of low-{beta} cavities nearly free from field emission. The first two cryostats of {beta}{sub 0} = 0.041 QWRsmore » are now in operation in the ReA3 linac. A 3rd generation design of the FRIB resonators allowed to further improve the cavity parameters, reducing the peak magnetic field in operation and increasing the possible operation gradient, with consequent reduction of the number of required resonators. The construction of the cavities for FRIB, which includes three phases for each cavity type (development, pre-production and production runs) has started. Cavity design, construction, treatment and performance will be described and discussed.« less

Analysis and measurement of the transfer matrix of a 9-cell, 1.3-GHz superconducting cavity

DOE PAGES

Halavanau, A.; Eddy, N.; Edstrom, D.; ...

2017-04-13

Superconducting linacs are capable of producing intense, stable, high-quality electron beams that have found widespread applications in science and industry. Here, the 9-cell, 1.3-GHz superconducting standing-wave accelerating rf cavity originally developed for e +/e - linear-collider applications has been broadly employed in various superconducting-linac designs. In this paper we discuss the transfer matrix of such a cavity and present its measurement performed at the Fermilab Accelerator Science and Technology (FAST) facility. Finally, the experimental results are found to be in agreement with analytical calculations and numerical simulations.

Digitally Controlled Four Harmonic Buncher for FSU LINAC

NASA Astrophysics Data System (ADS)

Moerland, Daniel S.; Wiedenhoever, Ingo; Baby, Lagy T.; Caussyn, David; Spingler, David

2012-03-01

Florida State University's John D. Fox Superconducting Accelerator Laboratory is operating a Tandem-Linac system for heavy ion beams at energies of 5-10 MeV/u. Recently, the accelerator has been used as the driver for the radioactive beam facility RESOLUT, which poses new demands on its high-intensity performance and time-resolution. These demands motivated us to optimize the RF bunching system and to switch the bunch frequency from 48.5 to 12.125 MHz. We installed a four-harmonic resonant transformer to create 3-4 kV potential oscillations across a pair of wire-mesh grids. This setup is modulating the energy of the beam injected into the tandem accelerator, with the aim to create short bunches of beam particles. Asawtooth-like wave-form is created using the Fourier series method, by combining the basis sinusoidal wave of 12.125MHz and its 3 higher order harmonics, in a manner similar to the systems used at ATLAS [1] and other RF-accelerators. A new aspect of our setup is the use of a digital 1GHz function generator, which allows us to optimize and stabilize the synthesized waveform. The control system was realized using labview and integrated into the recently updated controls of the accelerator. We characterize the bunching quality achievedand discuss the optimization of the bunching wave-form. The bunching system has been successfully used in a number of Linac-experiments performed during 2011.[4pt][1] S. Sharamentov, J. Bogaty, B.E. Clifft, R. Pardo, UPGRADE OF THE ATLAS POSITIVE ION INJECTOR BUNCHING SYSTEM, Proceedings of 2005 Particle Accelerator Conference, Knoxville, Tennessee

Noninterceptive transverse emittance measurements using BPM for Chinese ADS R&D project

NASA Astrophysics Data System (ADS)

Wang, Zhi-Jun; Feng, Chi; He, Yuan; Dou, Weiping; Tao, Yue; Chen, Wei-long; Jia, Huan; Liu, Shu-hui; Wang, Wang-sheng; Zhang, Yong; Wu, Jian-qiang; Zhang, Sheng-hu; Zhang, X. L.

2016-04-01

The noninterceptive four-dimensional transverse emittance measurements are essential for commissioning the high power continue-wave (CW) proton linacs as well as their operations. The conventional emittance measuring devices such as slits and wire scanners are not well suited under these conditions due to sure beam damages. Therefore, the method of using noninterceptive Beam Position Monitor (BPM) is developed and demonstrated on Injector Scheme II at the Chinese Accelerator Driven Sub-critical System (China-ADS) proofing facility inside Institute of Modern Physics (IMP) [1]. The results of measurements are in good agreements with wire scanners and slits at low duty-factor pulsed (LDFP) beam. In this paper, the detailed experiment designs, data analysis and result benchmarking are presented.

Progress towards 3-cell superconducting traveling wave cavity cryogenic test

NASA Astrophysics Data System (ADS)

Kostin, R.; Avrakhov, P.; Kanareykin, A.; Yakovlev, V.; Solyak, N.

2017-12-01

This paper describes a superconducting L-band travelling wave cavity for electron linacs as an alternative to the 9-cell superconducting standing wave Tesla type cavity. A superconducting travelling wave cavity may provide 20-40% higher accelerating gradient by comparison with conventional cavities. This feature arises from an opportunity to use a smaller phase advance per cell which increases the transit time factor and affords the opportunity to use longer cavities because of its significantly smaller sensitivity to manufacturing errors. Two prototype superconducting travelling wave cavities were designed and manufactured for a high gradient travelling wave demonstration at cryogenic temperature. This paper presents the main milestones achieved towards this test.

Estimates of dispersive effects in a bent NLC Main Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael Syphers and Leo Michelotti

2000-10-31

An alternative being considered for the Next Linear Collider (NLC) is not to tunnel in a straight line but to bend the Main Linac into an arc so as to follow a gravitational equipotential. The authors begin here an examination of the effects that this would have on vertical dispersion, with its attendant consequences on synchrotron radiation and emittance growth by looking at two scenarios: a gentle continuous bending of the beam to follow an equipotential surface, and an introduction of sharp bends at a few sites in the linac so as to reduce the maximum sagitta produced.

Ultra-High Gradient S-band Linac for Laboratory and Industrial Applications

NASA Astrophysics Data System (ADS)

Faillace, L.; Agustsson, R.; Dolgashev, V.; Frigola, P.; Murokh, A.; Rosenzweig, J.; Yakimenko, V.

2010-11-01

A strong demand for high gradient structures arises from the limited real estate available for linear accelerators. RadiaBeam Technologies is developing a Doubled Energy Compact Accelerator (DECA) structure: an S-band standing wave electron linac designed to operate at accelerating gradients of up to 50 MV/m. In this paper, we present the radio-frequency design of the DECA S-band accelerating structure, operating at 2.856 GHz in the π-mode. The structure design is heavily influenced by NLC collaboration experience with ultra high gradient X-band structures; S-band, however, is chosen to take advantage of commonly available high power S-band klystrons.

Cloud-based design of high average power traveling wave linacs

NASA Astrophysics Data System (ADS)

Kutsaev, S. V.; Eidelman, Y.; Bruhwiler, D. L.; Moeller, P.; Nagler, R.; Barbe Welzel, J.

2017-12-01

The design of industrial high average power traveling wave linacs must accurately consider some specific effects. For example, acceleration of high current beam reduces power flow in the accelerating waveguide. Space charge may influence the stability of longitudinal or transverse beam dynamics. Accurate treatment of beam loading is central to the design of high-power TW accelerators, and it is especially difficult to model in the meter-scale region where the electrons are nonrelativistic. Currently, there are two types of available codes: tracking codes (e.g. PARMELA or ASTRA) that cannot solve self-consistent problems, and particle-in-cell codes (e.g. Magic 3D or CST Particle Studio) that can model the physics correctly but are very time-consuming and resource-demanding. Hellweg is a special tool for quick and accurate electron dynamics simulation in traveling wave accelerating structures. The underlying theory of this software is based on the differential equations of motion. The effects considered in this code include beam loading, space charge forces, and external magnetic fields. We present the current capabilities of the code, provide benchmarking results, and discuss future plans. We also describe the browser-based GUI for executing Hellweg in the cloud.

QALMA: A computational toolkit for the analysis of quality protocols for medical linear accelerators in radiation therapy

NASA Astrophysics Data System (ADS)

Rahman, Md Mushfiqur; Lei, Yu; Kalantzis, Georgios

2018-01-01

Quality Assurance (QA) for medical linear accelerator (linac) is one of the primary concerns in external beam radiation Therapy. Continued advancements in clinical accelerators and computer control technology make the QA procedures more complex and time consuming which often, adequate software accompanied with specific phantoms is required. To ameliorate that matter, we introduce QALMA (Quality Assurance for Linac with MATLAB), a MALAB toolkit which aims to simplify the quantitative analysis of QA for linac which includes Star-Shot analysis, Picket Fence test, Winston-Lutz test, Multileaf Collimator (MLC) log file analysis and verification of light & radiation field coincidence test.

Predictive time-series modeling using artificial neural networks for Linac beam symmetry: an empirical study.

PubMed

Li, Qiongge; Chan, Maria F

2017-01-01

Over half of cancer patients receive radiotherapy (RT) as partial or full cancer treatment. Daily quality assurance (QA) of RT in cancer treatment closely monitors the performance of the medical linear accelerator (Linac) and is critical for continuous improvement of patient safety and quality of care. Cumulative longitudinal QA measurements are valuable for understanding the behavior of the Linac and allow physicists to identify trends in the output and take preventive actions. In this study, artificial neural networks (ANNs) and autoregressive moving average (ARMA) time-series prediction modeling techniques were both applied to 5-year daily Linac QA data. Verification tests and other evaluations were then performed for all models. Preliminary results showed that ANN time-series predictive modeling has more advantages over ARMA techniques for accurate and effective applicability in the dosimetry and QA field. © 2016 New York Academy of Sciences.

Beam Measurement of 11.424 GHz X-Band Linac for Compton Scattering X-ray Source

NASA Astrophysics Data System (ADS)

Natsui, Takuya; Mori, Azusa; Masuda, Hirotoshi; Uesaka, Mitsuru; Sakamoto, Fumito

2010-11-01

An inverse Compton scattering X-ray source for medical applications, consisting of an X-band (11.424 GHz) linac and Q-switched Nd:YAG laser, is currently being developed at the University of Tokyo. This system uses an X-band 3.5-cell thermionic cathode RF gun for electron beam generation. We can obtain a multi-bunch electron beam with this gun. The beam is accelerated to 30 MeV by a traveling-wave accelerating tube. So far, we have verified stable beam generation (around 2.3 MeV) by using the newly designed RF gun and we have succeeded in beam transportation to a beam dump.

SU-G-BRB-04: Automated Output Factor Measurements Using Continuous Data Logging for Linac Commissioning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, X; Li, S; Zheng, D

Purpose: Linac commissioning is a time consuming and labor intensive process, the streamline of which is highly desirable. In particular, manual measurement of output factors for a variety of field sizes and energy greatly hinders the commissioning efficiency. In this study, automated measurement of output factors was demonstrated as ‘one-click’ using data logging of an electrometer. Methods: Beams to be measured were created in the recording and verifying (R&V) system and configured for continuous delivery. An electrometer with an automatic data logging feature enabled continuous data collection for all fields without human intervention. The electrometer saved data into a spreadsheetmore » every 0.5 seconds. A Matlab program was developed to analyze the excel data to monitor and check the data quality. Results: For each photon energy, output factors were measured for five configurations, including open field and four wedges. Each configuration includes 72 fields sizes, ranging from 4×4 to 20×30 cm{sup 2}. Using automation, it took 50 minutes to complete the measurement of 72 field sizes, in contrast to 80 minutes when using the manual approach. The automation avoided the necessity of redundant Linac status checks between fields as in the manual approach. In fact, the only limiting factor in such automation is Linac overheating. The data collection beams in the R&V system are reusable, and the simplified process is less error-prone. In addition, our Matlab program extracted the output factors faithfully from data logging, and the discrepancy between the automatic and manual measurement is within ±0.3%. For two separate automated measurements 30 days apart, consistency check shows a discrepancy within ±1% for 6MV photon with a 60 degree wedge. Conclusion: Automated output factor measurements can save time by 40% when compared with conventional manual approach. This work laid ground for further improvement for the automation of Linac commissioning.« less

First heavy ion beam tests with a superconducting multigap CH cavity

NASA Astrophysics Data System (ADS)

Barth, W.; Aulenbacher, K.; Basten, M.; Busch, M.; Dziuba, F.; Gettmann, V.; Heilmann, M.; Kürzeder, T.; Miski-Oglu, M.; Podlech, H.; Rubin, A.; Schnase, A.; Schwarz, M.; Yaramyshev, S.

2018-02-01

Very compact accelerating-focusing structures, as well as short focusing periods, high accelerating gradients and short drift spaces are strongly required for superconducting (sc) accelerator sections operating at low and medium energies for continuous wave (cw) heavy ion beams. To keep the GSI-super heavy element (SHE) program competitive on a high level and even beyond, a standalone sc cw linac (Helmholtz linear accelerator) in combination with the GSI high charge state injector (HLI), upgraded for cw operation, is envisaged. Recently the first linac section (financed by Helmholtz Institute Mainz (HIM) and GSI) as a demonstration of the capability of 217 MHz multigap crossbar H-mode structures (CH) has been commissioned and extensively tested with heavy ion beam from the HLI. The demonstrator setup reached acceleration of heavy ions up to the design beam energy. The required acceleration gain was achieved with heavy ion beams even above the design mass to charge ratio at high beam intensity and full beam transmission. This paper presents systematic beam measurements with varying rf amplitudes and phases of the CH cavity, as well as phase space measurements for heavy ion beams with different mass to charge ratio. The worldwide first and successful beam test with a superconducting multigap CH cavity is a milestone of the R&D work of HIM and GSI in collaboration with IAP in preparation of the HELIAC project and other cw-ion beam applications.

Advanced low-beta cavity development for proton and ion accelerators

NASA Astrophysics Data System (ADS)

Conway, Z. A.; Kelly, M. P.; Ostroumov, P. N.

2015-05-01

Recent developments in designing and processing low-beta superconducting cavities at Argonne National Laboratory are very encouraging for future applications requiring compact proton and ion accelerators. One of the major benefits of these accelerating structures is achieving real-estate accelerating gradients greater than 3 MV/m very efficiently either continuously or for long-duty cycle operation (>1%). The technology has been implemented in low-beta accelerator cryomodules for the Argonne ATLAS heavy-ion linac where the cryomodules are required to have real-estate gradients of more than 3 MV/m. In offline testing low-beta cavities with even higher gradients have already been achieved. This paper will review this work where we have achieved surface fields greater than 166 mT magnetic and 117 MV/m electric in a 72 MHz quarter-wave resonator optimized for β = 0.077 ions.

Alternating phase focused linacs

DOEpatents

Swenson, Donald A.

1980-01-01

A heavy particle linear accelerator employing rf fields for transverse and ongitudinal focusing as well as acceleration. Drift tube length and gap positions in a standing wave drift tube loaded structure are arranged so that particles are subject to acceleration and succession of focusing and defocusing forces which contain the beam without additional magnetic or electric focusing fields.

The high Beta cryo-modules and the associated cryogenic system for the HIE-ISOLDE upgrade at CERN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delruelle, N.; Leclercq, Y.; Pirotte, O.

2014-01-29

The major upgrade of the energy and intensity of the existing ISOLDE and REX-ISOLDE radioactive ion beam facilities at CERN requires the replacement of most of the existing ISOLDE post-acceleration equipment by a superconducting linac based on quarter-wave resonators housed together with superconducting solenoids in a series of four high-β and two low-β cryo-modules. As well as providing optimum conditions for physics, the cryo-modules need to function under stringent vacuum and cryogenic conditions. We present the detail design and expected cryogenic performance of the high- β cryo-module together with the cryogenic supply and distribution system destined to service the completemore » superconducting linac.« less

Spiral 2 Cryogenic System for The Superconducting LINAC

NASA Astrophysics Data System (ADS)

Ghribi, A.; Bernaudin, P.-E.; Bert, Y.; Commeaux, C.; Houeto, M.; Lescalié, G.

2017-02-01

SPIRAL 21 is a rare isotope accelerator dedicated to the production of high intensity beams (E = 40 MeV, I = 5 mA). The driver is a linear accelerator (LINAC) that uses bulk Niobium made quarter wave RF cavities. 19 cryomodules inclose one or two cavities respectively for the low and the high energy sections. To supply the 1300 W at 4.2 K required to cool down the LINAC, a cryogenic system has been set up. The heart of the latter is a 3 turbines geared HELIAL®LF (ALAT2) cold box that delivers both the liquid helium for the cavities and the 60 K Helium gaz for the thermal screens. 19 valve-boxes insure cryogenic fluid distribution and management. Key issues like cool down speed or cavity RF frequency stability are closely linked to the cryogenic system management. To overcome these issues, modelling and simulation efforts are being undertaken prior to the first cool down trials. In this paper, we present a status update of the Spiral 2 cryogenic system and the cool down strategy considered for its commissioning.

Investigation of using shrinking method in construction of Institute for Research in Fundamental Sciences Electron Linear Accelerator TW-tube (IPM TW-Linac tube)

NASA Astrophysics Data System (ADS)

Ghasemi, F.; Abbasi Davani, F.

2015-06-01

Due to Iran's growing need for accelerators in various applications, IPM's electron Linac project has been defined. This accelerator is a 15 MeV energy S-band traveling-wave accelerator which is being designed and constructed based on the klystron that has been built in Iran. Based on the design, operating mode is π /2 and the accelerating chamber consists of two 60cm long tubes with constant impedance and a 30cm long buncher. Amongst all construction methods, shrinking method is selected for construction of IPM's electron Linac tube because it has a simple procedure and there is no need for large vacuum or hydrogen furnaces. In this paper, different aspects of this method are investigated. According to the calculations, linear ratio of frequency alteration to radius change is 787.8 MHz/cm, and the maximum deformation at the tube wall where disks and the tube make contact is 2.7μ m. Applying shrinking method for construction of 8- and 24-cavity tubes results in satisfactory frequency and quality factor. Average deviations of cavities frequency of 8- and 24-cavity tubes to the design values are 0.68 MHz and 1.8 MHz respectively before tune and 0.2 MHz and 0.4 MHz after tune. Accelerating tubes, buncher, and high power couplers of IPM's electron linac are constructed using shrinking method.

Overview of High Power Vacuum Dry RF Load Designs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krasnykh, Anatoly

2015-08-27

A specific feature of RF linacs based on the pulsed traveling wave (TW) mode of operation is that only a portion of the RF energy is used for the beam acceleration. The residual RF energy has to be terminated into an RF load. Higher accelerating gradients require higher RF sources and RF loads, which can stably terminate the residual RF power. RF feeders (from the RF source though the accelerating section to the load) are vacuumed to transmit multi-megawatt high power RF. This overview will outline vacuumed RF loads only. A common method to terminate multi-MW RF power is tomore » use circulated water (or other liquid) as an absorbing medium. A solid dielectric interface (a high quality ceramic) is required to separate vacuum and liquid RF absorber mediums. Using such RF load approaches in TW linacs is troubling because there is a fragile ceramic window barrier and a failure could become catastrophic for linac vacuum and RF systems. Traditional loads comprising of a ceramic disk have limited peak and average power handling capability and are therefore not suitable for high gradient TW linacs. This overview will focus on ''vacuum dry'' or ''all-metal'' loads that do not employ any dielectric interface between vacuum and absorber. The first prototype is an original design of RF loads for the Stanford Two-Mile Accelerator.« less

Terahertz radiation source using a high-power industrial electron linear accelerator

NASA Astrophysics Data System (ADS)

Kalkal, Yashvir; Kumar, Vinit

2017-04-01

High-power (˜ 100 kW) industrial electron linear accelerators (linacs) are used for irradiations, e.g., for pasteurization of food products, disinfection of medical waste, etc. We propose that high-power electron beam from such an industrial linac can first pass through an undulator to generate useful terahertz (THz) radiation, and the spent electron beam coming out of the undulator can still be used for the intended industrial applications. This will enhance the utilization of a high-power industrial linac. We have performed calculation of spontaneous emission in the undulator to show that for typical parameters, continuous terahertz radiation having power of the order of μW can be produced, which may be useful for many scientific applications such as multispectral imaging of biological samples, chemical samples etc.

SU-F-E-17: A Dedicated Teaching and Research Linac as a Stepping Stone to Introduce Medical Physics to Students

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beaulieu, L; Archambault, L; Universite Laval, Quebec, Quebec

Purpose: This work describes how a non-clinical, research and teaching Linac is used as an extremely motivating and exciting way to introduce students to medical physics. Methods: The dedicated facility was inaugurated in 2014. The facility is composed of a fully equipped and functional state-of-the-art Varian TrueBeam Linac and a complete set of physics instruments and QA phantoms for the Linac and onboard imaging. The Linac bunker and treatment console are oversized such that a class of 12–15 can comfortably fit, seated if needed for longer sessions. A 3cr undergraduate laboratory course that includes medical imaging, x-ray source characterization (mAs,more » kVp, and filtering) and many others including an introductory Linac laboratory was created. The latter is composed of one general 4-hours session and a weekly 4-hours session for teams of two students. The general session includes a hands-on presentation of the Linac, its environment and a formal safety and radiation protection course (with an exam). Results: Since the winter of 2015, senior undergraduate (total of 15) pursuing either the medical physics or the biomedical engineering tracks can register. At the Linac, the students are allowed full control of the experiments, including set-up and irradiation. Supervisor intervention is limited to safety concerns for students or equipment. Measurements of output factors using two chambers (regular and small field) for various field sizes (1×1 to 30×30 cm{sup 2}) and of detailed depth-dose curves for 6 MV, 6 and 12 MeV beams are to be performed and discussed in a formal report. Conclusion: Full access to, and control of, a Linac is the high point of this course. It provides a glimpse of medical physics and generates an experimental background for those continuing to CAMPEP programs. This dedicated, non-clinical facility further enable enhance CAMPEP graduate teaching and research activities not possible with a clinical device.« less

Advanced low-beta cavity development for proton and ion accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Conway, Z. A.; Kelly, M. P.; Ostroumov, P. N.

2015-05-01

Recent developments in designing and processing low-beta superconducting cavities at Argonne National Laboratory are very encouraging for future applications requiring compact proton and ion accelerators. One of the major benefits of these accelerating structures is achieving real-estate accelerating gradients greater than 3 MV/m very efficiently either continuously or for long-duty cycle operation (>1%). The technology has been implemented in low-beta accelerator cryomodules for the Argonne ATLAS heavy-ion linac where the cryomodules are required to have real-estate gradients of more than 3 MV/m. In offline testing low-beta cavities with even higher gradients have already been achieved. This paper will review thismore » work where we have achieved surface fields greater than 166 mT magnetic and 117 MV/m electric in a 72 MHz quarter-wave resonator optimized for beta = 0.077 ions.« less

MO-FG-202-03: Efficient Data Collection of Continuous 2D and Discrete Relative Dosimetric Data for Annual LINAC QA Using TrueBeam Developer Mode and a 1D Scanning Tank

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knutson, N; Schmidt, M; University of Rhode Island, Kingston, RI

2016-06-15

Purpose: To develop a method to exploit real-time dynamic machine and couch parameter control during linear accelerator (LINAC) beam delivery to facilitate efficient performance of TG-142 suggested, Annual LINAC QA tests. Methods: Varian’s TrueBeam Developer Mode (Varian Medical Systems, Palo Alto, CA) facilitates control of Varian’s TrueBeam LINAC via instructions provided in Extensible Markup Language (XML) files. This allows machine and couch parameters to be varied dynamically, in real-time, during beam delivery. Custom XML files were created to allow for the collection of (1) continuous Tissue Maximum Ratios (TMRs), (2) beam profiles, and (3) continuous output factors using a 1D-scanningmore » tank. TMRs were acquired by orienting an ionization chamber (IC) at isocenter (depth=25cm) and synchronizing a depth scan towards the water surface while lowering the couch at 1mm/s. For beam profiles, the couch was driven laterally and longitudinally while logging IC electrometer readings. Output factors (OFs) where collected by continually varying field sizes (4×4 to 30×30-cm{sup 2}) at a constant speed of 6.66 mm/s. To validate measurements, comparisons were made to data collected using traditional methods (e.g. 1D or 3D tank). Results: All data collecting using the proposed methods agreed with traditionally collected data (TMRs within 1%, OFs within 0.5% and beam profile agreement within 1% / 1mm) while taking less time to collect (factor of approximately 1/10) and with a finer sample resolution. Conclusion: TrueBeam developer mode facilitates collection of continuous data with the same accuracy as traditionally collected data with a finer resolution in less time. Results demonstrate an order of magnitude increase in sampled resolution and an order of magnitude reduction in collection time compared to traditional acquisition methods (e.g. 3D scanning tank). We are currently extending this approach to perform other TG-142 tasks.« less

Development Status of Ion Source at J-PARC Linac Test Stand

NASA Astrophysics Data System (ADS)

Yamazaki, S.; Takagi, A.; Ikegami, K.; Ohkoshi, K.; Ueno, A.; Koizumi, I.; Oguri, H.

The Japan Proton Accelerator Research Complex (J-PARC) linac power upgrade program is now in progress in parallel with user operation. To realize a nominal performance of 1 MW at 3 GeV Rapid Cycling Synchrotron and 0.75 MW at the Main Ring synchrotron, we need to upgrade the peak beam current (50 mA) of the linac. For the upgrade program, we are testing a new front-end system, which comprises a cesiated RF-driven H- ion source and a new radio -frequency quadrupole linac (RFQ). The H- ion source was developed to satisfy the J-PARC upgrade requirements of an H- ion-beam current of 60 mA and a lifetime of more than 50 days. On February 6, 2014, the first 50 mA H- beams were accelerated by the RFQ during a beam test. To demonstrate the performance of the ion source before its installation in the summer of 2014, we tested the long-term stability through continuous beam operation, which included estimating the lifetime of the RF antenna and evaluating the cesium consumption.

Beam Dynamics Simulation of Photocathode RF Electron Gun at the PBP-CMU Linac Laboratory

NASA Astrophysics Data System (ADS)

Buakor, K.; Rimjaem, S.

2017-09-01

Photocathode radio-frequency (RF) electron guns are widely used at many particle accelerator laboratories due to high quality of produced electron beams. By using a short-pulse laser to induce the photoemission process, the electrons are emitted with low energy spread. Moreover, the photocathode RF guns are not suffered from the electron back bombardment effect, which can cause the limited electron current and accelerated energy. In this research, we aim to develop the photocathode RF gun for the linac-based THz radiation source. Its design is based on the existing gun at the PBP-CMU Linac Laboratory. The gun consists of a one and a half cell S-band standing-wave RF cavities with a maximum electric field of about 60 MV/m at the centre of the full cell. We study the beam dynamics of electrons traveling through the electromagnetic field inside the RF gun by using the particle tracking program ASTRA. The laser properties i.e. transverse size and injecting phase are optimized to obtain low transverse emittance. In addition, the solenoid magnet is applied for beam focusing and emittance compensation. The proper solenoid magnetic field is then investigated to find the optimum value for proper emittance conservation condition.

Dewar Testing of Coaxial Resonators at MSU

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popielarski, J; Facco, A; Hodek, M

2012-07-01

Michigan State University is currently testing prototype and production cavities for two accelerator projects. 80.5 MHz {beta} = 0.085 quarter wave resonators (QWR) are being produced as part of a cryomodule for ReA3. 322 MHz {beta} = 0.53 half wave resonators (HWR) are being prototyped for a driver linac for the Facility for Rare Isotope Beams. This paper will discuss test results and how different cavity preparations effect cavity performs. Also various diagnostics methods have been developed, such as second sound quench location determination, and temperature mapping to determine hot spots from defects and multipacting location.

RF emittance in a low energy electron linear accelerator

NASA Astrophysics Data System (ADS)

Sanaye Hajari, Sh.; Haghtalab, S.; Shaker, H.; Kelisani, M. Dayyani

2018-04-01

Transverse beam dynamics of an 8 MeV low current (10 mA) S-band traveling wave electron linear accelerator has been studied and optimized. The main issue is to limit the beam emittance, mainly induced by the transverse RF forces. The linac is being constructed at Institute for Research in Fundamental Science (IPM), Tehran Iran Labeled as Iran's First Linac, nearly all components of this accelerator are designed and constructed within the country. This paper discusses the RF coupler induced field asymmetry and the corresponding emittance at different focusing levels, introduces a detailed beam dynamics design of a solenoid focusing channel aiming to reduce the emittance growth and studies the solenoid misalignment tolerances. In addition it has been demonstrated that a prebuncher cavity with appropriate parameters can help improving the beam quality in the transverse plane.

Optimization of the RF cavity heat load and trip rates for CEBAF at 12 GeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, He; Roblin, Yves R.; Freyberger, Arne P.

2017-05-01

The Continuous Electron Beam Accelerator Facility at JLab has 200 RF cavities in the north linac and the south linac respectively after the 12 GeV upgrade. The purpose of this work is to simultaneously optimize the heat load and the trip rate for the cavities and to reconstruct the pareto-optimal front in a timely manner when some of the cavities are turned down. By choosing an efficient optimizer and strategically creating the initial gradients, the pareto-optimal front for no more than 15 cavities down can be re-established within 20 seconds.

An electron linac-based system for BNCT of shallow tumors

NASA Astrophysics Data System (ADS)

Farhad Masoudi, S.; Ghiasi, Hedieh; Harif, Maryam; Rasouli, Fatemeh S.

2018-07-01

Although BNCT has been in existence since the 1950s, it continues to be of special significant and interest for wide groups of researchers. Recent studies, focused on investigating appropriate neutron sources as alternatives for nuclear reactors, revealed the high potential of electron linac-based facilities to improve the efficiency of this treatment method. The present simulation study has been devoted to both designing an optimized and geometrically simple target to be used as a photoneutron source based on an electron linac and designing a configuration composed of arrangement of materials to generate an appropriate beam for BNCT of shallow tumors considering the widely accepted criteria for pre-clinical survey. It has been found that the behavior of photoneutrons' current and their average energy on the surface of the target is independent of the incident energy. Accordingly, we managed to present a formula to predict the average energy of photoneutrons knowing the electron energy to an acceptable approximation avoiding Monte Carlo simulations. Considering the conflict between the beam intensity and its purity in the whole beam designing process, an optimized beam shaping assembly for electron linac of 18 MeV/ mA has been proposed. These results in essence confirm the ability of these sources for BNCT of shallow tumors and are therefore encouraging for further studies. Furthermore, the results show that this configuration, which the corresponding beam fulfills all the medical requirements, is also usable for electron linacs of other energies. This can be of high importance in practical point of view.

Studies of longitudinal instability with an electron beam

NASA Astrophysics Data System (ADS)

This progress report covers the research on the 'Study of Longitudinal Instability with an Electron Beam' performed at the University of Maryland during the period from September 1, 1993 to February 28, 1994 of the two-year grant sponsored by the Department of Energy, under Grant No. DEFG02-92ER54178. This research is motivated by the issue of longitudinal instability in induction linacs as drivers for heavy ion inertial fusion. The Fusion Policy Advisory Committee (FPAC) in its final report to DOE (September 1990) identified longitudinal instability as a key physics problem that needs to be solved if an induction linac is to be developed into a successful HIF driver. The FPAC report also stated that 'in parallel' to the design and construction of ILSE 'enhanced theoretical and experimental efforts are required for an improved understanding of potentially serious longitudinal beam instability issues'. The experiment with electron beams in this area is a low-cost way to gain a thorough understanding of the instability and to test computer codes in collaboration with LBL, LLNL, and I. Haber at NRL. The last six months saw the transition of the research activities from phase 1 to phase 2. By the end of last September, the experiments on space-charge waves had been completed. This had fulfilled the first year's goal of this two-year grant. Though the completion of the experiments was one month later than that scheduled and the data analysis still continues up to now, the authors have done much more than was originally proposed.

Commercial Superconducting Electron Linac for Radioisotope Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grimm, Terry Lee; Boulware, Charles H.; Hollister, Jerry L.

2015-08-13

The majority of radioisotopes used in the United States today come from foreign suppliers or are generated parasitically in large government accelerators and nuclear reactors. Both of these restrictions limit the availability of radioisotopes and discourage the development and evaluation of new isotopes and for nuclear medicine, science, and industry. Numerous studies have been recommending development of dedicated accelerators for production of radioisotopes for over 20 years (Institute of Medicine, 1995; Reba, et al, 2000; National Research Council, 2007; NSAC 2009). The 2015 NSAC Long Range Plan for Isotopes again identified electron accelerators as an area for continued research andmore » development. Recommendation 1(c) from the 2015 NSAC Isotope report specifically identifies electron accelerators for continued funding for the purpose of producing medical and industrial radioisotopes. Recognizing the pressing need for new production methods of radioisotopes, the United States Congress passed the American Medical Isotope Production Act of 2012 to develop a domestic production of 99Mo and to eliminate the use of highly enriched uranium (HEU) in the production of 99Mo. One of the advantages of high power electron linear accelerators (linacs) is they can create both proton- and neutron-rich isotopes by generating high energy x-rays that knock out protons or neutrons from stable atoms or by fission of uranium. This allows for production of isotopes not possible in nuclear reactors. Recent advances in superconducting electron linacs have decreased the size and complexity of these systems such that they are economically competitive with nuclear reactors and large, high energy accelerators. Niowave, Inc. has been developing a radioisotope production facility based on a superconducting electron linac with liquid metal converters.« less

Room temperature quarter wave resonator re-buncher development for a high power heavy-ion linear accelerator

NASA Astrophysics Data System (ADS)

Kim, Hye-Jin; Choi, B. H.; Han, Jaeeun; Hyun, Myung Ook; Park, Bum-Sik; Choi, Ohryoung; Lee, Doyoon; Son, Kitaek

2018-03-01

In the medium energy beam transport (MEBT) line system of the RAON which consists of several quadrupole magnets, three normal-conducting re-bunchers, and several diagnostic devices, a quarter wave resonator type re-buncher was chosen for minimizing longitudinal emittance growth and manipulating a longitudinal phase ellipse into the longitudinal acceptance of the low energy linac. The re-buncher has a resonant frequency of 81.25 MHz, geometrical beta (βg) of 0.049, and physical length of 24 cm. Based on the result of numerical calculations of electromagnetic field using CST-MWS and mechanical analysis of the heat distribution and deformation, an internal structure of the re-buncher was optimized to increase the effective voltage and to reduce power losses in the wall. The criteria of the multipacting effect was estimated and it was confirmed by the experiment. The position and specification of cooling channels are designed to recover a heat load up to 15 kW with reasonable margin of 25%. The coaxial and loop type RF power coupler are positioned on the high magnetic field region and two slug tuners are installed perpendicularly to the beam axis. The frequency sensitivity as a function of the tuner depth and cooling water temperature is measured and the frequency shift is in all cases within the provided tuner range. The test with a high power of 10 kW and the continuous wave is performed and the reflection power is observed less than 450 W.

Status of intense permanent magnet proton source for China-accelerator driven sub-critical system Linac.

PubMed

Wu, Q; Ma, H Y; Yang, Y; Sun, L T; Zhang, X Z; Zhang, Z M; Zhao, H Y; He, Y; Zhao, H W

2016-02-01

Two compact intense 2.45 GHz permanent magnet proton sources and their corresponding low energy beam transport (LEBT) system were developed successfully for China accelerator driven sub-critical system in 2014. Both the proton sources operate at 35 kV potential. The beams extracted from the ion source are transported by the LEBT, which is composed of two identical solenoids, to the 2.1 MeV Radio-Frequency Quadrupole (RFQ). In order to ensure the safety of the superconducting cavities during commissioning, an electrostatic-chopper has been designed and installed in the LEBT line that can chop the continuous wave beam into a pulsed one. The minimum width of the pulse is less than 10 μs and the fall/rise time of the chopper is about 20 ns. The performance of the proton source and the LEBT, such as beam current, beam profile, emittance and the impact to RFQ injection will be presented.

Status of intense permanent magnet proton source for China-accelerator driven sub-critical system Linac

NASA Astrophysics Data System (ADS)

Wu, Q.; Ma, H. Y.; Yang, Y.; Sun, L. T.; Zhang, X. Z.; Zhang, Z. M.; Zhao, H. Y.; He, Y.; Zhao, H. W.

2016-02-01

Two compact intense 2.45 GHz permanent magnet proton sources and their corresponding low energy beam transport (LEBT) system were developed successfully for China accelerator driven sub-critical system in 2014. Both the proton sources operate at 35 kV potential. The beams extracted from the ion source are transported by the LEBT, which is composed of two identical solenoids, to the 2.1 MeV Radio-Frequency Quadrupole (RFQ). In order to ensure the safety of the superconducting cavities during commissioning, an electrostatic-chopper has been designed and installed in the LEBT line that can chop the continuous wave beam into a pulsed one. The minimum width of the pulse is less than 10 μs and the fall/rise time of the chopper is about 20 ns. The performance of the proton source and the LEBT, such as beam current, beam profile, emittance and the impact to RFQ injection will be presented.

Cavity Processing and Preparation of 650 MHz Elliptical Cell Cavities for PIP-II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rowe, Allan; Chandrasekaran, Saravan Kumar; Grassellino, Anna

The PIP-II project at Fermilab requires fifteen 650 MHz SRF cryomodules as part of the 800 MeV LINAC that will provide a high intensity proton beam to the Fermilab neutrino program. A total of fifty-seven high-performance SRF cavities will populate the cryomodules and will operate in both pulsed and continuous wave modes. These cavities will be processed and prepared for performance testing utilizing adapted cavity processing infrastructure already in place at Fermilab and Argonne. The processing recipes implemented for these structures will incorporate state-of-the art processing and cleaning techniques developed for 1.3 GHz SRF cavities for the ILC, XFEL, andmore » LCLS-II projects. This paper describes the details of the processing recipes and associated chemistry, heat treatment, and cleanroom processes at the Fermilab and Argonne cavity processing facilities. This paper also presents single and multi-cell cavity test results with quality factors above 5·10¹⁰ and accelerating gradients above 30 MV/m.« less

Optimization of S/B in the detection of nuclear fission signatures via different accelerator pulsing modes

NASA Astrophysics Data System (ADS)

Brown, C.; Gozani, T.; Shaw, T.; Stevenson, J.

2011-10-01

In the search for concealed special nuclear materials (SNM) there are a number of fission specific signatures that can be measured. These include prompt and delayed neutron and gamma ray signatures. Here the focus will be on the delayed gamma signature with the assumption that a pulsed electron linac with a constant peak current will be used to generate bremsstrahlung radiation and induce photofission in 235U. In this case, the signal to background ratio (S/B) will depend on the choice of linac frequency, pulse mode, and "active" background due to linac activation products. The linac frequency is simply the rate at which it produces short bursts of radiation, typically 2-4 μs in duration. There are two pulse modes, micro-pulsing, and macro-pulsing. In the micro-pulsing mode, the linac runs continuously at its set frequency and data is collected between bursts. In the macro-pulsing mode, the linac is turned on for a given length of time, on the order of seconds, and then turned off for a period of time typically equal to the length of time it was turned on. Counting takes place during the time the linac is off and stops when the linac is turned on for another cycle. The time dependence of the delayed gamma population can be approximated by the use of 5 time groups with half-lives of 0.29, 1.7, 13, 100, and 940 s, respectively. Each group has its own relative population, which together with its half-life determines what time frame the group contributes most to the measured signal. For example, a group with a short half-life will contribute more signal to a short cycle macro pulsed measurement than it would to a macro pulse measurement with a very long cycle. An analytical expression can be derived that calculates the maximum obtainable signal (delayed gamma photons per fission gamma ray) in either a micro- or macro-pulsed measurement. Using this information along with the observed active background present in a given situation (which can constrain the micro-pulsing parameters), the preferred mode of operation can be chosen to maximize S/B and the detection sensitivity. The principles and experimental application of the optimization process will be shown.

The development of magnetic field measurement system for drift-tube linac quadrupole

NASA Astrophysics Data System (ADS)

Zhou, Jianxin; Kang, Wen; Yin, Baogui; Peng, Quanling; Li, Li; Liu, Huachang; Gong, Keyun; Li, Bo; Chen, Qiang; Li, Shuai; Liu, Yiqin

2015-06-01

In the China Spallation Neutron Source (CSNS) linac, a conventional 324 MHz drift-tube linac (DTL) accelerating an H- ion beam from 3 MeV to 80 MeV has been designed and manufactured. The electromagnetic quadrupoles (EMQs) are widely used in a DTL accelerator. The main challenge of DTLQ's structure is to house a strong gradient EMQ in the much reduced space of the drift-tube (DT). To verify the DTLQ's design specifications and fabrication quality, a precision harmonic coil measurement system has been developed, which is based on the high precision movement platform, the harmonic coil with ceramic frame and the special method to make the harmonic coil and the quadrupoles coaxial. After more than one year's continuous running, the magnetic field measurement system still performs accurately and stably. The field measurement of more than one hundred DTLQ has been finished. The components and function of the measurement system, the key point of the technology and the repeatability of the measurement results are described in this paper.

Dosimetric analysis of stereotactic body radiation therapy for pancreatic cancer using MR-guided Tri-60Co unit, MR-guided LINAC, and conventional LINAC-based plans.

PubMed

Ramey, Stephen James; Padgett, Kyle R; Lamichhane, Narottam; Neboori, Hanmath J; Kwon, Deukwoo; Mellon, Eric A; Brown, Karen; Duffy, Melissa; Victoria, James; Dogan, Nesrin; Portelance, Lorraine

2018-03-01

This study aims to perform a dosimetric comparison of 2 magnetic resonance (MR)-guided radiation therapy systems capable of performing online adaptive radiation therapy versus a conventional radiation therapy system for pancreas stereotactic body radiation therapy. Ten cases of patients with pancreatic adenocarcinoma previously treated in our institution were used for this analysis. MR-guided tri-cobalt 60 therapy (MR-cobalt) and MR-LINAC plans were generated and compared with conventional LINAC (volumetric modulated arc therapy) plans. The prescription dose was 40 Gy in 5 fractions covering 95% of the planning tumor volume for the 30 plans. The same organs at risk (OARs) dose constraints were used in all plans. Dose-volume-based indices were used to compare PTV coverage and OAR sparing. The conformity index of 40 Gy in 5 fractions covering 95% of the planning tumor volume demonstrated higher conformity in both LINAC-based plans compared with MR-cobalt plans. Although there was no difference in mean conformity index between LINAC and MR-LINAC plans (1.08 in both), there was a large difference between LINAC and MR-cobalt plans (1.08 vs 1.52). Overall, 79%, 72%, and 78% of critical structure dosimetric constraints were met with LINAC, MR-cobalt, and MR-LINAC plans, respectively. The MR-cobalt plans delivered more doses to all OARs compared with the LINAC plans. In contrast, the doses to the OARs of the MR-LINAC plans were similar to LINAC plans except in 2 cases: liver mean dose (MR-LINAC, 2 .8 Gy vs LINAC, 2.1 Gy) and volume of duodenum receiving at least 15 Gy (MR-LINAC, 13.2 mL vs LINAC, 15.4 mL). Both differences are likely not clinically significant. This study demonstrates that dosimetrically similar plans were achieved with conventional LINAC and MR-LINAC, whereas doses to OARs were statistically higher for MR-cobalt compared with conventional LINAC plans because of low-dose spillage. Given the improved tumor-tracking capabilities of MR-LINAC, further studies should evaluate potential benefits of adaptive radiation therapy-capable MR-guided LINAC treatment. Copyright © 2018. Published by Elsevier Inc.

On the Detectability of Acoustic Waves Induced Following Irradiation by a Radiotherapy Linear Accelerator.

PubMed

Hickling, Susannah; Leger, Pierre; El Naqa, Issam

2016-02-11

Irradiating an object with a megavoltage photon beam generated by a clinical radiotherapy linear accelerator (linac) induces acoustic waves through the photoacoustic effect. The detection and characterization of such acoustic waves has potential applications in radiation therapy dosimetry. The purpose of this work was to gain insight into the properties of such acoustic waves by simulating and experimentally detecting them in a well-defined system consisting of a metal block suspended in a water tank. A novel simulation workflow was developed by combining radiotherapy Monte Carlo and acoustic wave transport simulation techniques. Different set-up parameters such as photon beam energy, metal block depth, metal block width, and metal block material were varied, and the simulated and experimental acoustic waveforms showed the same relative amplitude trends and frequency variations for such setup changes. The simulation platform developed in this work can easily be extended to other irradiation situations, and will be an invaluable tool for developing a radiotherapy dosimetry system based on the detection of the acoustic waves induced following linear accelerator irradiation.

Impact of nitrogen doping of niobium superconducting cavities on the sensitivity of surface resistance to trapped magnetic flux

NASA Astrophysics Data System (ADS)

Gonnella, Dan; Kaufman, John; Liepe, Matthias

2016-02-01

Future particle accelerators such as the SLAC "Linac Coherent Light Source-II" (LCLS-II) and the proposed Cornell Energy Recovery Linac require hundreds of superconducting radio-frequency (SRF) niobium cavities operating in continuous wave mode. In order to achieve economic feasibility of projects such as these, the cavities must achieve a very high intrinsic quality factor (Q0) to keep cryogenic losses within feasible limits. To reach these high Q0's in the case of LCLS-II, nitrogen-doping of niobium cavities has been selected as the cavity preparation technique. When dealing with Q0's greater than 1 × 1010, the effects of ambient magnetic field on Q0 become significant. Here, we show that the sensitivity to RF losses from trapped magnetic field in a cavity's walls is strongly dependent on the cavity preparation. Specifically, standard electropolished and 120 °C baked cavities show a sensitivity of residual resistance from trapped magnetic flux of ˜0.6 and ˜0.8 nΩ/mG trapped, respectively, while nitrogen-doped cavities show a higher sensitivity of residual resistance from trapped magnetic flux of ˜1 to 5 nΩ/mG trapped. We show that this difference in sensitivities is directly related to the mean free path of the RF surface layer of the niobium: shorter mean free paths lead to less sensitivity of residual resistance to trapped magnetic flux in the dirty limit (ℓ ≪ ξ0), while longer mean free paths lead to lower sensitivity of residual resistance to trapped magnetic flux in the clean limit (ℓ ≫ ξ0). These experimental results are also shown to have good agreement with recent theoretical predictions for pinned vortex lines oscillating in RF fields.

Tunable Soft X-Ray Oscillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wurtele, Jonathan; Gandhi, Punut; Gu, X-W

A concept for a tunable soft x-ray free electron laser (FEL) photon source is presented and studied numerically. The concept is based on echo-enabled harmonic generation (EEHG), wherein two modulator-chicane sections impose high harmonic structure with much greater efficacy as compared to conventional high harmonic FELs that use only one modulator-chicane section. The idea proposed here is to replace the external laser power sources in the EEHG modulators with FEL oscillators, and to combine the bunching of the beam with the production of radiation. Tunability is accomplished by adjusting the magnetic chicanes while the two oscillators remain at a fixedmore » frequency. This scheme eliminates the need to develop coherent sources with the requisite power, pulse length, and stability requirements by exploiting the MHz bunch repetition rates of FEL continuous wave (CW) sources driven by superconducting (SC) linacs. We present time-dependent GINGER simulation results for an EEHG scheme with an oscillator modulator at 43 nm employing 50percent reflective dielectric mirrors and a second modulator employing an external, 215-nm drive laser. Peak output of order 300 MW is obtained at 2.7 nm, corresponding to the 80th harmonic of 215 nm. An alternative single-cavity echo-oscillator scheme based on a 13.4 nm oscillator is investigated with time-independent simulations that a 180-MW peak power at final wavelength of 1.12 nm. Three alternate configurations that use separate bunches to produce the radiation for EEHG microbunching are also presented. Our results show that oscillator-based soft x-ray FELs driven by CWSC linacs are extremely attractive because of their potential to produce tunable radiation at high average power together with excellent longitudinal coherence and narrow spectral bandwidth.« less

Design study of an S-band RF cavity of a dual-energy electron LINAC for the CIS

NASA Astrophysics Data System (ADS)

Lee, Byeong-No; Park, Hyungdal; Song, Ki-baek; Li, Yonggui; Lee, Byung Cheol; Cha, Sung-su; Lee, Jong-Chul; Shin, Seung-Wook; Chai, Jong-seo

2014-01-01

The design of a resonance frequency (RF) cavity for the dual-energy S-band electron linear accelerator (LINAC) has been carried out for the cargo inspection system (CIS). This Standing-wave-type RF cavity is operated at a frequency under the 2856-MHz resonance frequency and generates electron beams of 9 MeV (high mode) and 6 MeV (low mode). The electrons are accelerated from the initial energy of the electron gun to the target energy (9 or 6 MeV) inside the RF cavity by using the RF power transmitted from a 5.5-MW-class klystron. Then, electron beams with a 1-kW average power (both high mode and low mode) bombard an X-ray target a 2-mm spot size. The proposed accelerating gradient was 13 MV/m, and the designed Q value was about 7100. On going research on 15-MeV non-destructive inspections for military or other applications is presented.

Method for generating a plasma wave to accelerate electrons

DOEpatents

Umstadter, D.; Esarey, E.; Kim, J.K.

1997-06-10

The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention. 21 figs.

Method for generating a plasma wave to accelerate electrons

DOEpatents

Umstadter, Donald; Esarey, Eric; Kim, Joon K.

1997-01-01

The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention.

SU-F-BRB-16: A Spreadsheet Based Automatic Trajectory GEnerator (SAGE): An Open Source Tool for Automatic Creation of TrueBeam Developer Mode Robotic Trajectories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Etmektzoglou, A; Mishra, P; Svatos, M

Purpose: To automate creation and delivery of robotic linac trajectories with TrueBeam Developer Mode, an open source spreadsheet-based trajectory generation tool has been developed, tested and made freely available. The computing power inherent in a spreadsheet environment plus additional functions programmed into the tool insulate users from the underlying schema tedium and allow easy calculation, parameterization, graphical visualization, validation and finally automatic generation of Developer Mode XML scripts which are directly loadable on a TrueBeam linac. Methods: The robotic control system platform that allows total coordination of potentially all linac moving axes with beam (continuous, step-and-shoot, or combination thereof) becomesmore » available in TrueBeam Developer Mode. Many complex trajectories are either geometric or can be described in analytical form, making the computational power, graphing and programmability available in a spreadsheet environment an easy and ideal vehicle for automatic trajectory generation. The spreadsheet environment allows also for parameterization of trajectories thus enabling the creation of entire families of trajectories using only a few variables. Standard spreadsheet functionality has been extended for powerful movie-like dynamic graphic visualization of the gantry, table, MLC, room, lasers, 3D observer placement and beam centerline all as a function of MU or time, for analysis of the motions before requiring actual linac time. Results: We used the tool to generate and deliver extended SAD “virtual isocenter” trajectories of various shapes such as parameterized circles and ellipses. We also demonstrated use of the tool in generating linac couch motions that simulate respiratory motion using analytical parameterized functions. Conclusion: The SAGE tool is a valuable resource to experiment with families of complex geometric trajectories for a TrueBeam Linac. It makes Developer Mode more accessible as a vehicle to quickly translate research ideas into machine readable scripts without programming knowledge. As an open source initiative, it also enables researcher collaboration on future developments. I am a full time employee at Varian Medical Systems, Palo Alto, California.« less

Electron linear accelerator system for natural rubber vulcanization

NASA Astrophysics Data System (ADS)

Rimjaem, S.; Kongmon, E.; Rhodes, M. W.; Saisut, J.; Thongbai, C.

2017-09-01

Development of an electron accelerator system, beam diagnostic instruments, an irradiation apparatus and electron beam processing methodology for natural rubber vulcanization is underway at the Plasma and Beam Physics Research Facility, Chiang Mai University, Thailand. The project is carried out with the aims to improve the qualities of natural rubber products. The system consists of a DC thermionic electron gun, 5-cell standing-wave radio-frequency (RF) linear accelerator (linac) with side-coupling cavities and an electron beam irradiation apparatus. This system is used to produce electron beams with an adjustable energy between 0.5 and 4 MeV and a pulse current of 10-100 mA at a pulse repetition rate of 20-400 Hz. An average absorbed dose between 160 and 640 Gy is expected to be archived for 4 MeV electron beam when the accelerator is operated at 400 Hz. The research activities focus firstly on assembling of the accelerator system, study on accelerator properties and electron beam dynamic simulations. The resonant frequency of the RF linac in π/2 operating mode is 2996.82 MHz for the operating temperature of 35 °C. The beam dynamic simulations were conducted by using the code ASTRA. Simulation results suggest that electron beams with an average energy of 4.002 MeV can be obtained when the linac accelerating gradient is 41.7 MV/m. The rms transverse beam size and normalized rms transverse emittance at the linac exit are 0.91 mm and 10.48 π mm·mrad, respectively. This information can then be used as the input data for Monte Carlo simulations to estimate the electron beam penetration depth and dose distribution in the natural rubber latex. The study results from this research will be used to define optimal conditions for natural rubber vulcanization with different electron beam energies and doses. This is very useful for development of future practical industrial accelerator units.

LCLS-II Cryomodules Production at Fermilab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arkan, Tug; Grimm, Chuck; Kaluzny, Joshua

2017-05-01

LCLS-II is an upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLS-II linac will consist of thirty-five 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab (JLab) will assemble in collaboration with SLAC. The LCLS-II 1.3 GHz cryomodule design is based on the European XFEL pulsed-mode cryomodule design with modifications needed for CW operation. Fermilab and JLab will each assemble and test a prototype 1.3 GHz cryomodule to assess the results of the CW modifications, in advance of 16 and 17 production 1.3 GHz cryomodules, respectively. Fermilab ismore » solely responsible for the 3.9 GHz cryomodules. After the prototype cryomodule tests are complete and lessons learned incorporated, both laboratories will increase their cryomodule production rates to meet the challenging LCLS-II project requirement of approximately one cryomodule per month per laboratory. This paper presents the Fermilab Cryomodule Assembly Facility (CAF) infrastructure for LCLS-II cryomodule production, the Fermilab prototype 1.3 GHz CW cryomodule (pCM) assembly and readiness for production assembly.« less

High-intensity positron microprobe at the Thomas Jefferson National Accelerator Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golge, S., E-mail: serkan.golge@nasa.gov; Vlahovic, B.; Wojtsekhowski, B.

We present a conceptual design for a novel continuous wave electron-linac based high-intensity high-brightness slow-positron production source with a projected intensity on the order of 10{sup 10 }e{sup +}/s. Reaching this intensity in our design relies on the transport of positrons (T{sub +} below 600 keV) from the electron-positron pair production converter target to a low-radiation and low-temperature area for moderation in a high-efficiency cryogenic rare gas moderator, solid Ne. This design progressed through Monte Carlo optimizations of: electron/positron beam energies and converter target thickness, transport of the e{sup +} beam from the converter to the moderator, extraction of the e{sup +}more » beam from the magnetic channel, a synchronized raster system, and moderator efficiency calculations. For the extraction of e{sup +} from the magnetic channel, a magnetic field terminator plug prototype has been built and experimental results on the effectiveness of the prototype are presented. The dissipation of the heat away from the converter target and radiation protection measures are also discussed.« less

High-intensity positron microprobe at Jefferson Lab

DOE PAGES

Golge, Serkan; Vlahovic, Branislav; Wojtsekhowski, Bogdan B.

2014-06-19

We present a conceptual design for a novel continuous wave electron-linac based high-intensity slow-positron production source with a projected intensity on the order of 10 10 e +/s. Reaching this intensity in our design relies on the transport of positrons (T + below 600 keV) from the electron-positron pair production converter target to a low-radiation and low-temperature area for moderation in a high-efficiency cryogenic rare gas moderator, solid Ne. The performance of the integrated beamline has been verified through computational studies. The computational results include Monte Carlo calculations of the optimized electron/positron beam energies, converter target thickness, synchronized raster system,more » transport of the beam from the converter target to the moderator, extraction of the beam from the channel, and moderation efficiency calculations. For the extraction of positrons from the magnetic channel a magnetic field terminator plug prototype has been built and experimental data on the effectiveness of this prototype are presented. The dissipation of the heat away from the converter target and radiation protection measures are also discussed.« less

Design of a side coupled standing wave accelerating tube for NSTRI e-Linac

NASA Astrophysics Data System (ADS)

Zarei, S.; Abbasi Davani, F.; Lamehi Rachti, M.; Ghasemi, F.

2017-09-01

The design and construction of a 6 MeV electron linear accelerator (e-Linac) was defined in the Institute of Nuclear Science and Technology (NSTRI) for cargo inspection and medical applications. For this accelerator, a side coupled standing wave tube resonant at a frequency of 2998.5 MHZ in π/2 mode was selected. In this article, the authors provide a step-by-step explanation of the process of the design for this tube. The design and simulation of the accelerating and coupling cavities were carried out in five steps; (1) separate design of the accelerating and coupling cavities, (2) design of the coupling aperture between the cavities, (3) design of the entire structure for resonance at the nominal frequency, (4) design of the buncher, and (5) design of the power coupling port. At all design stages, in addition to finding the dimensions of the cavity, the impact of construction tolerances and simulation errors on the electromagnetic parameters were investigated. The values obtained for the coupling coefficient, coupling constant, quality factor and capture efficiency are 2.11, 0.011, 16203 and 36%, respectively. The results of beam dynamics study of the simulated tube in ASTRA have yielded a value of 5.14 π-mm-mrad for the horizontal emittance, 5.06 π-mm-mrad for the vertical emittance, 1.17 mm for the horizontal beam size, 1.16 mm for the vertical beam size and 1090 keV for the energy spread of the output beam.

An Rf Focused Interdigital Ion Accelerating Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swenson, D.A.

2003-08-26

An Rf Focused Interdigital (RFI) ion accelerating structure will be described. It represents an effective combination of the Wideroee (or interdigital) linac structure, used for many low frequency, heavy ion applications, and the rf electric quadrupole focusing used in the RFQ and RFD linac structures. As in the RFD linac structure, rf focusing is introduced into the RFI linac structure by configuring the drift tubes as two independent pieces operating at different electrical potentials as determined by the rf fields of the linac structure. Each piece (or electrode) of the RFI drift tube supports two fingers pointed inwards towards themore » opposite end of the drift tube forming a four-finger geometry that produces an rf quadrupole field along the axis of the linac for focusing the beam. However, because of the differences in the rf field configuration along the axis, the scheme for introducing rf focusing into the interdigital linac structure is quite different from that adopted for the RFD linac structure. The RFI linac structure promises to have significant size, efficiency, performance, and cost advantages over existing linac structures for the acceleration of low energy ion beams of all masses (light to heavy). These advantages will be reviewed. A 'cold model' of this new linac structure has been fabricated and the results of rf cavity measurements on this cold model will be presented.« less

Cobalt-60 Machines and Medical Linear Accelerators: Competing Technologies for External Beam Radiotherapy.

PubMed

Healy, B J; van der Merwe, D; Christaki, K E; Meghzifene, A

2017-02-01

Medical linear accelerators (linacs) and cobalt-60 machines are both mature technologies for external beam radiotherapy. A comparison is made between these two technologies in terms of infrastructure and maintenance, dosimetry, shielding requirements, staffing, costs, security, patient throughput and clinical use. Infrastructure and maintenance are more demanding for linacs due to the complex electric componentry. In dosimetry, a higher beam energy, modulated dose rate and smaller focal spot size mean that it is easier to create an optimised treatment with a linac for conformal dose coverage of the tumour while sparing healthy organs at risk. In shielding, the requirements for a concrete bunker are similar for cobalt-60 machines and linacs but extra shielding and protection from neutrons are required for linacs. Staffing levels can be higher for linacs and more staff training is required for linacs. Life cycle costs are higher for linacs, especially multi-energy linacs. Security is more complex for cobalt-60 machines because of the high activity radioactive source. Patient throughput can be affected by source decay for cobalt-60 machines but poor maintenance and breakdowns can severely affect patient throughput for linacs. In clinical use, more complex treatment techniques are easier to achieve with linacs, and the availability of electron beams on high-energy linacs can be useful for certain treatments. In summary, there is no simple answer to the question of the choice of either cobalt-60 machines or linacs for radiotherapy in low- and middle-income countries. In fact a radiotherapy department with a combination of technologies, including orthovoltage X-ray units, may be an option. Local needs, conditions and resources will have to be factored into any decision on technology taking into account the characteristics of both forms of teletherapy, with the primary goal being the sustainability of the radiotherapy service over the useful lifetime of the equipment. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Interleaving lattice for the Argonne Advanced Photon Source linac

NASA Astrophysics Data System (ADS)

Shin, S.; Sun, Y.; Dooling, J.; Borland, M.; Zholents, A.

2018-06-01

To realize and test advanced accelerator concepts and hardware, a beam line is being reconfigured in the linac extension area (LEA) of the Argonne Advanced Photon Source (APS) linac. A photocathode rf gun installed at the beginning of the APS linac will provide a low emittance electron beam into the LEA beam line. The thermionic rf gun beam for the APS storage ring and the photocathode rf gun beam for the LEA beam line will be accelerated through the linac in an interleaved fashion. In this paper, the design studies for interleaving lattice realization in the APS linac is described with the initial experiment result.

SU-E-T-211: Comparison of Seven New TrueBeam Linacs with Enhanced Beam Data Conformance Using a Beam Comparison Software Tool

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grzetic, S; Hessler, J; Gupta, N

2015-06-15

Purpose: To develop an independent software tool to assist in commissioning linacs with enhanced beam conformance, as well as perform ongoing QA for dosimetrically equivalent linacs. Methods: Linac manufacturers offer enhanced beam conformance as an option to allow for clinics to complete commissioning efficiently, as well as implement dosimetrically equivalent linacs. The specification for enhanced conformance includes PDD as well as profiles within 80% FWHM. Recently, we commissioned seven Varian TrueBeam linacs with enhanced beam conformance. We developed a software tool in Visual Basic to allow us to load the reference beam data and compare our beam data during commissioningmore » to evaluate enhanced beam conformance. This tool also allowed us to upload our beam data used for commissioning our dosimetrically equivalent beam models to compare and tweak each of our linac beams to match our modelled data in Varian’s Eclipse TPS. This tool will also be used during annual QA of the linacs to compare our beam data to our baseline data, as required by TG-142. Results: Our software tool was used to check beam conformance for seven TrueBeam linacs that we commissioned in the past six months. Using our tool we found that the factory conformed linacs showed up to 3.82% difference in their beam profile data upon installation. Using our beam comparison tool, we were able to adjust the energy and profiles of our beams to accomplish a better than 1.00% point by point data conformance. Conclusion: The availability of quantitative comparison tools is essential to accept and commission linacs with enhanced beam conformance, as well as to beam match multiple linacs. We further intend to use the same tool to ensure our beam data conforms to the commissioning beam data during our annual QA in keeping with the requirements of TG-142.« less

WE-G-17A-09: Novel Magnetic Shielding Design for Inline and Perpendicular Integrated 6 MV Linac and 1.0 T MRI Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, X; Ma, B; Kuang, Y

2014-06-15

Purpose: The influence of fringe magnetic fields delivered by magnetic resonance imaging (MRI) on the beam generation and transportation in Linac is still a major challenge for the integration of linear accelerator and MRI (Linac-MRI). In this study, we investigated an optimal magnetic shielding design for Linac-MRI and further characterized the beam trajectory in electron gun. Methods: Both inline and perpendicular configurations were analyzed in this study. The configurations, comprising a Linac-MRI with a 100cm SAD and an open 1.0 T superconductive magnet, were simulated by the 3D finite element method (FEM). The steel shielding around the Linac was includedmore » in the 3D model, the thickness of which was varied from 1mm to 20mm, and magnetic field maps were acquired with and without additional shielding. The treatment beam trajectory in electron gun was evaluated using OPERA 3d SCALA with and without shielding cases. Results: When Linac was not shielded, the uniformity of diameter sphere volume (DSV) (30cm) was about 5 parts per million (ppm) and the fringe magnetic fields in electron gun were more than 0.3 T. With shielding, the magnetic fields in electron gun were reduced to less than 0.01 T. For the inline configuration, the radial magnetic fields in the Linac were about 0.02T. A cylinder steel shield used (5mm thick) altered the uniformity of DSV to 1000 ppm. For the perpendicular configuration, the Linac transverse magnetic fields were more than 0.3T, which altered the beam trajectory significantly. A 8mm-thick cylinder steel shield surrounding the Linac was used to compensate the output losses of Linac, which shifted the magnetic fields' uniformity of DSV to 400 ppm. Conclusion: For both configurations, the Linac shielding was used to ensure normal operation of the Linac. The effect of magnetic fields on the uniformity of DSV could be modulated by the shimming technique of the MRI magnet. NIH/NIGMS grant U54 GM104944, Lincy Endowed Assistant Professorship.« less

SU-F-T-305: Clinical Effects of Dosimetric Leaf Gap (DLG) Values Between Matched Varian Truebeam (TB) Linacs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mihailidis, D; Mallah, J; Zhu, D

2016-06-15

Purpose: The dosimetric leaf gap (DLG) is an important parameter to be measured for dynamic beam delivery of modern linacs, like the Varian Truebeam (TB). The clinical effects of DLG-values on IMRT and/or VMAT commissioning of two “matched” TB linacs will be presented.Methods and Materials: The DLG values on two TB linacs were measured for all energy modalities (filtered and FFF-modes) as part of the dynamic delivery mode commissioning (IMRT and/or VMAT. After the standard beam data was modeled in eclipse treatment planning system (TPS) and validated, IMRT validation was performed based on TG1191 benchmark, IROC Head-Neck (H&N) phantom andmore » sample of clinical cases, all measured on both linacs. Although there was a single-set of data entered in the TPS, a noticeable difference was observed for the DLG-values between the linacs. The TG119, IROC phantom and selected patient plans were furnished with DLG-values of TB1 for both linacs and the delivery was performed on both TB linacs for comparison. Results: The DLG values of TB1 was first used for both linacs to perform the testing comparisons. The QA comparison of TG119 plans revealed a great dependence of the results to the DLG-values used for the linac for all energy modalities studied, especially when moving from 3%/3mm to 2%/2mm γ-analysis. Conclusion: The DLG-values have a definite influence on the dynamic dose, delivery that increases with the plan complexity. We recommend that the measured DLG-values are assigned to each of the “matched” linacs, even if a single set of beam data describes multiple linacs. The user should perform a detail test of the dynamic delivery of each linac based on end-to-end benchmark suites like TG119 and IROC phantoms.1Ezzel G., et al., “IMRT commissioning: Multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119.” Med. Phys. 36:5359–5373 (2009). partly supported by CAMC Cancer Center and Alliance Oncology.« less

TU-F-CAMPUS-J-05: Fast Volumetric MRI On An MRI-Linac Enables On-Line QA On Dose Deposition in the Patient

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crijns, S; Glitzner, M; Kontaxis, C

Purpose: The introduction of the MRI-linac in radiotherapy brings MRI-guided treatment with daily plan adaptions within reach. This paradigm demands on-line QA. With its ability to perform continuous volumetric imaging in an outstanding soft-tissue contrast, the MRI- linac promises to elucidate the dose deposition process during a treatment session. Here we study for a prostate case how dynamic MRI combined with linac machine parameters and a fast dose-engine can be used for on-line dose accumulation. Methods: Prostate imaging was performed in healthy volunteer on a 1.5T MR-scanner (Philips, Best, NL) according to a clinical MR-sim protocol, followed by 10min ofmore » dynamic imaging (FLASH, 4s/volume, FOV 40×40×12cm{sup 3}, voxels 3×3×3mm{sup 3}, TR/TE/α=3.5ms/1.7ms/5°). An experienced radiation oncologist made delineations, considering the prostate CTV. Planning was performed on a two-compartment pseudoCT (air/water density) according to clinical constraints (77Gy in PTV) using a Monte-Carlo (MC) based TPS that accounts for magnetic fields. Delivery of one fraction (2.2Gy) was simulated on an emulator for the Axesse linac (Elekta, Stockholm, SE). Machine parameters (MLC settings, gantry angle, dose rate, etc.) were recorded at 25Hz. These were re-grouped per dynamic volume and fed into the MC-engine to calculate a dose delivered for each of the dynamics. Deformations derived from non-rigid registration of each dynamic against the first allowed dose accumulation on a common reference grid. Results: The DVH parameters on the PTV compared to the optimized plan showed little changes. Local deformations however resulted in local deviations, primarily around the air/rectum interface. This clearly indicates the potential of intra-fraction adaptations based on the accumulated dose. Application in each fraction helps to track the influence of plan adaptations to the eventual dose distribution. Calculation times were about twice the delivery time. Conclusion: The current Result paves the way to perform on-line treatment delivery QA on the MRI-linac in the near future.« less

A new medium energy beam transport line for the proton injector of AGS-RHIC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okamura, M.; Briscoe, B.; Fite, J.

2010-09-12

In Brookhaven National Laboratory (BNL), a 750 keV medium energy beam transport line between the 201 MHz 750 keV proton RFQ and the 200 MeV Alvarez DTL is being modified to get a better transmission of the beam. Within a tight space, high field gradient quadrupoles (65 Tm) and newly designed steering magnets (6.5 mm in length) will be installed considering the cross-talk effects. Also a new half wave length 200 MHz buncher is being prepared. The beam commissioning will be done in this year. To enhance the performance of the proton linacs, the MEBT is being modified. New quadrupolemore » magnets, steering magnets and a half wave length buncher as shown in Figure 7 will be installed and be commissioned soon.« less

Poster - 53: Improving inter-linac DMLC IMRT dose precision by fine tuning of MLC leaf calibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakonechny, Keith; Tran, Muoi; Sasaki, David

Purpose: To develop a method to improve the inter-linac precision of DMLC IMRT dosimetry. Methods: The distance between opposing MLC leaf banks (“gap size”) can be finely tuned on Varian linacs. The dosimetric effect due to small deviations from the nominal gap size (“gap error”) was studied by introducing known errors for several DMLC sliding gap sizes, and for clinical plans based on the TG119 test cases. The plans were delivered on a single Varian linac and the relationship between gap error and the corresponding change in dose was measured. The plans were also delivered on eight Varian 2100 seriesmore » linacs (at two institutions) in order to quantify the inter-linac variation in dose before and after fine tuning the MLC calibration. Results: The measured dose differences for each field agreed well with the predictions of LoSasso et al. Using the default MLC calibration, the variation in the physical MLC gap size was determined to be less than 0.4 mm between all linacs studied. The dose difference between the linacs with the largest and smallest physical gap was up to 5.4% (spinal cord region of the head and neck TG119 test case). This difference was reduced to 2.5% after fine tuning the MLC gap calibration. Conclusions: The inter-linac dose precision for DMLC IMRT on Varian linacs can be improved using a simple modification of the MLC calibration procedure that involves fine adjustment of the nominal gap size.« less

Jefferson Lab 12 GEV Cebaf Upgrade

NASA Astrophysics Data System (ADS)

Rode, C. H.

2010-04-01

The existing continuous electron beam accelerator facility (CEBAF) at Thomas Jefferson National Accelerator Facility (TJNAF) is a 5-pass, recirculating cw electron Linac operating at ˜6 GeV and is devoted to basic research in nuclear physics. The 12 GeV CEBAF Upgrade is a 310 M project, sponsored by the Department of Energy (DOE) Office of Nuclear Physics, that will expand its research capabilities substantially by doubling the maximum energy and adding major new experimental apparatus. The project received construction approval in September 2008 and has started the major procurement process. The cryogenic aspects of the 12 GeV CEBAF Upgrade includes: doubling the accelerating voltages of the Linacs by adding ten new high-performance, superconducting radiofrequency (SRF) cryomodules (CMs) to the existing 42 1/4 cryomodules; doubling of the 2 K cryogenics plant; and the addition of eight superconducting magnets.

RF plasma modeling of the Linac4 H- ion source

NASA Astrophysics Data System (ADS)

Mattei, S.; Ohta, M.; Hatayama, A.; Lettry, J.; Kawamura, Y.; Yasumoto, M.; Schmitzer, C.

2013-02-01

This study focuses on the modelling of the ICP RF-plasma in the Linac4 H- ion source currently being constructed at CERN. A self-consistent model of the plasma dynamics with the RF electromagnetic field has been developed by a PIC-MCC method. In this paper, the model is applied to the analysis of a low density plasma discharge initiation, with particular interest on the effect of the external magnetic field on the plasma properties, such as wall loss, electron density and electron energy. The employment of a multi-cusp magnetic field effectively limits the wall losses, particularly in the radial direction. Preliminary results however indicate that a reduced heating efficiency results in such a configuration. The effect is possibly due to trapping of electrons in the multi-cusp magnetic field, preventing their continuous acceleration in the azimuthal direction.

An Overview of the MaRIE X-FEL and Electron Radiography LINAC RF Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bradley, Joseph Thomas III; Rees, Daniel Earl; Scheinker, Alexander

The purpose of the Matter-Radiation Interactions in Extremes (MaRIE) facility at Los Alamos National Laboratory is to investigate the performance limits of materials in extreme environments. The MaRIE facility will utilize a 12 GeV linac to drive an X-ray Free-Electron Laser (FEL). Most of the same linac will also be used to perform electron radiography. The main linac is driven by two shorter linacs; one short linac optimized for X-FEL pulses and one for electron radiography. The RF systems have historically been the one of the largest single component costs of a linac. We will describe the details of themore » different types of RF systems required by each part of the linacs. Starting with the High Power RF system, we will present our methodology for the choice of RF system peak power and pulselength with respect to klystron parameters, modulator parameters, performance requirements and relative costs. We will also present an overview of the Low Level RF systems that are proposed for MaRIE and briefly describe their use with some proposed control schemes.« less

High gradient linac for proton therapy

NASA Astrophysics Data System (ADS)

Benedetti, S.; Grudiev, A.; Latina, A.

2017-04-01

Proposed for the first time almost 30 years ago, the research on radio frequency linacs for hadron therapy experienced a sparkling interest in the past decade. The different projects found a common ground on a relatively high rf operating frequency of 3 GHz, taking advantage of the availability of affordable and reliable commercial klystrons at this frequency. This article presents for the first time the design of a proton therapy linac, called TULIP all-linac, from the source up to 230 MeV. In the first part, we will review the rationale of linacs for hadron therapy. We then divided this paper in two main sections: first, we will discuss the rf design of the different accelerating structures that compose TULIP; second, we will present the beam dynamics design of the different linac sections.

R & D on Beam Injection and Bunching Schemes in the Fermilab Booster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhat, C. M.

2016-01-01

Fermilab is committed to upgrade its accelerator complex to support HEP experiments at the intensity frontier. The ongoing Proton Improvement Plan (PIP) enables us to reach 700 kW beam power on the NuMI neutrino targets. By the end of the next decade, the current 400 MeV normal conducting LINAC will be replaced by an 800 MeV superconducting LINAC (PIP-II) with an increased beam power >50% of the PIP design goal. Both in PIP and PIP-II era, the existing Booster is going to play a very significant role, at least for next two decades. In the meanwhile, we have recently developedmore » an innovative beam injection and bunching scheme for the Booster called "early injection scheme" that continues to use the existing 400 MeV LINAC and implemented into operation. This scheme has the potential to increase the Booster beam intensity by >40% from the PIP design goal. Some benefits from the scheme have already been seen. In this paper, I will describe the basic principle of the scheme, results from recent beam experiments, our experience with the new scheme in operation, current status, issues and future plans. This scheme fits well with the current and future intensity upgrade programs at Fermilab.« less

A linear accelerator for simulated micrometeors.

NASA Technical Reports Server (NTRS)

Slattery, J. C.; Becker, D. G.; Hamermesh, B.; Roy, N. L.

1973-01-01

Review of the theory, design parameters, and construction details of a linear accelerator designed to impart meteoric velocities to charged microparticles in the 1- to 10-micron diameter range. The described linac is of the Sloan Lawrence type and, in a significant departure from conventional accelerator practice, is adapted to single particle operation by employing a square wave driving voltage with the frequency automatically adjusted from 12.5 to 125 kHz according to the variable velocity of each injected particle. Any output velocity up to about 30 km/sec can easily be selected, with a repetition rate of approximately two particles per minute.

Symplectic modeling of beam loading in electromagnetic cavities

DOE PAGES

Abell, Dan T.; Cook, Nathan M.; Webb, Stephen D.

2017-05-22

Simulating beam loading in radio frequency accelerating structures is critical for understanding higher-order mode effects on beam dynamics, such as beam break-up instability in energy recovery linacs. Full wave simulations of beam loading in radio frequency structures are computationally expensive, and while reduced models can ignore essential physics, it can be difficult to generalize. Here, we present a self-consistent algorithm derived from the least-action principle which can model an arbitrary number of cavity eigenmodes and with a generic beam distribution. It has been implemented in our new Open Library for Investigating Vacuum Electronics (OLIVE).

WE-D-BRD-01: Innovation in Radiation Therapy Delivery: Advanced Digital Linac Features

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xing, L; Wong, J; Li, R

2014-06-15

Last few years has witnessed significant advances in linac technology and therapeutic dose delivery method. Digital linacs equipped with high dose rate FFF beams have been clinically implemented in a number of hospitals. Gated VMAT is becoming increasingly popular in treating tumors affected by respiratory motion. This session is devoted to update the audience with these technical advances and to present our experience in clinically implementing the new linacs and dose delivery methods. Topics to be covered include, technical features of new generation of linacs from different vendors, dosimetric characteristics and clinical need for FFF-beam based IMRT and VMAT, respiration-gatedmore » VMAT, the concept and implementation of station parameter optimized radiation therapy (SPORT), beam level imaging and onboard image guidance tools. Emphasis will be on providing fundamental understanding of the new treatment delivery and image guidance strategies, control systems, and the associated dosimetric characteristics. Commissioning and acceptance experience on these new treatment delivery technologies will be reported. Clinical experience and challenges encountered during the process of implementation of the new treatment techniques and future applications of the systems will also be highlighted. Learning Objectives: Present background knowledge of emerging digital linacs and summarize their key geometric and dosimetric features. SPORT as an emerging radiation therapy modality specifically designed to take advantage of digital linacs. Discuss issues related to the acceptance and commissioning of the digital linacs and FFF beams. Describe clinical utility of the new generation of digital linacs and their future applications.« less

Industrialization of the nitrogen-doping preparation for SRF cavities for LCLS-II

DOE PAGES

Gonnella, D.; Aderhold, S.; Burrill, A.; ...

2017-12-02

The Linac Coherent Light Source II (LCLS-II) is a new state-of-the-art coherent X-ray source being constructed at SLAC National Accelerator Laboratory. It employs 280 superconducting radio frequency (SRF) cavities in order operate in continuous wave (CW) mode. To reduce the overall cryogenic cost of such a large accelerator, nitrogen-doping of the SRF cavities is being used. Nitrogen-doping has consistently been shown to increase the efficiency of SRF cavities operating in the 2.0 K regime and at medium fields (15–20 MV/m) in vertical cavity tests and horizontal cryomodule tests. While nitrogen-doping’s efficacy for improvement of cavity performance was demonstrated at threemore » independent labs, Fermilab, Jefferson Lab, and Cornell University, transfer of the technology to industry for LCLS-II production was not without challenges. Here in this paper, we present results from the beginning of LCLS-II cavity production. We discuss qualification of the cavity vendors and the first cavities from each vendor. Finally, we demonstrate that nitrogen-doping has been successfully transferred to SRF cavity vendors, resulting in consistent production of cavities with better cryogenic efficiency than has ever been achieved for a large-scale accelerator.« less

Design of a compact all-permanent magnet ECR ion source injector for ReA at the MSU NSCL

NASA Astrophysics Data System (ADS)

Pham, Alfonse N.; Leitner, Daniela; Glennon, Patrick; Ottarson, Jack; Lawton, Don; Portillo, Mauricio; Machicoane, Guillaume; Wenstrom, John; Lajoie, Andrew

2016-06-01

The design of a compact all-permanent magnet electron cyclotron resonance (ECR) ion source injector for the ReAccelerator Facility (ReA) at the Michigan State University (MSU) National Superconducting Cyclotron Laboratory (NSCL) is currently being carried out. The ECR ion source injector will complement the electron beam ion trap (EBIT) charge breeder as an off-line stable ion beam injector for the ReA linac. The objective of the ECR ion source injector is to provide continuous-wave beams of heavy ions from hydrogen to masses up to 136Xe within the ReA charge-to-mass ratio (Q / A) operational range from 0.2 to 0.5. The ECR ion source will be mounted on a high-voltage platform that can be adjusted to obtain the required 12 keV/u injection energy into a room temperature radio-frequency quadrupole (RFQ) for further acceleration. The beam line consists of a 30 kV tetrode extraction system, mass analyzing section, and optical matching section for injection into the existing ReA low energy beam transport (LEBT) line. The design of the ECR ion source and the associated beam line are discussed.

Industrialization of the nitrogen-doping preparation for SRF cavities for LCLS-II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonnella, D.; Aderhold, S.; Burrill, A.

The Linac Coherent Light Source II (LCLS-II) is a new state-of-the-art coherent X-ray source being constructed at SLAC National Accelerator Laboratory. It employs 280 superconducting radio frequency (SRF) cavities in order operate in continuous wave (CW) mode. To reduce the overall cryogenic cost of such a large accelerator, nitrogen-doping of the SRF cavities is being used. Nitrogen-doping has consistently been shown to increase the efficiency of SRF cavities operating in the 2.0 K regime and at medium fields (15–20 MV/m) in vertical cavity tests and horizontal cryomodule tests. While nitrogen-doping’s efficacy for improvement of cavity performance was demonstrated at threemore » independent labs, Fermilab, Jefferson Lab, and Cornell University, transfer of the technology to industry for LCLS-II production was not without challenges. Here in this paper, we present results from the beginning of LCLS-II cavity production. We discuss qualification of the cavity vendors and the first cavities from each vendor. Finally, we demonstrate that nitrogen-doping has been successfully transferred to SRF cavity vendors, resulting in consistent production of cavities with better cryogenic efficiency than has ever been achieved for a large-scale accelerator.« less

Industrialization of the nitrogen-doping preparation for SRF cavities for LCLS-II

NASA Astrophysics Data System (ADS)

Gonnella, D.; Aderhold, S.; Burrill, A.; Daly, E.; Davis, K.; Grassellino, A.; Grimm, C.; Khabiboulline, T.; Marhauser, F.; Melnychuk, O.; Palczewski, A.; Posen, S.; Ross, M.; Sergatskov, D.; Sukhanov, A.; Trenikhina, Y.; Wilson, K. M.

2018-03-01

The Linac Coherent Light Source II (LCLS-II) is a new state-of-the-art coherent X-ray source being constructed at SLAC National Accelerator Laboratory. It employs 280 superconducting radio frequency (SRF) cavities in order operate in continuous wave (CW) mode. To reduce the overall cryogenic cost of such a large accelerator, nitrogen-doping of the SRF cavities is being used. Nitrogen-doping has consistently been shown to increase the efficiency of SRF cavities operating in the 2.0 K regime and at medium fields (15-20 MV/m) in vertical cavity tests and horizontal cryomodule tests. While nitrogen-doping's efficacy for improvement of cavity performance was demonstrated at three independent labs, Fermilab, Jefferson Lab, and Cornell University, transfer of the technology to industry for LCLS-II production was not without challenges. Here we present results from the beginning of LCLS-II cavity production. We discuss qualification of the cavity vendors and the first cavities from each vendor. Finally, we demonstrate that nitrogen-doping has been successfully transferred to SRF cavity vendors, resulting in consistent production of cavities with better cryogenic efficiency than has ever been achieved for a large-scale accelerator.

Study on transient beam loading compensation for China ADS proton linac injector II

NASA Astrophysics Data System (ADS)

Gao, Zheng; He, Yuan; Wang, Xian-Wu; Chang, Wei; Zhang, Rui-Feng; Zhu, Zheng-Long; Zhang, Sheng-Hu; Chen, Qi; Powers, Tom

2016-05-01

Significant transient beam loading effects were observed during beam commissioning tests of prototype II of the injector for the accelerator driven sub-critical (ADS) system, which took place at the Institute of Modern Physics, Chinese Academy of Sciences, between October and December 2014. During these tests experiments were performed with continuous wave (CW) operation of the cavities with pulsed beam current, and the system was configured to make use of a prototype digital low level radio frequency (LLRF) controller. The system was originally operated in pulsed mode with a simple proportional plus integral and deviation (PID) feedback control algorithm, which was not able to maintain the desired gradient regulation during pulsed 10 mA beam operations. A unique simple transient beam loading compensation method which made use of a combination of proportional and integral (PI) feedback and feedforward control algorithm was implemented in order to significantly reduce the beam induced transient effect in the cavity gradients. The superconducting cavity field variation was reduced to less than 1.7% after turning on this control algorithm. The design and experimental results of this system are presented in this paper. Supported by National Natural Science Foundation of China (91426303, 11525523)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonnella, D.; Aderhold, S.; Burrill, A.

The Linac Coherent Light Source II (LCLS-II) is a new state-of-the-art coherent X-ray source being constructed at SLAC National Accelerator Laboratory. It employs 280 superconducting radio frequency (SRF) cavities in order operate in continuous wave (CW) mode. To reduce the overall cryogenic cost of such a large accelerator, nitrogen-doping of the SRF cavities is being used. Nitrogen-doping has consistently been shown to increase the efficiency of SRF cavities operating in the 2.0 K regime and at medium fields (15–20 MV/m) in vertical cavity tests and horizontal cryomodule tests. While nitrogen-doping’s efficacy for improvement of cavity performance was demonstrated at threemore » independent labs, Fermilab, Jefferson Lab, and Cornell University, transfer of the technology to industry for LCLS-II production was not without challenges. Here in this paper, we present results from the beginning of LCLS-II cavity production. We discuss qualification of the cavity vendors and the first cavities from each vendor. Finally, we demonstrate that nitrogen-doping has been successfully transferred to SRF cavity vendors, resulting in consistent production of cavities with better cryogenic efficiency than has ever been achieved for a large-scale accelerator.« less

Numerical simulations of stripping effects in high-intensity hydrogen ion linacs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carneiro, J.-P.; /Fermilab; Mustapha, B.

2008-12-01

Numerical simulations of H{sup -} stripping losses from blackbody radiation, electromagnetic fields, and residual gas have been implemented into the beam dynamics code TRACK. Estimates of the stripping losses along two high-intensity H{sup -} linacs are presented: the Spallation Neutron Source linac currently being operated at Oak Ridge National Laboratory and an 8 GeV superconducting linac currently being designed at Fermi National Accelerator Laboratory.

Physics design of APT linac with normal conducting rf cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nath, S.; Billen, J.H.; Stovall, J.E.

The accelerator based production of tritium calls for a high-power, cw proton linac. Previous designs for such a linac use a radiofrequency quadrupole (RFQ), followed by a drift-tube linac (DTL) to an intermediate energy and a coupled-cavity linc (CCL) to the final energy. The Los Alamos design uses a high-energy (6.7 MeV) RFQ followed by the newly developed coupled-cavity drift-tube linac (CCDTL) and a CCL. This design accommodates external electromagnetic quadrupole lenses which provide a strong uniform focusing lattice from the end of the RFQ to the end of the CCL. The cell lengths in linacs of traditional design aremore » typically graded as a function of particle velocity. By making groups of cells symmetric in both the CCDTL and CCL, the cavity design as well as mechanical design and fabrication is simplified without compromising the performance. At higher energies, there are some advantages of using superconducting rf cavities. Currently, such schemes are under vigorous study. This paper describes the linac design based on normal conducting cavities and presents simulation results.« less

Cornell-BNL Electron Energy Recovery Linac FFAG Test Accelerator (CBETA)

NASA Astrophysics Data System (ADS)

Trbojevic, Dejan; Peggs, Steve; Berg, Scott; Brooks, Stephen; Mahler, George; Meot, Francois; Tsoupas, Nicholaos; Witte, Holger; Hoffstaetter, Georg; Bazarov, Ivan; Mayes, Christopher; Patterson, Ritchie; Smolenski, Karl; Li, Yulin; Dobbins, John; BNL Team; Cornell University Team

A novel energy recovery linac (ERL) with Non-Scaling Fixed Field Alternating Gradient (NS-FFAG) racetrack is being constructed as a result of collaboration of the Cornell University with Brookhaven National Laboratory. The existing injector and superconducting linac at Cornell University are being installed together with a single NS-FFAG arcs and straight section at the opposite side of the linac to form an ERL system. The 6 MeV electron beam from injector is transferred into the 36 MeV superconducting linac and accelerated by four successive passes: from 42 to 150 MeV using the same NS-FFAG structure made of permanent magnets. After the maximum energy of 150 MeV is reached, the electron beam is brought back to the linac with opposite Radio Frequency (RF) phase and with 4 passes electron energy is recovered and brought back to the initial energy of 6 MeV. This is going to be the first 4 pass superconducting ERL and the first NS-FFAG permanent magnet structure to bring the electron beam back to the linac.

Design of high-energy high-current linac with focusing by superconducting solenoids

NASA Astrophysics Data System (ADS)

Batskikh, Guennady I.; Belugin, Vladimir M.; Bondarev, Boris I.; Fedotov, Arkady P.; Durkin, Alexander P.; Ivanov, Yury D.; Mikhailov, Vladimir N.; Murin, Boris P.; Mustafin, Kharis Kh.; Shumakov, Igor V.; Uksusov, Nikolay I.

1995-09-01

The advancement of MRTI design for 1.5 GeV and 250 mA ion CW linac is presented in the report. In new linac version all the way from input to output the ions are focused by magnetic fields of superconducting solenoids. The ion limit current is far beyond the needed value. The linac focusing channel offers major advantages over the more conventional ones. The acceptance is 1.7 times as large for such focusing channel as for quadrupole one. Concurrently, a random perturbation sensitivity for such channel is one order of magnitude smaller than in quadrupole channel. These focusing channel features allow to decrease beam matched radius and increase a linac radiation purity without aperture growth. ``Regotron'' is used as high power generator in linac main part. But D&W cavities need not be divided into sections connected by RF-bridges which denuded them of high coupling factor.

Coherent soft X-ray diffraction imaging of coliphage PR772 at the Linac coherent light source

PubMed Central

Reddy, Hemanth K.N.; Yoon, Chun Hong; Aquila, Andrew; Awel, Salah; Ayyer, Kartik; Barty, Anton; Berntsen, Peter; Bielecki, Johan; Bobkov, Sergey; Bucher, Maximilian; Carini, Gabriella A.; Carron, Sebastian; Chapman, Henry; Daurer, Benedikt; DeMirci, Hasan; Ekeberg, Tomas; Fromme, Petra; Hajdu, Janos; Hanke, Max Felix; Hart, Philip; Hogue, Brenda G.; Hosseinizadeh, Ahmad; Kim, Yoonhee; Kirian, Richard A.; Kurta, Ruslan P.; Larsson, Daniel S.D.; Duane Loh, N.; Maia, Filipe R.N.C.; Mancuso, Adrian P.; Mühlig, Kerstin; Munke, Anna; Nam, Daewoong; Nettelblad, Carl; Ourmazd, Abbas; Rose, Max; Schwander, Peter; Seibert, Marvin; Sellberg, Jonas A.; Song, Changyong; Spence, John C.H.; Svenda, Martin; Van der Schot, Gijs; Vartanyants, Ivan A.; Williams, Garth J.; Xavier, P. Lourdu

2017-01-01

Single-particle diffraction from X-ray Free Electron Lasers offers the potential for molecular structure determination without the need for crystallization. In an effort to further develop the technique, we present a dataset of coherent soft X-ray diffraction images of Coliphage PR772 virus, collected at the Atomic Molecular Optics (AMO) beamline with pnCCD detectors in the LAMP instrument at the Linac Coherent Light Source. The diameter of PR772 ranges from 65–70 nm, which is considerably smaller than the previously reported ~600 nm diameter Mimivirus. This reflects continued progress in XFEL-based single-particle imaging towards the single molecular imaging regime. The data set contains significantly more single particle hits than collected in previous experiments, enabling the development of improved statistical analysis, reconstruction algorithms, and quantitative metrics to determine resolution and self-consistency. PMID:28654088

Coherent-Radiation Spectroscopy of Few-Femtosecond Electron Bunches Using a Middle-Infrared Prism Spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maxwell, T. J.; Behrens, C.; Ding, Y.

2013-10-28

Modern, high-brightness electron beams such as those from plasma wakefield accelerators and free-electron laser linacs continue the drive to ever-shorter bunch durations. In low-charge operation ( ~ 20 pC ), bunches shorter than 10 fs are reported at the Linac Coherent Light Source (LCLS). Though suffering from a loss of phase information, spectral diagnostics remain appealing as compact, low-cost bunch duration monitors suitable for deployment in beam dynamics studies and operations instrumentation. Progress in middle-infrared (MIR) imaging has led to the development of a single-shot, MIR prism spectrometer to characterize the corresponding LCLS coherent beam radiation power spectrum for few-femtosecondmore » scale bunch length monitoring. In this Letter, we report on the spectrometer installation as well as the temporal reconstruction of 3 to 60 fs-long LCLS electron bunch profiles using single-shot coherent transition radiation spectra.« less

Coherent soft X-ray diffraction imaging of coliphage PR772 at the Linac coherent light source

DOE PAGES

Reddy, Hemanth K. N.; Yoon, Chun Hong; Aquila, Andrew; ...

2017-06-27

Single-particle diffraction from X-ray Free Electron Lasers offers the potential for molecular structure determination without the need for crystallization. In an effort to further develop the technique, we present a dataset of coherent soft X-ray diffraction images of Coliphage PR772 virus, collected at the Atomic Molecular Optics (AMO) beamline with pnCCD detectors in the LAMP instrument at the Linac Coherent Light Source. The diameter of PR772 ranges from 65–70 nm, which is considerably smaller than the previously reported ~600 nm diameter Mimivirus. This reflects continued progress in XFEL-based single-particle imaging towards the single molecular imaging regime. As a result, themore » data set contains significantly more single particle hits than collected in previous experiments, enabling the development of improved statistical analysis, reconstruction algorithms, and quantitative metrics to determine resolution and self-consistency.« less

Status of the RF-driven H{sup −} ion source for J-PARC linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oguri, H., E-mail: oguri.hidetomo@jaea.go.jp; Ohkoshi, K.; Ikegami, K.

2016-02-15

For the upgrade of the Japan Proton Accelerator Research Complex linac beam current, a cesiated RF-driven negative hydrogen ion source was installed during the 2014 summer shutdown period, with subsequent operations commencing on September 29, 2014. The ion source has been successfully operating with a beam current and duty factor of 33 mA and 1.25% (500 μs and 25 Hz), respectively. The result of recent beam operation has demonstrated that the ion source is capable of continuous operation for approximately 1100 h. The spark rate at the beam extractor was observed to be at a frequency of less than oncemore » a day, which is an acceptable level for user operation. Although an antenna failure occurred during operation on October 26, 2014, no subsequent serious issues have occurred since then.« less

Coherent soft X-ray diffraction imaging of coliphage PR772 at the Linac coherent light source.

PubMed

Reddy, Hemanth K N; Yoon, Chun Hong; Aquila, Andrew; Awel, Salah; Ayyer, Kartik; Barty, Anton; Berntsen, Peter; Bielecki, Johan; Bobkov, Sergey; Bucher, Maximilian; Carini, Gabriella A; Carron, Sebastian; Chapman, Henry; Daurer, Benedikt; DeMirci, Hasan; Ekeberg, Tomas; Fromme, Petra; Hajdu, Janos; Hanke, Max Felix; Hart, Philip; Hogue, Brenda G; Hosseinizadeh, Ahmad; Kim, Yoonhee; Kirian, Richard A; Kurta, Ruslan P; Larsson, Daniel S D; Duane Loh, N; Maia, Filipe R N C; Mancuso, Adrian P; Mühlig, Kerstin; Munke, Anna; Nam, Daewoong; Nettelblad, Carl; Ourmazd, Abbas; Rose, Max; Schwander, Peter; Seibert, Marvin; Sellberg, Jonas A; Song, Changyong; Spence, John C H; Svenda, Martin; Van der Schot, Gijs; Vartanyants, Ivan A; Williams, Garth J; Xavier, P Lourdu

2017-06-27

Single-particle diffraction from X-ray Free Electron Lasers offers the potential for molecular structure determination without the need for crystallization. In an effort to further develop the technique, we present a dataset of coherent soft X-ray diffraction images of Coliphage PR772 virus, collected at the Atomic Molecular Optics (AMO) beamline with pnCCD detectors in the LAMP instrument at the Linac Coherent Light Source. The diameter of PR772 ranges from 65-70 nm, which is considerably smaller than the previously reported ~600 nm diameter Mimivirus. This reflects continued progress in XFEL-based single-particle imaging towards the single molecular imaging regime. The data set contains significantly more single particle hits than collected in previous experiments, enabling the development of improved statistical analysis, reconstruction algorithms, and quantitative metrics to determine resolution and self-consistency.

Superconducting heavy ion injector linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shepard, K.W.

1985-01-01

A conceptual design for a very low velocity (.007 < v/c < .07) superconducting heavy-ion linac is reviewed. This type of linac may have significant cost and performance advantages over room-temperature linacs, at least for applications requiring modest beam currents. Some general features of the design of very-low velocity superconducting accelerating structures are discussed and a design for a 48.5 MHz, v/c = .009 structure, together with the status of a niobium prototype, is discussed in detail. Preliminary results of a beam dynamics study indicate that the low velocity linac may be able to produce heavy-ion beams with time-energy spreadsmore » of a few keV-nsec. 11 refs, 4 figs.« less

Electron linac for medical isotope production with improved energy efficiency and isotope recovery

DOEpatents

Noonan, John; Walters, Dean; Virgo, Matt; Lewellen, John

2015-09-08

A method and isotope linac system are provided for producing radio-isotopes and for recovering isotopes. The isotope linac is an energy recovery linac (ERL) with an electron beam being transmitted through an isotope-producing target. The electron beam energy is recollected and re-injected into an accelerating structure. The ERL provides improved efficiency with reduced power requirements and provides improved thermal management of an isotope target and an electron-to-x-ray converter.

rf traveling-wave electron gun for photoinjectors

NASA Astrophysics Data System (ADS)

Schaer, Mattia; Citterio, Alessandro; Craievich, Paolo; Reiche, Sven; Stingelin, Lukas; Zennaro, Riccardo

2016-07-01

The design of a photoinjector, in particular that of the electron source, is of central importance for free electron laser (FEL) machines where a high beam brightness is required. In comparison to standard designs, an rf traveling-wave photocathode gun can provide a more rigid beam with a higher brightness and a shorter pulse. This is illustrated by applying a specific optimization procedure to the SwissFEL photoinjector, for which a brightness improvement up to a factor 3 could be achieved together with a double gun output energy compared to the reference setup foreseeing a state-of-the-art S-band rf standing-wave gun. The higher brightness is mainly given by a (at least) double peak current at the exit of the gun which brings benefits for both the beam dynamics in the linac and the efficiency of the FEL process. The gun design foresees an innovative coaxial rf coupling at both ends of the structure which allows a solenoid with integrated bucking coil to be placed around the cathode in order to provide the necessary focusing right after emission.

Beam commissioning and measurements validating the beam model in a new TPS that converts helical tomotherapy plans to step-and-shoot IMRT plans.

PubMed

Petersson, Kristoffer; Ceberg, Crister; Engström, Per; Knöös, Tommy

2011-01-01

A new type of treatment planning system called SHAREPLAN has been studied, which enables the transfer of treatment plans generated for helical tomotherapy delivery to plans that can be delivered on C-arm linacs. The purpose is to ensure continuous patient treatment during periods of unscheduled downtime for the TomoTherapy unit, particularly in clinics without a backup unit. The purpose of this work was to verify that the plans generated in this novel planning system are deliverable and accurate. The work consists primarily of beam commissioning, verification of the beam model, and measurements verifying that generated plans are deliverable with sufficient accuracy. The beam commissioning process involves input of general geometric properties of the modeled linac, profiles and depth dose curves for a specific photon nominal energy (6 MV), and the automated modeling of other beam properties. Some manual tuning of the beam model is required. To evaluate its accuracy, the confidence limit concept [J. Venselaar et al., "Tolerances for the accuracy of photon beam dose calculations of treatment planning systems," Radiother. Oncol. 60, 191-201 (2001)] was used, which is a method supported by ESTRO. Measurements were conducted with a 2D diode array at the commissioned linac as a final check of the beam model and to evaluate whether the generated plans were deliverable and accurate. The comparison and evaluation of calculated data points and measured data according to the method applied confirmed the accuracy of the beam model. The profiles had a confidence limit of 1.1% and the depth dose curves had a confidence limit of 1.7%, both of which were well below the tolerance limit of 2%. Plan specific QC measurements and evaluation verified that different plans generated in the TPS were deliverable with sufficient accuracy at the commissioned linac, as none of the 160 beams for the 20 different plans evaluated had a fraction of approved data points below 90%, the local clinical approval criterion for delivery QA measurements. This study is a validation of the new TPS as it verifies that the generated plans are deliverable at a commissioned linac with adequate accuracy. A thorough investigation of the treatment plan quality will require a separate study. The TPS is proving to be a useful and time-saving complement, especially for clinics having a single unit for helical delivery among its conventional linacs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clendenin, James E

The International Committee supported the proposal of the Chairman of the XVIII International Linac Conference to issue a new Compendium of linear accelerators. The last one was published in 1976. The Local Organizing Committee of Linac96 decided to set up a sub-committee for this purpose. Contrary to the catalogues of the High Energy Accelerators which compile accelerators with energies above 1 GeV, we have not defined a specific limit in energy. Microtrons and cyclotrons are not in this compendium. Also data from thousands of medical and industrial linacs has not been collected. Therefore, only scientific linacs are listed in themore » present compendium. Each linac found in this research and involved in a physics context was considered. It could be used, for example, either as an injector for high energy accelerators, or in nuclear physics, materials physics, free electron lasers or synchrotron light machines. Linear accelerators are developed in three continents only: America, Asia, and Europe. This geographical distribution is kept as a basis. The compendium contains the parameters and status of scientific linacs. Most of these linacs are operational. However, many facilities under construction or design studies are also included. A special mention has been made at the end for the studies of future linear colliders.« less

Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario.

PubMed

Mishra, Bibekananda; Selvam, T Palani; Sharma, P K Dash

2017-01-01

Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%. respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes with an assumption that only 20% of the workload is shared in FFF mode. Primary and secondary barrier thicknesses calculated from MUs delivered on clinical practice method also show the same trend and are higher by 20% and 19%, respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes. Overall, the barrier thickness for a LINAC operated in FF mode is higher about 20% to that of a LINAC operated in both FF and FFF modes.

Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario

PubMed Central

Mishra, Bibekananda; Selvam, T. Palani; Sharma, P. K. Dash

2017-01-01

Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%. respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes with an assumption that only 20% of the workload is shared in FFF mode. Primary and secondary barrier thicknesses calculated from MUs delivered on clinical practice method also show the same trend and are higher by 20% and 19%, respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes. Overall, the barrier thickness for a LINAC operated in FF mode is higher about 20% to that of a LINAC operated in both FF and FFF modes. PMID:28405104

Crossbar H-mode drift-tube linac design with alternative phase focusing for muon linac

NASA Astrophysics Data System (ADS)

Otani, M.; Futatsukawa, K.; Hasegawa, K.; Kitamura, R.; Kondo, Y.; Kurennoy, S.

2017-07-01

We have developed a Crossbar H-mode (CH) drift-tube linac (DTL) design with an alternative phase focusing (APF) scheme for a muon linac, in order to measure the anomalous magnetic moment and electric dipole moment (EDM) of muons at the Japan Proton Accelerator Research Complex (J-PARC). The CH-DTL accelerates muons from β = v/c = 0.08 to 0.28 at an operational frequency of 324 MHz. The design and results are described in this paper.

Consequences of air around an ionization chamber: Are existing solid phantoms suitable for reference dosimetry on an MR-linac?

PubMed

Hackett, S L; van Asselen, B; Wolthaus, J W H; Kok, J G M; Woodings, S J; Lagendijk, J J W; Raaymakers, B W

2016-07-01

A protocol for reference dosimetry for the MR-linac is under development. The 1.5 T magnetic field changes the mean path length of electrons in an air-filled ionization chamber but has little effect on the electron trajectories in a surrounding phantom. It is therefore necessary to correct the response of an ionization chamber for the influence of the magnetic field. Solid phantoms are used for dosimetry measurements on the MR-linac, but air is present between the chamber wall and phantom insert. This study aimed to determine if this air influences the ion chamber measurements on the MR-linac. The absolute response of the chamber and reproducibility of dosimetry measurements were assessed on an MR-linac in solid and water phantoms. The sensitivity of the chamber response to the distribution of air around the chamber was also investigated. Measurements were performed on an MR-linac and replicated on a conventional linac for five chambers. The response of three waterproof chambers was measured with air and with water between the chamber and the insert to measure the influence of the air volume on absolute chamber response. The distribution of air around the chamber was varied indirectly by rotating each chamber about the longitudinal chamber axis in a solid phantom and a water phantom (waterproof chambers only) and measuring the angular dependence of the chamber response, and varied directly by displacing the chamber in the phantom insert using a paper shim positioned at different orientations between the chamber casing and the insert. The responses of the three waterproof chambers measured on the MR-linac were 0.7%-1.2% higher with water than air in the chamber insert. The responses of the chambers on the conventional linac changed by less than 0.3% when air in the insert was replaced with water. The angular dependence of the chambers ranged from 0.6% to 1.9% in the solid phantom on the MR-linac but was less than 0.5% in water on the MR-linac and less than 0.3% in the solid phantom on the conventional linac. Inserting a shim around the chamber induced changes of the chamber response in a magnetic field of up to 2.2%, but the change in chamber response on the conventional linac was less than 0.3%. The interaction between the magnetic field and secondary electrons in the air around the chamber reduces the charge collected from 0.7% to 1.2%. The large angular dependence of ion chambers measured in the plastic phantom in a magnetic field appears to arise from a change of air distribution as the chamber is moved within the insert, rather than an intrinsic isotropy of the chamber sensitivity to radiation. It is recommended that reference dosimetry measurements on the MR-linac can be performed only in water, rather than in existing plastic phantoms.

Design of high-energy high-current linac with focusing by superconducting solenoids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batskikh, Guennady I.; Belugin, Vladimir M.; Bondarev, Boris I.

1995-09-15

The advancement of MRTI design for 1.5 GeV and 250 mA ion CW linac is presented in the report. In new linac version all the way from input to output the ions are focused by magnetic fields of superconducting solenoids. The ion limit current is far beyond the needed value. The linac focusing channel offers major advantages over the more conventional ones. The acceptance is 1.7 times as large for such focusing channel as for quadrupole one. Concurrently, a random perturbation sensitivity for such channel is one order of magnitude smaller than in quadrupole channel. These focusing channel features allowmore » to decrease beam matched radius and increase a linac radiation purity without aperture growth. ''Regotron'' is used as high power generator in linac main part. But D and W cavities need not be divided into sections connected by RF-bridges which denuded them of high coupling factor.« less

Design of high-energy high-current linac with focusing by superconducting solenoids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batskikh, G.I.; Belugin, V.M.; Bondarev, B.I.

1995-10-01

The advancement of MRTI design for 1.5 GeV and 250 mA ion CW linac was presented in a previous report. In this new linac version all the way from input to output the ions are focused by magnetic fields of superconducting solenoids. The ion limit current is far beyond the needed value. The linac focusing channel offers major advantages over the more conventional ones. The acceptance is 1.7 times as large for such focusing channel as for quadrupole one. Concurrently, a random perturbation sensitivity for such channel is one order of magnitude smaller than in quadrupole channel. These focusing channelmore » features allow to decrease beam matched radius and increase a linac radiation purity without aperture growth. {open_quotes}Regotron{close_quotes} is used as high power generator in linac main part. But D&W cavities need not be divided into sections connected by RF-bridges which denuded them of high coupling factor.« less

Analysis of the LSC microbunching instability in MaRIE linac reference design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yampolsky, Nikolai

In this report we estimate the effect of the microbunching instability in the MaRIE XFEL linac. The reference design for the linac is described in a separate report. The parameters of the L1, L2, and L3 linacs as well as BC1 and BC2 bunch compressors were the same as in the referenced report. The beam dynamics was assumed to be linear along the accelerator (which is a reasonable assumption for estimating the effect of the microbunching instability). The parameters of the bunch also match the parameters described in the referenced report. Additionally, it was assumed that the beam radius ismore » equal to R = 100 m and does not change along linac. This assumption needs to be revisited at later studies. The beam dynamics during acceleration was accounted in the matrix formalism using a Matlab code. The input parameters for the linacs are: RF peak gradient, RF frequency, RF phase, linac length, and initial beam energy. The energy gain and the imposed chirp are calculated based on the RF parameters self-consistently. The bunch compressors are accounted in the matrix formalism as well. Each chicane is characterized by the beam energy and the R56 matrix element. It was confirmed that the linac and beam parameters described previously provide two-stage bunch compression with compression ratios of 10 and 20 resulting in the bunch of 3kA peak current.« less

FEM design and simulation of a short, 10 MV, S-band Linac with Monte Carlo dose simulations.

PubMed

Baillie, Devin; St Aubin, J; Fallone, B G; Steciw, S

2015-04-01

Current commercial 10 MV Linac waveguides are 1.5 m. The authors' current 6 MV linear accelerator-magnetic resonance imager (Linac-MR) system fits in typical radiotherapy vaults. To allow 10 MV treatments with the Linac-MR and still fit within typical vaults, the authors design a 10 MV Linac with an accelerator waveguide of the same length (27.5 cm) as current 6 MV Linacs. The first design stage is to design a cavity such that a specific experimental measurement for breakdown is applicable to the cavity. This is accomplished through the use of finite element method (FEM) simulations to match published shunt impedance, Q factor, and ratio of peak to mean-axial electric field strength from an electric breakdown study. A full waveguide is then designed and tuned in FEM simulations based on this cavity design. Electron trajectories are computed through the resulting radio frequency fields, and the waveguide geometry is modified by shifting the first coupling cavity in order to optimize the electron beam properties until the energy spread and mean energy closely match values published for an emulated 10 MV Linac. Finally, Monte Carlo dose simulations are used to compare the resulting photon beam depth dose profile and penumbra with that produced by the emulated 10 MV Linac. The shunt impedance, Q factor, and ratio of peak to mean-axial electric field strength are all matched to within 0.1%. A first coupling cavity shift of 1.45 mm produces an energy spectrum width of 0.347 MeV, very close to the published value for the emulated 10 MV of 0.315 MeV, and a mean energy of 10.53 MeV, nearly identical to the published 10.5 MeV for the emulated 10 MV Linac. The depth dose profile produced by their new Linac is within 1% of that produced by the emulated 10 MV spectrum for all depths greater than 1.5 cm. The penumbra produced is 11% narrower, as measured from 80% to 20% of the central axis dose. The authors have successfully designed and simulated an S-band waveguide of length of 27.5 cm capable of producing a 10 MV photon beam. This waveguide operates well within the breakdown threshold determined for the cavity geometry used. The designed Linac produces depth dose profiles similar to those of the emulated 10 MV Linac (waveguide-length of 1.5 m) but yields a narrower penumbra.

Status Of the ILC Main Linac Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saini, Arun; Kapin, Valery; Solyak, Nikolay

2017-05-01

International Linear collider (ILC) is a proposed accelerator facility which is primarily based on two 11-km long superconducting main linacs. In this paper we present recent updates on the main linac design and discuss changes made in order to meet specification outlined in the technical design report (TDR).

X-ray Laser Animated Fly-Through

ScienceCinema

None

2018-01-16

Take a tour with an electron's-eye-view through SLAC's revolutionary new X-ray laser facility with this 5 1/2 minute animation. See how the X-ray pulses are generated using the world's longest linear accelerator along with unique arrays of machinery specially designed for this one-of-a-kind tool. For more than 40 years, SLAC's two-mile-long linear accelerator (or linac) linac has produced high-energy electrons for cutting-edge physics experiments. Now, SLAC's linac has entered a new phase of its career with the creation of the Linac Coherent Light Source (LCLS).

Doubling The Intensity Of An ERL Based Light Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrew Hutton

2005-05-01

A light source based on an Energy Recovered Linac (ERL) [1] consists of a superconducting linac and a transfer line that includes wigglers and undulators to produce the synchrotron light. The transfer line brings the electron bunches back to the beginning of the linac so that their energy can be recovered when they traverse the linac a second time, {lambda}/2 out of RF phase. There is another interesting condition when the length of the transfer line is (n {+-} 1/4) {lambda}. In this case, the electrons drift through on the zero RF crossing, and make a further pass around themore » transfer line, effectively doubling the circulating current in the wigglers and undulators. On the third pass through the linac, they will be decelerated and their energy recovered. The longitudinal focusing at the zero crossing is a problem, but it can be canceled if the drifting beam sees a positive energy gradient for the first half of the linac and a negative gradient for the second half (or vice versa). This paper presents a proposal to use a double chicane at the center of the linac to provide this focusing inversion for the drifting beam while leaving the accelerating and decelerating beams on crest. [1] G. R. Neil, et al, Phys. Rev. Let. 84, 662 2000« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pang, Xiaoying; Rybarcyk, Larry

HPSim is a GPU-accelerated online multi-particle beam dynamics simulation tool for ion linacs. It was originally developed for use on the Los Alamos 800-MeV proton linac. It is a “z-code” that contains typical linac beam transport elements. The linac RF-gap transformation utilizes transit-time-factors to calculate the beam acceleration therein. The space-charge effects are computed using the 2D SCHEFF (Space CHarge EFFect) algorithm, which calculates the radial and longitudinal space charge forces for cylindrically symmetric beam distributions. Other space- charge routines to be incorporated include the 3D PICNIC and a 3D Poisson solver. HPSim can simulate beam dynamics in drift tubemore » linacs (DTLs) and coupled cavity linacs (CCLs). Elliptical superconducting cavity (SC) structures will also be incorporated into the code. The computational core of the code is written in C++ and accelerated using the NVIDIA CUDA technology. Users access the core code, which is wrapped in Python/C APIs, via Pythons scripts that enable ease-of-use and automation of the simulations. The overall linac description including the EPICS PV machine control parameters is kept in an SQLite database that also contains calibration and conversion factors required to transform the machine set points into model values used in the simulation.« less

Consequences of air around an ionization chamber: Are existing solid phantoms suitable for reference dosimetry on an MR-linac?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hackett, S. L., E-mail: S.S.Hackett@umcutrecht.nl

Purpose: A protocol for reference dosimetry for the MR-linac is under development. The 1.5 T magnetic field changes the mean path length of electrons in an air-filled ionization chamber but has little effect on the electron trajectories in a surrounding phantom. It is therefore necessary to correct the response of an ionization chamber for the influence of the magnetic field. Solid phantoms are used for dosimetry measurements on the MR-linac, but air is present between the chamber wall and phantom insert. This study aimed to determine if this air influences the ion chamber measurements on the MR-linac. The absolute responsemore » of the chamber and reproducibility of dosimetry measurements were assessed on an MR-linac in solid and water phantoms. The sensitivity of the chamber response to the distribution of air around the chamber was also investigated. Methods: Measurements were performed on an MR-linac and replicated on a conventional linac for five chambers. The response of three waterproof chambers was measured with air and with water between the chamber and the insert to measure the influence of the air volume on absolute chamber response. The distribution of air around the chamber was varied indirectly by rotating each chamber about the longitudinal chamber axis in a solid phantom and a water phantom (waterproof chambers only) and measuring the angular dependence of the chamber response, and varied directly by displacing the chamber in the phantom insert using a paper shim positioned at different orientations between the chamber casing and the insert. Results: The responses of the three waterproof chambers measured on the MR-linac were 0.7%–1.2% higher with water than air in the chamber insert. The responses of the chambers on the conventional linac changed by less than 0.3% when air in the insert was replaced with water. The angular dependence of the chambers ranged from 0.6% to 1.9% in the solid phantom on the MR-linac but was less than 0.5% in water on the MR-linac and less than 0.3% in the solid phantom on the conventional linac. Inserting a shim around the chamber induced changes of the chamber response in a magnetic field of up to 2.2%, but the change in chamber response on the conventional linac was less than 0.3%. Conclusions: The interaction between the magnetic field and secondary electrons in the air around the chamber reduces the charge collected from 0.7% to 1.2%. The large angular dependence of ion chambers measured in the plastic phantom in a magnetic field appears to arise from a change of air distribution as the chamber is moved within the insert, rather than an intrinsic isotropy of the chamber sensitivity to radiation. It is recommended that reference dosimetry measurements on the MR-linac can be performed only in water, rather than in existing plastic phantoms.« less

SU-E-T-395: Evaluation of Multiple Brain Metastases Stereotactic Treatment Planning in Cyberknife Versus Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vikraman, S; Rajesh, Thiyagarajan; Karrthick, Kp

2015-06-15

Purpose: The purpose of this study was to evaluate multiple brain metastases stereotactic treatment planning of Cyberknife versus linac using dose volume based indices. Methods: Fifteen multiple brain metastases patients were taken for this study from Cyberknife Multiplan TPSv4.6.0. All these patients underwent stereotactic treatment in Cyberknife. For each patient VMAT stereotactic treatment plan was generated in MONACO TPSv5.0 using Elekta beam modulator MLC and matched the delivered plan. A median dose of 8.5Gy(range 7–12Gy) per fraction was prescribed. Tumor volume was in the range of 0.06–4.33cc. Treatment plan quality was critically evaluated by comparing DVH indices such as D98,more » D95, CI, and HI for target volumes. Maximum point doses and volume doses were evaluated for critical organs. Results: For each case, target coverage of D98 was achieved with 100% prescription dose with SD of 0.29% and 0.41% in Linac and Cyberknife respectively. The average conformity index(CI) of 1.26±0.0796 SD for Cyberknife and 1.92±0.60SD for linac were observed. Better homogeneity Index (HI) of 1.17±0.09SD was observed in linac as compared to Cyberknife HI of 1.24±0.05SD.All the critical organ doses were well within tolerance limit in both linac and Cyberknife plans. There is no significant difference of maximum point doses for brainstem and optic chiasm. Treatment time and number of monitor units are more in Cyberknife compared to linac. The average volume receiving 12Gy in whole brain was 6% and 12% for Cyberknife and linac respectively. 1000cc of whole brain received 60% lesser dose in Linac compared to Cyberknife in all cases. Conclusion: The study shows that dosimetrically comparable plans are achievable Cyberknife and Linac. However, a better conformity, target coverage, lesser OAR dose is achieved with Cyberknife due to greater degrees of freedom with robotic gantry and smaller collimator for multiple targets.« less

Automating linear accelerator quality assurance.

PubMed

Eckhause, Tobias; Al-Hallaq, Hania; Ritter, Timothy; DeMarco, John; Farrey, Karl; Pawlicki, Todd; Kim, Gwe-Ya; Popple, Richard; Sharma, Vijeshwar; Perez, Mario; Park, SungYong; Booth, Jeremy T; Thorwarth, Ryan; Moran, Jean M

2015-10-01

The purpose of this study was 2-fold. One purpose was to develop an automated, streamlined quality assurance (QA) program for use by multiple centers. The second purpose was to evaluate machine performance over time for multiple centers using linear accelerator (Linac) log files and electronic portal images. The authors sought to evaluate variations in Linac performance to establish as a reference for other centers. The authors developed analytical software tools for a QA program using both log files and electronic portal imaging device (EPID) measurements. The first tool is a general analysis tool which can read and visually represent data in the log file. This tool, which can be used to automatically analyze patient treatment or QA log files, examines the files for Linac deviations which exceed thresholds. The second set of tools consists of a test suite of QA fields, a standard phantom, and software to collect information from the log files on deviations from the expected values. The test suite was designed to focus on the mechanical tests of the Linac to include jaw, MLC, and collimator positions during static, IMRT, and volumetric modulated arc therapy delivery. A consortium of eight institutions delivered the test suite at monthly or weekly intervals on each Linac using a standard phantom. The behavior of various components was analyzed for eight TrueBeam Linacs. For the EPID and trajectory log file analysis, all observed deviations which exceeded established thresholds for Linac behavior resulted in a beam hold off. In the absence of an interlock-triggering event, the maximum observed log file deviations between the expected and actual component positions (such as MLC leaves) varied from less than 1% to 26% of published tolerance thresholds. The maximum and standard deviations of the variations due to gantry sag, collimator angle, jaw position, and MLC positions are presented. Gantry sag among Linacs was 0.336 ± 0.072 mm. The standard deviation in MLC position, as determined by EPID measurements, across the consortium was 0.33 mm for IMRT fields. With respect to the log files, the deviations between expected and actual positions for parameters were small (<0.12 mm) for all Linacs. Considering both log files and EPID measurements, all parameters were well within published tolerance values. Variations in collimator angle, MLC position, and gantry sag were also evaluated for all Linacs. The performance of the TrueBeam Linac model was shown to be consistent based on automated analysis of trajectory log files and EPID images acquired during delivery of a standardized test suite. The results can be compared directly to tolerance thresholds. In addition, sharing of results from standard tests across institutions can facilitate the identification of QA process and Linac changes. These reference values are presented along with the standard deviation for common tests so that the test suite can be used by other centers to evaluate their Linac performance against those in this consortium.

Progress update on cryogenic system for ARIEL E-linac at TRIUMF

NASA Astrophysics Data System (ADS)

Koveshnikov, A.; Bylinskii, I.; Hodgson, G.; Yosifov, D.

2014-01-01

TRIUMF is involved in a major upgrade. The Advanced Rare IsotopeE Laboratory (ARIEL) has become a fully funded project in July 2010. A 10 mA 50 MeV SRF electron linac (e-linac) operating CW at 1.3 GHz is the key component of this initiative. This machine will serve as a second independent photo-fission driver for Rare Isotope Beams (RIB) production at TRIUMF's Isotope Separator and Accelerator (ISAC) facility. The cryogens delivery system requirements are driven by the electron accelerator cryomodule design [1, 2]. Since commencement of the project in 2010 the cryogenic system of e-linac has moved from the conceptual design phase into engineering design and procurement stage. The present document summarizes the progress in cryogenic system development and construction. Current status of e-linac cryogenic system including details of LN2 storage and delivery systems, and helium subatmospheric (SA) system is presented. The first phase of e-linac consisting of two cryomodules, cryogens storage, delivery, and distribution systems, and a 600 W class liquid helium cryoplant is scheduled for installation and commissioning by year 2014.

RFI-Based Ion Linac Systems

NASA Astrophysics Data System (ADS)

Swenson, Donald A.

A new company, Ion Linac Systems, Inc., has been formed to promote the development, manufacture, and marketing of intense, RFI-based, Ion Linac Systems. The Rf Focused Interdigital (RFI) linac structure was invented by the author while at Linac Systems, LLC. The first step, for the new company, will be to correct a flaw in an existing RFI-based linac system and to demonstrate "good transmission" through the system. The existing system, aimed at the BNCT medical application, is designed to produce a beam of 2.5 MeV protons with an average beam current of 20 mA. In conjunction with a lithium target, it will produce an intense beam of epithermal neutrons. This system is very efficient, requiring only 180 kW of rf power to produce a 50 kW proton beam. In addition to the BNCT medical application, the RFI-based systems should represent a powerful neutron generator for homeland security, defence applications, cargo container inspection, and contraband detection. The timescale to the demonstration of "good transmission" is early fall of this year. Our website is www.ionlinacs.com.

A novel electron gun for inline MRI-linac configurations.

PubMed

Constantin, Dragoş E; Holloway, Lois; Keall, Paul J; Fahrig, Rebecca

2014-02-01

This work introduces a new electron gun geometry capable of robust functioning in the presence of a high strength external magnetic field for axisymmetric magnetic resonance imaging (MRI)-linac configurations. This allows an inline MRI-linac to operate without the need to isolate the linear accelerator (linac) using a magnetic shield. This MRI-linac integration approach not only leaves the magnet homogeneity unchanged but also provides the linac flexibility to move along the magnet axis of symmetry if the source to target distance needs to be adjusted. Simple electron gun geometry modifications of a Varian 600 C electron gun are considered and solved in the presence of an external magnetic field in order to determine a set of design principles for the new geometry. Based on these results, a new gun geometry is proposed and optimized in the fringe field of a 0.5 T open bore MRI magnet (GE Signa SP). A computer model for the 6 MeV Varian 600 C linac is used to determine the capture efficiency of the new electron gun-linac system in the presence of the fringe field of the same MRI scanner. The behavior of the new electron gun plus the linac system is also studied in the fringe fields of two other magnets, a 1.0 T prototype open bore magnet and a 1.5 T GE Conquest scanner. Simple geometrical modifications of the original electron gun geometry do not provide feasible solutions. However, these tests show that a smaller transverse cathode diameter with a flat surface and a slightly larger anode diameter could alleviate the current loss due to beam interactions with the anode in the presence of magnetic fields. Based on these findings, an initial geometry resembling a parallel plate capacitor with a hole in the anode is proposed. The optimization procedure finds a cathode-anode distance of 5 mm, a focusing electrode angle of 5°, and an anode drift tube length of 17.1 mm. Also, the linac can be displaced with ± 15 cm along the axis of the 0.5 T magnet without capture efficiency reduction below the experimental value in zero field. In this range of linac displacements, the electron beam generated by the new gun geometry is more effectively injected into the linac in the presence of an external magnetic field, resulting in approximately 20% increase of the target current compared to the original gun geometry behavior at zero field. The new gun geometry can generate and accelerate electron beams in external magnetic fields without current loss for fields higher than 0.11 T. The new electron-gun geometry is robust enough to function in the fringe fields of the other two magnets with a target current loss of no more than 16% with respect to the current obtained with no external magnetic fields. In this work, a specially designed electron gun was presented which can operate in the presence of axisymmetric strong magnetic fringe fields of MRI magnets. Computer simulations show that the electron gun can produce high quality beams which can be injected into a straight through linac such as Varian 600 C and accelerated with more efficiency in the presence of the external magnetic fields. Also, the new configuration allows linac displacements along the magnet axis in a range equal to the diameter of the imaging spherical volume of the magnet under consideration. The new electron gun-linac system can function in the fringe field of a MRI magnet if the field strength at the cathode position is higher than 0.11 T. The capture efficiency of the linac depends on the magnetic field strength and the field gradient. The higher the gradient the better the capture efficiency. The capture efficiency does not degrade more than 16%.

A novel electron gun for inline MRI-linac configurations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Constantin, Dragoş E., E-mail: dragos.constantin@varian.com; Fahrig, Rebecca; Holloway, Lois

2014-02-15

Purpose: This work introduces a new electron gun geometry capable of robust functioning in the presence of a high strength external magnetic field for axisymmetric magnetic resonance imaging (MRI)-linac configurations. This allows an inline MRI-linac to operate without the need to isolate the linear accelerator (linac) using a magnetic shield. This MRI-linac integration approach not only leaves the magnet homogeneity unchanged but also provides the linac flexibility to move along the magnet axis of symmetry if the source to target distance needs to be adjusted. Methods: Simple electron gun geometry modifications of a Varian 600C electron gun are considered andmore » solved in the presence of an external magnetic field in order to determine a set of design principles for the new geometry. Based on these results, a new gun geometry is proposed and optimized in the fringe field of a 0.5 T open bore MRI magnet (GE Signa SP). A computer model for the 6 MeV Varian 600C linac is used to determine the capture efficiency of the new electron gun-linac system in the presence of the fringe field of the same MRI scanner. The behavior of the new electron gun plus the linac system is also studied in the fringe fields of two other magnets, a 1.0 T prototype open bore magnet and a 1.5 T GE Conquest scanner. Results: Simple geometrical modifications of the original electron gun geometry do not provide feasible solutions. However, these tests show that a smaller transverse cathode diameter with a flat surface and a slightly larger anode diameter could alleviate the current loss due to beam interactions with the anode in the presence of magnetic fields. Based on these findings, an initial geometry resembling a parallel plate capacitor with a hole in the anode is proposed. The optimization procedure finds a cathode-anode distance of 5 mm, a focusing electrode angle of 5°, and an anode drift tube length of 17.1 mm. Also, the linac can be displaced with ±15 cm along the axis of the 0.5 T magnet without capture efficiency reduction below the experimental value in zero field. In this range of linac displacements, the electron beam generated by the new gun geometry is more effectively injected into the linac in the presence of an external magnetic field, resulting in approximately 20% increase of the target current compared to the original gun geometry behavior at zero field. The new gun geometry can generate and accelerate electron beams in external magnetic fields without current loss for fields higher than 0.11 T. The new electron-gun geometry is robust enough to function in the fringe fields of the other two magnets with a target current loss of no more than 16% with respect to the current obtained with no external magnetic fields. Conclusions: In this work, a specially designed electron gun was presented which can operate in the presence of axisymmetric strong magnetic fringe fields of MRI magnets. Computer simulations show that the electron gun can produce high quality beams which can be injected into a straight through linac such as Varian 600C and accelerated with more efficiency in the presence of the external magnetic fields. Also, the new configuration allows linac displacements along the magnet axis in a range equal to the diameter of the imaging spherical volume of the magnet under consideration. The new electron gun-linac system can function in the fringe field of a MRI magnet if the field strength at the cathode position is higher than 0.11 T. The capture efficiency of the linac depends on the magnetic field strength and the field gradient. The higher the gradient the better the capture efficiency. The capture efficiency does not degrade more than 16%.« less

A novel electron gun for inline MRI-linac configurations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Constantin, Dragoş E., E-mail: dragos.constantin@varian.com; Fahrig, Rebecca; Holloway, Lois

Purpose: This work introduces a new electron gun geometry capable of robust functioning in the presence of a high strength external magnetic field for axisymmetric magnetic resonance imaging (MRI)-linac configurations. This allows an inline MRI-linac to operate without the need to isolate the linear accelerator (linac) using a magnetic shield. This MRI-linac integration approach not only leaves the magnet homogeneity unchanged but also provides the linac flexibility to move along the magnet axis of symmetry if the source to target distance needs to be adjusted. Methods: Simple electron gun geometry modifications of a Varian 600C electron gun are considered andmore » solved in the presence of an external magnetic field in order to determine a set of design principles for the new geometry. Based on these results, a new gun geometry is proposed and optimized in the fringe field of a 0.5 T open bore MRI magnet (GE Signa SP). A computer model for the 6 MeV Varian 600C linac is used to determine the capture efficiency of the new electron gun-linac system in the presence of the fringe field of the same MRI scanner. The behavior of the new electron gun plus the linac system is also studied in the fringe fields of two other magnets, a 1.0 T prototype open bore magnet and a 1.5 T GE Conquest scanner. Results: Simple geometrical modifications of the original electron gun geometry do not provide feasible solutions. However, these tests show that a smaller transverse cathode diameter with a flat surface and a slightly larger anode diameter could alleviate the current loss due to beam interactions with the anode in the presence of magnetic fields. Based on these findings, an initial geometry resembling a parallel plate capacitor with a hole in the anode is proposed. The optimization procedure finds a cathode-anode distance of 5 mm, a focusing electrode angle of 5°, and an anode drift tube length of 17.1 mm. Also, the linac can be displaced with ±15 cm along the axis of the 0.5 T magnet without capture efficiency reduction below the experimental value in zero field. In this range of linac displacements, the electron beam generated by the new gun geometry is more effectively injected into the linac in the presence of an external magnetic field, resulting in approximately 20% increase of the target current compared to the original gun geometry behavior at zero field. The new gun geometry can generate and accelerate electron beams in external magnetic fields without current loss for fields higher than 0.11 T. The new electron-gun geometry is robust enough to function in the fringe fields of the other two magnets with a target current loss of no more than 16% with respect to the current obtained with no external magnetic fields. Conclusions: In this work, a specially designed electron gun was presented which can operate in the presence of axisymmetric strong magnetic fringe fields of MRI magnets. Computer simulations show that the electron gun can produce high quality beams which can be injected into a straight through linac such as Varian 600C and accelerated with more efficiency in the presence of the external magnetic fields. Also, the new configuration allows linac displacements along the magnet axis in a range equal to the diameter of the imaging spherical volume of the magnet under consideration. The new electron gun-linac system can function in the fringe field of a MRI magnet if the field strength at the cathode position is higher than 0.11 T. The capture efficiency of the linac depends on the magnetic field strength and the field gradient. The higher the gradient the better the capture efficiency. The capture efficiency does not degrade more than 16%.« less

High gradient RF test results of S-band and C-band cavities for medical linear accelerators

NASA Astrophysics Data System (ADS)

Degiovanni, A.; Bonomi, R.; Garlasché, M.; Verdú-Andrés, S.; Wegner, R.; Amaldi, U.

2018-05-01

TERA Foundation has proposed and designed hadrontherapy facilities based on novel linacs, i.e. high gradient linacs which accelerate either protons or light ions. The overall length of the linac, and therefore its cost, is almost inversely proportional to the average accelerating gradient. With the scope of studying the limiting factors for high gradient operation and to optimize the linac design, TERA, in collaboration with the CLIC Structure Development Group, has conducted a series of high gradient experiments. The main goals were to study the high gradient behavior and to evaluate the maximum gradient reached in 3 and 5.7 GHz structures to direct the design of medical accelerators based on high gradient linacs. This paper summarizes the results of the high power tests of 3.0 and 5.7 GHz single-cell cavities.

SU-E-T-468: Implementation of the TG-142 QA Process for Seven Linacs with Enhanced Beam Conformance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woollard, J; Ayan, A; DiCostanzo, D

2015-06-15

Purpose: To develop a TG-142 compliant QA process for 7 Varian TrueBeam linear accelerators (linacs) with enhanced beam conformance and dosimetrically matched beam models. To ensure consistent performance of all 7 linacs, the QA process should include a common set of baseline values for use in routine QA on all linacs. Methods: The TG 142 report provides recommended tests, tolerances and frequencies for quality assurance of medical accelerators. Based on the guidance provided in the report, measurement tests were developed to evaluate each of the applicable parameters listed for daily, monthly and annual QA. These tests were then performed onmore » each of our 7 new linacs as they came on line at our institution. Results: The tolerance values specified in TG-142 for each QA test are either absolute tolerances (i.e. ±2mm) or require a comparison to a baseline value. The results of our QA tests were first used to ensure that all 7 linacs were operating within the suggested tolerance values provided in TG −142 for those tests with absolute tolerances and that the performance of the linacs was adequately matched. The QA test results were then used to develop a set of common baseline values for those QA tests that require comparison to a baseline value at routine monthly and annual QA. The procedures and baseline values were incorporated into a spreadsheets for use in monthly and annual QA. Conclusion: We have developed a set of procedures for daily, monthly and annual QA of our linacs that are consistent with the TG-142 report. A common set of baseline values was developed for routine QA tests. The use of this common set of baseline values for comparison at monthly and annual QA will ensure consistent performance of all 7 linacs.« less

Linac design for the European spallation source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klein, H.

1995-10-01

A study group has started to develop a conceptual design for a European Spallation Source (ESS). This pulsed 5 MW source presently consists of a 1.334 GeV linac and two compressor rings. In the following mainly the high intensity linac part will be discussed, which has some features of interest for accelerators for transmutation of radioactive waste too.

SU-E-P-32: Adapting An MMLC to a Conventional Linac to Perform Stereotactic Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Emam, I; Hosini, M

2015-06-15

Purpose: Micro-MLCs minimizes beam scalloping effects caused by conventional-MLCs and facilitates conformal dynamic treatment delivery. But their effect on dosimetric parameters require careful investigations. Physical and dosimetric parameters and Linac mechanical stability with mMLC (net weight 30 Kg) attached to the gantry are to be investigated. Moreover, output study along with recommended jaws offsets are studied. Adaptation of an mMLC to our 16-years old conventional Linac is investigated in this work Methods: BrainLab mMLC (m3) mounted in a detachable chassis to the Philips SL-15 Linac (30kg). Gantry and collimator spoke shots measurements are made using a calibrated film in amore » solid phantom and compared with pin-point measurements. Leaf penumbra, transmission, leakage between the leaves, percentage depth dose (PDD) are measured using IBA pin-point ion chamber at 6 and 10 MV. For output measurements (using brass build-up cap), jaws are modified continuously regarding to m3-fields while output factor are compared with fixed jaws situation, while the mMLC leaf configuration is modified for different m3-fields Results: Mean transmission through leaves is 1.9±0.1% and mean leakage between leaves is 2.8±0.15%. Between opposing leaves abutting along the central beam-axis mean transmission is 15±3%, but it is reduced to 4.5±0.6% by moving the abutment position 4.5cm off-axis. The penumbra was sharper for m3 -fields than jaws-fields (maximum difference is 1.51±0.2%). m3-fields PDD show ∼3% variation from those of jaws-fields. m3-fields output factors show large variations (<4%) from Jaws defined fields. Output for m3-rectangular fields show slight variation in case of leaf-end&leaf-side as well as X-jaw&Y-jaw exchange. Circular m3-fields output factors shows close agreement with their corresponding square jaws-defined fields using 2mm Jaws offsets, If jaws are retracted to m3 limits, differences become <5%. Conclusion: BrainLab m3 is successfully adapted to our 16 old Philips-SL-15 Linac. Dosimetric properties should be taken into account for treatment planning considerations.« less

SU-E-T-451: Accuracy and Application of the Standard Imaging W1 Scintillator Dosimeter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kowalski, M; McEwen, M

2014-06-01

Purpose: To evaluate the Standard Imaging W1 scintillator dosimeter in a range of clinical radiation beams to determine its range of possible applications. Methods: The W1 scintillator is a small perturbation-free dosimeter which is of interest in absolute and relative clinical dosimetry due to its small size and water equivalence. A single version of this detector was evaluated in Co-60 and linac photon and electron beams to investigate the following: linearity, sensitivity, precision, and dependence on electrometer type. In addition, depth-dose and cross-plane profiles were obtained in both photon and electron beams and compared with data obtained with wellbehaved ionizationmore » chambers. Results: In linac beams the precision and linearity was very impressive, with typical values of 0.3% and 0.1% respectively. Performance in a Co-60 beam was much poorer (approximately three times worse) and it is not clear whether this is due to the lower signal current or the effect of the continuous beam (rather than pulsed beam of the linac measurements). There was no significant difference in the detector reading when using either the recommended SI Supermax electrometer or two independent high-quality electrometers, except for low signal levels, where the Supermax exhibited an apparent threshold effect, preventing the measurement of the bremsstrahlung background in electron depth-dose curves. Comparisons with ion chamber measurements in linac beams were somewhat variable: good agreement was seen for cross-profiles (photon and electron beams) and electron beam depth-dose curves, generally within the 0.3% precision of the scintillator but systematic differences were observed as a function of measurement depth in photon beam depth-dose curves. Conclusion: A first look would suggest that the W1 scintillator has applications beyond small field dosimetry but performance appears to be limited to higher doserate and/or pulsed radiation beams. Further work is required to resolve discrepancies compared to ion chambers.« less

SU-E-T-599: Patient Safety Enhancements Through a Study of R&V System Override Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hendrickson, K; Vimolchalao, S

2015-06-15

Purpose: Record and verify (R&V) software systems include safety checks that compare actual machine parameters with prescribed values for a patient’s treatment, such as treatment couch position, linac, energy, and MUs. The therapist is warned of a mismatch with a pop-up and prompted to approve an override in order to continue without changes. Override approval is often legitimate, but the pop-up can also genuinely indicate a problem that would Result in the wrong treatment. When there are numerous pop-up warnings, human nature leads us to approve any override without careful reading, undermining the effectiveness of the safety mechanism. Methods: Overridemore » data was collected from our R&V system for all patients treated between October 8 and 29, 2012, on four linacs and entered into a spreadsheet. Additional data collected included treatment technique, disease site, immobilization, time, linac, and whether localization images were obtained. Data were analyzed using spreadsheet tools to reveal trends, patterns and associations that might suggest appropriate process changes that could decrease the total number of overrides. Results: 76 out of 113 patients had overrides. Out of the 944 treatments, 599 override items were generated. The majority were due to couch positions. 74 of the 84 overrides on a linac equipped with a 6D couch were due to the use of the rotational corrections and the fact that the 6D couch control does not communicate with the R&V system; translations required to rotate the couch appear to the R&V system as translations outside the tolerance range. Conclusion: Many findings were interesting but did not suggest a process change. Proposed process changes include creating site-specific instead of just technique-specific tolerance tables for couch shifts. Proposed improvements to the vendor are to facilitate direct communication between the 6D couch and the R&V system to eliminate those override warnings related to lack of communication.« less

Unfolding linac photon spectra and incident electron energies from experimental transmission data, with direct independent validation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ali, E. S. M.; McEwen, M. R.; Rogers, D. W. O.

2012-11-15

Purpose: In a recent computational study, an improved physics-based approach was proposed for unfolding linac photon spectra and incident electron energies from transmission data. In this approach, energy differentiation is improved by simultaneously using transmission data for multiple attenuators and detectors, and the unfolding robustness is improved by using a four-parameter functional form to describe the photon spectrum. The purpose of the current study is to validate this approach experimentally, and to demonstrate its application on a typical clinical linac. Methods: The validation makes use of the recent transmission measurements performed on the Vickers research linac of National Research Councilmore » Canada. For this linac, the photon spectra were previously measured using a NaI detector, and the incident electron parameters are independently known. The transmission data are for eight beams in the range 10-30 MV using thick Be, Al and Pb bremsstrahlung targets. To demonstrate the approach on a typical clinical linac, new measurements are performed on an Elekta Precise linac for 6, 10 and 25 MV beams. The different experimental setups are modeled using EGSnrc, with the newly added photonuclear attenuation included. Results: For the validation on the research linac, the 95% confidence bounds of the unfolded spectra fall within the noise of the NaI data. The unfolded spectra agree with the EGSnrc spectra (calculated using independently known electron parameters) with RMS energy fluence deviations of 4.5%. The accuracy of unfolding the incident electron energy is shown to be {approx}3%. A transmission cutoff of only 10% is suitable for accurate unfolding, provided that the other components of the proposed approach are implemented. For the demonstration on a clinical linac, the unfolded incident electron energies and their 68% confidence bounds for the 6, 10 and 25 MV beams are 6.1 {+-} 0.1, 9.3 {+-} 0.1, and 19.3 {+-} 0.2 MeV, respectively. The unfolded spectra for the clinical linac agree with the EGSnrc spectra (calculated using the unfolded electron energies) with RMS energy fluence deviations of 3.7%. The corresponding measured and EGSnrc-calculated transmission data agree within 1.5%, where the typical transmission measurement uncertainty on the clinical linac is 0.4% (not including the uncertainties on the incident electron parameters). Conclusions: The approach proposed in an earlier study for unfolding photon spectra and incident electron energies from transmission data is accurate and practical for clinical use.« less

Conceptional design of a heavy ion linac injector for HIRFL-CSRm

NASA Astrophysics Data System (ADS)

Zhang, Xiao-Hu; Yuan, You-Jin; Xia, Jia-Wen; Yin, Xue-Jun; Du, Heng; Li, Zhong-Shan

2014-10-01

A room temperature heavy ion linac has been proposed as a new injector of the main Cooler Storage Ring (CSRm) at the Heavy Ion Research Facility in Lanzhou (HIRFL), which is expected to improve the performance of HIRFL. The linac injector can supply heavy ions with a maximum mass to charge ratio of 7 and an injection kinetic energy of 7.272 MeV/u for CSRm; the pulsed beam intensity is 3 emA with the duty factor of 3%. Compared with the present cyclotron injector, the Sector Focusing Cyclotron (SFC), the beam current from linac can be improved by 10-100 times. As the pre-accelerator of the linac, the 108.48 MHz 4-rod Radio Frequency Quadrupole (RFQ) accelerates the ion beam from 4 keV/u to 300 keV/u, which achieves the transmission efficiency of 95.3% with a 3.07 m long vane. The phase advance has been taken into account in the analysis of the error tolerance, and parametric resonances have been carefully avoided by adjusting the structure parameters. Kombinierte Null Grad Struktur Interdigital H-mode Drift Tube Linacs (KONUS IH-DTLs), which follow the RFQ, accelerate ions up to the energy of 7.272 MeV/u for CSRm. The resonance frequency is 108.48 MHz for the first two cavities and 216.96 MHz for the last 5 Drift Tube Linacs (DTLs). The maximum accelerating gradient can reach 4.95 MV/m in a DTL section with the length of 17.066 m, and the total pulsed RF power is 2.8 MW. A new strategy, for the determination of resonance frequency, RFQ vane voltage and DTL effective accelerating voltage, is described in detail. The beam dynamics design of the linac will be presented in this paper.

MO-DE-BRA-02: SIMAC: A Simulation Tool for Teaching Linear Accelerator Physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlone, M; Harnett, N; Department of Radiation Oncology, University of Toronto, Toronto, Ontario

Purpose: The first goal of this work is to develop software that can simulate the physics of linear accelerators (linac). The second goal is to show that this simulation tool is effective in teaching linac physics to medical physicists and linac service engineers. Methods: Linacs were modeled using analytical expressions that can correctly describe the physical response of a linac to parameter changes in real time. These expressions were programmed with a graphical user interface in order to produce an environment similar to that of linac service mode. The software, “SIMAC”, has been used as a learning aid in amore » professional development course 3 times (2014 – 2016) as well as in a physics graduate program. Exercises were developed to supplement the didactic components of the courses consisting of activites designed to reinforce the concepts of beam loading; the effect of steering coil currents on beam symmetry; and the relationship between beam energy and flatness. Results: SIMAC was used to teach 35 professionals (medical physicists; regulators; service engineers; 1 week course) as well as 20 graduate students (1 month project). In the student evaluations, 85% of the students rated the effectiveness of SIMAC as very good or outstanding, and 70% rated the software as the most effective part of the courses. Exercise results were collected showing that 100% of the students were able to use the software correctly. In exercises involving gross changes to linac operating points (i.e. energy changes) the majority of students were able to correctly perform these beam adjustments. Conclusion: Software simulation(SIMAC), can be used to effectively teach linac physics. In short courses, students were able to correctly make gross parameter adjustments that typically require much longer training times using conventional training methods.« less

High gradient RF test results of S-band and C-band cavities for medical linear accelerators

DOE PAGES

Degiovanni, A.; Bonomi, R.; Garlasche, M.; ...

2018-02-09

TERA Foundation has proposed and designed hadrontherapy facilities based on novel linacs, i.e. high gradient linacs which accelerate either protons or light ions. The overall length of the linac, and therefore its cost, is almost inversely proportional to the average accelerating gradient. With the scope of studying the limiting factors for high gradient operation and to optimize the linac design, TERA, in collaboration with the CLIC Structure Development Group, has conducted a series of high gradient experiments. The main goals were to study the high gradient behavior and to evaluate the maximum gradient reached in 3 and 5.7 GHz structuresmore » to direct the design of medical accelerators based on high gradient linacs. Lastly, this paper summarizes the results of the high power tests of 3.0 and 5.7 GHz single-cell cavities.« less

Computational study of radiation doses at UNLV accelerator facility

NASA Astrophysics Data System (ADS)

Hodges, Matthew; Barzilov, Alexander; Chen, Yi-Tung; Lowe, Daniel

2017-09-01

A Varian K15 electron linear accelerator (linac) has been considered for installation at University of Nevada, Las Vegas (UNLV). Before experiments can be performed, it is necessary to evaluate the photon and neutron spectra as generated by the linac, as well as the resulting dose rates within the accelerator facility. A computational study using MCNPX was performed to characterize the source terms for the bremsstrahlung converter. The 15 MeV electron beam available in the linac is above the photoneutron threshold energy for several materials in the linac assembly, and as a result, neutrons must be accounted for. The angular and energy distributions for bremsstrahlung flux generated by the interaction of the 15 MeV electron beam with the linac target were determined. This source term was used in conjunction with the K15 collimators to determine the dose rates within the facility.

High gradient RF test results of S-band and C-band cavities for medical linear accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Degiovanni, A.; Bonomi, R.; Garlasche, M.

TERA Foundation has proposed and designed hadrontherapy facilities based on novel linacs, i.e. high gradient linacs which accelerate either protons or light ions. The overall length of the linac, and therefore its cost, is almost inversely proportional to the average accelerating gradient. With the scope of studying the limiting factors for high gradient operation and to optimize the linac design, TERA, in collaboration with the CLIC Structure Development Group, has conducted a series of high gradient experiments. The main goals were to study the high gradient behavior and to evaluate the maximum gradient reached in 3 and 5.7 GHz structuresmore » to direct the design of medical accelerators based on high gradient linacs. Lastly, this paper summarizes the results of the high power tests of 3.0 and 5.7 GHz single-cell cavities.« less

Structural analysis and evaluation of actual PC bridge using 950 keV/3.95 MeV X-band linacs

NASA Astrophysics Data System (ADS)

Takeuchi, H.; Yano, R.; Ozawa, I.; Mitsuya, Y.; Dobashi, K.; Uesaka, M.; Kusano, J.; Oshima, Y.; Ishida, M.

2017-07-01

In Japan, bridges constructed during the strong economic growth era are facing an aging problem and advanced maintenance methods have become strongly required recently. To meet this demand, we develop the on-site inspection system using 950 keV/3.95 MeV X-band (9.3 GHz) linac X-ray sources. These systems can visualize in seconds the inner states of bridges, including cracks of concrete, location and state of tendons (wires) and other imperfections. At the on-site inspections, 950 keV linac exhibited sufficient performance. But, for thicker concrete, it is difficult to visualize the internal state by 950 keV linac. Therefore, we proceeded the installation of 3.95 MeV linac for on-site bridge inspection. In addition, for accurate evaluation, verification on the parallel motion CT technique and FEM analysis are in progress.

Separated-orbit bisected energy-recovered linear accelerator

DOEpatents

Douglas, David R.

2015-09-01

A separated-orbit bisected energy-recovered linear accelerator apparatus and method. The accelerator includes a first linac, a second linac, and a plurality of arcs of differing path lengths, including a plurality of up arcs, a plurality of downgoing arcs, and a full energy arc providing a path independent of the up arcs and downgoing arcs. The up arcs have a path length that is substantially a multiple of the RF wavelength and the full energy arc includes a path length that is substantially an odd half-integer multiple of the RF wavelength. Operation of the accelerator includes accelerating the beam utilizing the linacs and up arcs until the beam is at full energy, at full energy executing a full recirculation to the second linac using a path length that is substantially an odd half-integer of the RF wavelength, and then decelerating the beam using the linacs and downgoing arcs.

The IPHI Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferdinand, Robin; Beauvais, Pierre-Yves

High Power Proton Accelerators (HPPAs) are studied for several projects based on high-flux neutron sources driven by proton or deuteron beams. Since the front end is considered as the most critical part of such accelerators, the two French national research agencies CEA and CNRS decided to collaborate in 1997 to study and build a High-Intensity Proton Injector (IPHI). The main objective of this project is to master the complex technologies used and the concepts of manufacturing and controlling the HPPAs. Recently, a collaboration agreement was signed with CERN and led to some evolutions in the design and in the schedule.more » The IPHI design current was maintained at 100 mA in Continuous Wave mode. This choice should allow to produce a high reliability beam at reduced intensity (typically 30 mA) tending to fulfill the Accelerator Driven System requirements. The output energy of the Radio Frequency Quadrupole (RFQ), was reduced from 5 to 3 MeV, allowing then the adjunction and the test, in pulsed operation of a chopper line developed by CERN for the Superconducting Proton Linac (SPL). In a final step, the IPHI RFQ and the chopper line should become parts of the SPL injector. In this paper, the IPHI project and the recent evolutions are reported together with the construction and operation schedule.« less

Magnetic shielding investigation for a 6 MV in-line linac within the parallel configuration of a linac-MR system.

PubMed

Santos, D M; St Aubin, J; Fallone, B G; Steciw, S

2012-02-01

In our current linac-magnetic resonance (MR) design, a 6 MV in-line linac is placed along the central axis of the MR's magnet where the MR's fringe magnetic fields are parallel to the overall electron trajectories in the linac waveguide. Our previous study of this configuration comprising a linac-MR SAD of 100 cm and a 0.5 T superconducting (open, split) MR imager. It showed the presence of longitudinal magnetic fields of 0.011 T at the electron gun, which caused a reduction in target current to 84% of nominal. In this study, passive and active magnetic shielding was investigated to recover the linac output losses caused by magnetic deflections of electron trajectories in the linac within a parallel linac-MR configuration. Magnetic materials and complex shield structures were used in a 3D finite element method (FEM) magnetic field model, which emulated the fringe magnetic fields of the MR imagers. The effects of passive magnetic shielding was studied by surrounding the electron gun and its casing with a series of capped steel cylinders of various inner lengths (26.5-306.5 mm) and thicknesses (0.75-15 mm) in the presence of the fringe magnetic fields from a commercial MR imager. In addition, the effects of a shield of fixed length (146.5 mm) with varying thicknesses were studied against a series of larger homogeneous magnetic fields (0-0.2 T). The effects of active magnetic shielding were studied by adding current loops around the electron gun and its casing. The loop currents, separation, and location were optimized to minimize the 0.011 T longitudinal magnetic fields in the electron gun. The magnetic field solutions from the FEM model were added to a validated linac simulation, consisting of a 3D electron gun (using OPERA-3d/scala) and 3D waveguide (using comsol Multiphysics and PARMELA) simulations. PARMELA's target current and output phase-space were analyzed to study the linac's output performance within the magnetic shields. The FEM model above agreed within 1.5% with the manufacturer supplied fringe magnetic field isoline data. When passive magnetic shields are used, the target current is recoverable to greater than 99% of nominal for shield thicknesses greater than 0.75 mm. The optimized active shield which resulted in 100% target current recovery consists of two thin current rings 110 mm in diameter with 625 and 430 A-turns in each ring. With the length of the passive shield kept constant, the thickness of the shield had to be increased to achieve the same target current within the increased longitudinal magnetic fields. A ≥99% original target current is recovered with passive shield thicknesses >0.75 mm. An active shield consisting of two current rings of diameter of 110 mm with 625 and 430 A-turns fully recovers the loss that would have been caused by the magnetic fields. The minimal passive or active shielding requirements to essentially fully recover the current output of the linac in our parallel-configured linac-MR system have been determined and are easily achieved for practical implementation of the system.

Isac Sc-Linac Phase-II Helium Refrigerator Commissioning and First Operational Experience at Triumf

NASA Astrophysics Data System (ADS)

Sekachev, I.; Kishi, D.; Laxdal, R. E.

2010-04-01

ISAC Phase-II is an upgrade of the radioactive isotope superconducting linear accelerator, SC-linac, at TRIUMF. The Phase-I section of the accelerator, medium-beta, is operational and is cooled with a 600 W helium refrigerator, commissioned in March 2005. An identical refrigerator is being used with the Phase-II segment of the accelerator; which is now under construction. The second refrigerator has been commissioned and tested with the Phase-I section of the linac and is used for Phase-II linac development, including new SC-cavity performance tests. The commissioning of the Phase-II refrigeration system and recent operational experience is presented.

Magnetic decoupling of the linac in a low field biplanar linac-MR system.

PubMed

St Aubin, J; Steciw, S; Fallone, B G

2010-09-01

The integration of a low field biplanar magnetic resonance (MR) imager and linear accelerator (linac) causes magnetic interference at the linac due to the MR fringe fields. In order to eliminate this interference, passive and active magnetic shielding designs are investigated. The optimized design of passive magnetic shielding was performed using the finite element method. The design was required to achieve no greater than a 20% electron beam loss within the linac waveguide and electron gun, no greater than 0.06 T at the multileaf collimator (MLC) motors, and generate a distortion of the main MR imaging volume of no greater than 300 ppm. Through the superposition of the analytical solution for a single current carrying wire loop, active shielding designs in the form of three and four sets of coil pairs surrounding the linac waveguide and electron gun were also investigated. The optimized current and coil center locations that yielded the best cancellation of the MR fringe fields at the linac were determined using sequential quadratic programming. Optimized passive shielding in the form of two steel cylinders was designed to meet the required constraints. When shielding the MLC motors along with the waveguide and electron gun, the thickness of the cylinders was less than 1 mm. If magnetically insensitive MLC motors are used, no MLC shielding would be required and the waveguide shield (shielding the waveguide and electron gun) became 1.58 mm thick. In addition, the optimized current and coil spacing for active shielding was determined for both three and four coil pair configurations. The results of the active shielding optimization produced no beam loss within the waveguide and electron gun and a maximum MR field distortion of 91 ppm over a 30 cm diameter spherical volume. Very simple passive and active shielding designs have been shown to magnetically decouple the linac from the MR imager in a low field biplanar linac-MR system. The MLC passive shielding produced the largest distortion of the MR field over the imaging volume. With the use of magnetically insensitive motors, the MR field distortion drops substantially since no MLC shield is required. The active shielding designs yielded no electron beam loss within the linac.

Dosimetric comparison of different treatment modalities for stereotactic radiotherapy.

PubMed

Hsu, Shih-Ming; Lai, Yuan-Chun; Jeng, Chien-Chung; Tseng, Chia-Ying

2017-09-16

The modalities for performing stereotactic radiotherapy (SRT) on the brain include the cone-based linear accelerator (linac), the flattening filter-free (FFF) volumetric modulated arc therapy (VMAT) linac, and tomotherapy. In this study, the cone-based linac, FFF-VMAT linac, and tomotherapy modalities were evaluated by measuring the differences in doses delivered during brain SRT and experimentally assessing the accuracy of the output radiation doses through clinical measurements. We employed a homemade acrylic dosimetry phantom representing the head, within which a thermoluminescent dosimeter (TLD) and radiochromic EBT3 film were installed. Using the conformity/gradient index (CGI) and Paddick methods, the quality of the doses delivered by the various SRT modalities was evaluated. The quality indicators included the uniformity, conformity, and gradient indices. TLDs and EBT3 films were used to experimentally assess the accuracy of the SRT dose output. The dose homogeneity indices of all the treatment modalities were lower than 1.25. The cone-based linac had the best conformity for all tumors, regardless of the tumor location and size, followed by the FFF-VMAT linac; tomography was the worst-performing treatment modality in this regard. The cone-based linac had the best gradient, regardless of the tumor location and size, whereas the FFF-VMAT linac had a better gradient than tomotherapy for a large tumor diameter (28 mm). The TLD and EBT3 measurements of the dose at the center of tumors indicated that the average difference between the measurements and the calculated dose was generally less than 4%. When the 3% 3-mm gamma passing rate metric was used, the average passing rates of all three treatment modalities exceeded 98%. Regarding the dose, the cone-based linac had the best conformity and steepest dose gradient for tumors of different sizes and distances from the brainstem. The results of this study suggest that SRT should be performed using the cone-based linac on tumors that require treatment plans with a steep dose gradient, even as the tumor is slightly irregular, we should also consider using a high dose gradient of the cone base to treat and protect the normal tissue. If normal tissues require special protection exist at positions that are superior or inferior to the tumor, we can consider using tomotherapy or Cone base with couch at 0° for treatment.

High-resolution imaging of a shock front in plastic by phase contrast imaging at LCLS

NASA Astrophysics Data System (ADS)

Beckwith, M.; Jiang, S.; Zhao, Y.; Schropp, A.; Fernandez-Panella, A.; Rinderknecht, H. G.; Wilks, S.; Fournier, K.; Galtier, E.; Xing, Z.; Granados, E.; Gamboa, E.; Glenzer, S. H.; Heimann, P.; Zastrau, U.; Cho, B. I.; Eggert, J. H.; Collins, G. W.; Ping, Y.

2017-10-01

Understanding the propagation of shock waves is important for many areas of high energy density physics, including inertial confinement fusion (ICF) and shock compression science. In order to probe the shock front structures in detail, a diagnostic capable of detecting both the small spatial and temporal changes in the material is required. Here we show the experiment using hard X-ray phase contrast imaging (PCI) to probe the shock wave propagation in polyimide with submicron spatial resolution. The experiment was performed at the Matter in Extreme Conditions (MEC) endstation of the Linac Coherent Lightsource (LCLS). PCI together with the femtosecond time scales of x-ray free electron lasers enables the imaging of optically opaque materials that undergo rapid temporal and spatial changes. The result reveals the evolution of the density profile with time. Work performed under DOE Contract No. DE-AC52-07NA27344 with support from OFES Early Career and LLNL LDRD program.

SU-F-T-479: Estimation of the Accuracy in Respiratory-Gated Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurosawa, T; Miyakawa, S; Sato, M

Purpose: Irregular respiratory patterns affects dose outputs in respiratorygated radiotherapy and there is no commercially available quality assurance (QA) system for it. We designed and developed a patient specific QA system for respiratory-gated radiotherapy to estimate irradiated output. Methods: Our in-house QA system for gating was composed of a personal computer with the USB-FSIO electronic circuit connecting to the linear accelerator (ONCOR-K, Toshiba Medical Systems). The linac implements a respiratory gating system (AZ-733V, Anzai Medical). During the beam was on, 4.2 V square-wave pulses were continually sent to the system. Our system can receive and count the pulses. At first,more » our system and an oscilloscope were compared to check the performance of our system. Next, basic estimation models were generated when ionization-chamber measurements were performed in gating using regular sinusoidal wave patterns (2.0, 2.5, 4.0, 8.0, 15 sec/cycle). During gated irradiation with the regular patterns, the number of the pulses per one gating window was measured using our system. Correlation between the number of the pulses per one gating and dose per the gating window were assessed to generate the estimation model. Finally, two irregular respiratory patterns were created and the accuracy of the estimation was evaluated. Results: Compared to the oscilloscope, our system worked similarly. The basic models were generated with the accuracy within 0.1%. The results of the gated irradiations with two irregular respiratory patterns show good agreement within 0.4% estimation accuracy. Conclusion: Our developed system shows good estimation for even irregular respiration patterns. The system would be a useful tool to verify the output for respiratory-gated radiotherapy.« less

Treating locally advanced lung cancer with a 1.5T MR-Linac - Effects of the magnetic field and irradiation geometry on conventionally fractionated and isotoxic dose-escalated radiotherapy.

PubMed

Bainbridge, Hannah E; Menten, Martin J; Fast, Martin F; Nill, Simeon; Oelfke, Uwe; McDonald, Fiona

2017-11-01

This study investigates the feasibility and potential benefits of radiotherapy with a 1.5T MR-Linac for locally advanced non-small cell lung cancer (LA NSCLC) patients. Ten patients with LA NSCLC were retrospectively re-planned six times: three treatment plans were created according to a protocol for conventionally fractionated radiotherapy and three treatment plans following guidelines for isotoxic target dose escalation. In each case, two plans were designed for the MR-Linac, either with standard (∼7mm) or reduced (∼3mm) planning target volume (PTV) margins, while one conventional linac plan was created with standard margins. Treatment plan quality was evaluated using dose-volume metrics or by quantifying dose escalation potential. All generated treatment plans fulfilled their respective planning constraints. For conventionally fractionated treatments, MR-Linac plans with standard margins had slightly increased skin dose when compared to conventional linac plans. Using reduced margins alleviated this issue and decreased exposure of several other organs-at-risk (OAR). Reduced margins also enabled increased isotoxic target dose escalation. It is feasible to generate treatment plans for LA NSCLC patients on a 1.5T MR-Linac. Margin reduction, facilitated by an envisioned MRI-guided workflow, enables increased OAR sparing and isotoxic target dose escalation for the respective treatment approaches. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Linking log files with dosimetric accuracy--A multi-institutional study on quality assurance of volumetric modulated arc therapy.

PubMed

Pasler, Marlies; Kaas, Jochem; Perik, Thijs; Geuze, Job; Dreindl, Ralf; Künzler, Thomas; Wittkamper, Frits; Georg, Dietmar

2015-12-01

To systematically evaluate machine specific quality assurance (QA) for volumetric modulated arc therapy (VMAT) based on log files by applying a dynamic benchmark plan. A VMAT benchmark plan was created and tested on 18 Elekta linacs (13 MLCi or MLCi2, 5 Agility) at 4 different institutions. Linac log files were analyzed and a delivery robustness index was introduced. For dosimetric measurements an ionization chamber array was used. Relative dose deviations were assessed by mean gamma for each control point and compared to the log file evaluation. Fourteen linacs delivered the VMAT benchmark plan, while 4 linacs failed by consistently terminating the delivery. The mean leaf error (±1SD) was 0.3±0.2 mm for all linacs. Large MLC maximum errors up to 6.5 mm were observed at reversal positions. Delivery robustness index accounting for MLC position correction (0.8-1.0) correlated with delivery time (80-128 s) and depended on dose rate performance. Dosimetric evaluation indicated in general accurate plan reproducibility with γ(mean)(±1 SD)=0.4±0.2 for 1 mm/1%. However single control point analysis revealed larger deviations and attributed well to log file analysis. The designed benchmark plan helped identify linac related malfunctions in dynamic mode for VMAT. Log files serve as an important additional QA measure to understand and visualize dynamic linac parameters. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Design and development of a new SRF cavity cryomodule for the ATLAS intensity upgrade

NASA Astrophysics Data System (ADS)

Kedzie, Mark; Conway, Zachary; Fuerst, Joel; Gerbick, Scott; Kelly, Michael; Morgan, James; Ostroumov, Peter; O'Toole, Michael; Shepard, Kenneth

2012-06-01

The ATLAS heavy ion linac at Argonne National Laboratory is undergoing an intensity upgrade that includes the development and implementation of a new cryomodule containing four superconducting solenoids and seven quarter-wave drift-tube-loaded superconducting rf cavities. The rf cavities extend the state of the art for this class of structure and feature ASME code stamped stainless steel liquid helium containment vessels. The cryomodule design is a further evolution of techniques recently implemented in a previous upgrade [1]. We provide a status report on the construction effort and describe the vacuum vessel, thermal shield, cold mass support and alignment, and other subsystems including couplers and tuners. Cavity mechanical design is also reviewed.

Long path-length experimental studies of longitudinal phenomena in intense beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beaudoin, B. L.; Haber, I.; Kishek, R. A.

2016-05-15

Intense charged particle beams are nonneutral plasmas as they can support a host of plasma waves and instabilities. The longitudinal physics, for a long beam, can often be reasonably described by a 1-D cold-fluid model with a geometry factor to account for the transverse effects. The plasma physics of such beams has been extensively studied theoretically and computationally for decades, but until recently, the only experimental measurements were carried out on relatively short linacs. This work reviews experimental studies over the past five years on the University of Maryland Electron Ring, investigating longitudinal phenomena over time scales of thousands ofmore » plasma periods, illustrating good agreement with simulations.« less

Shielding Requirements for an Energy-Recovery Linac Free Electron Laser

DTIC Science & Technology

2011-12-01

Radiofrequency TLD Thermo Luminescent Dosimeter xviii THIS PAGE INTENTIONALLY LEFT BLANK xix ACKNOWLEDGMENTS I would like to first thank Professor...FOR AN ENERGY- RECOVERY LINAC FREE ELECTRON LASER by Robert E. Peterson December 2011 Thesis Co-Advisors: William B. Colson Keith...COVERED Master’s Thesis 4. TITLE AND SUBTITLE Shielding Requirements for an Energy-Recovery Linac Free Electron Laser 5. FUNDING NUMBERS 6

Dedicated Linac for Radioneurosurgery at the National Institute of Neurology and Neurosurgery of Mexico

NASA Astrophysics Data System (ADS)

Celis-López, Miguel A.; Lárraga-Gutiérrez, José M.

2003-09-01

The objective is to present a description and the main clinical applications of this dedicated Linac for benign and malignant tumors in the central nervous system. The Novalis (BrainLab, Germany) is a 6 MV dedicated linac for a single high dose Radiosurgery (RS) and for fractionated doses in Stereotactic Radiotherapy with a high level of precision at the isocenter.

X-band RF gun and linac for medical Compton scattering X-ray source

NASA Astrophysics Data System (ADS)

Dobashi, Katsuhito; Uesaka, Mitsuru; Fukasawa, Atsushi; Sakamoto, Fumito; Ebina, Futaro; Ogino, Haruyuki; Urakawa, Junji; Higo, Toshiyasu; Akemoto, Mitsuo; Hayano, Hitoshi; Nakagawa, Keiichi

2004-12-01

Compton scattering hard X-ray source for 10-80 keV are under construction using the X-band (11.424 GHz) electron linear accelerator and YAG laser at Nuclear Engineering Research laboratory, University of Tokyo. This work is a part of the national project on the development of advanced compact medical accelerators in Japan. National Institute for Radiological Science is the host institute and U.Tokyo and KEK are working for the X-ray source. Main advantage is to produce tunable monochromatic hard (10-80 keV) X-rays with the intensities of 108-1010 photons/s (at several stages) and the table-top size. Second important aspect is to reduce noise radiation at a beam dump by adopting the deceleration of electrons after the Compton scattering. This realizes one beamline of a 3rd generation SR source at small facilities without heavy shielding. The final goal is that the linac and laser are installed on the moving gantry. We have designed the X-band (11.424 GHz) traveling-wave-type linac for the purpose. Numerical consideration by CAIN code and luminosity calculation are performed to estimate the X-ray yield. X-band thermionic-cathode RF-gun and RDS(Round Detuned Structure)-type X-band accelerating structure are applied to generate 50 MeV electron beam with 20 pC microbunches (104) for 1 microsecond RF macro-pulse. The X-ray yield by the electron beam and Q-switch Nd:YAG laser of 2 J/10 ns is 107 photons/RF-pulse (108 photons/sec at 10 pps). We design to adopt a technique of laser circulation to increase the X-ray yield up to 109 photons/pulse (1010 photons/s). 50 MW X-band klystron and compact modulator have been constructed and now under tuning. The construction of the whole system has started. X-ray generation and medical application will be performed in the early next year.

SU-F-T-611: Critical Analysis and Efficacy of Linac Based (Beam Modulator) and Cyberknife Treatment Plans for Acoustic Neuroma/schwannoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

KP, Karrthick; Kataria, T; Thiyagarajan, R

Purpose: To study the critical analysis and efficacy of Linac and Cyberknife (CK) treatment plans for acoustic neuroma/schwannoma. Methods: Twelve of acoustic neuroma/schwannoma patients were taken for these study that. Treatment plans were generated in Multiplan treatment planning system (TPS) for CK using 5,7.5 and 10mm diameter collimators. Target volumes were in the range of 0.280 cc to 9.256 cc. Prescription dose (Rx) ranges from 1150cGy to 1950cGy delivered over 1 to 3 Fractions. For same patients stereotactic Volumetric modulated arc plans were generated using Elekta Linac with MLC thickness of 4mm in Monaco TPS. Appropriate calculation algorithms and gridmore » size were used with same Rx and organ at risk (OAR) constrains for both Linac and CK plans. Treatment plans were developed to achieve at least 95% of the target volume to receive the Rx. The dosimetric indices such as conformity index (CI), coverage, OAR dose and volume receiving 50% of Rx (V50%) were used to evaluate the plans. Results: Target volumes ranges from 0.280 cc to 3.5cc shows the CI of 1.16±0.109 and 1.53±0.360 for cyberknife and Linac plans respectively. For small volume targets, the OARs were well spared in CK plans. There are no significant differences in CI and OAR doses were observed between CK and Linac plans that have the target volume >3.5 cc. Perhaps the V50% were lesser in CK plans, and found to be 12.8± 8.4 and 22.8 ± 15.0 for CK and Linac respectively. Conclusion: The analysis shows the importance of collimator size for small volume targets. The target volumes >3.5 cc can be treated in Linac as comparable with CK. For targets <3.5cc CK plans showed superior plan quality with better CI and OAR sparing than the Linac based plans. Further studies may require evaluating the clinical advantage of CK robotic system.« less

Coupled-cavity drift-tube linac

DOEpatents

Billen, James H.

1996-01-01

A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the .pi.-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is .beta..lambda., where .lambda. is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a .pi./2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range.

Coupled-cavity drift-tube linac

DOEpatents

Billen, J.H.

1996-11-26

A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the {pi}-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is {beta}{lambda}, where {lambda} is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a {pi}/2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range. 5 figs.

ARIEL e-LINAC: Commissioning and Development

NASA Astrophysics Data System (ADS)

Laxdal, R. E.; Zvyagintsev, V.

2016-09-01

A superconducting electron Linac (e-Linac) will be a part of the ARIEL facility for the production of radioactive ion beams (RIB) at TRIUMF. The e-Linac will consist of five 1.3GHz 9-cell cavities in three cryomodules delivering a 50MeV 10mA beam. The baseline operation will be single pass but a re-circulating ring is planned to allow either energy boost or energy recovery operation. The first stage of the accelerator which consists of two cryomodules has been successfully commissioned in 2014. The paper will discuss the superconducting radio-frequency (SRF) challenges of the accelerator. Cavities, crymodules and RF system design, preparation, and performance will be presented.

Experimental demonstration of electron longitudinal-phase-space linearization by shaping the photoinjector laser pulse.

PubMed

Penco, G; Danailov, M; Demidovich, A; Allaria, E; De Ninno, G; Di Mitri, S; Fawley, W M; Ferrari, E; Giannessi, L; Trovó, M

2014-01-31

Control of the electron-beam longitudinal-phase-space distribution is of crucial importance in a number of accelerator applications, such as linac-driven free-electron lasers, colliders and energy recovery linacs. Some longitudinal-phase-space features produced by nonlinear electron beam self- fields, such as a quadratic energy chirp introduced by geometric longitudinal wakefields in radio-frequency (rf) accelerator structures, cannot be compensated by ordinary tuning of the linac rf phases nor corrected by a single high harmonic accelerating cavity. In this Letter we report an experimental demonstration of the removal of the quadratic energy chirp by properly shaping the electron beam current at the photoinjector. Specifically, a longitudinal ramp in the current distribution at the cathode linearizes the longitudinal wakefields in the downstream linac, resulting in a flat electron current and energy distribution. We present longitudinal-phase-space measurements in this novel configuration compared to those typically obtained without longitudinal current shaping at the FERMI linac.

Machine Protection System Research and Development for the Fermilab PIP-II Proton Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warner, Arden; Carmichael, Linden; Harrison, Beau

PIP-II is a high intensity proton linac being design to support a world-leading physics program at Fermilab. Initially it will provide high intensity beams for Fermilab's neutrino program with a future extension to other applications requiring an upgrade to CW linac operation (e.g. muon experiments). The machine is conceived to be 2 mA CW, 800 MeV H⁻ linac capable of working initially in a pulse (0.55 ms, 20 Hz) mode for injection into the existing Booster. The planned upgrade to CW operation implies that the total beam current and damage potential will be greater than in any present HEP hadronmore » linac. To mitigate the primary technical risk and challenges associated PIP-II an integrated system test for the PIP-II front-end technology is being developed. As part of the R&D a robust machine protection system (MPS) is being designed. This paper describes the progress and challenges associated with the MPS.« less

Recirculating linacs for a neutrino factory - Arc optics design and optimization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alex Bogacz; Valeri Lebedev

2001-10-21

A conceptual lattice design for a muon accelerator based on recirculating linacs (Nucl. Instr. and Meth. A 472 (2001) 499, these proceedings) is presented here. The challenge of accelerating and transporting a large phase space of short-lived muons is answered here by presenting a proof-of-principle lattice design for a recirculating linac accelerator. It is the centerpiece of a chain of accelerators consisting of a 3GeV linac and two consecutive recirculating linear accelerators, which facilitates acceleration starting after ionization cooling at 190MeV/c and proceeding to 50GeV. Beam transport issues for large-momentum-spread beams are accommodated by appropriate lattice design choices. The resultingmore » arc optics is further optimized with a sextupole correction to suppress chromatic effects contributing to the emittance dilution. The presented proof-of-principle design of the arc optics with horizontal separation of multi-pass beams can be extended to all passes in both recirculating linacs.« less

Recirculating linacs for a neutrino factory - Arc optics design and optimization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valeri Lebedev; S. Bogacz

2001-10-25

A conceptual lattice design for a muon accelerator based on recirculating linacs (Nucl. Instr. and Meth. A 472 (2001) 499, these proceedings) is presented here. The challenge of accelerating and transporting a large phase space of short-lived muons is answered here by presenting a proof-of-principle lattice design for a recirculating linac accelerator. It is the centerpiece of a chain of accelerators consisting of a 3 GeV linac and two consecutive recirculating linear accelerators, which facilitates acceleration starting after ionization cooling at 190 MeV/c and proceeding to 50 GeV. Beam transport issues for large-momentum-spread beams are accommodated by appropriate lattice designmore » choices. The resulting arc optics is further optimized with a sextupole correction to suppress chromatic effects contributing to the emittance dilution. The presented proof-of-principle design of the arc optics with horizontal separation of multi-pass beams can be extended to all passes in both recirculating linacs.« less

Report of the eRHIC Ring-Ring Working Group

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aschenauer, E. C.; Berg, S.; Blaskiewicz, M.

2015-10-13

This report evaluates the ring-ring option for eRHIC as a lower risk alternative to the linac-ring option. The reduced risk goes along with a reduced initial luminosity performance. However, a luminosity upgrade path is kept open. This upgrade path consists of two branches, with the ultimate upgrade being either a ring-ring or a linac-ring scheme. The linac-ring upgrade could be almost identical to the proposed linac-ring scheme, which is based on an ERL in the RHIC tunnel. This linac-ring version has been studied in great detail over the past ten years, and its significant risks are known. On the othermore » hand, no detailed work on an ultimate performance ring-ring scenario has been performed yet, other than the development of a consistent parameter set. Pursuing the ring-ring upgrade path introduces high risks and requires significant design work that is beyond the scope of this report.« less

SLAC Linac Preparations for FACET

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erickson, R.; Bentson, L.; Kharakh, D.

The SLAC 3km linear electron accelerator has been cut at the two-thirds point to provide beams to two independent programs. The last third provides the electron beam for the Linac Coherent Light Source (LCLS), leaving the first two-thirds available for FACET, the new experimental facility for accelerator science and test beams. In this paper, we describe this separation and projects to prepare the linac for the FACET experimental program.

Feasibility of using the linac real-time log data for VMAT treatment verification

NASA Astrophysics Data System (ADS)

Midi, N. S.; Zin, Hafiz M.

2017-05-01

This study investigates the feasibility of using the real-time log data from a linac to verify Volumetric Modulated Arc Therapy (VMAT) treatment. The treatment log data for an Elekta Synergy linac can be recorded at a sampling rate of 4 Hz using the service graphing tool on the linac control computer. A treatment plan that simulates a VMAT treatment was delivered from the linac and all the dynamic treatment parameters including monitor unit (MU), Multileaf Collimator (MLC) position, jaw position, gantry angle and collimator angle were recorded in real-time using the service graphing tool. The recorded raw data were extracted and analysed using algorithms written in Matlab (MathWorks, Natick, MA). The actual treatment parameters logged using the service graphing tool was compared to the prescription and the deviations were analysed. The MLC position errors travelling at the speed range from -3.25 to 5.92 cm/s were between -1.7 mm to 2.5 mm, well within the 3.5 mm tolerance value (AAPM TG-142). The discrepancies of other delivery parameters were also within the tolerance. The real-time linac parameters logged using the service graphing tool can be used as a supplementary data for patient specific VMAT pre-treatment quality assurance.

Novel Linac Structures For Low-Beta Ions And For Muons

NASA Astrophysics Data System (ADS)

Kurennoy, Sergey S.

2011-06-01

Development of two innovative linacs is discussed. (1) High-efficiency normal-conducting accelerating structures for ions with beam velocities in the range of a few percent of the speed of light. Two existing accelerator technologies—the H-mode resonator cavities and transverse beam focusing by permanent-magnet quadrupoles (PMQ)—are merged to create efficient structures for light-ion beams of considerable currents. The inter-digital H-mode accelerator with PMQ focusing (IH-PMQ) has the shunt impedance 10-20 times higher than the standard drift-tube linac. Results of the combined 3-D modeling for an IH-PMQ accelerator tank—electromagnetic computations, beam-dynamics simulations, and thermal-stress analysis—are presented. H-PMQ structures following a short RFQ accelerator can be used in the front end of ion linacs or in stand-alone applications like a compact mobile deuteron-beam accelerator up to a few MeV. (2) A large-acceptance high-gradient linac for accelerating low-energy muons in a strong solenoidal magnetic field. When a proton beam hits a target, many low-energy pions are produced almost isotropically, in addition to a small number of high-energy pions in the forward direction. We propose to collect and accelerate copious muons created as the low-energy pions decay. The acceleration should bring muons to a kinetic energy of ˜200 MeV in about 10 m, where both an ionization cooling of the muon beam and its further acceleration in a superconducting linac become feasible. One potential solution is a normal-conducting linac consisting of independently fed 0-mode RF cavities with wide apertures closed by thin metal windows or grids. The guiding magnetic field is provided by external superconducting solenoids. The cavity choice, overall linac design considerations, and simulation results of muon acceleration are presented. Potential applications range from basic research to homeland defense to industry and medicine.

SU-E-T-270: Optimized Shielding Calculations for Medical Linear Accelerators (LINACs).

PubMed

Muhammad, W; Lee, S; Hussain, A

2012-06-01

The purpose of radiation shielding is to reduce the effective equivalent dose from a medical linear accelerator (LINAC) to a point outside the room to a level determined by individual state/international regulations. The study was performed to design LINAC's room for newly planned radiotherapy centers. Optimized shielding calculations were performed for LINACs having maximum photon energy of 20 MV based on NCRP 151. The maximum permissible dose limits were kept 0.04 mSv/week and 0.002 mSv/week for controlled and uncontrolled areas respectively by following ALARA principle. The planned LINAC's room was compared to the already constructed (non-optimized) LINAC's room to evaluate the shielding costs and the other facilities those are directly related to the room design. In the evaluation process it was noted that the non-optimized room size (i.e., 610 × 610 cm 2 or 20 feet × 20 feet) is not suitable for total body irradiation (TBI) although the machine installed inside was having not only the facility of TBI but the license was acquired. By keeping this point in view, the optimized INAC's room size was kept 762 × 762 cm 2. Although, the area of the optimized rooms was greater than the non-planned room (i.e., 762 × 762 cm 2 instead of 610 × 610 cm 2), the shielding cost for the optimized LINAC's rooms was reduced by 15%. When optimized shielding calculations were re-performed for non-optimized shielding room (i.e., keeping room size, occupancy factors, workload etc. same), it was found that the shielding cost may be lower to 41 %. In conclusion, non- optimized LINAC's room can not only put extra financial burden on the hospital but also can cause of some serious issues related to providing health care facilities for patients. © 2012 American Association of Physicists in Medicine.

SU-E-T-670: Radiotherapy Vault Shielding Evaluation Method for a Flattening Filter-Free (FFF) Linac-Practical Considerations and Recommendations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mihailidis, D

2015-06-15

Purpose: To date, there isn’t formal approach for flattening filter-free (FFF) linac vault shielding evaluation, thus, we propose an extension to NCRP#151 to accommodate the recent large number of FFF linac installations.Methods and Materials: We extended the approach in NCRP#151 to design two Truebeam vaults in our new cancer center for hypofractionated treatments. Monte Carlo calculations have characterized primary, scattered, leakage and neutron radiations from FFF-modes. These calculations have shown that: a) FFF primary beam is softer on the central-axis compared to flattening filtered (FF), b) the lateral dose profile is peaked on the central axis and less integral targetmore » current is required to generate the same tumor dose with the FF beam. Thus, the TVLs for FFF mode are smaller than those of the FF mode and the scatter functions of the FF mode (NCRP#151) may not be appropriate for FFF-mode, c) the neutron source strength and fluence for 18X-FFF is smaller than 18X-FF, but it is not of a concern here, no 18X-FFF-mode is available on the linac under investigation. Results: These barrier thickness are smaller (12% reduction on the average) than those computed for conventional FF mode with same realistic primary workload since, the primary TVLs used here are smaller and the WL is smaller than the conventional (almost half reduced), keeping the TADR in tolerance. Conclusions: A comprehensive method for shielding barrier calculations based on dedicated data for FFF-mode linacs is highly desired. Meanwhile, we provide an extension to NCRP#151 to accommodate the shielding design of such installations. It is also shown that if a vault is already designed for IMRT/VMAT and SABR hypofractionated treatments with FFF-mode linac, the vault can also be used for a FFF mode linac replacement, leaving some leeway for slightly higher workload on the FFF linac.« less

SU-E-P-30: Clinical Applications of Spatially Fractionated Radiation Therapy (GRID) Using Helical Tomotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, X; Liang, X; Penagaricano, J

2015-06-15

Purpose: To present the first clinical applications of Helical Tomotherapy-based spatially fractionated radiotherapy (HT-GRID) for deep seated tumors and associated dosimetric study. Methods: Ten previously treated GRID patients were selected (5 HT-GRID and 5 LINAC-GRID using a commercially available GRID block). Each case was re-planned either in HT-GRID or LINAC-GRID for a total of 10 plans for both techniques using same prescribed dose of 20 Gy to maximum point dose of GRID GTV. For TOMO-GRID, a programmable virtual TOMOGRID template mimicking a GRID pattern was generated. Dosimetric parameters compared included: GRID GTV mean dose (Dmean) and equivalent uniform dose (EUD),more » GRID GTV dose inhomogeneity (Ratio(valley/peak)), normal tissue Dmean and EUD, and other organs-at-risk(OARs) doses. Results: The median tumor volume was 634 cc, ranging from 182 to 4646 cc. Median distance from skin to the deepest part of tumor was 22cm, ranging from 8.9 to 38cm. The median GRID GTV Dmean and EUD was 10.65Gy (9.8–12.5Gy) and 7.62Gy (4.31–11.06Gy) for HT-GRID and was 6.73Gy (4.44–8.44Gy) and 3.95Gy (0.14–4.2Gy) for LINAC-GRID. The median Ratio(valley/peak) was 0.144(0.05–0.29) for HT-GRID and was 0.055(0.0001–0.14) for LINAC-GRID. For normal tissue in HT-GRID, the median Dmean and EUD was 1.24Gy (0.34–2.54Gy) and 5.45 Gy(3.45–6.89Gy) and was 0.61 Gy(0.11–1.52Gy) and 6Gy(4.45–6.82Gy) for LINAC-GRID. The OAR doses were comparable between the HT-GRID and LINAC-GRID. However, in some cases it was not possible to avoid a critical structure in LINAC-GRID; while HT-GRID can spare more tissue doses for certain critical structures. Conclusion: HT-GRID delivers higher GRID GTV Dmean, EUD and Ratio(valley/peak) compared to LINAC-GRID. HT-GRID delivers higher Dmean and lower EUD for normal tissue compared to LINAC-GRID. TOMOGRID template can be highly patient-specific and allows adjustment of the GRID pattern to different tumor sizes and shapes when they are deeply-seated and cannot be safely treated with LINAC-GRID.« less

FEM design and simulation of a short, 10 MV, S-band Linac with Monte Carlo dose simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baillie, Devin; Aubin, J. St.; Steciw, S., E-mail: ssteciw@ualberta.ca

2015-04-15

Purpose: Current commercial 10 MV Linac waveguides are 1.5 m. The authors’ current 6 MV linear accelerator–magnetic resonance imager (Linac–MR) system fits in typical radiotherapy vaults. To allow 10 MV treatments with the Linac–MR and still fit within typical vaults, the authors design a 10 MV Linac with an accelerator waveguide of the same length (27.5 cm) as current 6 MV Linacs. Methods: The first design stage is to design a cavity such that a specific experimental measurement for breakdown is applicable to the cavity. This is accomplished through the use of finite element method (FEM) simulations to match publishedmore » shunt impedance, Q factor, and ratio of peak to mean-axial electric field strength from an electric breakdown study. A full waveguide is then designed and tuned in FEM simulations based on this cavity design. Electron trajectories are computed through the resulting radio frequency fields, and the waveguide geometry is modified by shifting the first coupling cavity in order to optimize the electron beam properties until the energy spread and mean energy closely match values published for an emulated 10 MV Linac. Finally, Monte Carlo dose simulations are used to compare the resulting photon beam depth dose profile and penumbra with that produced by the emulated 10 MV Linac. Results: The shunt impedance, Q factor, and ratio of peak to mean-axial electric field strength are all matched to within 0.1%. A first coupling cavity shift of 1.45 mm produces an energy spectrum width of 0.347 MeV, very close to the published value for the emulated 10 MV of 0.315 MeV, and a mean energy of 10.53 MeV, nearly identical to the published 10.5 MeV for the emulated 10 MV Linac. The depth dose profile produced by their new Linac is within 1% of that produced by the emulated 10 MV spectrum for all depths greater than 1.5 cm. The penumbra produced is 11% narrower, as measured from 80% to 20% of the central axis dose. Conclusions: The authors have successfully designed and simulated an S-band waveguide of length of 27.5 cm capable of producing a 10 MV photon beam. This waveguide operates well within the breakdown threshold determined for the cavity geometry used. The designed Linac produces depth dose profiles similar to those of the emulated 10 MV Linac (waveguide-length of 1.5 m) but yields a narrower penumbra.« less

Calorimetry of electron beams and the calibration of dosimeters at high doses

NASA Astrophysics Data System (ADS)

Humphreys, J. C.; McLaughlin, W. L.

Graphite or metal calorimeters are used to make absolute dosimetric measurements of high-energy electron beams. These calibrated beams are then used to calibrate several types of dosimeters for high-dose applications such as medical-product sterilization, polymer modification, food processing, or electronic-device hardness testing. The electron beams are produced either as continuous high-power beams at approximately 4.5 MeV by d.c. type accelerators or in the energy range of approximately 8 to 50 MeV using pulsed microwave linear accelerators (linacs). The continuous beams are generally magnetically scanned to produce a broad, uniform radiation environment for the processing of materials of extended lateral dimensions. The higher-energy pulsed beams may also be scanned for processing applications or may be used in an unscanned, tightly-focused mode to produce maximum absorbed dose rates such as may be required for electronic-device radiation hardness testing. The calorimeters are used over an absorbed dose range of 10 2 to 10 4 Gy. Intercomparison studies are reported between National Institute of Standards and Technology (NIST) and UK National Physical Laboratory (NPL) graphite disk calorimeters at high doses, using the NPL 10-MeV linac, and agreement was found within 1.5%. It was also shown that the electron-beam responses of radiochromic film dosimeters and alanine pellet dosimeters can be accurately calibrated by comparison with calorimeter readings.

BEAM DYNAMICS STUDIES FOR A COMPACT CARBON ION LINAC FOR THERAPY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plastun, A.; Mustapha, B.; Nassiri, A.

2016-05-01

Feasibility of an Advanced Compact Carbon Ion Linac (ACCIL) for hadron therapy is being studied at Argonne National Laboratory in collaboration with RadiaBeam Technologies. The 45-meter long linac is designed to deliver 109 carbon ions per second with variable energy from 45 MeV/u to 450 MeV/u. S-band structure provides the acceleration in this range. The carbon beam energy can be adjusted from pulse to pulse, making 3D tumor scanning straightforward and fast. Front end accelerating structures such as RFQ, DTL and coupled DTL are designed to operate at lower frequencies. The design of the linac was accompanied with extensive end-to-endmore » beam dynamics studies which are presented in this paper.« less

The LCLS Project

NASA Astrophysics Data System (ADS)

Paterson, James M.

2000-04-01

The Linac Coherent Light Source (LCLS) is a linac driven FEL which uses a 1km electron linac (the last third of the SLAC linac) and a 100m long undulator to produce 1.5 angstrom X-rays of extremely high peak brightness. This radiation is fully tranversely coherent and is in sub-picosecond long pulses. The LCLS Project is a four year R&D program to solidify the design, to develop required technologies, to optimize the cost and performance and to study the potential experimental programs using these unique beam characteristics. The program is conducted by a multi-institutional collaboration consisting of SLAC as the lead laboratory, along with ANL, BNL, LLNL, LANL and UCLA.The LCLS design and the R&D programs are described.

SU-F-T-495: Method for Simultaneous Commissioning of Multiple Truebeam (TB) Linacs: Small Field Data and the Choice of Dosimetric Lead Gap (DLG)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mihailidis, D; Mallah, J

2016-06-15

Purpose: Many times a set of multiple Varian-Truebeam (TB) linacs are acquired by an institution. Since “beam matching” is an important requirement for many facilities, we developed a strategy to perform a “simultaneous” commissioning between multiple linacs.Methods and Materials: We first commissioned the required photon beam data for eclipse on the 1st TB for all the energy modalities with a beam scanning system, while integrated measurements for output factors, of all field sizes (from 1×1 to 40×40cm{sup 2}) were conducted on the 2nd TB. Care was exercised during small field dosimetry so the appropriate detectors were used with data takenmore » between two detectors be “linked” to a larger field size (4×4cm{sup 2}) with the “daisy-chaining” technique via: OF=[M-PTW(fs)×(M-PTW(4×4))-1]×[MA12s(4×4)×(M-A12S(10×10))−1]. For all energy modalities, data that span the entire range of field size, was repeated on the next TB linac, for verification. The primarily energy-dependent dosimetric leaf gap (DLG) which was measured separately on each TB. The modeled data was validated with special measurements conducted on both linacs during commissioning. Results: Our data agreed with the “TB representative beam data” to within 0.5% for all energy modalities and field sizes ≥3×3cm2. Sample depth-doses and cross-profiles of a 3×3cm2 between the linacs agreeing to within 1% between linacs. The measured DLGs were quite different with a uniform difference of 1.3% between the two linacs. The measured DLG values are independent of the average dose rate and medium used for the measurements. Conclusion: A comprehensive method of commissioning identical Varian-TB linacs, outlining the critical issues, especially small field dosimetry and DLG. The dosimetric effect of different DLG values, when it comes to, dynamic delivery and data comparisons will be presented. The dependence of DLG value on the measurement medium (in-air vs. water) or dose rate used will also be discussed. This work was supported by CAMC Cancer Center and Alliance Oncology.« less

Volumetric modulated arc therapy of head-and-neck cancer on a fast-rotating O-ring linac: Plan quality and delivery time comparison with a C-arm linac.

PubMed

Michiels, Steven; Poels, Kenneth; Crijns, Wouter; Delombaerde, Laurence; De Roover, Robin; Vanstraelen, Bianca; Haustermans, Karin; Nuyts, Sandra; Depuydt, Tom

2018-05-05

Linac improvements in gantry speed, leaf speed and dose rate may increase the time-efficiency of volumetric modulated arc therapy (VMAT) delivery. The plan quality achievable with faster VMAT however remains to be investigated. In this study, a fast-rotating O-ring linac with fast-moving leaves is compared with a C-arm linac in terms of plan quality and delivery time for VMAT of head-and-neck cancer (HNC). For 30 patients with HNC, treatment planning was performed using dual-arc (HA2) and triple-arc (HA3) VMAT on a Halcyon fast-rotating O-ring linac and using dual-arc VMAT on a TrueBeam C-arm linac (TB2). Target coverage metrics and complication probabilities were compared. Plan delivery was verified using 3%/3 mm gamma-index analysis of helical diode array measurements. Volumetric image acquisition and plan delivery times were compared. All studied VMAT-techniques fulfilled the target coverage objectives. D 2% to the boost volume was higher for HA2 (median 103.7%, 1st-3rd quartile [103.5%;104.0%]) and HA3 (103.2% [103.0%;103.7%)] than for TB2 (102.6% [102.3%;103.0%)], resulting in an increased boost target dose heterogeneity for HA2 and HA3. Complication probabilities were comparable between HA2 and TB2, while HA3 showed a xerostomia probability reduction (0.8% [0.2%;1.8%]) and dysphagia probability reduction (1.0% [0.2%;1.8%]) compared with TB2. Gamma-index agreement scores were never below 93.0% for HA2, HA3 and TB2. Volumetric imaging and plan delivery time was shorter for HA2 (1 m 24 s ± 1 s) and HA3 (1 m 54 s ± 1 s) than for TB2 (2 m 47 s ± 1 s). For VMAT of HNC, the fast-rotating O-ring linac at least maintains the plan quality of two arcs on a C-arm linac while reducing the image acquisition and plan delivery time. Copyright © 2018 Elsevier B.V. All rights reserved.

Project for the development of the linac based NCT facility in University of Tsukuba.

PubMed

Kumada, H; Matsumura, A; Sakurai, H; Sakae, T; Yoshioka, M; Kobayashi, H; Matsumoto, H; Kiyanagi, Y; Shibata, T; Nakashima, H

2014-06-01

A project team headed by University of Tsukuba launched the development of a new accelerator based BNCT facility. In the project, we have adopted Radio-Frequency Quadrupole (RFQ)+Drift Tube Linac (DTL) type linac as proton accelerators. Proton energy generated from the linac was set to 8MeV and average current was 10mA. The linac tube has been constructed by Mitsubishi Heavy Industry Co. For neutron generator device, beryllium is selected as neutron target material; high intensity neutrons are generated by the reaction with beryllium and the 80kW proton beam. Our team chose beryllium as the neutron target material. At present beryllium target system is being designed with Monte-Carlo estimations and heat analysis with ANSYS. The neutron generator consists of moderator, collimator and shielding. It is being designed together with the beryllium target system. We also acquired a building in Tokai village; the building has been renovated for use as BNCT treatment facility. It is noteworthy that the linac tube had been installed in the facility in September 2012. In BNCT procedure, several medical devices are required for BNCT treatment such as treatment planning system, patient positioning device and radiation monitors. Thus these are being developed together with the linac based neutron source. For treatment planning system, we are now developing a new multi-modal Monte-Carlo treatment planning system based on JCDS. The system allows us to perform dose estimation for BNCT as well as particle radiotherapy and X-ray therapy. And the patient positioning device can navigate a patient to irradiation position quickly and properly. Furthermore the device is able to monitor movement of the patient׳s position during irradiation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Compact, inexpensive, epithermal neutron source for BNCT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swenson, D. A.

1999-06-10

A new rf-focused linac structure, designed specifically to increase the acceleration efficiency and reduce the cost of linac structures in the few-MeV range, may win the role as the optimum accelerator-based epithermal neutron source for the BNCT application. This new linac structure resembles a drift tube linac (DTL) with radio frequency quadrupole (RFQ) focusing incorporated into each 'drift tube,' hence the name R lowbar f F lowbar ocused D lowbar TL, or RFD. It promises superior acceleration properties, focusing properties, and CW capabilities. We have a proposal under consideration for the development of an epithermal neutron source, based on themore » 2.5-MeV RFD linac system with an average current of 10 mA, having the following components: an ion source, a short low-energy transport system, a short RFQ linac section, an RFD linac section, an rf power system, a high-energy beam transport system, a proton beam target, and a neutron beam moderator system. We propose to develop a solid lithium target for this application in the form of a thin lithium layer on the inner surface of a truncated aluminum cone, cooled by the heavy water moderator, where the proton beam is expanded to a diameter of 3 cm and scanned along a circular path, striking the lithium layer at the cone's half-angle of 30 degrees. We propose to develop a moderator assembly designed to transmit a large fraction of the source neutrons from the target to the patient treatment port, while shifting the neutron energies to an appropriate epithermal energy spectrum and minimizing the gamma-ray dose. The status of this proposal and these plans are presented.« less

Commissioning of the 112 MHz SRF Gun and 500 MHz bunching cavities for the CeC PoP Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belomestnykh, S.; Ben-Zvi, I.; Brutus, J. C.

The Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL includes a short electron linac. During Phase 1, a 112 MHz superconducting RF photo-emission gun and two 500 MHz normal conducting bunching cavities were installed and are under commissioning. The paper describes the Phase1 linac layout and presents commissioning results for the cavities and associated RF, cryogenic and other sub-systems

Installation and Commissioning of the Super Conducting RF Linac Cryomodules for the Erlp

NASA Astrophysics Data System (ADS)

Goulden, A. R.; Bate, R.; Buckley, R. K.; Pattalwar, S. M.

2008-03-01

An Energy Recovery Linac Prototype (ERLP) is currently being constructed at Daresbury Laboratory, (UK) to promote the necessary skills in science & technology, particularly in photocathode electron gun and Superconducting RF (SRF), to enable the construction of a fourth generation light source, based on energy recovery linacs-4GLS [1]. The ERLP uses two identical cryomodules, one as a booster Linac used to accelerate the beam to 8.5 MeV, the other as an Energy Recovery Linac (ERL) module with an energy gain of 26.5 MeV. Each module consists of two 9- cell cavities operating at a frequency of 1.3 GHz and a temperature of 2 K. As there is no energy recovery in the booster it requires a peak power of 53 kW; whereas the linac module only requires 8 kW. The RF power is supplied by Inductive Output Tube (IOT) amplifiers. The maximum heat load (or the cooling power) required in the SRF system is 180 W at 2 K and is achieved in two stages: a LN2 pre-cooled Linde TCF50 liquefier produces liquid helium at 4.5 K, followed by a 2 K cold box consisting of a JT valve, recuperator and an external room temperature vacuum pumping system. This presentation reports the experience gained during, installation, commissioning and the initial operation of the cryomodules.

Linear Accelerator (LINAC)

MedlinePlus

... equipment? How is safety ensured? What is this equipment used for? A linear accelerator (LINAC) is the ... Therapy (SBRT) . top of page How does the equipment work? The linear accelerator uses microwave technology (similar ...

SINGLE BUNCH BEAM BREAKUP - A GENERAL SOLUTION.

DOE Office of Scientific and Technical Information (OSTI.GOV)

WANG,J.M.; MANE,S.R.; TOWNE,N.

2000-06-26

Caporaso, Barletta and Neil (CBN) found in a solution to the problem of the single-bunch beam breakup in a linac[1]. However, their method applies only to the case of a beam traveling in a strongly betatron-focused linac under the influence of the resistive wall impedance. We suggest in this paper a method for dealing with the same problem. Our methods is more general; it applies to the same problem under any impedance, and it applies to a linac with or without external betatron focusing.

SU-E-T-781: Using An Electronic Portal Imaging Device (EPID) for Correlating Linac Photon Beam Energies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yaddanapudi, S; Cai, B; Sun, B

2015-06-15

Purpose: Electronic portal imaging devices (EPIDs) have proven to be useful for measuring several parameters of interest in linear accelerator (linac) quality assurance (QA). The purpose of this project was to evaluate the feasibility of using EPIDs for determining linac photon beam energies. Methods: Two non-clinical Varian TrueBeam linacs (Varian Medical Systems, Palo Alto, CA) with 6MV and 10MV photon beams were used to perform the measurements. The linacs were equipped with an amorphous silicon based EPIDs (aSi1000) that were used for the measurements. We compared the use of flatness versus percent depth dose (PDD) for predicting changes in linacmore » photon beam energy. PDD was measured in 1D water tank (Sun Nuclear Corporation, Melbourne FL) and the profiles were measured using 2D ion-chamber array (IC-Profiler, Sun Nuclear) and the EPID. Energy changes were accomplished by varying the bending magnet current (BMC). The evaluated energies conformed with the AAPM TG142 tolerance of ±1% change in PDD. Results: BMC changes correlating with a ±1% change in PDD corresponded with a change in flatness of ∼1% to 2% from baseline values on the EPID. IC Profiler flatness values had the same correlation. We observed a similar trend for the 10MV beam energy changes. Our measurements indicated a strong correlation between changes in linac photon beam energy and changes in flatness. For all machines and energies, beam energy changes produced change in the uniformity (AAPM TG-142), varying from ∼1% to 2.5%. Conclusions: EPID image analysis of beam profiles can be used to determine linac photon beam energy changes. Flatness-based metrics or uniformity as defined by AAPM TG-142 were found to be more sensitive to linac photon beam energy changes than PDD. Research funding provided by Varian Medical Systems. Dr. Sasa Mutic receives compensation for providing patient safety training services from Varian Medical Systems, the sponsor of this study.« less

The SLAC linac as used in the SLC collider

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seeman, J.T.; Abrams, G.; Adolphsen, C.

The linac of the SLAC Linear Collider (SLC) must accelerate three high intensity bunches on each linac pulse from 1.2 GeV to 50 GeV with minimal increase of the small transverse emittance. The procedures and adjustments used to obtain this goal are outlined. Some of the accelerator parameters and components which interact are the beam energy, transverse position, component alignment, RF manipulation, feedback systems, quadrupole lattice, BNS damping, energy spectra, phase space matching, collimation, instrumentation and modelling. The method to bring these interdependent parameters collectively into specification has evolved over several years. This review is ordered in the sequence whichmore » is used to turn on the linac from a cold start and produce acceptable beams for the final focus and collisions. Approximate time estimates for the various activities are given. 21 refs.« less

The estimation of occupational dose in 15 MV varian clinac iX room by Argon-41 as an activation product of photoneutron

NASA Astrophysics Data System (ADS)

Latifah, R.; Bunawas; Noor, J. A. E.

2018-03-01

Linear accelerator (linac) becomes the most commonly used treatment to damage and kill cancer cell. Photon and electron as the radiation beam are produced by accelerating electrons to very high energy. Neutrons are generated when incident high photon energy interacts with component of linac such as target, flattering filter and collimator via photoneutrons reaction. The neutrons can also produce activation of materials in treatment room to generate radioactive materials. We have estimated the concentration of Argon-41 as activated product from argon-40 in the linac room using foil activation. The results show that the Argon-41 concentration in linac room which is operated 15 MV for 1 treatment (1 minute) is 1440 Bq/m3. Accordingly that concentration, the occupational dose is 6.4 mSv per year.

Investigating the effect of a magnetic field on dose distributions at phantom-air interfaces using PRESAGE® 3D dosimeter and Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Costa, Filipa; Doran, Simon J.; Hanson, Ian M.; Nill, Simeon; Billas, Ilias; Shipley, David; Duane, Simon; Adamovics, John; Oelfke, Uwe

2018-03-01

Dosimetric quality assurance (QA) of the new Elekta Unity (MR-linac) will differ from the QA performed of a conventional linac due to the constant magnetic field, which creates an electron return effect (ERE). In this work we aim to validate PRESAGE® dosimetry in a transverse magnetic field, and assess its use to validate the research version of the Monaco TPS of the MR-linac. Cylindrical samples of PRESAGE® 3D dosimeter separated by an air gap were irradiated with a cobalt-60 unit, while placed between the poles of an electromagnet at 0.5 T and 1.5 T. This set-up was simulated in EGSnrc/Cavity Monte Carlo (MC) code and relative dose distributions were compared with measurements using 1D and 2D gamma criteria of 3% and 1.5 mm. The irradiation conditions were adapted for the MR-linac and compared with Monaco TPS simulations. Measured and EGSnrc/Cavity simulated profiles showed good agreement with a gamma passing rate of 99.9% for 0.5 T and 99.8% for 1.5 T. Measurements on the MR-linac also compared well with Monaco TPS simulations, with a gamma passing rate of 98.4% at 1.5 T. Results demonstrated that PRESAGE® can accurately measure dose and detect the ERE, encouraging its use as a QA tool to validate the Monaco TPS of the MR-linac for clinically relevant dose distributions at tissue-air boundaries.

Towards laser spectroscopy of the proton-halo candidate boron-8

NASA Astrophysics Data System (ADS)

Maaß, Bernhard; Müller, Peter; Nörtershäuser, Wilfried; Clark, Jason; Gorges, Christian; Kaufmann, Simon; König, Kristian; Krämer, Jörg; Levand, Anthony; Orford, Rodney; Sánchez, Rodolfo; Savard, Guy; Sommer, Felix

2017-11-01

We propose to determine the nuclear charge radius of 8B by high-resolution laser spectroscopy. 8B (t 1/2 = 770 ms) is perhaps the best candidate of a nucleus exhibiting an extended proton wave-function or "one-proton-halo" in a more descriptive picture. Laser spectroscopic measurements of the isotope shift will be used to probe the change in nuclear charge radius along the three boron isotopes 8B, 10B and 11B. The change in nuclear charge radius directly correlates with the extent of the proton wave function. In-flight production and preparation of sufficient yields of 8B ions at low energies is provided by the Argonne Tandem Linac Accelerator System (ATLAS) at Argonne National Laboratory (ANL) in Chicago, IL, USA. Subsequently, the ions will be guided through a charge exchange cell for neutralization and the fluorescence signal of the atoms which interact with the resonant laser light will be detected. The charge radius can then be extracted from the measured isotope shift by employing highly accurate atomic theory calculations of this five-electron system which are carried out presently.

Waveguide detuning caused by transverse magnetic fields on a simulated in-line 6 MV linac.

PubMed

St Aubin, J; Steciw, S; Fallone, B G

2010-09-01

Due to the close proximity of the linear accelerator (linac) to the magnetic resonance (MR) imager in linac-MR systems, it will be subjected to magnet fringe fields larger than the Earth's magnetic field of 5 x 10(-5) T. Even with passive or active shielding designed to reduce these fields, some magnitude of the magnetic field is still expected to intersect the linac, causing electron deflection and beam loss. This beam loss, resulting from magnetic fields that cannot be eliminated with shielding, can cause a detuning of the waveguide due to excessive heating. The detuning, if significant, could lead to an even further decrease in output above what would be expected strictly from electron deflections caused by an external magnetic field. Thus an investigation of detuning was performed through various simulations. According to the Lorentz force, the electrons will be deflected away from their straight course to the target, depositing energy as they impact the linac copper waveguide. The deposited energy would lead to a heating and deformation of the copper structure resulting in resonant frequency changes. PARMELA was used to determine the mean energy and fraction of total beam lost in each linac cavity. The energy deposited into the copper waveguide from the beam losses caused by transverse magnetic fields was calculated using the Monte Carlo program DOSRZnrc. From the total energy deposited, the rise in temperature and ultimately the deformation of the structure was estimated. The deformed structure was modeled using the finite element method program COMSOL MULTIPHYSICS to determine the change in cavity resonant frequency. The largest changes in resonant frequency were found in the first two accelerating cavities for each field strength investigated. This was caused by a high electron fluence impacting the waveguide inner structures coupled with their low kinetic energies. At each field strength investigated, the total change in accelerator frequency was less than a manufacturing tolerance of 10 kHz and is thus not expected to have a noticeable effect on accelerator performance. The amount of beam loss caused by magnetic fringe fields for a linac in a linac-MR system depends on the effectiveness of its magnetic shielding. Despite the best efforts to shield the linac from the magnetic fringe fields, some persistent magnetic field is expected which would result in electron beam loss. This investigation showed that the detuning of the waveguide caused by additional electron beam loss in persistent magnetic fields is not a concern.

A theoretical model for the production of Ac-225 for cancer therapy by photon-induced transmutation of Ra-226.

PubMed

Melville, G; Fan Liu, Sau; Allen, B J

2006-09-01

Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. We are investigating the reduction of radium by transmutation on a small scale by bombarding Ra-226 with high-energy photons from a medical linear accelerator (linac) to produce Ra-225, which subsequently decays to Ac-225, which can be used as a generator to produce Bi-213 for use in 'targeted alpha therapy' for cancer. This paper examines the possibility of producing Ac-225 with a linac using an accurate theoretical model in which the bremsstrahlung photon spectrum at 18 MV linac electron energy is convoluted with the corresponding photonuclear cross sections of Ra-226. The total integrated yield can then be obtained and is compared with a computer simulation. This study shows that at 18 MV, the photonuclear reaction on Ra-226 can produce low activities of Ac-225 with a linac. However, a high power linac with high current, pulse length and frequency is needed to produce practical amounts of Ac-225 and a useful reduction of Ra-226.

Image quality and stability of image-guided radiotherapy (IGRT) devices: A comparative study.

PubMed

Stock, Markus; Pasler, Marlies; Birkfellner, Wolfgang; Homolka, Peter; Poetter, Richard; Georg, Dietmar

2009-10-01

Our aim was to implement standards for quality assurance of IGRT devices used in our department and to compare their performances with that of a CT simulator. We investigated image quality parameters for three devices over a period of 16months. A multislice CT was used as a benchmark and results related to noise, spatial resolution, low contrast visibility (LCV) and uniformity were compared with a cone beam CT (CBCT) at a linac and simulator. All devices performed well in terms of LCV and, in fact, exceeded vendor specifications. MTF was comparable between CT and linac CBCT. Integral nonuniformity was, on average, 0.002 for the CT and 0.006 for the linac CBCT. Uniformity, LCV and MTF varied depending on the protocols used for the linac CBCT. Contrast-to-noise ratio was an average of 51% higher for the CT than for the linac and simulator CBCT. No significant time trend was observed and tolerance limits were implemented. Reasonable differences in image quality between CT and CBCT were observed. Further research and development are necessary to increase image quality of commercially available CBCT devices in order for them to serve the needs for adaptive and/or online planning.

Calculation of Nuclear Particles Production at High-Energy Photon Beams from a Linac Operating at 6, 10 and 15 MV.

PubMed

Marchesini, Renato; Bettega, Daniela; Calzolari, Paola; Pignoli, Emanuele

2017-05-01

Production of photonuclear particles in a tissue-equivalent medium has been calculated for linacs at 6, 10 and 15 MV from Varian TrueBeam. Based on the knowledge of bremsstrahlung fluence spectra and linac photon beam parameters, numerical integration was performed on the cross sections for photoparticle production of the constituent elements of tissue (2H,12C,13C,16O,17O,18O,14N,15N). At 15 MV, at the depth of photon maximum dose, the total absorbed dose due to neutrons, protons, alphas and residual nuclei from photon reactions in tissue (5.5E-05 Gy per Gy of photons) is comparable to that due to neutrons from accelerator head. Results reasonably agree with data reported in the literature using Monte Carlo models simulating linac head components. This work suggests a simple method to estimate the dose contributed by the photon-induced nuclear particles for high-energy photon beams produced by linacs in use, as it might be relevant for late stochastic effects. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Dark current and radiation shielding studies for the ILC main linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mokhov, Nikolai V.; Rakhno, I. L.; Solyak, N. A.

2016-12-05

Electrons of dark current (DC), generated in high-gradient superconducting RF cavities (SRF) due to field emission, can be accelerated up to very high energies—19 GeV in the case of the International Linear Collider (ILC) main linac—before they are removed by focusing and steering magnets. Electromagnetic and hadron showers generated by such electrons can represent a significant radiation threat to the linac equipment and personnel. In our study, an operational scenario is analysed which is believed can be considered as the worst case scenario for the main linac regarding the DC contribution to the radiation environment in the main linac tunnel.more » A detailed modelling is performed for the DC electrons which are emitted from the surface of the SRF cavities and can be repeatedly accelerated in the high-gradient fields in many SRF cavities. Results of MARS15 Monte Carlo calculations, performed for the current main linac tunnel design, reveal that the prompt dose design level of 25 μSv/hr in the service tunnel can be provided by a 2.3-m thick concrete wall between the main and service ls.« less

Field characteristics of an alvarez-type linac structure having chain-like electrode array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Odera, M.; Goto, A.; Hemmi, M.

1985-10-01

A chain-like electrode configuration in an Alvarez-type linac cavity was studied by models. The structure has been devised to get a moderate shunt impedance together with simplicity of operation, in ion velocity region of more than a few percent of that of light by incorporating focusing scheme by high frequency quadrupolar fields into an TM-010 accelerating field of an Alvarez linac. It has a chain-like electrode array instead of drift tubes containing quadrupole lenses for ordinary linacs. The chain-like electrode structure generates along its central axis, high frequency acceleration and focusing fields alternately, separating the acceleration and focusing functions inmore » space. The separation discriminates this structure from spatially uniform acceleration and focusing scheme of the RFQs devised by Kapchinsky and Teplyakov. It gives beam acceleration effects different from those by conventional linacs and reveals possibility of getting a high acceleration efficiency. Resonant frequency spectrum was found relatively simple by measurements on high frequency models. Separation of unwanted modes from the TM-010 acceleration mode is large; a few 10 MHz, at least. Tilt of the acceleration field is not very sensitive to pertubation in gap capacitance for the TM-010 mode.« less

Advanced photoinjector experiment photogun commissioning results

NASA Astrophysics Data System (ADS)

Sannibale, F.; Filippetto, D.; Papadopoulos, C. F.; Staples, J.; Wells, R.; Bailey, B.; Baptiste, K.; Corlett, J.; Cork, C.; De Santis, S.; Dimaggio, S.; Doolittle, L.; Doyle, J.; Feng, J.; Garcia Quintas, D.; Huang, G.; Huang, H.; Kramasz, T.; Kwiatkowski, S.; Lellinger, R.; Moroz, V.; Norum, W. E.; Padmore, H.; Pappas, C.; Portmann, G.; Vecchione, T.; Vinco, M.; Zolotorev, M.; Zucca, F.

2012-10-01

The Advanced Photoinjector Experiment (APEX) at the Lawrence Berkeley National Laboratory is dedicated to the development of a high-brightness high-repetition rate (MHz-class) electron injector for x-ray free-electron laser (FEL) and other applications where high repetition rates and high brightness are simultaneously required. The injector is based on a new concept rf gun utilizing a normal-conducting (NC) cavity resonating in the VHF band at 186 MHz, and operating in continuous wave (cw) mode in conjunction with high quantum efficiency photocathodes capable of delivering the required charge at MHz repetition rates with available laser technology. The APEX activities are staged in three phases. In phase 0, the NC cw gun is built and tested to demonstrate the major milestones to validate the gun design and performance. Also, starting in phase 0 and continuing in phase I, different photocathodes are tested at the gun energy and at full repetition rate for validating candidate materials to operate in a high-repetition rate FEL. In phase II, a room-temperature pulsed linac is added for accelerating the beam at several tens of MeV to reduce space charge effects and allow the measurement of the brightness of the beam from the gun when integrated in an injector scheme. The installation of the phase 0 beam line and the commissioning of the VHF gun are completed, phase I components are under fabrication, and initial design and specification of components and layout for phase II are under way. This paper presents the phase 0 commissioning results with emphasis on the experimental milestones that have successfully demonstrated the APEX gun capability of operating at the required performance.

Micro-SHINE Uranyl Sulfate Irradiations at the Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Youker, Amanda J.; Kalensky, Michael; Chemerisov, Sergey

2016-08-01

Peroxide formation due to water radiolysis in a uranyl sulfate solution is a concern for the SHINE Medical Technologies process in which Mo-99 is generated from the fission of dissolved low enriched uranium. To investigate the effects of power density and fission on peroxide formation and uranyl-peroxide precipitation, uranyl sulfate solutions were irradiated using a 50-MeV electron linac as part of the micro-SHINE experimental setup. Results are given for uranyl sulfate solutions with both high and low enriched uranium irradiated at different linac powers.

Beam position monitor for energy recovered linac beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powers, Thomas; Evtushenko, Pavel

A method of determining the beam position in an energy recovered linac (ERL). The method makes use of in phase and quadrature (I/Q) demodulation techniques to separate the pickup signal generated by the electromagnetic fields generated by the first and second pass beam in the energy recovered linac. The method includes using analog or digital based I/Q demodulation techniques in order to measure the relative amplitude of the signals from a position sensitive beam pickup such as a button, strip line or microstripline beam position monitor.

Technical Note: Development and performance of a software tool for quality assurance of online replanning with a conventional Linac or MR-Linac.

PubMed

Chen, Guang-Pei; Ahunbay, Ergun; Li, X Allen

2016-04-01

To develop an integrated quality assurance (QA) software tool for online replanning capable of efficiently and automatically checking radiation treatment (RT) planning parameters and gross plan quality, verifying treatment plan data transfer from treatment planning system (TPS) to record and verify (R&V) system, performing a secondary monitor unit (MU) calculation with or without a presence of a magnetic field from MR-Linac, and validating the delivery record consistency with the plan. The software tool, named ArtQA, was developed to obtain and compare plan and treatment parameters from both the TPS and the R&V system database. The TPS data are accessed via direct file reading and the R&V data are retrieved via open database connectivity and structured query language. Plan quality is evaluated with both the logical consistency of planning parameters and the achieved dose-volume histograms. Beams in between the TPS and R&V system are matched based on geometry configurations. To consider the effect of a 1.5 T transverse magnetic field from MR-Linac in the secondary MU calculation, a method based on modified Clarkson integration algorithm was developed and tested for a series of clinical situations. ArtQA has been used in their clinic and can quickly detect inconsistencies and deviations in the entire RT planning process. With the use of the ArtQA tool, the efficiency for plan check including plan quality, data transfer, and delivery check can be improved by at least 60%. The newly developed independent MU calculation tool for MR-Linac reduces the difference between the plan and calculated MUs by 10%. The software tool ArtQA can be used to perform a comprehensive QA check from planning to delivery with conventional Linac or MR-Linac and is an essential tool for online replanning where the QA check needs to be performed rapidly.

Technical Note: Development and performance of a software tool for quality assurance of online replanning with a conventional Linac or MR-Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Guang-Pei, E-mail: gpchen@mcw.edu; Ahunbay, Ergun; Li, X. Allen

Purpose: To develop an integrated quality assurance (QA) software tool for online replanning capable of efficiently and automatically checking radiation treatment (RT) planning parameters and gross plan quality, verifying treatment plan data transfer from treatment planning system (TPS) to record and verify (R&V) system, performing a secondary monitor unit (MU) calculation with or without a presence of a magnetic field from MR-Linac, and validating the delivery record consistency with the plan. Methods: The software tool, named ArtQA, was developed to obtain and compare plan and treatment parameters from both the TPS and the R&V system database. The TPS data aremore » accessed via direct file reading and the R&V data are retrieved via open database connectivity and structured query language. Plan quality is evaluated with both the logical consistency of planning parameters and the achieved dose–volume histograms. Beams in between the TPS and R&V system are matched based on geometry configurations. To consider the effect of a 1.5 T transverse magnetic field from MR-Linac in the secondary MU calculation, a method based on modified Clarkson integration algorithm was developed and tested for a series of clinical situations. Results: ArtQA has been used in their clinic and can quickly detect inconsistencies and deviations in the entire RT planning process. With the use of the ArtQA tool, the efficiency for plan check including plan quality, data transfer, and delivery check can be improved by at least 60%. The newly developed independent MU calculation tool for MR-Linac reduces the difference between the plan and calculated MUs by 10%. Conclusions: The software tool ArtQA can be used to perform a comprehensive QA check from planning to delivery with conventional Linac or MR-Linac and is an essential tool for online replanning where the QA check needs to be performed rapidly.« less

Peripheral dose measurements with diode and thermoluminescence dosimeters for intensity modulated radiotherapy delivered with conventional and un-conventional linear accelerator

PubMed Central

Kinhikar, Rajesh; Gamre, Poonam; Tambe, Chandrashekhar; Kadam, Sudarshan; Biju, George; Suryaprakash; Magai, C. S.; Dhote, Dipak; Shrivastava, Shyam; Deshpande, Deepak

2013-01-01

The objective of this paper was to measure the peripheral dose (PD) with diode and thermoluminescence dosimeter (TLD) for intensity modulated radiotherapy (IMRT) with linear accelerator (conventional LINAC), and tomotherapy (novel LINAC). Ten patients each were selected from Trilogy dual-energy and from Hi-Art II tomotherapy. Two diodes were kept at 20 and 25 cm from treatment field edge. TLDs (LiF:MgTi) were also kept at same distance. TLDs were also kept at 5, 10, and 15 cm from field edge. The TLDs were read with REXON reader. The readings at the respective distance were recorded for both diode and TLD. The PD was estimated by taking the ratio of measured dose at the particular distance to the prescription dose. PD was then compared with diode and TLD for LINAC and tomotherapy. Mean PD for LINAC with TLD and diode was 2.52 cGy (SD 0.69), 2.07 cGy (SD 0.88) at 20 cm, respectively, while at 25 cm, it was 1.94 cGy (SD 0.58) and 1.5 cGy (SD 0.75), respectively. Mean PD for tomotherapy with TLD and diode was 1.681 cGy SD 0.53) and 1.58 (SD 0.44) at 20 cm, respectively. The PD was 1.24 cGy (SD 0.42) and 1.088 cGy (SD 0.35) at 25 cm, respectively, for tomotherapy. Overall, PD from tomotherapy was found lower than LINAC by the factor of 1.2-1.5. PD measurement is essential to find out the potential of secondary cancer. PD for both (conventional LINAC) and novel LINACs (tomotherapy) were measured and compared with each other. The comparison of the values for PD presented in this work and those published in the literature is difficult because of the different experimental conditions. The diode and TLD readings were reproducible and both the detector readings were comparable. PMID:23531765

Lung density change after SABR: A comparative study between tri-Co-60 magnetic resonance-guided system and linear accelerator

PubMed Central

Kim, Eunji; Wu, Hong-Gyun; Park, Jong Min; Kim, Jung-in; Kim, Hak Jae

2018-01-01

Radiation-induced lung damage is an important treatment-related toxicity after lung stereotactic ablative radiotherapy (SABR). After implementing a tri-60Co magnetic-resonance image guided system, ViewRayTM, we compared the associated early radiological lung density changes to those associated with a linear accelerator (LINAC). Eight patients treated with the tri-60Co system were matched 1:1 with patients treated with LINAC. Prescription doses were 52 Gy or 60 Gy in four fractions, and lung dose-volumetric parameters were calculated from each planning system. The first two follow-up computed tomography (CT) were co-registered with the planning CT through deformable registration software, and lung density was measured by isodose levels. Tumor size was matched between the two groups, but the planning target volume of LINAC was larger than that of the tri-60Co system (p = 0.036). With regard to clinically relevant dose-volumetric parameters in the lungs, the ipsilateral lung mean dose, V10Gy and V20Gy were significantly poorer in tri-60Co plans compared to LINAC plans (p = 0.012, 0.036, and 0.017, respectively). Increased lung density was not observed in the first follow-up scan compared to the planning scan. A significant change of lung density was shown in the second follow-up scan and there was no meaningful difference between the tri-60Co system and LINAC for all dose regions. In addition, no patient developed clinical radiation pneumonitis until the second follow-up scan. Therefore, there was no significant difference in the early radiological lung damage between the tri-60Co system and LINAC for lung SABR despite of the inferior plan quality of the tri-60Co system compared to that of LINAC. Further studies with a longer follow-up period are needed to confirm our findings. PMID:29608606

TH-AB-BRA-12: Experimental Results From the First High-Field Inline MRI-Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keall, P; Dong, B; Zhang, K

Purpose: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid MRI-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-Linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-Linac system. This work describes our experimental results from the first high-field inline MRI-Linac. Methods: A 1.5 Tesla magnet (Sonata, Siemens) was located in a purpose built RF cage enabling shielding from and close proximity to a linear accelerator with inline orientation. A portable linear acceleratormore » (Linatron, Varian) was installed together with a multi-leaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-Linac experiments was performed to investigate: (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom; (2) the noise as a function of beam state measured using a 6-channel surface coil array and; (3) electron focusing measured using GafChromic film. Results: (1) The macropodine phantom image quality with the beam on was almost identical to that with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background noise when the radiation beam was on. (3) Film measurements demonstrated electron focusing occurring at the center of the radiation field. Conclusion: The first high-field MRI-Linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field in-line MRI-Linac and study a number of the technical challenges and solutions. Supported by the Australian National Health and Medical Research Council, the Australian Research Council, the Australian Cancer Research Foundation and the Health and Hospitals Fund.« less

Technical Note: Experimental results from a prototype high-field inline MRI-linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liney, G. P., E-mail: gary.liney@sswahs.nsw.gov.au

Purpose: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid magnetic resonance imaging (MRI)-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-linac system. This work describes results from a prototype experimental system to demonstrate the feasibility of a high field inline MR-linac. Methods: The magnet is a 1.5 T MRI system (Sonata, Siemens Healthcare) was located in a purpose built radiofrequency (RF) cage enablingmore » shielding from and close proximity to a linear accelerator with inline (and future perpendicular) orientation. A portable linear accelerator (Linatron, Varian) was installed together with a multileaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-linac experiments was performed to investigate (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom; (2) the noise as a function of beam state measured using a 6-channel surface coil array; and (3) electron contamination effects measured using Gafchromic film and an electronic portal imaging device (EPID). Results: (1) Image quality was unaffected by the radiation beam with the macropodine phantom image with the beam on being almost identical to the image with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background intensity when the radiation beam was on. (3) Film and EPID measurements demonstrated electron focusing occurring along the centerline of the magnet axis. Conclusions: A proof-of-concept high-field MRI-linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field inline MRI-linac and study a number of the technical challenges and solutions.« less

Analysis of energy resolution in the KURRI-LINAC pulsed neutron facility

NASA Astrophysics Data System (ADS)

Sano, Tadafumi; Hori, Jun-ichi; Takahashi, Yoshiyuki; Yashima, Hiroshi; Lee, Jaehong; Harada, Hideo

2017-09-01

In this study, we carried out Monte Carlo simulations to obtain the energy resolution of the neutron flux for TOF measurements in the KURRI-LINAC pulsed neutron facility. The simulation was performed on the moderated neutron flux from the pac-man type moderator at the energy range from 0.1 eV to 10 keV. As the result, we obtained the energy resolutions (ΔE/E) of about 0.7% to 1.3% between 0.1 eV to 10 keV. The energy resolution obtained from Monte Carlo simulation agreed with the resolution using the simplified evaluation formula. In addition, we compared the energy resolution among KURRI-LINAC and other TOF facilities, the energy dependency of the energy resolution with the pac-man type moderator in KURRI-LINAC was similar to the J-PARC ANNRI for the single-bunch mode.

Calculation of Dose for Skyshine Radiation From a 45 MeV Electron LINAC

NASA Astrophysics Data System (ADS)

Hori, M.; Hikoji, M.; Takahashi, H.; Takahashi, K.; Kitaichi, M.; Sawamura, S.; Nojiri, I.

1996-11-01

Dose estimation for skyshine plays an important role in the evaluation of the environment around nuclear facilities. We performed calculations for the skyshine radiation from a Hokkaido University 45 MeV linear accelerator using a general purpose user's version of the EGS4 Monte Carlo Code. To verify accuracy of the code, the simulation results have been compared with our experimental results, in which a gated counting method was used to measure low-level pulsed leakage radiation. In experiment, measurements were carried out up to 600 m away from the LINAC. The simulation results are consistent with the experimental values at the distance between 100 and 400 m from the LINAC. However, agreements of both results up to 100 m from the LINAC are not as good because of the simplification of geometrical modeling in the simulation. It could be said that it is useful to apply this version to the calculation for skyshine.

Notes on the design of experiments and beam diagnostics with synchrotron light detected by a gated photomultiplier for the Fermilab superconducting electron linac and for the Integrable Optics Test Accelerator (IOTA)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stancari, Giulio; Romanov, Aleksandr; Ruan, Jinhao

We outline the design of beam experiments for the electron linac at the Fermilab Accelerator Science and Technology (FAST) facility and for the Integrable Optics Test Accelerator (IOTA), based on synchrotron light emitted by the electrons in bend dipoles, detected with gated microchannel-plate photomultipliers (MCP-PMTs). The system can be used both for beam diagnostics (e.g., beam intensity with full dynamic range, turn-by-turn beam vibrations, etc.) and for scientific experiments, such as the direct observation of the time structure of the radiation emitted by single electrons in a storage ring. The similarity between photon pulses and spectrum at the downstream endmore » of the electron linac and in the IOTA ring allows one to test the apparatus during commissioning of the linac.« less

Development and performance test of a new high power RF window in S-band PLS-II LINAC

NASA Astrophysics Data System (ADS)

Hwang, Woon-Ha; Joo, Young-Do; Kim, Seung-Hwan; Choi, Jae-Young; Noh, Sung-Ju; Ryu, Ji-Wan; Cho, Young-Ki

2017-12-01

A prototype of RF window was developed in collaboration with the Pohang Accelerator Laboratory (PAL) and domestic companies. High power performance tests of the single RF window were conducted at PAL to verify the operational characteristics for its application in the Pohang Light Source-II (PLS-II) linear accelerator (Linac). The tests were performed in the in-situ facility consisting of a modulator, klystron, waveguide network, vacuum system, cooling system, and RF analyzing equipment. The test results with Stanford linear accelerator energy doubler (SLED) have shown no breakdown up to 75 MW peak power with 4.5 μs RF pulse width at a repetition rate of 10 Hz. The test results with the current operation level of PLS-II Linac confirm that the RF window well satisfies the criteria for PLS-II Linac operation.

A Particle-in-cell scheme of the RFQ in the SSC-Linac

NASA Astrophysics Data System (ADS)

Xiao, Chen; He, Yuan; Lu, Yuan-Rong; Yuri, Batygin; Yin, Ling; Wang, Zhi-Jun; Yuan, You-Jin; Liu, Yong; Chang, Wei; Du, Xiao-Nan; Wang, Zhi; Xia, Jia-Wen

2010-11-01

A 52 MHz Radio Frequency Quadrupole (RFQ) linear accelerator (linac) is designed to serve as an initial structure for the SSC-Linac system (injector into Separated Sector Cyclotron). The designed injection and output energy are 3.5 keV/u and 143 keV/u, respectively. The beam dynamics in this RFQ have been studied using a three-dimensional Particle-In-Cell (PIC) code BEAMPATH. Simulation results show that this RFQ structure is characterized by stable values of beam transmission efficiency (at least 95%) for both zero-current mode and the space charge dominated regime. The beam accelerated in the RFQ has good quality in both transverse and longitudinal directions, and could easily be accepted by Drift Tube Linac (DTL). The effect of the vane error and that of the space charge on the beam parameters have been studied as well to define the engineering tolerance for RFQ vane machining and alignment.

Beam dynamics in THz dielectric-loaded waveguides for the AXSIS project

NASA Astrophysics Data System (ADS)

Vinatier, T.; Assmann, R. W.; Dorda, U.; Lemery, F.; Marchetti, B.

2017-07-01

In this paper, we investigate with ASTRA simulations the beam dynamics in dielectric-loaded waveguides driven by THz pulses, used as linac structure for the AXSIS project. We show that the bunch properties at the linac exit are very sensitive to the phase velocity of the THz pulse and are limited by the strong phase slippage of the bunch respective to it. We also show that the bunch properties are optimized when low frequencies (< 300 GHz) are used inside the linac, and that the longitudinal focal point can be put several tens of cm away from the linac exit thanks to ballistic bunching. However, a strong asymmetry in the bunch transverse sizes remains for which a solution is still to be found. Work supported by the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement n. 609920.

Collective electron driven linac for high energy physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seeman, J.T.

1983-08-01

A linac design is presented in which an intense ultrarelativistic electron bunch is used to excite fields in a series of cavities and accelerate charged particles. The intense electron bunch is generated in a simple storage ring to have the required transverse and longitudinal dimensions. The bunch is then transferred to the linac. The linac structure can be inexpensively constructed of spacers and washers. The fields in the cells resulting from the bunch passage are calculated using the program BCI. The results show that certain particles within the driving bunch and also trailing particles of any sign charge can bemore » accelerated. With existing electron storage rings, accelerating gradients greater than 16 MV/m are possible. Examples of two accelerators are given: a 30 GeV electron/positron accelerator useful as an injector for a high energy storage ring and 2) a 110 GeV per beam electron-positron collider.« less

Skin dose in longitudinal and transverse linac-MRIs using Monte Carlo and realistic 3D MRI field models.

PubMed

Keyvanloo, A; Burke, B; Warkentin, B; Tadic, T; Rathee, S; Kirkby, C; Santos, D M; Fallone, B G

2012-10-01

The magnetic fields of linac-MR systems modify the path of contaminant electrons in photon beams, which alters patient skin dose. To accurately quantify the magnitude of changes in skin dose, the authors use Monte Carlo calculations that incorporate realistic 3D magnetic field models of longitudinal and transverse linac-MR systems. Finite element method (FEM) is used to generate complete 3D magnetic field maps for 0.56 T longitudinal and transverse linac-MR magnet assemblies, as well as for representative 0.5 and 1.0 T Helmholtz MRI systems. EGSnrc simulations implementing these 3D magnetic fields are performed. The geometry for the BEAMnrc simulations incorporates the Varian 600C 6 MV linac, magnet poles, the yoke, and the magnetic shields of the linac-MRIs. Resulting phase-space files are used to calculate the central axis percent depth-doses in a water phantom and 2D skin dose distributions for 70 μm entrance and exit layers using DOSXYZnrc. For comparison, skin doses are also calculated in the absence of magnetic field, and using a 1D magnetic field with an unrealistically large fringe field. The effects of photon field size, air gap (longitudinal configuration), and angle of obliquity (transverse configuration) are also investigated. Realistic modeling of the 3D magnetic fields shows that fringe fields decay rapidly and have a very small magnitude at the linac head. As a result, longitudinal linac-MR systems mostly confine contaminant electrons that are generated in the air gap and have an insignificant effect on electrons produced further upstream. The increase in the skin dose for the longitudinal configuration compared to the zero B-field case varies from ∼1% to ∼14% for air gaps of 5-31 cm, respectively. (All dose changes are reported as a % of D(max).) The increase is also field-size dependent, ranging from ∼3% at 20 × 20 cm(2) to ∼11% at 5 × 5 cm(2). The small changes in skin dose are in contrast to significant increases that are calculated for the unrealistic 1D magnetic field. For the transverse configuration, the entrance skin dose is equal or smaller than that of the zero B-field case for perpendicular beams. For a 10 × 10 cm(2) oblique beam the transverse magnetic field decreases the entry skin dose for oblique angles less than ±20° and increases it by no more than 10% for larger angles up to ±45°. The exit skin dose is increased by 42% for a 10 × 10 cm(2) perpendicular beam, but appreciably drops and approaches the zero B-field case for large oblique angles of incidence. For longitudinal linac-MR systems only a small increase in the entrance skin dose is predicted, due to the rapid decay of the realistic magnetic fringe fields. For transverse linac-MR systems, changes to the entrance skin dose are small for most scenarios. For the same geometry, on the exit side a fairly large increase is observed for perpendicular beams, but significantly drops for large oblique angles of incidence. The observed effects on skin dose are not expected to limit the application of linac-MR systems in either the longitudinal or transverse configuration.

Frequency choice of eRHIC SRF linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, W.; Ben-Zvi, I.; Roser, T.

2016-01-05

eRHIC is a FFAG lattice-based multipass ERL. The eRHIC SRF linac has been decided to change from 422 MHz 5-cell cavity to 647 MHz 5-cell cavity. There are several considerations affecting the frequency choice for a high-current multipass-ERL: the beam structure, bunch length, energy spread, beam-break-up (BBU) threshold, SRF loss considerations. Beyond the physics considerations, cost and complexity or risk is an important consideration for the frequency choice, especially when we are designing a machine to be built in a few years. Although there are some benefits of using a 422 MHz cavity for eRHIC ERL, however, there are somemore » very critical drawbacks, including lack of facilities to fabricate a 422 MHz 5-cell cavity, very few facilities to process such a cavity and no existing facility to test the cavity anywhere. As the cavity size is big and its weight is large, it is difficult to handle it during fabrication, processing and testing, and no one has experience in this area. As the cavity size is large, the cryomodule becomes big as well. All of these considerations drive the risk of building eRHIC ERL with 422 MHz cavities to a very high level. Therefore, a decision was made to change the frequency of main linac to be 647 MHz 5-cell cavities. This note will compare these two linacs: 422MHz 5-cell cavity linac and 647Mz 5-cell cavity SRF linac, from both practical point of view and physics point of view.« less

Intensity-modulated radiation therapy (IMRT) with different combinations of treatment-planning systems and linacs: issues and how to detect them.

PubMed

Dobler, Barbara; Lorenz, Friedlieb; Wertz, Hansjörg; Polednik, Martin; Wolff, Dirk; Steil, Volker; Lohr, Frank; Wenz, Frederik

2006-08-01

To compare different combinations of intensity-modulated radiation therapy (IMRT) system components with regard to quality assurance (QA), especially robustness against malfunctions and dosimetry. Three different treatment-planning systems (TPS), two types of linacs and three multileaf collimator (MLC) types were compared: commissioning procedures were performed for the combination of the TPS Corvus 5.0 (Nomos) and KonRad v2.1.3 (Siemens OCS) with the linacs KD2 (Siemens) and Synergy (Elekta). For PrecisePLAN 2.03 (Elekta) measurements were performed for Elekta Synergy only. As record and verify (R&V) system Multi-Access v7 (IMPAC) was used. The use of the serial tomotherapy system Peacock (Nomos) was investigated in combination with the Siemens KD2 linac. In the comparison of calculated to measured dose, problems were encountered for the combination of KonRad and Elekta MLC as well as for the Peacock system. Multi-Access failed to assign the collimator angle correctly for plans with multiple collimator angles per beam. Communication problems of Multi-Access with both linacs were observed, resulting in incorrect recording of the treatment. All reported issues were addressed by the manufacturers. For the commissioning of IMRT systems, the whole chain from the TPS to the linac has to be investigated. Components that passed the commissioning in another clinical environment can have severe malfunctions when used in a new environment. Therefore, not only single components but the whole chain from planning to delivery has to be evaluated in commissioning and checked regularly for QA.

A microcosting study of microsurgery, LINAC radiosurgery, and gamma knife radiosurgery in meningioma patients

PubMed Central

van Putten, Erik; Nijdam, Wideke M.; Hanssens, Patrick; Beute, Guus N.; Nowak, Peter J.; Dirven, Clemens M.; Hakkaart-van Roijen, Leona

2010-01-01

The aim of the present study is to determine and compare initial treatment costs of microsurgery, linear accelerator (LINAC) radiosurgery, and gamma knife radiosurgery in meningioma patients. Additionally, the follow-up costs in the first year after initial treatment were assessed. Cost analyses were performed at two neurosurgical departments in The Netherlands from the healthcare providers’ perspective. A total of 59 patients were included, of whom 18 underwent microsurgery, 15 underwent LINAC radiosurgery, and 26 underwent gamma knife radiosurgery. A standardized microcosting methodology was employed to ensure that the identified cost differences would reflect only actual cost differences. Initial treatment costs, using equipment costs per fraction, were €12,288 for microsurgery, €1,547 for LINAC radiosurgery, and €2,412 for gamma knife radiosurgery. Higher initial treatment costs for microsurgery were predominantly due to inpatient stay (€5,321) and indirect costs (€4,350). LINAC and gamma knife radiosurgery were equally expensive when equipment was valued per treatment (€2,198 and €2,412, respectively). Follow-up costs were slightly, but not significantly, higher for microsurgery compared with LINAC and gamma knife radiosurgery. Even though initial treatment costs were over five times higher for microsurgery compared with both radiosurgical treatments, our study gives indications that the relative cost difference may decrease when follow-up costs occurring during the first year after initial treatment are incorporated. This reinforces the need to consider follow-up costs after initial treatment when examining the relative costs of alternative treatments. PMID:20526795

Cost analysis of Gamma Knife stereotactic radiosurgery.

PubMed

Griffiths, Alison; Marinovich, Luke; Barton, Michael B; Lord, Sarah J

2007-01-01

Stereotactic radiosurgery (SRS) is used to treat intracranial lesions and vascular malformations as an addition or replacement to whole brain radiotherapy and microsurgery. SRS can be delivered by hardware and software appended to standard linear accelerators (Linacs) or by dedicated systems such as Gamma Knife, which has been proposed as a more accurate and user friendly technology. Internationally, dedicated systems have been funded, despite limitations in evidence. However, some countries including Australia have not recommended additional reimbursement for dedicated systems. This study compares the costs of Linac radiosurgery with Gamma Knife radiosurgery. Due to limited evidence on comparative effects, the economic analysis was restricted to a cost evaluation. The base-case analysis assumed a modified Linac was used only to treat SRS patients. However, because a modified Linac could be used to treat other radiotherapy patients, a second analysis assumed spare time was used to meet other radiotherapy needs, and Linac capital costs were apportioned according to SRS use. The incremental cost of Gamma Knife versus a modified Linac was estimated as AU$209 per patient. This result is sensitive to variations in assumptions. A second analysis proportioning capital costs according to SRS use showed that Gamma Knife may cost up to AU$1673 more per patient. Gamma Knife may be cost competitive only if demand for SRS services is high enough to fully use equipment working time. However, given low patient demand and competing radiotherapy needs, Gamma Knife appears more costly and further evidence of survival or quality of life advantages may be required to justify reimbursement.

Development and application of compact and on-chip electron linear accelerators for dynamic tracking cancer therapy and DNA damage/repair analysis

NASA Astrophysics Data System (ADS)

Uesaka, M.; Demachi, K.; Fujiwara, T.; Dobashi, K.; Fujisawa, H.; Chhatkuli, R. B.; Tsuda, A.; Tanaka, S.; Matsumura, Y.; Otsuki, S.; Kusano, J.; Yamamoto, M.; Nakamura, N.; Tanabe, E.; Koyama, K.; Yoshida, M.; Fujimori, R.; Yasui, A.

2015-06-01

We are developing compact electron linear accelerators (hereafter linac) with high RF (Radio Frequency) frequency (9.3 GHz, wavelength 32.3 mm) of X-band and applying to medicine and non-destructive testing. Especially, potable 950 keV and 3.95 MeV linac X-ray sources have been developed for on-site transmission testing at several industrial plants and civil infrastructures including bridges. 6 MeV linac have been made for pinpoint X-ray dynamic tracking cancer therapy. The length of the accelerating tube is ∼600 mm. The electron beam size at the X-ray target is less than 1 mm and X-ray spot size at the cancer is less than 3 mm. Several hardware and software are under construction for dynamic tracking therapy for moving lung cancer. Moreover, as an ultimate compact linac, we are designing and manufacturing a laser dielectric linac of ∼1 MeV with Yr fiber laser (283 THz, wavelength 1.06 pm). Since the wavelength is 1.06 μm, the length of one accelerating strcture is tens pm and the electron beam size is in sub-micro meter. Since the sizes of cell and nuclear are about 10 and 1 μm, respectively, we plan to use this “On-chip” linac for radiation-induced DNA damage/repair analysis. We are thinking a system where DNA in a nucleus of cell is hit by ∼1 μm electron or X-ray beam and observe its repair by proteins and enzymes in live cells in-situ.

Intern Programs | Tours

Science.gov Websites

accelerated through the Linac (Linear Accelerator) to an energy of 400 MeV. The Linac consists of two main of linear accelerators at NML ! Meet at the South entrance to NML (New Muon Lab) Building. 1:00 PM 1

A pulsed electron gun for the Plane Wave Transformer Linac

NASA Astrophysics Data System (ADS)

Mahadevan, S.; Gandhi, M. L.; Nandedkar, R. V.

2003-01-01

A pulsed diode electron gun delivering 500 mA current at 40 kV is described. The gun geometry is optimized using the Electron Trajectory Program EGUN at higher scaling factors by choosing the closest converging starting surface. The effect of an annular gap between cathode and focusing electrode on beam behaviour is compensated by using a suitable focusing electrode. The estimated perveance is 0.065 μperv and the normalized emittance is within 5 π mm mrad. The variation in current density at the cathode has been limited to within 10% across the face of the cathode. Salient features of the pulsed power supply and an insight of its interconnection with the gun are presented. The current measured at the Faraday cup is in agreement with the designed perveance.

Shielding design for the front end of the CERN SPL.

PubMed

Magistris, Matteo; Silari, Marco; Vincke, Helmut

2005-01-01

CERN is designing a 2.2-GeV Superconducting Proton Linac (SPL) with a beam power of 4 MW, to be used for the production of a neutrino superbeam. The SPL front end will initially accelerate 2 x 10(14) negative hydrogen ions per second up to an energy of 120 MeV. The FLUKA Monte Carlo code was employed for shielding design. The proposed shielding is a combined iron-concrete structure, which also takes into consideration the required RF wave-guide ducts and access labyrinths to the machine. Two beam-loss scenarios were investigated: (1) constant beam loss of 1 Wm(-1) over the whole accelerator length and (2) full beam loss occurring at various locations. A comparison with results based on simplified approaches is also presented.

The MRI-Linear Accelerator Consortium: Evidence-Based Clinical Introduction of an Innovation in Radiation Oncology Connecting Researchers, Methodology, Data Collection, Quality Assurance, and Technical Development.

PubMed

Kerkmeijer, Linda G W; Fuller, Clifton D; Verkooijen, Helena M; Verheij, Marcel; Choudhury, Ananya; Harrington, Kevin J; Schultz, Chris; Sahgal, Arjun; Frank, Steven J; Goldwein, Joel; Brown, Kevin J; Minsky, Bruce D; van Vulpen, Marco

2016-01-01

An international research consortium has been formed to facilitate evidence-based introduction of MR-guided radiotherapy (MR-linac) and to address how the MR-linac could be used to achieve an optimized radiation treatment approach to improve patients' survival, local, and regional tumor control and quality of life. The present paper describes the organizational structure of the clinical part of the MR-linac consortium. Furthermore, it elucidates why collaboration on this large project is necessary, and how a central data registry program will be implemented.

Intraoperative radiotherapy using a mobile electron LINAC: a retroperitoneal sarcoma case.

PubMed

Beddar, A Sam; Krishnan, Sunil

2005-01-01

The advent of mobile LINACs for use in intraoperative radiation therapy (IORT) promises to make IORT more accessible than before and easier to deliver to patients undergoing surgery. Although mobile IORT systems have been available since 1999, few treatment centers currently use them. Here, we present the case of a typical patient undergoing IORT for retroperitoneal sarcoma to show how easy these mobile systems are to use and how adaptable they are within the operating room (OR) environment. We also discuss the roles and coordination of multidisciplinary team members during IORT and the feasibility of using mobile LINACs for IORT.

INCREASED UNDERSTANDING OF BEAM LOSSES FROM THE SNS LINAC PROTON EXPERIMENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aleksandrov, Alexander V; Shishlo, Andrei P; Plum, Michael A

Beam loss is a major concern for high power hadron accelerators such as the Spallation Neutron Source (SNS). An unexpected beam loss in the SNS superconducting linac (SCL) was observed during the power ramp up and early operation. Intra-beam-stripping (IBS) loss, in which interactions between H- particles within the accelerated bunch strip the outermost electron, was recently identified as a possible cause of the beam loss. A set of experiments using proton beam acceleration in the SNS linac was conducted, which supports IBS as the primary beam loss mechanism in the SNS SCL.

Image quality and stability of image-guided radiotherapy (IGRT) devices: A comparative study

PubMed Central

Stock, Markus; Pasler, Marlies; Birkfellner, Wolfgang; Homolka, Peter; Poetter, Richard; Georg, Dietmar

2010-01-01

Introduction Our aim was to implement standards for quality assurance of IGRT devices used in our department and to compare their performances with that of a CT simulator. Materials and methods We investigated image quality parameters for three devices over a period of 16 months. A multislice CT was used as a benchmark and results related to noise, spatial resolution, low contrast visibility (LCV) and uniformity were compared with a cone beam CT (CBCT) at a linac and simulator. Results All devices performed well in terms of LCV and, in fact, exceeded vendor specifications. MTF was comparable between CT and linac CBCT. Integral nonuniformity was, on average, 0.002 for the CT and 0.006 for the linac CBCT. Uniformity, LCV and MTF varied depending on the protocols used for the linac CBCT. Contrast-to-noise ratio was an average of 51% higher for the CT than for the linac and simulator CBCT. No significant time trend was observed and tolerance limits were implemented. Discussion Reasonable differences in image quality between CT and CBCT were observed. Further research and development are necessary to increase image quality of commercially available CBCT devices in order for them to serve the needs for adaptive and/or online planning. PMID:19695725

950 keV X-Band Linac For Material Recognition Using Two-Fold Scintillator Detector As A Concept Of Dual-Energy X-Ray System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Kiwoo; Natsui, Takuya; Hirai, Shunsuke

2011-06-01

One of the advantages of applying X-band linear accelerator (Linac) is the compact size of the whole system. That shows us the possibility of on-site system such as the custom inspection system in an airport. As X-ray source, we have developed X-band Linac and achieved maximum X-ray energy 950 keV using the low power magnetron (250 kW) in 2 {mu}s pulse length. The whole size of the Linac system is 1x1x1 m{sup 3}. That is realized by introducing X-band system. In addition, we have designed two-fold scintillator detector in dual energy X-ray concept. Monte carlo N-particle transport (MCNP) code wasmore » used to make up sensor part of the design with two scintillators, CsI and CdWO4. The custom inspection system is composed of two equipments: 950 keV X-band Linac and two-fold scintillator and they are operated simulating real situation such as baggage check in an airport. We will show you the results of experiment which was performed with metal samples: iron and lead as targets in several conditions.« less

Investigation of Microbunching Instabilities in Modern Recirculating Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, Cheng

Particle accelerators are machines to accelerate and store charged particles, such as electrons or protons, to the energy levels for various scientific applications. A collection of charged particles usually forms a particle beam. There are three basic types of particle accelerators: linear accelerators (linac), storage-ring (or circular) accelerators, and recirculating accelerators. In a linac, particles are accelerated and pass through once along a linear or straight beamline. Storage-ring accelerators propel particles around a circular track and repetitively append the energy to the stored beam. The third type, also the most recent one in chronology, the recirculating accelerator, is designed tomore » accelerate the particle beam in a short section of linac, circulate the beam, and then either continue to accelerate for energy boost or decelerate it for energy recovery. The beam properties of a linac machine are set at best by the initial particle sources. For storage rings, the beam equilibria are instead determined by the overall machine design. The modern recirculating machines share with linacs the advantages to both accelerate and preserve the beam with high beam quality, as well as efficiently reuse the accelerating components. The beamline design in such a machine configuration can however be much more complicated than that of linacs. As modern accelerators push toward the high-brightness or high-intensity frontier by demanding particles in a highly charged bunch (about nano-Coulomb per bunch) to concentrate in an ever-decreasing beam phase space (transverse normalized emittance about 1 μm and relative energy spread of the order of 10^-5 in GeV beam energy), the interaction amongst particles via their self-generated electromagnetic fields can potentially lead to coherent instabilities of the beam and thus pose significant challenges to the machine design and operation. In the past decade and a half, microbunching instability (MBI) has been one of the most challenging issues for such high-brightness or high-intensity beam transport, as it would degrade lasing performance in the fourth-generation light sources, reduce cooling efficiency in electron cooling facilities, and compromise the luminosity of colliding beams in lepton or lepton-hadron colliders. The dissertation work will focus on the MBI in modern recirculating electron accelerators. It has been known that the collective interactions, the coherent synchrotron radiation (CSR) and the longitudinal space charge (LSC) forces, can drive MBI. The CSR effect is a collective phenomenon in which the electrons in a curved motion, e.g. a bending dipole, emit radiation at a scale comparable to the micro-bunched structure of the bunch distribution. The LSC effect stems from non-uniformity of the charge distribution, acts as plasma oscillation, and can eventually accumulate an amount of energy modulation when the beam traverses a long section of a beamline. MBI can be seeded by non-uniformity or shot noise of the beam, which originates from granularity of the elementary charge. Through the aforementioned collective effects, the modulation of the bunch sub-structure can be amplified and, once the beam-wave interaction formed a positive feedback, can result in MBI. The problem of MBI has been intensively studied for linac-based facilities and for storage-ring accelerators. However, systematic studies for recirculation machines are still very limited and form a knowledge gap. Because of the much more complicated machine configuration of the recirculating accelerators than that of linacs, the existing MBI analysis needs to be extended to accommodate the high-brightness particle beam transport in modern recirculating accelerators. This dissertation is focused on theoretical investigation of MBI in such machine configuration in the following seven themes: (1) Development and generalization of MBI theory The theoretical formulation has been extended so as to be applicable to a general linear beamline lattice including horizontal and vertical transport bending elements, and beam acceleration or deceleration. These featured generalizations are required for MBI analysis in recirculation accelerators. (2) Construction of CSR impedance models In addition to the steady-state CSR interaction, it has been found that the exit transient effect (or CSR drift) can even result in more serious MBI in high-brightness recirculation arcs. The onedimensional free-space CSR impedances, especially the exit transients, are derived. The steady-state CSR impedance is also extended to non-ultrarelativistic beam energy for MBI analysis of low-energy merger sections in recirculating accelerators. (3) Numerical implementation of the derived semi-analytical formulation This includes the development of a semi-analytical Vlasov solver for MBI analysis, and also benchmarking of the solver against massive particle tracking simulations. (4) Exploration of multistage amplification behavior of CSR microbunching development The CSR-induced MBI acts as an amplifier, which amplifies the sub-bunch modulation of a beam. The amplification is commonly quantified by the amplification gain. A beam transport system can be considered as a cascaded amplifier. Unlike the two-stage amplification of four-dipole bunch compressor chicanes employed in linacs, the recirculation arcs, which are usually constituted by several tens of bending magnets, show a distinguishing feature of up to six-stage microbunching amplification for our example arc lattices. That is, the maximal CSR amplification gain can be proportional to the peak bunch current up to sixth power. A method to compare lattice performance has been developed in terms of gain coefficients, which nearly depend on the lattice properties only. This method has also proven to be an effective way to quantify the current dependence of the maximal (5) Control of CSR MBI in multibend transport or recirculation arcs The existing mitigation schemes of MBI mostly aim to linac-based accelerators and may not be practical to the recirculating accelerator facilities. Thus a set of conditions for suppression of CSR MBI was proposed and examined for example lattices from low (~100 MeV) to high (~1 GeV) energies. (6) Study of more aspects of microbunched structures in beam phase spaces For a cascaded amplifier in circuit electronics, the total amplification gain can be estimated as the product of individual gains. In a beam transport line of an accelerator, the (scalar) gain multiplication was examined and found to under-estimate the overall microbunching amplification. The concept of gain matrix was developed, which includes the density, energy and transverse-longitudinal modulations in a beam phase space, and used to analyze MBI for a proposed recirculating machine. Throughout the gain matrix approach, it reasonably gives the upper limit of spectral MBI gain curves. This extended analysis can be employed to study multi-pass recirculation. (7) Study of MBI for magnetized beams Driven by a recent energy-recovery-linac based cooler design for electron cooling at Jefferson Lab Electron-Ion Collider Project, the generalized theoretical formulation for MBI to a transversely coupled beam has been developed and applied to this study. A magnetized beam in general features non-zero canonical angular momentum, thus considered to be a transversely coupled beam. A novel idea of utilizing magnetized beam transport was proposed for improvement of cooling efficiency and possible mitigation of collective effects. A concern of MBI regarding this design was studied and excluded. The large transverse beam size associated with the beam magnetization is found to help suppress MBI via the transverse-longitudinal correlation.« less

The LAMP instrument at the Linac Coherent Light Source free-electron laser

NASA Astrophysics Data System (ADS)

Osipov, Timur; Bostedt, Christoph; Castagna, J.-C.; Ferguson, Ken R.; Bucher, Maximilian; Montero, Sebastian C.; Swiggers, Michele L.; Obaid, Razib; Rolles, Daniel; Rudenko, Artem; Bozek, John D.; Berrah, Nora

2018-03-01

The Laser Applications in Materials Processing (LAMP) instrument is a new end-station for soft X-ray imaging, high-field physics, and ultrafast X-ray science experiments that is available to users at the Linac Coherent Light Source (LCLS) free-electron laser. While the instrument resides in the Atomic, Molecular and Optical science hutch, its components can be used at any LCLS beamline. The end-station has a modular design that provides high flexibility in order to meet user-defined experimental requirements and specifications. The ultra-high-vacuum environment supports different sample delivery systems, including pulsed and continuous atomic, molecular, and cluster jets; liquid and aerosols jets; and effusive metal vapor beams. It also houses movable, large-format, high-speed pnCCD X-ray detectors for detecting scattered and fluorescent photons. Multiple charged-particle spectrometer options are compatible with the LAMP chamber, including a double-sided spectrometer for simultaneous and even coincident measurements of electrons, ions, and photons produced by the interaction of the high-intensity X-ray beam with the various samples. Here we describe the design and capabilities of the spectrometers along with some general aspects of the LAMP chamber and show some results from the initial instrument commissioning.

Quality of Intensity Modulated Radiation Therapy Treatment Plans Using a ⁶⁰Co Magnetic Resonance Image Guidance Radiation Therapy System.

PubMed

Wooten, H Omar; Green, Olga; Yang, Min; DeWees, Todd; Kashani, Rojano; Olsen, Jeff; Michalski, Jeff; Yang, Deshan; Tanderup, Kari; Hu, Yanle; Li, H Harold; Mutic, Sasa

2015-07-15

This work describes a commercial treatment planning system, its technical features, and its capabilities for creating (60)Co intensity modulated radiation therapy (IMRT) treatment plans for a magnetic resonance image guidance radiation therapy (MR-IGRT) system. The ViewRay treatment planning system (Oakwood Village, OH) was used to create (60)Co IMRT treatment plans for 33 cancer patients with disease in the abdominal, pelvic, thorax, and head and neck regions using physician-specified patient-specific target coverage and organ at risk (OAR) objectives. Backup plans using a third-party linear accelerator (linac)-based planning system were also created. Plans were evaluated by attending physicians and approved for treatment. The (60)Co and linac plans were compared by evaluating conformity numbers (CN) with 100% and 95% of prescription reference doses and heterogeneity indices (HI) for planning target volumes (PTVs) and maximum, mean, and dose-volume histogram (DVH) values for OARs. All (60)Co IMRT plans achieved PTV coverage and OAR sparing that were similar to linac plans. PTV conformity for (60)Co was within <1% and 3% of linac plans for 100% and 95% prescription reference isodoses, respectively, and heterogeneity was on average 4% greater. Comparisons of OAR mean dose showed generally better sparing with linac plans in the low-dose range <20 Gy, but comparable sparing for organs with mean doses >20 Gy. The mean doses for all (60)Co plan OARs were within clinical tolerances. A commercial (60)Co MR-IGRT device can produce highly conformal IMRT treatment plans similar in quality to linac IMRT for a variety of disease sites. Additional work is in progress to evaluate the clinical benefit of other novel features of this MR-IGRT system. Copyright © 2015 Elsevier Inc. All rights reserved.

Dosimetric feasibility of magnetic resonance imaging-guided tri-cobalt 60 preoperative intensity modulated radiation therapy for soft tissue sarcomas of the extremity.

PubMed

Kishan, Amar U; Cao, Minsong; Mikaeilian, Argin G; Low, Daniel A; Kupelian, Patrick A; Steinberg, Michael L; Kamrava, Mitchell

2015-01-01

The purpose of this study was to investigate the dosimetric differences of delivering preoperative intensity modulated radiation therapy (IMRT) to patients with soft tissue sarcomas of the extremity (ESTS) with a teletherapy system equipped with 3 rotating (60)Co sources and a built-in magnetic resonance imaging and with standard linear accelerator (LINAC)-based IMRT. The primary study population consisted of 9 patients treated with preoperative radiation for ESTS between 2008 and 2014 with LINAC-based static field IMRT. LINAC plans were designed to deliver 50 Gy in 25 fractions to 95% of the planning target volume (PTV). Tri-(60)Co system IMRT plans were designed with ViewRay system software. Tri-(60)Co-based IMRT plans achieved equivalent target coverage and dosimetry for organs at risk (long bone, skin, and skin corridor) compared with LINAC-based IMRT plans. The maximum and minimum PTV doses, heterogeneity indices, and ratio of the dose to 50% of the volume were equivalent for both planning systems. One LINAC plan violated the maximum bone dose constraint, whereas none of the tri-(60)Co plans did. Using a tri-(60)Co system, we were able to achieve equivalent dosimetry to the PTV and organs at risk for patients with ESTS compared with LINAC-based IMRT plans. The tri-(60)Co system may be advantageous over current treatment platforms by allowing PTV reduction and by elimination of the additional radiation dose associated with daily image guidance, but this needs to be evaluated prospectively. Copyright © 2015 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.

Development of high intensity linear accelerator for heavy ion inertial fusion driver

NASA Astrophysics Data System (ADS)

Lu, Liang; Hattori, Toshiyuki; Hayashizaki, Noriyosu; Ishibashi, Takuya; Okamura, Masahiro; Kashiwagi, Hirotsugu; Takeuchi, Takeshi; Zhao, Hongwei; He, Yuan

2013-11-01

In order to verify the direct plasma injection scheme (DPIS), an acceleration test was carried out in 2001 using a radio frequency quadrupole (RFQ) heavy ion linear accelerator (linac) and a CO2-laser ion source (LIS) (Okamura et al., 2002) [1]. The accelerated carbon beam was observed successfully and the obtained current was 9.22 mA for C4+. To confirm the capability of the DPIS, we succeeded in accelerating 60 mA carbon ions with the DPIS in 2004 (Okamura et al., 2004; Kashiwagi and Hattori, 2004) [2,3]. We have studied a multi-beam type RFQ with an interdigital-H (IH) cavity that has a power-efficient structure in the low energy region. We designed and manufactured a two-beam type RFQ linac as a prototype for the multi-beam type linac; the beam acceleration test of carbon beams showed that it successfully accelerated from 5 keV/u up to 60 keV/u with an output current of 108 mA (2×54 mA/channel) (Ishibashi et al., 2011) [4]. We believe that the acceleration techniques of DPIS and the multi-beam type IH-RFQ linac are technical breakthroughs for heavy-ion inertial confinement fusion (HIF). The conceptual design of the RF linac with these techniques for HIF is studied. New accelerator-systems using these techniques for the HIF basic experiment are being designed to accelerate 400 mA carbon ions using four-beam type IH-RFQ linacs with DPIS. A model with a four-beam acceleration cavity was designed and manufactured to establish the proof of principle (PoP) of the accelerator.

Coherent Soft X-ray Diffraction Imaging of Coliphage PR772 at the Linac Coherent Light Source

DOE Data Explorer

Reddy, Hemanth, K.N.

2017-01-05

A dataset of coherent soft X-ray diffraction images of Coliphage PR772 virus, collected at the Atomic Molecular Optics (AMO) beamline with pnCCD detectors in the LAMP instrument at the Linac Coherent Light Source.

Matching the laser generated p bunch into a crossbar-H drift tube linac

NASA Astrophysics Data System (ADS)

Almomani, A.; Droba, M.; Ratzinger, U.; Hofmann, I.

2012-05-01

Proton bunches with energies up to 30 MeV have been measured at the PHELIX laser. Because of the laser-plasma interactions at a power density of about 4×1019W/cm2, a total yield of 1.5×1013protons was produced. For the reference energy of 10 MeV, the yield within ±0.5MeV was exceeding 1010protons. The important topic for a further acceleration of the laser generated bunch is the matching into the acceptance of an rf accelerator stage. With respect to the high space charge forces and the transit energy range, only drift tube linacs seem adequate for this purpose. A crossbar H-type (CH) cavity was chosen as the linac structure. Optimum emittance values for the linac injection are compared with the available laser generated beam parameters. Options for beam matching into a CH structure by a pulsed magnetic solenoid and by using the simulation codes LASIN and LORASR are presented.

Full Geant4 and FLUKA simulations of an e-LINAC for its use in particle detectors performance tests

NASA Astrophysics Data System (ADS)

Alpat, B.; Pilicer, E.; Servoli, L.; Menichelli, M.; Tucceri, P.; Italiani, M.; Buono, E.; Di Capua, F.

2012-03-01

In this work we present the results of full Geant4 and FLUKA simulations and comparison with dosimetry data of an electron LINAC of St. Maria Hospital located in Terni, Italy. The facility is being used primarily for radiotherapy and the goal of the present study is the detailed investigation of electron beam parameters to evaluate the possibility to use the e-LINAC (during time slots when it is not used for radiotherapy) to test the performance of detector systems, in particular those designed to operate in space. The critical beam parameters are electron energy, profile and flux available at the surface of device to be tested. The present work aims to extract these parameters from dosimetry calibration data available at the e-LINAC. The electron energy ranges from 4 MeV to 20 MeV. The dose measurements have been performed by using an Advanced Markus Chamber which has a small sensitive volume.

Electron Beam Focusing in the Linear Accelerator (linac)

NASA Astrophysics Data System (ADS)

Jauregui, Luis

2015-10-01

To produce consistent data with an electron accelerator, it is critical to have a well-focused beam. To keep the beam focused, quadrupoles (quads) are employed. Quads are magnets, which focus the beam in one direction (x or y) and defocus in the other. When two or more quads are used in series, a net focusing effect is achieved in both vertical and horizontal directions. At start up there is a 5% calibration error in the linac at Thomas Jefferson National Accelerator Facility. This means that the momentum of particles passing through the quads isn't always what is expected, which affects the focusing of the beam. The objective is to find exactly how sensitive the focusing in the linac is to this 5% error. A linac was simulated, which contained 290 RF Cavities with random electric fields (to simulate the 5% calibration error), and a total momentum kick of 1090 MeV. National Science Foundation, Department of Energy, Jefferson Lab, Old Dominion University.

Machine Imperfection Studies of the RAON Superconducting Linac

NASA Astrophysics Data System (ADS)

Jeon, D.; Jang, J.-H.; Jin, H.

2018-05-01

Studies of the machine imperfections in the RAON superconducting linac (SCL) that employs normal conducting (NC) quadrupoles were done to assess the tolerable error budgets of the machine imperfections that ensure operation of the beam. The studies show that the beam loss requirement is met even before the orbit correction and that the beam loss requirement is met even without the MHB (multi-harmonic buncher) and VE (velocity equalizer) thanks to the RAON's radio-frequency quadrupole (RFQ) design feature. For the low energy section of the linac (SCL3), a comparison is made between the two superconducting linac lattice types: one lattice that employs NC quadrupoles and the other that employs SC solenoids. The studies show that both lattices meet the beam loss requirement after the orbit correction. However, before the orbit correction, the lattice employing SC solenoids does not meet the beam loss requirement and can cause a significant beam loss, while the lattice employing NC quadrupoles meets the requirement. For the lattice employing SC solenoids, care must be taken during the beam commissioning.

Neutron production in the interaction of 12 and 18 MeV electrons with a scattering foil inside a simple LINAC head.

PubMed

Soto-Bernal, Tzinnia Gabriela; Baltazar-Raigosa, Antonio; Medina-Castro, Diego; Vega-Carrillo, Hector Rene

2018-04-18

The characteristics of photons and neutrons produced during the interaction between a monoenergetic (12 and 18 MeV) electron beam and a tungsten scattering foil enclosed into a 10 cm-thick tungsten shell have been determined using Monte Carlo methods. This model was used aiming to represent a linac head working in electron-mode for cancer treatment. Photon and neutron spectra were determined around the scattering foil and to 50 and 100 cm below the electron source. Induced photons are mainly produced along the direction of the incoming electron beam. On the other hand, neutrons are produced in two sites, mainly in the inner surface of the linac head and in less extent in the scattering foil. The neutron spectra are evaporation neutrons which are emitted isotropically from the site where are produced leaking out from the linac head, reaching locations were the patient is allocated. Copyright © 2018 Elsevier Ltd. All rights reserved.

Status and operation of the Linac4 ion source prototypes

NASA Astrophysics Data System (ADS)

Lettry, J.; Aguglia, D.; Andersson, P.; Bertolo, S.; Butterworth, A.; Coutron, Y.; Dallocchio, A.; Chaudet, E.; Gil-Flores, J.; Guida, R.; Hansen, J.; Hatayama, A.; Koszar, I.; Mahner, E.; Mastrostefano, C.; Mathot, S.; Mattei, S.; Midttun, Ø.; Moyret, P.; Nisbet, D.; Nishida, K.; O'Neil, M.; Ohta, M.; Paoluzzi, M.; Pasquino, C.; Pereira, H.; Rochez, J.; Sanchez Alvarez, J.; Sanchez Arias, J.; Scrivens, R.; Shibata, T.; Steyaert, D.; Thaus, N.; Yamamoto, T.

2014-02-01

CERN's Linac4 45 kV H- ion sources prototypes are installed at a dedicated ion source test stand and in the Linac4 tunnel. The operation of the pulsed hydrogen injection, RF sustained plasma, and pulsed high voltages are described. The first experimental results of two prototypes relying on 2 MHz RF-plasma heating are presented. The plasma is ignited via capacitive coupling, and sustained by inductive coupling. The light emitted from the plasma is collected by viewports pointing to the plasma chamber wall in the middle of the RF solenoid and to the plasma chamber axis. Preliminary measurements of optical emission spectroscopy and photometry of the plasma have been performed. The design of a cesiated ion source is presented. The volume source has produced a 45 keV H- beam of 16-22 mA which has successfully been used for the commissioning of the Low Energy Beam Transport (LEBT), Radio Frequency Quadrupole (RFQ) accelerator, and chopper of Linac4.

SU-E-T-119: Dosimetric and Mechanical Characteristics of Elekta Infinity LINAC with Agility MLC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, J; Xu, Q; Xue, J

2014-06-01

Purpose: Elekta Infinity is the one of the latest generation LINAC with unique features. Two Infinity LINACs are recently commissioned at our institution. The dosimetric and mechanical characteristics of the machines are presented. Methods: Both Infinity LINACs with Agility MLC (160 leaves with 0.5 cm leaf width) are configured with five electron energies (6, 9, 12, 15, and 18 MeV) and two photon energies (6 and 15 MV). One machine has additional photon energy (10 MV). The commissioning was performed by following the manufacturer's specifications and AAPM TG recommendations. Beam data of both electron and photon beams are measured withmore » scanning ion chambers and linear diode array. Machines are adjusted to have the dosimetrically equivalent characteristics. Results: The commissioning of mechanical and imaging system meets the tolerances by TG recommendations. The PDD{sub 10} of various field sizes for 6 and 15 MV shows < 0.5% difference between two machines. For each electron beams, R{sub 80} matches with < 0.4 mm difference. The symmetry and flatness agree within 0.8% and 0.9% differences for photon beams, respectively. For electron beams, the differences of the symmetry and flatness are within 1.2% and 0.8%, respectively. The mean inline penumbras for 6, 10, and 15 MV are respectively 5.1±0.24, 5.6±0.07, and 5.9±0.10 mm for 10x10 cm at 10 cm depth. The crossline penumbras are larger than inline penumbras by 2.2, 1.4, and 1.0 mm, respectively. The MLC transmission factor with interleaf leakage is 0.5 % for all photon energies. Conclusion: The dosimetric and mechanical characteristics of two Infinity LINACs show good agreements between them. Although the Elekta Infinity has been used in many institutions, the detailed characteristics of the machine have not been reported. This study provides invaluable information to understand the Infinity LINAC and to compare the quality of commissioning data for other LINACs.« less

SU-F-J-147: Magnetic Field Dose Response Considerations for a Linac Monitor Chamber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reynolds, M; Fallone, B

Purpose: The impact of magnetic fields on the readings of a linac monitor chamber have not yet been investigated. Herein we examine the total dose response as well as any deviations in the beam parameters of flatness and symmetry when a Varian monitor chamber is irradiated within an applied magnetic field. This work has direct application to the development of Linac-MR systems worldwide. Methods: A Varian monitor chamber was modeled in the Monte Carlo code PENELOPE and irradiated in the presence of a magnetic field with a phase space generated from a model of a Linac-MR prototype system. The magneticmore » field strength was stepped from 0 to 3.0T in both parallel and perpendicular directions with respect to the normal surface of the phase space. Dose to each of the four regions in the monitor chamber were scored separately for every magnetic field adaptation to evaluate the effect of the magnetic field on flatness and symmetry. Results: When the magnetic field is perpendicular to the phase space normal we see a change in dose response with a maximal deviation (10–25% depending on the chamber region) near 0.75T. In the direction of electron deflection we expectedly see opposite responses in chamber regions leading to a measured asymmetry. With a magnetic field parallel to the phase space normal we see no measured asymmetries, however there is a monotonic rise in dose response leveling off at about +12% near 2.5T. Conclusion: Attention must be given to correct for the strength and direction of the magnetic field at the location of the linac monitor chamber in hybrid Linac-MR devices. Elsewise the dose sampled by these chambers may not represent the actual dose expected at isocentre; additionally there may be a need to correct for the symmetry of the beam recorded by the monitor chamber. Fallone is a co-founder and CEO of MagnetTx Oncology Solutions (under discussions to license Alberta bi-planar linac MR for commercialization).« less

Telerobotic system concept for real-time soft-tissue imaging during radiotherapy beam delivery.

PubMed

Schlosser, Jeffrey; Salisbury, Kenneth; Hristov, Dimitre

2010-12-01

The curative potential of external beam radiation therapy is critically dependent on having the ability to accurately aim radiation beams at intended targets while avoiding surrounding healthy tissues. However, existing technologies are incapable of real-time, volumetric, soft-tissue imaging during radiation beam delivery, when accurate target tracking is most critical. The authors address this challenge in the development and evaluation of a novel, minimally interfering, telerobotic ultrasound (U.S.) imaging system that can be integrated with existing medical linear accelerators (LINACs) for therapy guidance. A customized human-safe robotic manipulator was designed and built to control the pressure and pitch of an abdominal U.S. transducer while avoiding LINAC gantry collisions. A haptic device was integrated to remotely control the robotic manipulator motion and U.S. image acquisition outside the LINAC room. The ability of the system to continuously maintain high quality prostate images was evaluated in volunteers over extended time periods. Treatment feasibility was assessed by comparing a clinically deployed prostate treatment plan to an alternative plan in which beam directions were restricted to sectors that did not interfere with the transabdominal U.S. transducer. To demonstrate imaging capability concurrent with delivery, robot performance and U.S. target tracking in a phantom were tested with a 15 MV radiation beam active. Remote image acquisition and maintenance of image quality with the haptic interface was successfully demonstrated over 10 min periods in representative treatment setups of volunteers. Furthermore, the robot's ability to maintain a constant probe force and desired pitch angle was unaffected by the LINAC beam. For a representative prostate patient, the dose-volume histogram (DVH) for a plan with restricted sectors remained virtually identical to the DVH of a clinically deployed plan. With reduced margins, as would be enabled by real-time imaging, gross tumor volume coverage was identical while notable reductions of bladder and rectal volumes exposed to large doses were possible. The quality of U.S. images obtained during beam operation was not appreciably degraded by radiofrequency interference and 2D tracking of a phantom object in U.S. images obtained with the beam on/off yielded no significant differences. Remotely controlled robotic U.S. imaging is feasible in the radiotherapy environment and for the first time may offer real-time volumetric soft-tissue guidance concurrent with radiotherapy delivery.

Solenoid Fringe Field Effects for the Neutrino Factory Linac - MAD-X Investigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

M. Aslaninejad,C. Bontoiu,J. Pasternak,J. Pozimski,Alex Bogacz

2010-05-01

International Design Study for the Neutrino Factory (IDS-NF) assumes the first stage of muon acceleration (up to 900 MeV) to be implemented with a solenoid based Linac. The Linac consists of three styles of cryo-modules, containing focusing solenoids and varying number of SRF cavities for acceleration. Fringe fields of the solenoids and the focusing effects in the SRF cavities have significant impact on the transverse beam dynamics. Using an analytical formula, the effects of fringe fields are studied in MAD-X. The resulting betatron functions are compared with the results of beam dynamics simulations using OptiM code.

Beam dynamics pre-design with KONUS principle for the DTL of SPPC p-Linac

NASA Astrophysics Data System (ADS)

Liu, Jing; Li, Haipeng; Lu, Yuanrong; Su, Jiancang; Liu, Xiaolong; Fu, Qi

2018-04-01

As the Higgs bosons were observed on the LHC in 2012, a two-stage particle collider program named CEPC-SPPC is proposed for precise measurement of Higgs properties and exploring the new physics models. In order to deliver a 2.1-TeV proton beam into the Super Proton-Proton Collider (SPPC), the injector chain will use a 1.2-GeV proton linac (p-Linac) and three synchrotrons of p-RCS, MSS and SS. This paper focuses on the preliminary conceptual design of the DTL within the p-Linac and mainly concerns about the beam dynamics studies. Taking advantages of the KONUS principle and LORASR code, a 325 MHz, 50.65 MeV DTL design which is composed of three tanks in 15.6 m will be presented. The whole DTL contains 129 gaps for beam acceleration, one quadruple doublet which is behind the buncher and eight quadruple triplets of which three are located after each tank, respectively. The aims of this pre-study are to optimize the acceleration electric field distribution together with the focusing magnetic field parameters, enhance the beam transmission quality of beam envelopes, particle distribution and energy spread, then improve the DTL performance in terms of transmission efficiency and so on. The results of the analyses show that the DTL pre-design achieves 16.8 times high energy gain and meets all the p-Linac requirements well.

Photoneutron Flux Measurement via Neutron Activation Analysis in a Radiotherapy Bunker with an 18 MV Linear Accelerator

NASA Astrophysics Data System (ADS)

Çeçen, Yiğit; Gülümser, Tuğçe; Yazgan, Çağrı; Dapo, Haris; Üstün, Mahmut; Boztosun, Ismail

2017-09-01

In cancer treatment, high energy X-rays are used which are produced by linear accelerators (LINACs). If the energy of these beams is over 8 MeV, photonuclear reactions occur between the bremsstrahlung photons and the metallic parts of the LINAC. As a result of these interactions, neutrons are also produced as secondary radiation products (γ,n) which are called photoneutrons. The study aims to map the photoneutron flux distribution within the LINAC bunker via neutron activation analysis (NAA) using indium-cadmium foils. Irradiations made at different gantry angles (0°, 90°, 180° and 270°) with a total of 91 positions in the Philips SLI-25 linear accelerator treatment room and location-based distribution of thermal neutron flux was obtained. Gamma spectrum analysis was carried out with high purity germanium (HPGe) detector. Results of the analysis showed that the maximum neutron flux in the room occurred at just above of the LINAC head (1.2x105 neutrons/cm2.s) which is compatible with an americium-beryllium (Am-Be) neutron source. There was a 90% decrease of flux at the walls and at the start of the maze with respect to the maximum neutron flux. And, just in front of the LINAC door, inside the room, neutron flux was measured less than 1% of the maximum.

Beam energy tracking system on Optima XEx high energy ion implanter

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, Jonathan; Satoh, Shu; Wu Xiangyang

2012-11-06

The Axcelis Optima XEx high energy implanter is an RF linac-based implanter with 12 RF resonators for beam acceleration. Even though each acceleration field is an alternating, sinusoidal RF field, the well known phase-focusing principle produces a beam with a sharp quasi-monoenergetic energy spectrum. A magnetic energy filter after the linac further attenuates the low energy continuum in the energy spectrum often associated with RF acceleration. The final beam energy is a function of the phase and amplitude of the 12 resonators in the linac. When tuning a beam, the magnetic energy filter is set to the desired energy, andmore » each linac parameter is tuned to maximize the transmission through the filter. Once a beam is set up, all the parameters are stored in a recipe, which can be easily tuned and has proven to be quite repeatable. The magnetic field setting of the energy filter selects the beam energy from the RF Linac accelerator, and in-situ verification of beam energy in addition to the magnetic energy filter setting has long been desired. An independent energy tracking system was developed for this purpose, using the existing electrostatic beam scanner as a deflector to construct an in-situ electrostatic energy analyzer. This paper will describe the system and performance of the beam energy tracking system.« less

New concept on an integrated interior magnetic resonance imaging and medical linear accelerator system for radiation therapy.

PubMed

Jia, Xun; Tian, Zhen; Xi, Yan; Jiang, Steve B; Wang, Ge

2017-01-01

Image guidance plays a critical role in radiotherapy. Currently, cone-beam computed tomography (CBCT) is routinely used in clinics for this purpose. While this modality can provide an attenuation image for therapeutic planning, low soft-tissue contrast affects the delineation of anatomical and pathological features. Efforts have recently been devoted to several MRI linear accelerator (LINAC) projects that lead to the successful combination of a full diagnostic MRI scanner with a radiotherapy machine. We present a new concept for the development of the MRI-LINAC system. Instead of combining a full MRI scanner with the LINAC platform, we propose using an interior MRI (iMRI) approach to image a specific region of interest (RoI) containing the radiation treatment target. While the conventional CBCT component still delivers a global image of the patient's anatomy, the iMRI offers local imaging of high soft-tissue contrast for tumor delineation. We describe a top-level system design for the integration of an iMRI component into an existing LINAC platform. We performed numerical analyses of the magnetic field for the iMRI to show potentially acceptable field properties in a spherical RoI with a diameter of 15 cm. This field could be shielded to a sufficiently low level around the LINAC region to avoid electromagnetic interference. Furthermore, we investigate the dosimetric impacts of this integration on the radiotherapy beam.

Experimental Platform for Ultra-high Dose Rate FLASH Irradiation of Small Animals Using a Clinical Linear Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schüler, Emil; Trovati, Stefania; King, Gregory

Purpose: A key factor limiting the effectiveness of radiation therapy is normal tissue toxicity, and recent preclinical data have shown that ultra-high dose rate irradiation (>50 Gy/s, “FLASH”) potentially mitigates this effect. However, research in this field has been strongly limited by the availability of FLASH irradiators suitable for small animal experiments. We present a simple methodologic approach for FLASH electron small animal irradiation with a clinically available linear accelerator (LINAC). Methods and Materials: We investigated the FLASH irradiation potential of a Varian Clinac 21EX in both clinical mode and after tuning of the LINAC. We performed detailed FLUKA Monte Carlomore » and experimental dosimetric characterization at multiple experimental locations within the LINAC head. Results: Average dose rates of ≤74 Gy/s were achieved in clinical mode, and the dose rate after tuning exceeded 900 Gy/s. We obtained 220 Gy/s at 1-cm depth for a >4-cm field size with 90% homogeneity throughout a 2-cm-thick volume. Conclusions: We present an approach for using a clinical LINAC for FLASH irradiation. We obtained dose rates exceeding 200 Gy/s after simple tuning of the LINAC, with excellent dosimetric properties for small animal experiments. This will allow for increased availability of FLASH irradiation to the general research community.« less

Peregrine rogue waves induced by the interaction between a continuous wave and a soliton.

PubMed

Yang, Guangye; Li, Lu; Jia, Suotang

2012-04-01

Based on the soliton solution on a continuous wave background for an integrable Hirota equation, the reduction mechanism and the characteristics of the Peregrine rogue wave in the propagation of femtosecond pulses of optical fiber are discussed. The results show that there exist two processes of the formation of the Peregrine rogue wave: one is the localized process of the continuous wave background, and the other is the reduction process of the periodization of the bright soliton. The characteristics of the Peregrine rogue wave are exhibited by strong temporal and spatial localization. Also, various initial excitations of the Peregrine rogue wave are performed and the results show that the Peregrine rogue wave can be excited by a small localized (single peak) perturbation pulse of the continuous wave background, even for the nonintegrable case. The numerical simulations show that the Peregrine rogue wave is unstable. Finally, through a realistic example, the influence of the self-frequency shift to the dynamics of the Peregrine rogue wave is discussed. The results show that in the absence of the self-frequency shift, the Peregrine rogue wave can split into several subpulses; however, when the self-frequency shift is considered, the Peregrine rogue wave no longer splits and exhibits mainly a peak changing and an increasing evolution property of the field amplitude.

COMPARATIVE DISINFECTION EFFICIENCY OF PULSED AND CONTINUOUS-WAVE UV IRRADIATION TECHNOLOGIES

EPA Science Inventory

Pulsed UV (PUV) is novel UV irradiation system that is a non-mercury lamp based alternative to currently used continuous-wave systems for water disinfection. To compare the polychromatic PUV irradiation disinfection efficiency with that from continuous wave monochromatic low-pre...

Monte Carlo based, patient-specific RapidArc QA using Linac log files.

PubMed

Teke, Tony; Bergman, Alanah M; Kwa, William; Gill, Bradford; Duzenli, Cheryl; Popescu, I Antoniu

2010-01-01

A Monte Carlo (MC) based QA process to validate the dynamic beam delivery accuracy for Varian RapidArc (Varian Medical Systems, Palo Alto, CA) using Linac delivery log files (DynaLog) is presented. Using DynaLog file analysis and MC simulations, the goal of this article is to (a) confirm that adequate sampling is used in the RapidArc optimization algorithm (177 static gantry angles) and (b) to assess the physical machine performance [gantry angle and monitor unit (MU) delivery accuracy]. Ten clinically acceptable RapidArc treatment plans were generated for various tumor sites and delivered to a water-equivalent cylindrical phantom on the treatment unit. Three Monte Carlo simulations were performed to calculate dose to the CT phantom image set: (a) One using a series of static gantry angles defined by 177 control points with treatment planning system (TPS) MLC control files (planning files), (b) one using continuous gantry rotation with TPS generated MLC control files, and (c) one using continuous gantry rotation with actual Linac delivery log files. Monte Carlo simulated dose distributions are compared to both ionization chamber point measurements and with RapidArc TPS calculated doses. The 3D dose distributions were compared using a 3D gamma-factor analysis, employing a 3%/3 mm distance-to-agreement criterion. The dose difference between MC simulations, TPS, and ionization chamber point measurements was less than 2.1%. For all plans, the MC calculated 3D dose distributions agreed well with the TPS calculated doses (gamma-factor values were less than 1 for more than 95% of the points considered). Machine performance QA was supplemented with an extensive DynaLog file analysis. A DynaLog file analysis showed that leaf position errors were less than 1 mm for 94% of the time and there were no leaf errors greater than 2.5 mm. The mean standard deviation in MU and gantry angle were 0.052 MU and 0.355 degrees, respectively, for the ten cases analyzed. The accuracy and flexibility of the Monte Carlo based RapidArc QA system were demonstrated. Good machine performance and accurate dose distribution delivery of RapidArc plans were observed. The sampling used in the TPS optimization algorithm was found to be adequate.

Electron contamination modeling and reduction in a 1 T open bore inline MRI-linac system.

PubMed

Oborn, B M; Kolling, S; Metcalfe, P E; Crozier, S; Litzenberg, D W; Keall, P J

2014-05-01

A potential side effect of inline MRI-linac systems is electron contamination focusing causing a high skin dose. In this work, the authors reexamine this prediction for an open bore 1 T MRI system being constructed for the Australian MRI-Linac Program. The efficiency of an electron contamination deflector (ECD) in purging electron contamination from the linac head is modeled, as well as the impact of a helium gas region between the deflector and phantom surface for lowering the amount of air-generated contamination. Magnetic modeling of the 1 T MRI was used to generate 3D magnetic field maps both with and without the presence of an ECD located immediately below the MLC's. Forty-seven different ECD designs were modeled and for each the magnetic field map was imported into Geant4 Monte Carlo simulations including the linac head, ECD, and a 30 × 30 × 30 cm(3) water phantom located at isocenter. For the first generation system, the x-ray source to isocenter distance (SID) will be 160 cm, resulting in an 81.2 cm long air gap from the base of the ECD to the phantom surface. The first 71.2 cm was modeled as air or helium gas, with the latter encased between two windows of 50 μm thick high density polyethlyene. 2D skin doses (at 70 μm depth) were calculated across the phantom surface at 1 × 1 mm(2) resolution for 6 MV beams of field size of 5 × 5, 10 × 10, and 20 × 20 cm(2). The skin dose was predicted to be of similar magnitude as the generic systems modeled in previous work, 230% to 1400% of D(max) for 5 × 5 to 20 × 20 cm(2), respectively. Inclusion of the ECD introduced a nonuniformity to the MRI imaging field that ranged from ∼20 to ∼140 ppm while the net force acting on the ECD ranged from ∼151 N to ∼1773 N. Various ECD designs were 100% efficient at purging the electron contamination into the ECD magnet banks; however, a small percentage were scattered back into the beam and continued to the phantom surface. Replacing a large portion of the extended air-column between the ECD and phantom surface with helium gas is a key element as it significantly minimized the air-generated contamination. When using an optimal ECD and helium gas region, the 70 μm skin dose is predicted to increase moderately inside a small hot spot over that of the case with no magnetic field present for the jaw defined square beams examined here. These increases include from 12% to 40% of [Formula: see text] for 5 × 5 cm(2), 18% to 55% of D(max) for 10 × 10 cm(2), and from 23% to 65% of D(max) for 20 × 20 cm(2). Coupling an efficient ECD and helium gas region below the MLCs in the 160 cm isocenter MRI-linac system is predicted to ameliorate the impact electron contamination focusing has on skin dose increases. An ECD is practical as its impact on the MRI imaging distortion is correctable, and the mechanical forces acting on it manageable from an engineering point of view.

Impact of cool-down conditions at Tc on the superconducting rf cavity quality factor

NASA Astrophysics Data System (ADS)

Vogt, J.-M.; Kugeler, O.; Knobloch, J.

2013-10-01

Many next-generation, high-gradient accelerator applications, from energy-recovery linacs to accelerator-driven systems (ADS) rely on continuous wave (CW) operation for which superconducting radio-frequency (SRF) systems are the enabling technology. However, while SRF cavities dissipate little power, they must be cooled by liquid helium and for many CW accelerators the complexity as well as the investment and operating costs of the cryoplant can prove to be prohibitive. We investigated ways to reduce the dynamic losses by improving the residual resistance (Rres) of niobium cavities. Both the material treatment and the magnetic shielding are known to have an impact. In addition, we found that Rres can be reduced significantly when the cool-down conditions during the superconducting phase transition of the niobium are optimized. We believe that not only do the cool-down conditions impact the level to which external magnetic flux is trapped in the cavity but also that thermoelectric currents are generated which in turn create additional flux that can be trapped. Therefore, we investigated the generation of flux and the dynamics of flux trapping and release in a simple model niobium-titanium system that mimics an SRF cavity in its helium tank. We indeed found that thermal gradients along the system during the superconducting transition can generate a thermoelectric current and magnetic flux, which subsequently can be trapped. These effects may explain the observed variation of the cavity’s Rres with cool-down conditions.

Characterization of the Photon Energy Spectrum of a 6 MV Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernandez Bojorquez, M.; Larraga, J. M.; Garcia, A.

2006-09-08

In this work we study the influence of the purity of the materials used in experimental transmission measurements to obtain data to reconstruct the photon energy spectrum of a 6 MV Linac. We also evaluate the contribution to PDDs due to electron contamination in the reconstructed spectrum.

SRF test facility for the superconducting LINAC ``RAON'' — RRR property and e-beam welding

NASA Astrophysics Data System (ADS)

Jung, Yoochul; Hyun, Myungook; Joo, Jongdae; Joung, Mijoung

2015-02-01

Equipment, such as a vacuum furnace, high pressure rinse (HPR), eddy current test (ECT) and buffered chemical polishing (BCP), are installed in the superconducting radio frequency (SRF) test facility. Three different sizes of cryostats (diameters of 600 mm for a quarter wave resonator (QWR), 900 mm for a half wave resonator (HWR), and 1200 mm for single spoke resonator 1&2 (SSR 1&2)) for vertical RF tests are installed for testing cavities. We confirmed that as-received niobium sheets (ASTM B393, RRR300) good electrical properties because they showed average residual resistance ratio (RRR) values higher than 300. However, serious RRR degradation occurred after joining two pieces of Nb by e-beam welding because the average RRR values of the samples were ˜179, which was only ˜60% of as-received RRR value. From various e-beam welding experiments in which the welding current and a speed at a fixed welding voltage were changed, we confirmed that good welding results were obtained at a 53 mA welding current and a 20-mm/s welding speed at a fixed welding voltage of 150 kV.

Investigation and Prediction of RF Window Performance in APT Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humphries, S. Jr.

1997-05-01

The work described in this report was performed between November 1996 and May 1997 in support of the APT (Accelerator Production of Tritium) Program at Los Alamos National Laboratory. The goal was to write and to test computer programs for charged particle orbits in RF fields. The well-documented programs were written in portable form and compiled for standard personal computers for easy distribution to LANL researchers. They will be used in several APT applications including the following. Minimization of multipactor effects in the moderate {beta} superconducting linac cavities under design for the APT accelerator. Investigation of suppression techniques for electronmore » multipactoring in high-power RF feedthroughs. Modeling of the response of electron detectors for the protection of high power RF vacuum windows. In the contract period two new codes, Trak{_}RF and WaveSim, were completed and several critical benchmark etests were carried out. Trak{_}RF numerically tracks charged particle orbits in combined electrostatic, magnetostatic and electromagnetic fields. WaveSim determines frequency-domain RF field solutions and provides a key input to Trak{_}RF. The two-dimensional programs handle planar or cylindrical geometries. They have several unique characteristics.« less

Beam dynamics studies of a 30 MeV RF linac for neutron production

NASA Astrophysics Data System (ADS)

Nayak, B.; Krishnagopal, S.; Acharya, S.

2018-02-01

Design of a 30 MeV, 10 Amp RF linac as neutron source has been carried out by means of ASTRA simulation code. Here we discuss details of design simulations for three different cases i.e Thermionic , DC and RF photocathode guns and compare them as injectors to a 30 MeV RF linac for n-ToF production. A detailed study on choice of input parameters of the beam from point of view of transmission efficiency and beam quality at the output have been described. We found that thermionic gun isn't suitable for this application. Both DC and RF photocathode gun can be used. RF photocathode gun would be of better performance.

RESULTS OF THE 2015 HELIUM PROCESSING OF CEBAF CRYOMODULES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drury, Michael A.; Humphry, Jr., Frank J.; King, Larry

2016-10-01

Many conference series have adopted the same The CEBAF accelerator at Jefferson Lab consists of an injec-tor and two linacs connected by arcs. Each linac contains 25 cryomodules that are designed to deliver an integrated energy of 2.2 GeV per pass to an electron beam in order to meet 12 GeV energy requirements. Helium processing is a processing technique that is used to reduce field emis-sion (FE) in SRF cavities. Helium processing of the 50 installed linac cryomodules was seen as necessary to support 12 GeV energy requirements. This paper will describe the processing procedure and summarize the results ofmore » this effort.« less

Neutron H*(10) estimation and measurements around 18MV linac.

PubMed

Cerón Ramírez, Pablo Víctor; Díaz Góngora, José Antonio Irán; Paredes Gutiérrez, Lydia Concepción; Rivera Montalvo, Teodoro; Vega Carrillo, Héctor René

2016-11-01

Thermoluminescent dosimetry, analytical techniques and Monte Carlo calculations were used to estimate the dose of neutron radiation in a treatment room with a linear electron accelerator of 18MV. Measurements were carried out through neutron ambient dose monitors which include pairs of thermoluminescent dosimeters TLD 600 ( 6 LiF: Mg, Ti) and TLD 700 ( 7 LiF: Mg, Ti), which were placed inside a paraffin spheres. The measurements has allowed to use NCRP 151 equations, these expressions are useful to find relevant dosimetric quantities. In addition, photoneutrons produced by linac head were calculated through MCNPX code taking into account the geometry and composition of the linac head principal parts. Copyright © 2016 Elsevier Ltd. All rights reserved.

Capacitive beam position monitors for the low-β beam of the Chinese ADS proton linac

NASA Astrophysics Data System (ADS)

Zhang, Yong; Wu, Jun-Xia; Zhu, Guang-Yu; Jia, Huan; Xue, Zong-Heng; Zheng, Hai; Xie, Hong-Ming; Kang, Xin-Cai; He, Yuan; Li, Lin; Denard, Jean Claude

2016-02-01

Beam Position Monitors (BPMs) for the low-β beam of the Chinese Accelerator Driven Subcritical system (CADS) Proton linac are of the capacitive pick-up type. They provide higher output signals than that of the inductive type. This paper will describe the design and tests of the capacitive BPM system for the low-β proton linac, including the pick-ups, the test bench and the read-out electronics. The tests done with an actual proton beam show a good agreement between the measurements and the simulations in the time domain. Supported by National Natural Science Foundation of China (11405240) and “Western Light” Talents Training Program of Chinese Academy of Sciences

The Linac Coherent Light Source

DOE PAGES

White, William E.; Robert, Aymeric; Dunne, Mike

2015-05-01

The Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory was the first hard X-ray free-electron laser (FEL) to operate as a user facility. After five years of operation, LCLS is now a mature FEL user facility. Our personal views about opportunities and challenges inherent to these unique light sources are discussed.

Plasma characterization of the superconducting proton linear accelerator plasma generator using a 2 MHz compensated Langmuir probe.

PubMed

Schmitzer, C; Kronberger, M; Lettry, J; Sanchez-Arias, J; Störi, H

2012-02-01

The CERN study for a superconducting proton Linac (SPL) investigates the design of a pulsed 5 GeV Linac operating at 50 Hz. As a first step towards a future SPL H(-) volume ion source, a plasma generator capable of operating at Linac4 or nominal SPL settings has been developed and operated at a dedicated test stand. The hydrogen plasma is heated by an inductively coupled RF discharge e(-) and ions are confined by a magnetic multipole cusp field similar to the currently commissioned Linac4 H(-) ion source. Time-resolved measurements of the plasma potential, temperature, and electron energy distribution function obtained by means of a RF compensated Langmuir probe along the axis of the plasma generator are presented. The influence of the main tuning parameters, such as RF power and frequency and the timing scheme is discussed with the aim to correlate them to optimum H(-) ion beam parameters measured on an ion source test stand. The effects of hydrogen injection settings which allow operation at 50 Hz repetition rate are discussed.

AN INTERNET RACK MONITOR-CONTROLLER FOR APS LINAC RF ELECTRONICS UPGRADE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Hengjie; Smith, Terry; Nassiri, Alireza

To support the research and development in APS LINAC area, the existing LINAC rf control performance needs to be much improved, and thus an upgrade of the legacy LINAC rf electronics becomes necessary. The proposed upgrade plan centers on the concept of using a modern, network-attached, rackmount digital electronics platform –Internet Rack Monitor-Controller (or IRMC) to achieve the goal of modernizing the rf electronics at a lower cost. The system model of the envisioned IRMC is basically a 3-tier stack with a high-performance DSP in the mid-layer to perform the core tasks of real-time rf data processing and controls. Themore » Digital Front-End (DFE) attachment layer at bottom bridges the applicationspecific rf front-ends to the DSP. A network communication gateway, together with an embedded event receiver (EVR) in the top layer merges the Internet Rack MonitorController node into the networks of the accelerator controls infrastructure. Although the concept is very much in trend with today’s Internet-of-Things (IoT), this implementation has actually been used in the accelerators for over two decades.« less

Plasma characterization of the superconducting proton linear accelerator plasma generator using a 2 MHz compensated Langmuir probea)

NASA Astrophysics Data System (ADS)

Schmitzer, C.; Kronberger, M.; Lettry, J.; Sanchez-Arias, J.; Störi, H.

2012-02-01

The CERN study for a superconducting proton Linac (SPL) investigates the design of a pulsed 5 GeV Linac operating at 50 Hz. As a first step towards a future SPL H- volume ion source, a plasma generator capable of operating at Linac4 or nominal SPL settings has been developed and operated at a dedicated test stand. The hydrogen plasma is heated by an inductively coupled RF discharge e- and ions are confined by a magnetic multipole cusp field similar to the currently commissioned Linac4 H- ion source. Time-resolved measurements of the plasma potential, temperature, and electron energy distribution function obtained by means of a RF compensated Langmuir probe along the axis of the plasma generator are presented. The influence of the main tuning parameters, such as RF power and frequency and the timing scheme is discussed with the aim to correlate them to optimum H- ion beam parameters measured on an ion source test stand. The effects of hydrogen injection settings which allow operation at 50 Hz repetition rate are discussed.

Sci-Sat AM: Brachy - 04: Neutron production around a radiation therapy linac bunker - monte carlo simulations and physical measurements.

PubMed

Khatchadourian, R; Davis, S; Evans, M; Licea, A; Seuntjens, J; Kildea, J

2012-07-01

Photoneutrons are a major component of the equivalent dose in the maze and near the door of linac bunkers. Physical measurements and Monte Carlo (MC) calculations of neutron dose are key for validating bunker design with respect to health regulations. We attempted to use bubble detectors and a 3 He neutron spectrometer to measure neutron equivalent dose and neutron spectra in the maze and near the door of one of our bunkers. We also ran MC simulations with MCNP5 to measure the neutron fluence in the same region. Using a point source of neutrons, a Clinac 1800 linac operating at 10 MV was simulated and the fluence measured at various locations of interest. We describe the challenges faced when measuring dose with bubble detectors in the maze and the complexity of photoneutron spectrometry with linacs operating in pulsed mode. Finally, we report on the development of a userfriendly GUI for shielding calculations based on the NCRP 151 formalism. © 2012 American Association of Physicists in Medicine.

Upgrade of the beam extraction system of the GTS-LHC electron cyclotron resonance ion source at CERN.

PubMed

Toivanen, V; Bellodi, G; Dimov, V; Küchler, D; Lombardi, A M; Maintrot, M

2016-02-01

Linac3 is the first accelerator in the heavy ion injector chain of the Large Hadron Collider (LHC), providing multiply charged heavy ion beams for the CERN experimental program. The ion beams are produced with GTS-LHC, a 14.5 GHz electron cyclotron resonance ion source, operated in afterglow mode. Improvement of the GTS-LHC beam formation and beam transport along Linac3 is part of the upgrade program of the injector chain in preparation for the future high luminosity LHC. A mismatch between the ion beam properties in the ion source extraction region and the acceptance of the following Low Energy Beam Transport (LEBT) section has been identified as one of the factors limiting the Linac3 performance. The installation of a new focusing element, an einzel lens, into the GTS-LHC extraction region is foreseen as a part of the Linac3 upgrade, as well as a redesign of the first section of the LEBT. Details of the upgrade and results of a beam dynamics study of the extraction region and LEBT modifications will be presented.

The use of a virtual reality simulator to explore and understand the impact of Linac mis-calibrations

NASA Astrophysics Data System (ADS)

Beavis, Andrew W.; Ward, James W.

2014-03-01

Purpose: In recent years there has been interest in using Computer Simulation within Medical training. The VERT (Virtual Environment for Radiotherapy Training) system is a Flight Simulator for Radiation Oncology professionals, wherein fundamental concepts, techniques and problematic scenarios can be safely investigated. Methods: The system provides detailed simulations of several Linacs and the ability to display DICOM treatment plans. Patients can be mis-positioned with 'set-up errors' which can be explored visually, dosimetrically and using IGRT. Similarly, a variety of Linac calibration and configuration parameters can be altered manually or randomly via controlled errors in the simulated 3D Linac and its component parts. The implication of these can be investigated by following through a treatment scenario or using QC devices available within a Physics software module. Results: One resultant exercise is a systematic mis-calibration of 'lateral laser height' by 2mm. The offset in patient alignment is easily identified using IGRT and once corrected by reference to the 'in-room monitor'. The dosimetric implication is demonstrated to be 0.4% by setting a dosimetry phantom by the lasers (and ignoring TSD information). Finally, the need for recalibration can be shown by the Laser Alignment Phantom or by reference to the front pointer. Conclusions: The VERT system provides a realistic environment for training and enhancing understanding of radiotherapy concepts and techniques. Linac error conditions can be explored in this context and valuable experience gained in a controlled manner in a compressed period of time.

New concept on an integrated interior magnetic resonance imaging and medical linear accelerator system for radiation therapy

PubMed Central

Jia, Xun; Tian, Zhen; Xi, Yan; Jiang, Steve B.; Wang, Ge

2017-01-01

Abstract. Image guidance plays a critical role in radiotherapy. Currently, cone-beam computed tomography (CBCT) is routinely used in clinics for this purpose. While this modality can provide an attenuation image for therapeutic planning, low soft-tissue contrast affects the delineation of anatomical and pathological features. Efforts have recently been devoted to several MRI linear accelerator (LINAC) projects that lead to the successful combination of a full diagnostic MRI scanner with a radiotherapy machine. We present a new concept for the development of the MRI-LINAC system. Instead of combining a full MRI scanner with the LINAC platform, we propose using an interior MRI (iMRI) approach to image a specific region of interest (RoI) containing the radiation treatment target. While the conventional CBCT component still delivers a global image of the patient’s anatomy, the iMRI offers local imaging of high soft-tissue contrast for tumor delineation. We describe a top-level system design for the integration of an iMRI component into an existing LINAC platform. We performed numerical analyses of the magnetic field for the iMRI to show potentially acceptable field properties in a spherical RoI with a diameter of 15 cm. This field could be shielded to a sufficiently low level around the LINAC region to avoid electromagnetic interference. Furthermore, we investigate the dosimetric impacts of this integration on the radiotherapy beam. PMID:28331888

High duty factor plasma generator for CERN's Superconducting Proton Linac.

PubMed

Lettry, J; Kronberger, M; Scrivens, R; Chaudet, E; Faircloth, D; Favre, G; Geisser, J-M; Küchler, D; Mathot, S; Midttun, O; Paoluzzi, M; Schmitzer, C; Steyaert, D

2010-02-01

CERN's Linac4 is a 160 MeV linear accelerator currently under construction. It will inject negatively charged hydrogen ions into CERN's PS-Booster. Its ion source is a noncesiated rf driven H(-) volume source directly inspired from the one of DESY and is aimed to deliver pulses of 80 mA of H(-) during 0.4 ms at a 2 Hz repetition rate. The Superconducting Proton Linac (SPL) project is part of the luminosity upgrade of the Large Hadron Collider. It consists of an extension of Linac4 up to 5 GeV and is foreseen to deliver protons to a future 50 GeV synchrotron (PS2). For the SPL high power option (HP-SPL), the ion source would deliver pulses of 80 mA of H(-) during 1.2 ms and operate at a 50 Hz repetition rate. This significant upgrade motivates the design of the new water cooled plasma generator presented in this paper. Its engineering is based on the results of a finite element thermal study of the Linac4 H(-) plasma generator that identified critical components and thermal barriers. A cooling system is proposed which achieves the required heat dissipation and maintains the original functionality. Materials with higher thermal conductivity are selected and, wherever possible, thermal barriers resulting from low pressure contacts are removed by brazing metals on insulators. The AlN plasma chamber cooling circuit is inspired from the approach chosen for the cesiated high duty factor rf H(-) source operating at SNS.

Modeling radiation loads in the ILC main linac and a novel approach to treat dark current

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mokhov, Nilolai V.; Rakhno, Igor L.; Tropin, Igor S.

Electromagnetic and hadron showers generated by electrons of dark current (DC) can represent a significant radiation threat to the ILC linac equipment and personnel. In this study, a commissioning scenario is analysed which is considered as the worst-case scenario for the main linac regarding the DC contribution to the radiation environment in the tunnel. A normal operation scenario is analysed as well. An emphasis is made on radiation load to sensitive electronic equipment—cryogenic thermometers inside the cryomodules. Prompt and residual dose rates in the ILC main linac tunnels were also calculated in these new high-statistics runs. A novel approach wasmore » developed—as a part of general purpose Monte Carlo code MARS15—to model generation, acceleration and transport of DC electrons in electromagnetic fields inside SRF cavities. Comparisons were made with a standard approach when a set of pre-calculated DC electron trajectories is used, with a proper normalization, as a source for Monte Carlo modelling. Results of MARS15 Monte Carlo calculations, performed for the current main linac tunnel design, reveal that the peak absorbed dose in the cryogenic thermometers in the main tunnel for 20 years of operation is about 0.8 MGy. The calculated contact residual dose on cryomodules and tunnel walls in the main tunnel for typical irradiation and cooling conditions is 0.1 and 0.01 mSv/hr, respectively.« less

Effect of transverse magnetic fields on a simulated in-line 6 MV linac

NASA Astrophysics Data System (ADS)

St. Aubin, J.; Steciw, S.; Fallone, B. G.

2010-08-01

The effects of a transverse magnetic field on an in-line side-coupled 6 MV linear accelerator are given. The results are directly applicable to a linac-MR system used for real-time image guided adaptive radiotherapy. Our previously designed end-to-end linac simulation incorporated the results from the axisymmetric 2D electron gun program EGN2w. However, since the magnetic fields being investigated are non-axisymmetric in nature for the work presented here, the electron gun simulation was performed using OPERA-3d/SCALA. The simulation results from OPERA-3d/SCALA showed excellent agreement with previous results. Upon the addition of external magnetic fields to our fully 3D linac simulation, it was found that a transverse magnetic field of 6 G resulted in a 45 ± 1% beam loss, and by 14 G, no electrons were incident on the target. Transverse magnetic fields on the linac simulation produced a highly asymmetric focal spot at the target, which translated into a 13% profile asymmetry at 6 G. Upon translating the focal spot with respect to the target coordinates, profile symmetry was regained at the expense of a lateral shift in the dose profiles. It was found that all points in the penumbra failed a 1%/1 mm acceptance criterion for fields between 4 and 6 G. However, it was also found that the lateral profile shifts were corrected by adjusting the jaw positions asymmetrically.

Patterns of heterotypic continuity associated with the cross-sectional correlational structure of prevalent mental disorders in adults.

PubMed

Lahey, Benjamin B; Zald, David H; Hakes, Jahn K; Krueger, Robert F; Rathouz, Paul J

2014-09-01

Mental disorders predict future occurrences of both the same disorder (homotypic continuity) and other disorders (heterotypic continuity). Heterotypic continuity is inconsistent with a view of mental disorders as fixed entities. In contrast, hierarchical-dimensional conceptualizations of psychopathology, in which each form of psychopathology is hypothesized to have both unique and broadly shared etiologies and mechanisms, predict both homotypic and heterotypic continuity. To test predictions derived from a hierarchical-dimensional model of psychopathology that (1) heterotypic continuity is widespread, even controlling for homotypic continuity, and that (2) the relative magnitudes of heterotypic continuities recapitulate the relative magnitudes of cross-sectional correlations among diagnoses at baseline. Ten prevalent diagnoses were assessed in the same person twice (ie, in 2 waves separated by 3 years). We used a representative sample of adults in the United States (i.e., 28,958 participants 18-64 years of age in the National Epidemiologic Study of Alcohol and Related Conditions who were assessed in both waves). Diagnoses from reliable and valid structured interviews. Adjusting for sex and age, we found that bivariate associations of all pairs of diagnoses from wave 1 to wave 2 exceeded chance levels (P < .05) for all homotypic (median tetrachoric correlation of ρ = 0.54 [range, 0.41-0.79]) and for nearly all heterotypic continuities (median tetrachoric correlation of ρ = 0.28 [range, 0.07-0.50]). Significant heterotypic continuity was widespread even when all wave 1 diagnoses (including the same diagnosis) were simultaneous predictors of each wave 2 diagnosis. The rank correlation between age- and sex-adjusted tetrachoric correlation for cross-sectional associations among wave 1 diagnoses and for heterotypic associations from wave 1 to wave 2 diagnoses was ρ = 0.86 (P < .001). For these prevalent mental disorders, heterotypic continuity was nearly universal and not an artifact of failure to control for homotypic continuity. Furthermore, the relative magnitudes of heterotypic continuity closely mirrored the relative magnitudes of cross-sectional associations among these disorders, consistent with the hypothesis that both sets of associations reflect the same factors. Mental disorders are not fixed and independent entities. Rather, each diagnosis is robustly related to other diagnoses in a correlational structure that is manifested both concurrently and in patterns of heterotypic continuity across time.

Quality of Intensity Modulated Radiation Therapy Treatment Plans Using a {sup 60}Co Magnetic Resonance Image Guidance Radiation Therapy System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wooten, H. Omar, E-mail: hwooten@radonc.wustl.edu; Green, Olga; Yang, Min

2015-07-15

Purpose: This work describes a commercial treatment planning system, its technical features, and its capabilities for creating {sup 60}Co intensity modulated radiation therapy (IMRT) treatment plans for a magnetic resonance image guidance radiation therapy (MR-IGRT) system. Methods and Materials: The ViewRay treatment planning system (Oakwood Village, OH) was used to create {sup 60}Co IMRT treatment plans for 33 cancer patients with disease in the abdominal, pelvic, thorax, and head and neck regions using physician-specified patient-specific target coverage and organ at risk (OAR) objectives. Backup plans using a third-party linear accelerator (linac)-based planning system were also created. Plans were evaluated bymore » attending physicians and approved for treatment. The {sup 60}Co and linac plans were compared by evaluating conformity numbers (CN) with 100% and 95% of prescription reference doses and heterogeneity indices (HI) for planning target volumes (PTVs) and maximum, mean, and dose-volume histogram (DVH) values for OARs. Results: All {sup 60}Co IMRT plans achieved PTV coverage and OAR sparing that were similar to linac plans. PTV conformity for {sup 60}Co was within <1% and 3% of linac plans for 100% and 95% prescription reference isodoses, respectively, and heterogeneity was on average 4% greater. Comparisons of OAR mean dose showed generally better sparing with linac plans in the low-dose range <20 Gy, but comparable sparing for organs with mean doses >20 Gy. The mean doses for all {sup 60}Co plan OARs were within clinical tolerances. Conclusions: A commercial {sup 60}Co MR-IGRT device can produce highly conformal IMRT treatment plans similar in quality to linac IMRT for a variety of disease sites. Additional work is in progress to evaluate the clinical benefit of other novel features of this MR-IGRT system.« less

Performance of a PTW 60019 microDiamond detector in a 1.5 T MRI-linac

NASA Astrophysics Data System (ADS)

Woodings, S. J.; Wolthaus, J. W. H.; van Asselen, B.; de Vries, J. H. W.; Kok, J. G. M.; Lagendijk, J. J. W.; Raaymakers, B. W.

2018-03-01

Accurate small-field dosimetry is critical for a magnetic resonance linac (MRI-linac). The PTW 60019 microDiamond is close to an ideal detector for small field dosimetry due to its small physical size, high signal-to-noise ratio and approximate water equivalence. It is important to fully characterise the performance of the detector in a 1.5 T magnetic field prior to its use for MRI-linac commissioning and quality assurance. Standard techniques of detector testing have been implemented, or adapted where necessary to suit the capabilities of the MRI-linac. Detector warmup, constancy, dose linearity, dose rate linearity, field size dependence and leakage were within tolerance. Measurements with the detector were consistent with ion chamber measurements for medium sized fields. The effective point of measurement of the detector when used within a 1.5 T magnetic field was determined to be 0.80 ± 0.23 mm below the top surface of the device, consistent with the existing vendor recommendation and alignment mark at 1.0 mm. The angular dependence was assessed. Variations of up to 9.7% were observed, which are significantly greater than in a 0 T environment. Within the expected range of use, the maximum effect is approximately 0.6% which is within tolerance. However for large beams within a magnetic field, the divergence and consequent variation in angle of photon incidence means that the microDiamond would not be ideal for characterising the profiles and it would not be suitable for determining large-field beam parameters such as symmetry. It would also require a correction factor prior to use for patient-specific QA measurements where radiation is delivered from different gantry angles. The results of this study demonstrate that the PTW 60019 microDiamond detector is suitable for measuring small radiation fields within a 1.5 T magnetic field and thus is suitable for use in MRI-linac commissioning and quality assurance.

Quality assurance for a six degrees-of-freedom table using a 3D printed phantom.

PubMed

Woods, Kyle; Ayan, Ahmet S; Woollard, Jeffrey; Gupta, Nilendu

2018-01-01

To establish a streamlined end-to-end test of a 6 degrees-of-freedom (6DoF) robotic table using a 3D printed phantom for periodic quality assurance. A 3D printed phantom was fabricated with translational and rotational offsets and an imbedded central ball-bearing (BB). The phantom underwent each step of the radiation therapy process: CT simulation in a straight orientation, plan generation using the treatment planning software, setup to offset marks at the linac, registration and corrected 6DoF table adjustments via hidden target test, delivery of a Winston-Lutz test to the BB, and verification of table positioning via field and laser lights. The registration values, maximum total displacement of the combined Winston-Lutz fields, and a pass or fail criterion of the laser and field lights were recorded. The quality assurance process for each of the three linacs were performed for the first 30 days. Within a 95% confidence interval, the overall uncertainty values for both translation and rotation were below 1.0 mm and 0.5° for each linac respectively. When combining the registration values and other uncertainties for all three linacs, the average deviations were within 2.0 mm and 1.0° of the designed translation and rotation offsets of the 3D print respectively. For all three linacs, the maximum total deviation for the Winston-Lutz test did not exceed 1.0 mm. Laser and light field verification was within tolerance every day for all three linacs given the latest guidance documentation for table repositioning. The 3D printer is capable of accurately fabricating a quality assurance phantom for 6DoF positioning verification. The end-to-end workflow allows for a more efficient test of the 6DoF mechanics while including other important tests needed for routine quality assurance. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

SU-G-TeP2-04: Comprehensive Machine Isocenter Evaluation with Separation of Gantry, Collimator, and Table Variables

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hancock, S; Clements, C; Hyer, D

2016-06-15

Purpose: To develop and demonstrate application of a method that characterizes deviation of linac x-ray beams from the centroid of the volumetric radiation isocenter as a function of gantry, collimator, and table variables. Methods: A set of Winston-Lutz ball-bearing images was used to determine the gantry radiation isocenter as the midrange of deviation values resulting from gantry and collimator rotation. Also determined were displacement of table axis from gantry isocenter and recommended table axis adjustment. The method, previously reported, has been extended to include the effect of collimator walkout by obtaining measurements with 0 and 180 degree collimator rotation formore » each gantry angle. Twelve images were used to characterize the volumetric isocenter for the full range of available gantry, collimator, and table rotations. Results: Three Varian True Beam, two Elekta Infinity and four Versa HD linacs at five institutions were tested using identical methodology. Varian linacs exhibited substantially less deviation due to head sag than Elekta linacs (0.4 mm vs. 1.2 mm on average). One linac from each manufacturer had additional isocenter deviation of 0.3 to 0.4 mm due to jaw instability with gantry and collimator rotation. For all linacs, the achievable isocenter tolerance was dependent on adjustment of collimator position offset, transverse position steering, and alignment of the table axis with gantry isocenter, facilitated by these test results. The pattern and magnitude of table axis wobble vs. table angle was reproducible and unique to each machine. Conclusion: This new method provides a comprehensive set of isocenter deviation values including all variables. It effectively facilitates minimization of deviation between beam center and target (ball-bearing) position. This method was used to quantify the effect of jaw instability on isocenter deviation and to identify the offending jaw. The test is suitable for incorporation into a routine machine QA program. Software development was performed by Radiological Imaging Technology, Inc.« less

High-gradient low-β accelerating structure using the first negative spatial harmonic of the fundamental mode

NASA Astrophysics Data System (ADS)

Kutsaev, Sergey V.; Agustsson, Ronald; Boucher, Salime; Fischer, Richard; Murokh, Alex; Mustapha, Brahim; Nassiri, Alireza; Ostroumov, Peter N.; Plastun, Alexander; Savin, Evgeny; Smirnov, Alexander Yu.

2017-12-01

The development of high-gradient accelerating structures for low-β particles is the key for compact hadron linear accelerators. A particular example of such a machine is a hadron therapy linac, which is a promising alternative to cyclic machines, traditionally used for cancer treatment. Currently, the practical utilization of linear accelerators in radiation therapy is limited by the requirement to be under 50 m in length. A usable device for cancer therapy should produce 200-250 MeV protons and/or 400 - 450 MeV /u carbon ions, which sets the requirement of having 35 MV /m average "real-estate gradient" or gradient per unit of actual accelerator length, including different accelerating sections, focusing elements and beam transport lines, and at least 50 MV /m accelerating gradients in the high-energy section of the linac. Such high accelerating gradients for ion linacs have recently become feasible for operations at S-band frequencies. However, the reasonable application of traditional S-band structures is practically limited to β =v /c >0.4 . However, the simulations show that for lower phase velocities, these structures have either high surface fields (>200 MV /m ) or low shunt impedances (<35 M Ω /m ). At the same time, a significant (˜10 % ) reduction in the linac length can be achieved by using the 50 MV /m structures starting from β ˜0.3 . To address this issue, we have designed a novel radio frequency structure where the beam is synchronous with the higher spatial harmonic of the electromagnetic field. In this paper, we discuss the principles of this approach, the related beam dynamics and especially the electromagnetic and thermomechanical designs of this novel structure. Besides the application to ion therapy, the technology described in this paper can be applied to future high gradient normal conducting ion linacs and high energy physics machines, such as a compact hadron collider. This approach preserves linac compactness in settings with limited space availability.

MO-F-CAMPUS-T-04: Implementation of a Standardized Monthly Quality Check for Linac Output Management in a Large Multi-Site Clinic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, H; Yi, B; Prado, K

2015-06-15

Purpose: This work is to investigate the feasibility of a standardized monthly quality check (QC) of LINAC output determination in a multi-site, multi-LINAC institution. The QC was developed to determine individual LINAC output using the same optimized measurement setup and a constant calibration factor for all machines across the institution. Methods: The QA data over 4 years of 7 Varian machines over four sites, were analyzed. The monthly output constancy checks were performed using a fixed source-to-chamber-distance (SCD), with no couch position adjustment throughout the measurement cycle for all the photon energies: 6 and 18MV, and electron energies: 6, 9,more » 12, 16 and 20 MeV. The constant monthly output calibration factor (Nconst) was determined by averaging the machines’ output data, acquired with the same monthly ion chamber. If a different monthly ion chamber was used, Nconst was then re-normalized to consider its different NDW,Co-60. Here, the possible changes of Nconst over 4 years have been tracked, and the precision of output results based on this standardized monthly QA program relative to the TG-51 calibration for each machine was calculated. Any outlier of the group was investigated. Results: The possible changes of Nconst varied between 0–0.9% over 4 years. The normalization of absorbed-dose-to-water calibration factors corrects for up to 3.3% variations of different monthly QA chambers. The LINAC output precision based on this standardized monthly QC relative to the TG-51 output calibration is within 1% for 6MV photon energy and 2% for 18MV and all the electron energies. A human error in one TG-51 report was found through a close scrutiny of outlier data. Conclusion: This standardized QC allows for a reasonably simplified, precise and robust monthly LINAC output constancy check, with the increased sensitivity needed to detect possible human errors and machine problems.« less

Performance of a PTW 60019 microDiamond detector in a 1.5 T MRI-linac.

PubMed

Woodings, S J; Wolthaus, J W H; van Asselen, B; de Vries, J H W; Kok, J G M; Lagendijk, J J W; Raaymakers, B W

2018-03-08

Accurate small-field dosimetry is critical for a magnetic resonance linac (MRI-linac). The PTW 60019 microDiamond is close to an ideal detector for small field dosimetry due to its small physical size, high signal-to-noise ratio and approximate water equivalence. It is important to fully characterise the performance of the detector in a 1.5 T magnetic field prior to its use for MRI-linac commissioning and quality assurance. Standard techniques of detector testing have been implemented, or adapted where necessary to suit the capabilities of the MRI-linac. Detector warmup, constancy, dose linearity, dose rate linearity, field size dependence and leakage were within tolerance. Measurements with the detector were consistent with ion chamber measurements for medium sized fields. The effective point of measurement of the detector when used within a 1.5 T magnetic field was determined to be 0.80 ± 0.23 mm below the top surface of the device, consistent with the existing vendor recommendation and alignment mark at 1.0 mm. The angular dependence was assessed. Variations of up to 9.7% were observed, which are significantly greater than in a 0 T environment. Within the expected range of use, the maximum effect is approximately 0.6% which is within tolerance. However for large beams within a magnetic field, the divergence and consequent variation in angle of photon incidence means that the microDiamond would not be ideal for characterising the profiles and it would not be suitable for determining large-field beam parameters such as symmetry. It would also require a correction factor prior to use for patient-specific QA measurements where radiation is delivered from different gantry angles. The results of this study demonstrate that the PTW 60019 microDiamond detector is suitable for measuring small radiation fields within a 1.5 T magnetic field and thus is suitable for use in MRI-linac commissioning and quality assurance.

SU-E-T-624: Portal Dosimetry Commissioning of Multiple (6) Varian TrueBeam Linacs Equipped with PortalVision DMI MV Imager

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weldon, M; DiCostanzo, D; Grzetic, S

2015-06-15

Purpose: To show that a single model for Portal Domisetry (PD) can be established for beam-matched TrueBeam™ linacs that are equipped with the DMI imager (43×43cm effective area). Methods: Our department acquired 6 new TrueBeam™s, 4 “Slim” and 2 “Edge” models. The Slims were equipped with 6 and 10MV photons, and the Edges with 6MV. MLCs differed between the Slims and Edges (Millennium 120 vs HD-MLC respectively). PD model was created from data acquired using a single linac (Slim). This includes maximum field size profile, as well as output factors and acquired measured fluence using the DMI imager. All identicalmore » linacs were beam-matched, profiles were within 1% at maximum field size at a variety of depths. The profile correction file was generated from 40×40 profile acquired at 5cm depth, 95cm SSD, and was adjusted for deviation at the field edges and corners. The PD model and profile correction was applied to all six TrueBeam™s and imagers. A variety of jaw only and sliding window (SW) MLC test fields, as well as TG-119 and clinical SW and VMAT plans were run on each linac to validate the model. Results: For 6X and 10X, field by field comparison using 3mm/3% absolute gamma criteria passed 90% or better for all cases. This was also true for composite comparisons of TG-199 and clinical plans, matching our current department criteria. Conclusion: Using a single model per photon energy for PD for the TrueBeam™ equipped with a DMI imager can produce clinically acceptable results across multiple identical and matched linacs. It is also possible to use the same PD model despite different MLCs. This can save time during commissioning and software updates.« less

Continuous-wave terahertz imaging of nonmelanoma skin cancers

NASA Astrophysics Data System (ADS)

Joseph, Cecil Sudhir

Continuous wave terahertz imaging has the potential to offer a safe, non-invasive medical imaging modality for detecting different types of human skin cancers. Terahertz pulse imaging (TPI) has already shown that there is contrast between basal cell carcinoma and normal skin. Continuous-wave imaging offers a simpler, lower cost alternative to terahertz pulse imaging. This project aims to isolate the optimal contrast frequency for a continuous wave terahertz imaging system and demonstrate transmission based, in-vitro , imaging of thin sections of non-melanoma skin cancers and correlate the images to sample histology. The aim of this project is to conduct a proof-of-principle experiment that establishes whether continuous-wave terahertz imaging can detect differences between cancerous and normal tissue while outlining the basic requirements for building a system capable of performing in vivo tests.

SU-F-T-496: An Investigation of Two Novel Devices for Testing Linac Clearance During CT Simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrow, A; Massingill, B

Purpose: This work’s objective is to determine the efficacy of two newly patented devices termed the Mor-O rings, Mark1 and Mark2, developed to predict collisions between the patient and a linac at the time of CT simulation. Methods: Mark1: A ring with an inner radius equal to the distance between the isocenter and the nearest portion of a linac head(diso) was made. This is mounted to a stand that allows vertical repositioning. The ring is placed around the patient on the CT table and aligned with isocenter. The patient is moved through the ring. If the ring touches the patient,more » a collision is predicted. To test this device, predicted collisions were marked on a phantom. The phantom was then repositioned on the linac table where the collisions were verified. Mark2: An arc with the radius diso was created with a re-locatable half-linac head wire-frame. The Mark2 is positioned in the same way as the Mark1 but can additionally mimic couch and gantry angulations. The Mark2 was tested with a volunteer using multiple couch, gantry and isocenter positions. The volunteer was then repositioned on the linac table to verify the angles of collisions. Results: Mark1: One isocenter out of ten showed negative clearance (0.9mm) on the linac table. All other collisions were predicted with 1 to 36mm of additional clearance. Mark2: All collisions were prevented with an additional 1.3 to 14.8 degrees of clearance. Conclusion: The Mark1 prototype is able to predict all collisions when no couch angulation is used. This device takes less than a minute to setup and is simple to use. The Mark2, when testing beam geometries used for noncoplanar SBRT, was able to prevent all collisions with 1.3 to 14.8 degrees additional clearance. Improvements in construction for both devices could increase accuracy and usability. Andrew Morrow owns Morrow Physics, LLC and Brian Massingill owns Spur Physics, LLC. We are both listed on the patent for the devices investigated in this work (patent 9220922). Our current employer, Baylor Scott and White, is also on the patent.« less

Integrating respiratory gating into a megavoltage cone-beam CT system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang Jenghwa; Sillanpaa, Jussi; Ling, Clifton C.

2006-07-15

We have previously described a low-dose megavoltage cone beam computed tomography (MV CBCT) system capable of producing projection image using one beam pulse. In this study, we report on its integration with respiratory gating for gated radiotherapy. The respiratory gating system tracks a reflective marker on the patient's abdomen midway between the xiphoid and umbilicus, and disables radiation delivery when the marker position is outside predefined thresholds. We investigate two strategies for acquiring gated scans. In the continuous rotation-gated acquisition, the linear accelerator (LINAC) is set to the fixed x-ray mode and the gantry makes a 5 min, 360 deg.continuousmore » rotation, during which the gating system turns the radiation beam on and off, resulting in projection images with an uneven distribution of projection angles (e.g., in 70 arcs each covering 2 deg.). In the gated rotation-continuous acquisition, the LINAC is set to the dynamic arc mode, which suspends the gantry rotation when the gating system inhibits the beam, leading to a slightly longer (6-7 min) scan time, but yielding projection images with more evenly distributed projection angles (e.g., {approx}0.8 deg.between two consecutive projection angles). We have tested both data acquisition schemes on stationary (a contrast detail and a thoracic) phantoms and protocol lung patients. For stationary phantoms, a separate motion phantom not visible in the images is used to trigger the RPM system. Frame rate is adjusted so that approximately 450 images (13 MU) are acquired for each scan and three-dimensional tomographic images reconstructed using a Feldkamp filtered backprojection algorithm. The gated rotation-continuous acquisition yield reconstructions free of breathing artifacts. The tumor in parenchymal lung and normal tissues are easily discernible and the boundary between the diaphragm and the lung sharply defined. Contrast-to-noise ratio (CNR) is not degraded relative to nongated scans of stationary phantoms. The continuous rotation-gated acquisition scan also yields tomographic images with discernible anatomic features; however, streak artifacts are observed and CNR is reduced by approximately a factor of 4. In conclusion, we have successfully developed a gated MV CBCT system to verify the patient positioning for gated radiotherapy.« less

Review of third and next generation synchrotron light sources

NASA Astrophysics Data System (ADS)

Bilderback, Donald H.; Elleaume, Pascal; Weckert, Edgar

2005-05-01

Synchrotron radiation (SR) is having a very large impact on interdisciplinary science and has been tremendously successful with the arrival of third generation synchrotron x-ray sources. But the revolution in x-ray science is still gaining momentum. Even though new storage rings are currently under construction, even more advanced rings are under design (PETRA III and the ultra high energy x-ray source) and the uses of linacs (energy recovery linac, x-ray free electron laser) can take us further into the future, to provide the unique synchrotron light that is so highly prized for today's studies in science in such fields as materials science, physics, chemistry and biology, for example. All these machines are highly reliant upon the consequences of Einstein's special theory of relativity. The consequences of relativity account for the small opening angle of synchrotron radiation in the forward direction and the increasing mass an electron gains as it is accelerated to high energy. These are familiar results to every synchrotron scientist. In this paper we outline not only the origins of SR but discuss how Einstein's strong character and his intuition and excellence have not only marked the physics of the 20th century but provide the foundation for continuing accelerator developments into the 21st century.

The LAMP instrument at the Linac Coherent Light Source free-electron laser

DOE PAGES

Osipov, Timur; Bostedt, Christoph; Castagna, J. -C.; ...

2018-03-23

The Laser Applications in Materials Processing (LAMP) instrument is a new end-station for soft X-ray imaging, high-field physics, and ultrafast X-ray science experiments that is available to users at the Linac Coherent Light Source (LCLS) free-electron laser. While the instrument resides in the Atomic, Molecular and Optical science hutch, its components can be used at any LCLS beamline. The end-station has a modular design that provides high flexibility in order to meet user-defined experimental requirements and specifications. The ultra-high-vacuum environment supports different sample delivery systems, including pulsed and continuous atomic, molecular, and cluster jets; liquid and aerosols jets; and effusivemore » metal vapor beams. It also houses movable, large-format, high-speed pnCCD X-ray detectors for detecting scattered and fluorescent photons. Multiple charged-particle spectrometer options are compatible with the LAMP chamber, including a double-sided spectrometer for simultaneous and even coincident measurements of electrons, ions, and photons produced by the interaction of the high-intensity X-ray beam with the various samples. Here in this paper we describe the design and capabilities of the spectrometers along with some general aspects of the LAMP chamber and show some results from the initial instrument commissioning.« less

The LAMP instrument at the Linac Coherent Light Source free-electron laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osipov, Timur; Bostedt, Christoph; Castagna, J. -C.

The Laser Applications in Materials Processing (LAMP) instrument is a new end-station for soft X-ray imaging, high-field physics, and ultrafast X-ray science experiments that is available to users at the Linac Coherent Light Source (LCLS) free-electron laser. While the instrument resides in the Atomic, Molecular and Optical science hutch, its components can be used at any LCLS beamline. The end-station has a modular design that provides high flexibility in order to meet user-defined experimental requirements and specifications. The ultra-high-vacuum environment supports different sample delivery systems, including pulsed and continuous atomic, molecular, and cluster jets; liquid and aerosols jets; and effusivemore » metal vapor beams. It also houses movable, large-format, high-speed pnCCD X-ray detectors for detecting scattered and fluorescent photons. Multiple charged-particle spectrometer options are compatible with the LAMP chamber, including a double-sided spectrometer for simultaneous and even coincident measurements of electrons, ions, and photons produced by the interaction of the high-intensity X-ray beam with the various samples. Here in this paper we describe the design and capabilities of the spectrometers along with some general aspects of the LAMP chamber and show some results from the initial instrument commissioning.« less

Reduce, reuse and recycle: a green solution to Canada's medical isotope shortage.

PubMed

Galea, R; Ross, C; Wells, R G

2014-05-01

Due to the unforeseen maintenance issues at the National Research Universal (NRU) reactor at Chalk River and coincidental shutdowns of other international reactors, a global shortage of medical isotopes (in particular technetium-99m, Tc-99m) occurred in 2009. The operation of these research reactors is expensive, their age creates concerns about their continued maintenance and the process results in a large amount of long-lived nuclear waste, whose storage cost has been subsidized by governments. While the NRU has since revived its operations, it is scheduled to cease isotope production in 2016. The Canadian government created the Non-reactor based medical Isotope Supply Program (NISP) to promote research into alternative methods for producing medical isotopes. The NRC was a member of a collaboration looking into the use of electron linear accelerators (LINAC) to produce molybdenum-99 (Mo-99), the parent isotope of Tc-99m. This paper outlines NRC's involvement in every step of this process, from the production, chemical processing, recycling and preliminary animal studies to demonstrate the equivalence of LINAC Tc-99m with the existing supply. This process stems from reusing an old idea, reduces the nuclear waste to virtually zero and recycles material to create a green solution to Canada's medical isotope shortage. © 2013 Published by Elsevier Ltd.

Conceptual Design for the New RPI 2020 Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adolphsen, C.; Bane, K.; Dolgashev, V.

2014-10-29

The Rensselaer Polytechnic Institute (RPI) spectrometer is an installation based on an L-band linear accelerator designed and installed many decades ago. While this installation has served many important experiments over the decades, a new more powerful and more flexible linac to serve a wider range of experiments is envisioned as an upgrade to the existing installation by 2020.

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacLachlan, J.A.

The basic premises of the conceptual design for the linac upgrade are pursued to establish lengths, gradients, power dissipation, etc., for the 400 MeV linac and matching section. The discussion is limited to accelerating and focusing components. Wherever values depend on the choice of the accelerating structure, the disk-and-washer structure is emphasized; the results are generally relevant to the side coupled cavity choice also.

Design of long induction linacs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caporaso, G.J.; Cole, A.G.

1990-09-06

A self-consistent design strategy for induction linacs is presented which addresses the issues of brightness preservation against space charge induced emittance growth, minimization of the beam breakup instability and the suppression of beam centroid motion due to chromatic effects (corkscrew) and misaligned focusing elements. A simple steering algorithm is described that widens the effective energy bandwidth of the transport system.

Use of the CEBAF Accelerator for IR and UV Free Electron Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yunn, Byung; Sinclair, Charles; Leemann, Christoph

1992-08-01

The CEBAF superconducting linac is capable of accelerating electron beams suitable for driving high-power free-electron lasers. The 45 MeV injector linac with a 6 cm period wiggler can produce kilowatt output powers of infrared light (3.6-17 micrometer), while the 400 MeV north linac can produce ultraviolet light (~200 nm) at similar powers. The FELs require the addition of a high-peak intensity electron source (~ 60 A peak current) and extraction beam lines to wigglers with appropriate electron and photon optics. FEL operation is compatible with simultaneous baseline CEBAF nuclear physics operation. A design for a CEBAF-based FEL facility has beenmore » developed. The current status of the FEL project is reported.« less

Production of Ac-225 for cancer therapy by photon-induced transmutation of Ra-226.

PubMed

Melville, G; Meriarty, H; Metcalfe, P; Knittel, T; Allen, B J

2007-09-01

The increasing application of Ac-225 for cancer therapy indicates the potential need for its increased production and availability. The production of Ac-225 has been achieved using bremsstrahlung photons from an 18 MV medical linear accelerator (linac) to bombard a Ra-226 target. A linac dose of 2800 Gy produced about 64 microCi of Ra-225, which decays to Ac-225. This result, while consistent with the theoretical calculations, is far too low to be of practical use. A more powerful linac is required that runs at a higher current, longer pulse length and higher frequency for practical production. This process could also lead to the reduction of the nuclear waste product Ra-226.

R-IDEAL: A Framework for Systematic Clinical Evaluation of Technical Innovations in Radiation Oncology.

PubMed

Verkooijen, Helena M; Kerkmeijer, Linda G W; Fuller, Clifton D; Huddart, Robbert; Faivre-Finn, Corinne; Verheij, Marcel; Mook, Stella; Sahgal, Arjun; Hall, Emma; Schultz, Chris

2017-01-01

The pace of innovation in radiation oncology is high and the window of opportunity for evaluation narrow. Financial incentives, industry pressure, and patients' demand for high-tech treatments have led to widespread implementation of innovations before, or even without, robust evidence of improved outcomes has been generated. The standard phase I-IV framework for drug evaluation is not the most efficient and desirable framework for assessment of technological innovations. In order to provide a standard assessment methodology for clinical evaluation of innovations in radiotherapy, we adapted the surgical IDEAL framework to fit the radiation oncology setting. Like surgery, clinical evaluation of innovations in radiation oncology is complicated by continuous technical development, team and operator dependence, and differences in quality control. Contrary to surgery, radiotherapy innovations may be used in various ways, e.g., at different tumor sites and with different aims, such as radiation volume reduction and dose escalation. Also, the effect of radiation treatment can be modeled, allowing better prediction of potential benefits and improved patient selection. Key distinctive features of R-IDEAL include the important role of predicate and modeling studies (Stage 0), randomization at an early stage in the development of the technology, and long-term follow-up for late toxicity. We implemented R-IDEAL for clinical evaluation of a recent innovation in radiation oncology, the MRI-guided linear accelerator (MR-Linac). MR-Linac combines a radiotherapy linear accelerator with a 1.5-T MRI, aiming for improved targeting, dose escalation, and margin reduction, and is expected to increase the use of hypofractionation, improve tumor control, leading to higher cure rates and less toxicity. An international consortium, with participants from seven large cancer institutes from Europe and North America, has adopted the R-IDEAL framework to work toward coordinated, evidence-based introduction of the MR-Linac. R-IDEAL holds the promise for timely, evidence-based introduction of radiotherapy innovations with proven superior effectiveness, while preventing unnecessary exposure of patients to potentially harmful interventions.

Neutron dose measurements of Varian and Elekta linacs by TLD600 and TLD700 dosimeters and comparison with MCNP calculations

PubMed Central

Nedaie, Hassan Ali; Darestani, Hoda; Banaee, Nooshin; Shagholi, Negin; Mohammadi, Kheirollah; Shahvar, Arjang; Bayat, Esmaeel

2014-01-01

High-energy linacs produce secondary particles such as neutrons (photoneutron production). The neutrons have the important role during treatment with high energy photons in terms of protection and dose escalation. In this work, neutron dose equivalents of 18 MV Varian and Elekta accelerators are measured by thermoluminescent dosimeter (TLD) 600 and TLD700 detectors and compared with the Monte Carlo calculations. For neutron and photon dose discrimination, first TLDs were calibrated separately by gamma and neutron doses. Gamma calibration was carried out in two procedures; by standard 60Co source and by 18 MV linac photon beam. For neutron calibration by 241Am-Be source, irradiations were performed in several different time intervals. The Varian and Elekta linac heads and the phantom were simulated by the MCNPX code (v. 2.5). Neutron dose equivalent was calculated in the central axis, on the phantom surface and depths of 1, 2, 3.3, 4, 5, and 6 cm. The maximum photoneutron dose equivalents which calculated by the MCNPX code were 7.06 and 2.37 mSv.Gy-1 for Varian and Elekta accelerators, respectively, in comparison with 50 and 44 mSv.Gy-1 achieved by TLDs. All the results showed more photoneutron production in Varian accelerator compared to Elekta. According to the results, it seems that TLD600 and TLD700 pairs are not suitable dosimeters for neutron dosimetry inside the linac field due to high photon flux, while MCNPX code is an appropriate alternative for studying photoneutron production. PMID:24600167

Clinical implementation and rapid commissioning of an EPID based in-vivo dosimetry system.

PubMed

Hanson, Ian M; Hansen, Vibeke N; Olaciregui-Ruiz, Igor; van Herk, Marcel

2014-10-07

Using an Electronic Portal Imaging Device (EPID) to perform in-vivo dosimetry is one of the most effective and efficient methods of verifying the safe delivery of complex radiotherapy treatments. Previous work has detailed the development of an EPID based in-vivo dosimetry system that was subsequently used to replace pre-treatment dose verification of IMRT and VMAT plans. Here we show that this system can be readily implemented on a commercial megavoltage imaging platform without modification to EPID hardware and without impacting standard imaging procedures. The accuracy and practicality of the EPID in-vivo dosimetry system was confirmed through a comparison with traditional TLD in-vivo measurements performed on five prostate patients.The commissioning time required for the EPID in-vivo dosimetry system was initially prohibitive at approximately 10 h per linac. Here we present a method of calculating linac specific EPID dosimetry correction factors that allow a single energy specific commissioning model to be applied to EPID data from multiple linacs. Using this method reduced the required per linac commissioning time to approximately 30 min.The validity of this commissioning method has been tested by analysing in-vivo dosimetry results of 1220 patients acquired on seven linacs over a period of 5 years. The average deviation between EPID based isocentre dose and expected isocentre dose for these patients was (-0.7  ±  3.2)%.EPID based in-vivo dosimetry is now the primary in-vivo dosimetry tool used at our centre and has replaced nearly all pre-treatment dose verification of IMRT treatments.

Clinical implementation and rapid commissioning of an EPID based in-vivo dosimetry system

NASA Astrophysics Data System (ADS)

Hanson, Ian M.; Hansen, Vibeke N.; Olaciregui-Ruiz, Igor; van Herk, Marcel

2014-10-01

Using an Electronic Portal Imaging Device (EPID) to perform in-vivo dosimetry is one of the most effective and efficient methods of verifying the safe delivery of complex radiotherapy treatments. Previous work has detailed the development of an EPID based in-vivo dosimetry system that was subsequently used to replace pre-treatment dose verification of IMRT and VMAT plans. Here we show that this system can be readily implemented on a commercial megavoltage imaging platform without modification to EPID hardware and without impacting standard imaging procedures. The accuracy and practicality of the EPID in-vivo dosimetry system was confirmed through a comparison with traditional TLD in-vivo measurements performed on five prostate patients. The commissioning time required for the EPID in-vivo dosimetry system was initially prohibitive at approximately 10 h per linac. Here we present a method of calculating linac specific EPID dosimetry correction factors that allow a single energy specific commissioning model to be applied to EPID data from multiple linacs. Using this method reduced the required per linac commissioning time to approximately 30 min. The validity of this commissioning method has been tested by analysing in-vivo dosimetry results of 1220 patients acquired on seven linacs over a period of 5 years. The average deviation between EPID based isocentre dose and expected isocentre dose for these patients was (-0.7  ±  3.2)%. EPID based in-vivo dosimetry is now the primary in-vivo dosimetry tool used at our centre and has replaced nearly all pre-treatment dose verification of IMRT treatments.

Development of new S-band SLED for PAL-XFEL Linac

NASA Astrophysics Data System (ADS)

Joo, Youngdo; Park, Yongjung; Heo, Hoon; Heo, Jinyul; Park, Sung-Soo; Kim, Sang-Hee; Kim, Kwang-Hoon; Kang, Heung-Sik; Lee, Heung-Soo; Noh, Sungju; Oh, Kyoungmin

2017-01-01

In order to achieve beam acceleration to the beam energy of 10 GeV at the end of its 716 m-long linear accelerator (Linac), the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) is going to operate the Stanford Linear Accelerator Energy Doubler (SLED) at the maximum klystron output peak power of 80 MW, with a pulse length of 4 μs, and at a repetition rate of 60 Hz. The original SLED that had been used in Pohang Light Source-II (PLS-II) can no longer sustain such a high-power operation because excessive radiation caused by RF breakdown has been frequently detected even at the lower klystron peak power during the PLS-II operation. Therefore, a new SLED is designed by modifying both the 3-dB power hybrid and the waveguide-cavity coupling structure of the original SLED where the excessive radiation has been mainly detected. The finite-difference time-domain (FDTD) simulation in the CST Microwave Studio shows that the new SLED has a peak electric field and a surface current lower than those of the original SLED at the same level of the RF input peak power, which would secure stable high-power operation. All of the 42 SLEDs in the PAL-XFEL Linac are newly fabricated and installed. During the RF conditioning of the PAL-XFEL Linac, no significant vacuum and radiation issue was found in the new SLEDs. Finally, the accelerated electron beam energy of 10 GeV obtained at the end of the PAL-XFEL Linac verified that the RF performance of the new SLED is stable.

Inverse planning in the age of digital LINACs: station parameter optimized radiation therapy (SPORT)

NASA Astrophysics Data System (ADS)

Xing, Lei; Li, Ruijiang

2014-03-01

The last few years have seen a number of technical and clinical advances which give rise to a need for innovations in dose optimization and delivery strategies. Technically, a new generation of digital linac has become available which offers features such as programmable motion between station parameters and high dose-rate Flattening Filter Free (FFF) beams. Current inverse planning methods are designed for traditional machines and cannot accommodate these features of new generation linacs without compromising either dose conformality and/or delivery efficiency. Furthermore, SBRT is becoming increasingly important, which elevates the need for more efficient delivery, improved dose distribution. Here we will give an overview of our recent work in SPORT designed to harness the digital linacs and highlight the essential components of SPORT. We will summarize the pros and cons of traditional beamlet-based optimization (BBO) and direct aperture optimization (DAO) and introduce a new type of algorithm, compressed sensing (CS)-based inverse planning, that is capable of automatically removing the redundant segments during optimization and providing a plan with high deliverability in the presence of a large number of station control points (potentially non-coplanar, non-isocentric, and even multi-isocenters). We show that CS-approach takes the interplay between planning and delivery into account and allows us to balance the dose optimality and delivery efficiency in a controlled way and, providing a viable framework to address various unmet demands of the new generation linacs. A few specific implementation strategies of SPORT in the forms of fixed-gantry and rotational arc delivery are also presented.

Neutron dose measurements of Varian and Elekta linacs by TLD600 and TLD700 dosimeters and comparison with MCNP calculations.

PubMed

Nedaie, Hassan Ali; Darestani, Hoda; Banaee, Nooshin; Shagholi, Negin; Mohammadi, Kheirollah; Shahvar, Arjang; Bayat, Esmaeel

2014-01-01

High-energy linacs produce secondary particles such as neutrons (photoneutron production). The neutrons have the important role during treatment with high energy photons in terms of protection and dose escalation. In this work, neutron dose equivalents of 18 MV Varian and Elekta accelerators are measured by thermoluminescent dosimeter (TLD) 600 and TLD700 detectors and compared with the Monte Carlo calculations. For neutron and photon dose discrimination, first TLDs were calibrated separately by gamma and neutron doses. Gamma calibration was carried out in two procedures; by standard 60Co source and by 18 MV linac photon beam. For neutron calibration by (241)Am-Be source, irradiations were performed in several different time intervals. The Varian and Elekta linac heads and the phantom were simulated by the MCNPX code (v. 2.5). Neutron dose equivalent was calculated in the central axis, on the phantom surface and depths of 1, 2, 3.3, 4, 5, and 6 cm. The maximum photoneutron dose equivalents which calculated by the MCNPX code were 7.06 and 2.37 mSv.Gy(-1) for Varian and Elekta accelerators, respectively, in comparison with 50 and 44 mSv.Gy(-1) achieved by TLDs. All the results showed more photoneutron production in Varian accelerator compared to Elekta. According to the results, it seems that TLD600 and TLD700 pairs are not suitable dosimeters for neutron dosimetry inside the linac field due to high photon flux, while MCNPX code is an appropriate alternative for studying photoneutron production.

Beam focal spot position determination for an Elekta linac with the Agility® head; practical guide with a ready-to-go procedure.

PubMed

Chojnowski, Jacek M; Taylor, Lee M; Sykes, Jonathan R; Thwaites, David I

2018-05-14

A novel phantomless, EPID-based method of measuring the beam focal spot offset of a linear accelerator was proposed and validated for Varian machines. In this method, one set of jaws and the MLC were utilized to form a symmetric field and then a 180 o collimator rotation was utilized to determine the radiation isocenter defined by the jaws and the MLC, respectively. The difference between these two isocentres is directly correlated with the beam focal spot offset of the linear accelerator. In the current work, the method has been considered for Elekta linacs. An Elekta linac with the Agility ® head does not have two set of jaws, therefore, a modified method is presented making use of one set of diaphragms, the MLC and a full 360 o collimator rotation. The modified method has been tested on two Elekta Synergy ® linacs with Agility ® heads and independently validated. A practical guide with instructions and a MATLAB ® code is attached for easy implementation. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Magnet design for the splitter/combiner regions of CBETA, the Cornell-Brookhaven Energy-Recovery-Linac Test Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crittendon, J. A.; Burke, D. C.; Fuentes, Y. L.P.

2017-01-06

The Cornell-Brookhaven Energy-Recovery-Linac Test Accelerator (CBETA) will provide a 150-MeV electron beam using four acceleration and four deceleration passes through the Cornell Main Linac Cryomodule housing six 1.3-GHz superconducting RF cavities. The return path of this 76-m-circumference accelerator will be provided by 106 fixed-field alternating-gradient (FFAG) cells which carry the four beams of 42, 78, 114 and 150 MeV. Here we describe magnet designs for the splitter and combiner regions which serve to match the on-axis linac beam to the off-axis beams in the FFAG cells, providing the path-length adjustment necessary to energy recovery for each of the four beams.more » The path lengths of the four beamlines in each of the splitter and combiner regions are designed to be adapted to 1-, 2-, 3-, and 4-pass staged operations. Design specifi- cations and modeling for the 24 dipole and 32 quadrupole electromagnets in each region are presented. The CBETA project will serve as the first demonstration of multi-pass energy recovery using superconducting RF cavities with FFAG cell optics for the return loop.« less

Upgrade of the beam extraction system of the GTS-LHC electron cyclotron resonance ion source at CERN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toivanen, V., E-mail: ville.aleksi.toivanen@cern.ch; Bellodi, G.; Dimov, V.

2016-02-15

Linac3 is the first accelerator in the heavy ion injector chain of the Large Hadron Collider (LHC), providing multiply charged heavy ion beams for the CERN experimental program. The ion beams are produced with GTS-LHC, a 14.5 GHz electron cyclotron resonance ion source, operated in afterglow mode. Improvement of the GTS-LHC beam formation and beam transport along Linac3 is part of the upgrade program of the injector chain in preparation for the future high luminosity LHC. A mismatch between the ion beam properties in the ion source extraction region and the acceptance of the following Low Energy Beam Transport (LEBT)more » section has been identified as one of the factors limiting the Linac3 performance. The installation of a new focusing element, an einzel lens, into the GTS-LHC extraction region is foreseen as a part of the Linac3 upgrade, as well as a redesign of the first section of the LEBT. Details of the upgrade and results of a beam dynamics study of the extraction region and LEBT modifications will be presented.« less

Noise Reduction and Correction in the IPNS Linac ESEM

NASA Astrophysics Data System (ADS)

Dooling, J. C.; Brumwell, F. R.; Donley, L.; McMichael, G. E.; Stipp, V. F.

2004-11-01

The Energy Spread and Energy Monitor (ESEM) is an on-line, non-intrusive diagnostic used to characterize the output beam from the 200-MHz, 50-MeV IPNS linac. The energy spread is determined from a 3-size, longitudinal emittance measurement; whereas the energy is derived from time of flight (TOF) analysis. Signals are detected on 50-ohm, stripline beam position monitors (BPMs) terminated in their characteristic impedance. Each BPM is constructed with four striplines: top, bottom, left and right. The ESEM signals are taken from the bottom stripline in four separate BPM locations in the 50-MeV transport line between the linac and the synchrotron. Deterministic linac noise is sampled before and after the 70-microsecond macropulse. The noise phasor is vectorially subtracted from the beam signal. Noise subtraction is required at several frequencies, especially the fundamental and fifth harmonics (200 MHz and 1 GHz). It is also necessary to correct for attenuation and dispersion in the co-axial signal cables. Presently, the analysis assumes a single particle distribution to determine energy and energy spread. Work is on-going to allow for more realistic longitudinal distributions to be included in the analysis.

Patterns of Heterotypic Continuity Associated With the Cross-Sectional Correlational Structure of Prevalent Mental Disorders in Adults

PubMed Central

Lahey, Benjamin B.; Zald, David H.; Hakes, Jahn K.; Krueger, Robert F.; Rathouz, Paul J.

2014-01-01

Importance Mental disorders predict future occurrences of both the same disorder (homotypic continuity) and other disorders (heterotypic continuity). Heterotypic continuity is inconsistent with a view of mental disorders as fixed entities. In contrast, hierarchical-dimensional conceptualizations of psychopathology, in which each form of psychopathology is hypothesized to have both unique and broadly shared etiologies and mechanisms, predict both homotypic and heterotypic continuity. Objective To test predictions derived from a hierarchical-dimensional model of psychopathology that (a) heterotypic continuity is widespread, even controlling for homotypic continuity, and (b) the relative magnitudes of heterotypic continuities recapitulate the relative magnitudes of cross-sectional correlations among diagnoses at baseline. Design Assess 10 prevalent diagnoses in the same persons 3 years apart. Setting Representative sample of adults in the United States. Participants The 28,958 participants in the National Epidemiologic Study of Alcohol and Related Condition aged 18–64 years who were assessed in both waves. Main Outcome Measure Diagnoses from reliable and valid structured interviews. Results Bivariate associations of all pairs of diagnoses from wave 1 to wave 2 exceeded chance levels for all homotypic (tetrachoric ρ = 0.41 – 0.79, median = 0.54) and for nearly all heterotypic continuities (tetrachoric ρ = 0.07 – 0.50, median = 0.28), adjusted for sex and age. Significant heterotypic continuity was widespread even when all other wave 1 diagnoses (including the same diagnosis) were simultaneous predictors of each wave 2 diagnosis. The rank correlation between age and sex adjusted tetrachoric ρs for cross-sectional associations among wave 1 diagnoses and heterotypic associations from wave 1 to wave 2 diagnoses was ρ = .86. Conclusions and Relevance For these prevalent mental disorders, heterotypic continuity was nearly universal and not an artifact of failure to control for homotypic continuity. Furthermore, the relative magnitudes of heterotypic continuity closely mirrored the relative magnitudes of cross-sectional associations among these disorders, consistent with the hypothesis that both sets of associations reflect the same factors. Mental disorders are not fixed and independent entities. Rather, each diagnosis is robustly related to other diagnoses in a correlational structure that is manifested both concurrently and in patterns of heterotypic continuity across time. PMID:24989054

Pulsed-focusing recirculating linacs for muon acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Rolland

2014-12-31

Since the muon has a short lifetime, fast acceleration is essential for high-energy applications such as muon colliders, Higgs factories, or neutrino factories. The best one can do is to make a linear accelerator with the highest possible accelerating gradient to make the accelerating time as short as possible. However, the cost of such a single linear accelerator is prohibitively large due to expensive power sources, cavities, tunnels, and related infrastructure. As was demonstrated in the Thomas Jefferson Accelerator Facility (Jefferson Lab) Continuous Electron Beam Accelerator Facility (CEBAF), an elegant solution to reduce cost is to use magnetic return arcsmore » to recirculate the beam through the accelerating RF cavities many times, where they gain energy on each pass. In such a Recirculating Linear Accelerator (RLA), the magnetic focusing strength diminishes as the beam energy increases in a conventional linac that has constant strength quadrupoles. After some number of passes the focusing strength is insufficient to keep the beam from going unstable and being lost. In this project, the use of fast pulsed quadrupoles in the linac sections was considered for stronger focusing as a function of time to allow more successive passes of a muon beam in a recirculating linear accelerator. In one simulation, it was shown that the number of passes could be increased from 8 to 12 using pulsed magnet designs that have been developed and tested. This could reduce the cost of linac sections of a muon RLA by 8/12, where more improvement is still possible. The expense of a greater number of passes and corresponding number of return arcs was also addressed in this project by exploring the use of ramped or FFAG-style magnets in the return arcs. A better solution, invented in this project, is to use combined-function dipole-quadrupole magnets to simultaneously transport two beams of different energies through one magnet string to reduce costs of return arcs by almost a factor of two. A patent application was filed for this invention and a detailed report published in Physical Review Special Topics. A scaled model using an electron beam was developed and proposed to test the concept of a dog bone RLA with combined-function return arcs. The efforts supported by this grant were reported in a series of contributions to particle accelerator conferences that are reproduced in the appendices and summarized in the body of this report.« less

Prompt radiation, shielding and induced radioactivity in a high-power 160 MeV proton linac

NASA Astrophysics Data System (ADS)

Magistris, Matteo; Silari, Marco

2006-06-01

CERN is designing a 160 MeV proton linear accelerator, both for a future intensity upgrade of the LHC and as a possible first stage of a 2.2 GeV superconducting proton linac. A first estimate of the required shielding was obtained by means of a simple analytical model. The source terms and the attenuation lengths used in the present study were calculated with the Monte Carlo cascade code FLUKA. Detailed FLUKA simulations were performed to investigate the contribution of neutron skyshine and backscattering to the expected dose rate in the areas around the linac tunnel. An estimate of the induced radioactivity in the magnets, vacuum chamber, the cooling system and the concrete shield was performed. A preliminary thermal study of the beam dump is also discussed.

Minimization of three-dimensional beam emittance growth in rare-isotope accelerator

NASA Astrophysics Data System (ADS)

Oh, B. H.; Yoon, M.

2016-12-01

In this paper, we describe a research to minimize the three-dimensional (3D) emittance growth (EG) in the RAON accelerator, a heavy ion accelerator currently being developed in Korea to produce various rare isotopes. The emittance minimization is performed using the multi-objective genetic algorithm and the simplex method. We use them to analyze the driver linac for the in-flight fragmentation separator of the RAON facility and show that redesign of the 90-degree bending section of the RAON accelerator together with adjustment of optics in the upstream and downstream superconducting linacs can limit the 3D EG to 20 % in the entire region of the driver linac. Effects of various magnet and rf accelerating cavity errors on the beam-EG are also discussed.

RF transient analysis and stabilization of the phase and energy of the proposed PIP-II LINAC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edelen, J. P.; Chase, B. E.

This paper describes a recent effort to develop and benchmark a simulation tool for the analysis of RF transients and their compensation in an H- linear accelerator. Existing tools in this area either focus on electron LINACs or lack fundamental details about the LLRF system that are necessary to provide realistic performance estimates. In our paper we begin with a discussion of our computational models followed by benchmarking with existing beam-dynamics codes and measured data. We then analyze the effect of RF transients and their compensation in the PIP-II LINAC, followed by an analysis of calibration errors and how amore » Newton’s Method based feedback scheme can be used to regulate the beam energy to within the specified limits.« less

Characterization of the radiation environment at the UNLV accelerator facility during operation of the Varian M6 linac

NASA Astrophysics Data System (ADS)

Hodges, M.; Barzilov, A.; Chen, Y.; Lowe, D.

2016-10-01

The bremsstrahlung photon flux from the UNLV particle accelerator (Varian M6 model) was determined using MCNP5 code for 3 MeV and 6 MeV incident electrons. Human biological equivalent dose rates due to accelerator operation were evaluated using the photon flux with the flux-to-dose conversion factors. Dose rates were computed for the accelerator facility for M6 linac use under different operating conditions. The results showed that the use of collimators and linac internal shielding significantly reduced the dose rates throughout the facility. It was shown that the walls of the facility, in addition to the earthen berm enveloping the building, provide equivalent shielding to reduce dose rates outside to below the 2 mrem/h limit.

Numerical study of the inductive plasma coupling to ramp up the plasma density for the Linac4 H- ion source

NASA Astrophysics Data System (ADS)

Ohta, M.; Mattei, S.; Yasumoto, M.; Hatayama, A.; Lettry, J.

2014-02-01

In the Linac4 H- ion source, the plasma is generated by an RF antenna operated at 2 MHz. In order to investigate the conditions necessary for ramping up the plasma density of the Linac4 H- ion source in the low plasma density, a numerical study has been performed for a wide range of parameter space of RF coil current and initial pressure from H2 gas injection. We have employed an Electromagnetic Particle in Cell model, in which the collision processes have been calculated by a Monte Carlo method. The results have shown that the range of initial gas pressure from 2 to 3 Pa is suitable for ramping up plasma density via inductive coupling.

Advanced Accelerators for Medical Applications

NASA Astrophysics Data System (ADS)

Uesaka, Mitsuru; Koyama, Kazuyoshi

We review advanced accelerators for medical applications with respect to the following key technologies: (i) higher RF electron linear accelerator (hereafter "linac"); (ii) optimization of alignment for the proton linac, cyclotron and synchrotron; (iii) superconducting magnet; (iv) laser technology. Advanced accelerators for medical applications are categorized into two groups. The first group consists of compact medical linacs with high RF, cyclotrons and synchrotrons downsized by optimization of alignment and superconducting magnets. The second group comprises laserbased acceleration systems aimed of medical applications in the future. Laser plasma electron/ion accelerating systems for cancer therapy and laser dielectric accelerating systems for radiation biology are mentioned. Since the second group has important potential for a compact system, the current status of the established energy and intensity and of the required stability are given.

The design of a simulated in-line side-coupled 6 MV linear accelerator waveguide.

PubMed

St Aubin, Joel; Steciw, Stephen; Fallone, B G

2010-02-01

The design of a 3D in-line side-coupled 6 MV linac waveguide for medical use is given, and the effect of the side-coupling and port irises on the radio frequency (RF), beam dynamics, and dosimetric solutions is examined. This work was motivated by our research on a linac-MR hybrid system, where accurate electron trajectory information for a clinical medical waveguide in the presence of an external magnetic field was needed. For this work, the design of the linac waveguide was generated using the finite element method. The design outlined here incorporates the necessary geometric changes needed to incorporate a full-end accelerating cavity with a single-coupling iris, a waveguide-cavity coupling port iris that allows power transfer into the waveguide from the magnetron, as well as a method to control the RF field magnitude within the first half accelerating cavity into which the electrons from the gun are injected. With the full waveguide designed to resonate at 2998.5 +/- 0.1 MHz, a full 3D RF field solution was obtained. The accuracy of the 3D RF field solution was estimated through a comparison of important linac parameters (Q factor, shunt impedance, transit time factor, and resonant frequency) calculated for one accelerating cavity with the benchmarked program SUPERFISH. It was found that the maximum difference between the 3D solution and SUPERFISH was less than 0.03%. The eigenvalue solver, which determines the resonant frequencies of the 3D side-coupled waveguide simulation, was shown to be highly accurate through a comparison with lumped circuit theory. Two different waveguide geometries were examined, one incorporating a 0.5 mm first side cavity shift and another with a 1.5 mm first side cavity shift. The asymmetrically placed side-coupling irises and the port iris for both models were shown to introduce asymmetries in the RF field large enough to cause a peak shift and skewing (center of gravity minus peak shift) of an initially cylindrically uniform electron beam accelerating within the waveguide. The shifting and skewing of the electron beam were found to be greatest due to the effects of the side-coupling irises on the RF field. A further Monte Carlo study showed that this effect translated into a 1% asymmetry in a 40 x 40 cm2 field dose profile. A full 3D design for an in-line side-coupled 6 MV linear accelerator that emulates a common commercial waveguide has been given. The effect of the side coupling on the dose distribution has been shown to create a slight asymmetry, but overall does not affect the clinical applicability of the linac. The 3D in-line side-coupled linac model further provides a tool for the investigation of linac performance within an external magnetic field, which exists in an integrated linac-MR system.

Response of a hypersonic boundary layer to freestream pulse acoustic disturbance.

PubMed

Wang, Zhenqing; Tang, Xiaojun; Lv, Hongqing

2014-01-01

The response of hypersonic boundary layer over a blunt wedge to freestream pulse acoustic disturbance was investigated. The stability characteristics of boundary layer for freestream pulse wave and continuous wave were analyzed comparatively. Results show that freestream pulse disturbance changes the thermal conductivity characteristics of boundary layer. For pulse wave, the number of main disturbance clusters decreases and the frequency band narrows along streamwise. There are competition and disturbance energy transfer among different modes in boundary layer. The dominant mode of boundary layer has an inhibitory action on other modes. Under continuous wave, the disturbance modes are mainly distributed near fundamental and harmonic frequencies, while under pulse wave, the disturbance modes are widely distributed in different modes. For both pulse and continuous waves, most of disturbance modes slide into a lower-growth or decay state in downstream, which is tending towards stability. The amplitude of disturbance modes in boundary layer under continuous wave is considerably larger than pulse wave. The growth rate for the former is also considerably larger than the later the disturbance modes with higher growth are mainly distributed near fundamental and harmonic frequencies for the former, while the disturbance modes are widely distributed in different frequencies for the latter.

Response of a Hypersonic Boundary Layer to Freestream Pulse Acoustic Disturbance

PubMed Central

Wang, Zhenqing; Tang, Xiaojun; Lv, Hongqing

2014-01-01

The response of hypersonic boundary layer over a blunt wedge to freestream pulse acoustic disturbance was investigated. The stability characteristics of boundary layer for freestream pulse wave and continuous wave were analyzed comparatively. Results show that freestream pulse disturbance changes the thermal conductivity characteristics of boundary layer. For pulse wave, the number of main disturbance clusters decreases and the frequency band narrows along streamwise. There are competition and disturbance energy transfer among different modes in boundary layer. The dominant mode of boundary layer has an inhibitory action on other modes. Under continuous wave, the disturbance modes are mainly distributed near fundamental and harmonic frequencies, while under pulse wave, the disturbance modes are widely distributed in different modes. For both pulse and continuous waves, most of disturbance modes slide into a lower-growth or decay state in downstream, which is tending towards stability. The amplitude of disturbance modes in boundary layer under continuous wave is considerably larger than pulse wave. The growth rate for the former is also considerably larger than the later the disturbance modes with higher growth are mainly distributed near fundamental and harmonic frequencies for the former, while the disturbance modes are widely distributed in different frequencies for the latter. PMID:24737993

Studies of electron cooling at DESY

NASA Astrophysics Data System (ADS)

Balewski, K.; Brinkmann, R.; Derbenev, Y.; Floettmann, K.; Wesolowski, P.; Gentner, M.; Husmann, D.; Steier, C.

2000-02-01

A possibility to improve the luminosity in hadron colliders is to apply electron cooling. For the e-p and possibly in the future for e-ion a cooling scheme is proposed for the HERA collider which improves the brightness of the hadron beam in two steps. In a first step the hadron beam is cooled at an energy of 15-20 GeV in the pre-accelerator PETRA. In a second step the hadrons are cooled at top energy in HERA, mainly to maintain the beam quality. The first part of the cooler in PETRA consists of a thermionic gun which delivers electron bunches of 120 keV. These bunches are then compressed so that they fit into a 208 MHz travelling wave linac where they are accelerated to an energy of 10 MeV. Gun, compressor, and linac are surrounded by a solenoid so that emittance growth is avoided especially at the low energy end. In order to reduce the energy spread of the electron beam and to lengthen it, the electrons run through a decompressor before they are brought together with the hadron beam in a 40 m long cooling section which is again surrounded by a solenoid. In this paper a schematic layout of the system will be presented and simulation results of the first part of the cooler will be shown. The cooler in HERA consists of a small electron storage ring with two long straight sections. It is shown that all requirements of such a ring running at an energy between 180 and 450 MeV can be met to fight emittance growth in case of light hadron beams (protons) and to cool heavy ions sufficiently fast.

Robert R. Wilson Prize: The Quest for Bright, Coherent X-Rays: A Personal Story

NASA Astrophysics Data System (ADS)

Kim, Kwang Je

2014-03-01

Stories associated with the advances in x-ray source techniques during the last several decades will be told from a personal viewpoint. I will start from the ``third-generation'' x-ray sources based on storage-ring-based undulators and a struggle to find a proper way to quantify the radiation strength. I will then discuss how the initially incoherent undulator radiation evolves into an intense-quasi-coherent radiation via free-electron laser (FEL) interaction. This so-called self-amplified spontaneous emission (SASE) in the x-ray region could be realized with the advent of laser-induced electron guns and forms the basis of the linac-driven ``fourth generation'' x-ray facilities. An x-ray FEL oscillator (XFELO) will also be feasible if Bragg reflectors, such as diamond crystals, are used as cavity mirrors. An XFELO driven by a CW superconducting linac would be a ``real x-ray laser,'' producing a steady stream of fully coherent, spectrally pure x-ray pulses. An XFELO can be mode-locked, thus producing x-ray spectral comb, if the cavity length can be fixed to a fraction of the x-ray wavelength by referencing to a narrow nuclear resonance. A mode-locked XFELO will enable x-ray quantum optics experiments, such as matter-wave interferometry, for fundamental physics. Alongside these main themes, stories for novel and ``cute'' schemes, such as a crossed undulator for polarization switching and an emittance exchanger for swapping the transverse and longitudinal phase space, will also be presented. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357.

Heavy ion linear accelerator for radiation damage studies of materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kutsaev, Sergey V.; Mustapha, Brahim; Ostroumov, Peter N.

A new eXtreme MATerial (XMAT) research facility is being proposed at Argonne National Laboratory to enable rapid in situ mesoscale bulk analysis of ion radiation damage in advanced materials and nuclear fuels. This facility combines a new heavy-ion accelerator with the existing high-energy X-ray analysis capability of the Argonne Advanced Photon Source. The heavy-ion accelerator and target complex will enable experimenters to emulate the environment of a nuclear reactor making possible the study of fission fragment damage in materials. Material scientists will be able to use the measured material parameters to validate computer simulation codes and extrapolate the response ofmore » the material in a nuclear reactor environment. Utilizing a new heavy-ion accelerator will provide the appropriate energies and intensities to study these effects with beam intensities which allow experiments to run over hours or days instead of years. The XMAT facility will use a CW heavy-ion accelerator capable of providing beams of any stable isotope with adjustable energy up to 1.2 MeV/u for U-238(50+) and 1.7 MeV for protons. This energy is crucial to the design since it well mimics fission fragments that provide the major portion of the damage in nuclear fuels. The energy also allows damage to be created far from the surface of the material allowing bulk radiation damage effects to be investigated. The XMAT ion linac includes an electron cyclotron resonance ion source, a normal-conducting radio-frequency quadrupole and four normal-conducting multi-gap quarter-wave resonators operating at 60.625 MHz. This paper presents the 3D multi-physics design and analysis of the accelerating structures and beam dynamics studies of the linac.« less

Heavy ion linear accelerator for radiation damage studies of materials

NASA Astrophysics Data System (ADS)

Kutsaev, Sergey V.; Mustapha, Brahim; Ostroumov, Peter N.; Nolen, Jerry; Barcikowski, Albert; Pellin, Michael; Yacout, Abdellatif

2017-03-01

A new eXtreme MATerial (XMAT) research facility is being proposed at Argonne National Laboratory to enable rapid in situ mesoscale bulk analysis of ion radiation damage in advanced materials and nuclear fuels. This facility combines a new heavy-ion accelerator with the existing high-energy X-ray analysis capability of the Argonne Advanced Photon Source. The heavy-ion accelerator and target complex will enable experimenters to emulate the environment of a nuclear reactor making possible the study of fission fragment damage in materials. Material scientists will be able to use the measured material parameters to validate computer simulation codes and extrapolate the response of the material in a nuclear reactor environment. Utilizing a new heavy-ion accelerator will provide the appropriate energies and intensities to study these effects with beam intensities which allow experiments to run over hours or days instead of years. The XMAT facility will use a CW heavy-ion accelerator capable of providing beams of any stable isotope with adjustable energy up to 1.2 MeV/u for 238U50+ and 1.7 MeV for protons. This energy is crucial to the design since it well mimics fission fragments that provide the major portion of the damage in nuclear fuels. The energy also allows damage to be created far from the surface of the material allowing bulk radiation damage effects to be investigated. The XMAT ion linac includes an electron cyclotron resonance ion source, a normal-conducting radio-frequency quadrupole and four normal-conducting multi-gap quarter-wave resonators operating at 60.625 MHz. This paper presents the 3D multi-physics design and analysis of the accelerating structures and beam dynamics studies of the linac.

Toward continuous-wave operation of organic semiconductor lasers

PubMed Central

Sandanayaka, Atula S. D.; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

2017-01-01

The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi–continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture. PMID:28508042

Toward continuous-wave operation of organic semiconductor lasers.

PubMed

Sandanayaka, Atula S D; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

2017-04-01

The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi-continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture.

Superconducting energy recovery linacs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ben-Zvi, Ilan

High-average-power and high-brightness electron beams from a combination of laser photocathode electron guns and a superconducting energy recovery linac (ERL) is an emerging accelerator science with applications in ERL light sources, high repetition rate free electron lasers , electron cooling, electron ion colliders and more. This paper reviews the accelerator physics issues of superconducting ERLs, discusses major subsystems and provides a few examples of superconducting ERLs.

Superconducting energy recovery linacs

DOE PAGES

Ben-Zvi, Ilan

2016-09-01

High-average-power and high-brightness electron beams from a combination of laser photocathode electron guns and a superconducting energy recovery linac (ERL) is an emerging accelerator science with applications in ERL light sources, high repetition rate free electron lasers , electron cooling, electron ion colliders and more. This paper reviews the accelerator physics issues of superconducting ERLs, discusses major subsystems and provides a few examples of superconducting ERLs.

Beam dynamics in heavy ion induction LINACS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, L.

1981-10-01

Interest in the use of an induction linac to accelerate heavy ions for the purpose of providing the energy required to initiate an inertially confined fusion reaction has stimulated a theoretical effort to investigate various beam dynamical effects associated with high intensity heavy ion beams. This paper presents a summary of the work that has been done so far; transverse, longitudinal and coupled longitudinal transverse effects are discussed.

Accelerator and Fusion Research Division. Annual report, October 1978-September 1979

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1980-03-01

Topics covered include: Super HILAC and Bevalac operations; high intensity uranium beams line item; advanced high charge state ion source; 184-inch synchrocyclotron; VENUS project; positron-electron project; high field superconducting accelerator magnets; beam cooling; accelerator theory; induction linac drivers; RF linacs and storage rings; theory; neutral beam systems development; experimental atomic physics; neutral beam plasma research; plasma theory; and the Tormac project. (GHT)

H- ion sources for CERN's Linac4

NASA Astrophysics Data System (ADS)

Lettry, J.; Aguglia, D.; Coutron, Y.; Chaudet, E.; Dallocchio, A.; Gil Flores, J.; Hansen, J.; Mahner, E.; Mathot, S.; Mattei, S.; Midttun, O.; Moyret, P.; Nisbet, D.; O'Neil, M.; Paoluzzi, M.; Pasquino, C.; Pereira, H.; Arias, J. Sanchez; Schmitzer, C.; Scrivens, R.; Steyaert, D.

2013-02-01

The specifications set to the Linac4 ion source are: H- ion pulses of 0.5 ms duration, 80 mA intensity and 45 keV energy within a normalized emittance of 0.25 mmmrad RMS at a repetition rate of 2 Hz. In 2010, during the commissioning of a prototype based on H- production from the plasma volume, it was observed that the powerful co-extracted electron beam inherent to this type of ion source could destroy its electron beam dump well before reaching nominal parameters. However, the same source was able to provide 80 mA of protons mixed with a small fraction of H2+ and H3+ molecular ions. The commissioning of the radio frequency quadrupole accelerator (RFQ), beam chopper and H- beam diagnostics of the Linac4 are scheduled for 2012 and its final installation in the underground building is to start in 2013. Therefore, a crash program was launched in 2010 and reviewed in 2011 aiming at keeping the original Linac4 schedule with the following deliverables: Design and production of a volume ion source prototype suitable for 20-30 mA H- and 80 mA proton pulses at 45 keV by mid-2012. This first prototype will be dedicated to the commissioning of the low energy components of the Linac4. Design and production of a second prototype suitable for 40-50 mA H- based on an external RF solenoid plasma heating and cesiated-surface production mechanism in 2013 and a third prototype based on BNL's Magnetron aiming at reliable 2 Hz and 80 mA H- operations in 2014. In order to ease the future maintenance and allow operation with Ion sources based on three different production principles, an ion source "front end" providing alignment features, pulsed gas injection, pumping units, beam tuning capabilities and pulsed bipolar high voltage acceleration was designed and is being produced. This paper describes the progress of the Linac4 ion source program, the design of the Front end and first ion source prototype. Preliminary results of the summer 2012 commissioning are presented. The outlook on the future prototype ion sources is sketched.

SU-F-T-371: Development of a Linac Monte Carlo Model to Calculate Surface Dose

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prajapati, S; Yan, Y; Gifford, K

2016-06-15

Purpose: To generate and validate a linac Monte Carlo (MC) model for surface dose prediction. Methods: BEAMnrc V4-2.4.0 was used to model 6 and 18 MV photon beams for a commercially available linac. DOSXYZnrc V4-2.4.0 calculated 3D dose distributions in water. Percent depth dose (PDD) and beam profiles were extracted for comparison to measured data. Surface dose and at depths in the buildup region was measured with radiochromic film at 100 cm SSD for 4 × 4 cm{sup 2} and 10 × 10 cm{sup 2} collimator settings for open and MLC collimated fields. For the 6 MV beam, films weremore » placed at depths ranging from 0.015 cm to 2 cm and for 18 MV, 0.015 cm to 3.5 cm in Solid Water™. Films were calibrated for both photon energies at their respective dmax. PDDs and profiles were extracted from the film and compared to the MC data. The MC model was adjusted to match measured PDD and profiles. Results: For the 6 MV beam, the mean error(ME) in PDD between film and MC for open fields was 1.9%, whereas it was 2.4% for MLC. For the 18 MV beam, the ME in PDD for open fields was 2% and was 3.5% for MLC. For the 6 MV beam, the average root mean square(RMS) deviation for the central 80% of the beam profile for open fields was 1.5%, whereas it was 1.6% for MLC. For the 18 MV beam, the maximum RMS for open fields was 3%, and was 3.1% for MLC. Conclusion: The MC model of a linac agreed to within 4% of film measurements for depths ranging from the surface to dmax. Therefore, the MC linac model can predict surface dose for clinical applications. Future work will focus on adjusting the linac MC model to reduce RMS error and improve accuracy.« less

SU-F-T-268: A Feasibility Study of Independent Dose Verification for Vero4DRT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamashita, M; Kokubo, M; Institute of Biomedical Research and Innovation, Kobe, Hyogo

2016-06-15

Purpose: Vero4DRT (Mitsubishi Heavy Industries Ltd.) has been released for a few years. The treatment planning system (TPS) of Vero4DRT is dedicated, so the measurement is the only method of dose verification. There have been no reports of independent dose verification using Clarksonbased algorithm for Vero4DRT. An independent dose verification software program of the general-purpose linac using a modified Clarkson-based algorithm was modified for Vero4DRT. In this study, we evaluated the accuracy of independent dose verification program and the feasibility of the secondary check for Vero4DRT. Methods: iPlan (Brainlab AG) was used as the TPS. PencilBeam Convolution was used formore » dose calculation algorithm of IMRT and X-ray Voxel Monte Carlo was used for the others. Simple MU Analysis (SMU, Triangle Products, Japan) was used as the independent dose verification software program in which CT-based dose calculation was performed using a modified Clarkson-based algorithm. In this study, 120 patients’ treatment plans were collected in our institute. The treatments were performed using the conventional irradiation for lung and prostate, SBRT for lung and Step and shoot IMRT for prostate. Comparison in dose between the TPS and the SMU was done and confidence limits (CLs, Mean ± 2SD %) were compared to those from the general-purpose linac. Results: As the results of the CLs, the conventional irradiation (lung, prostate), SBRT (lung) and IMRT (prostate) show 2.2 ± 3.5% (CL of the general-purpose linac: 2.4 ± 5.3%), 1.1 ± 1.7% (−0.3 ± 2.0%), 4.8 ± 3.7% (5.4 ± 5.3%) and −0.5 ± 2.5% (−0.1 ± 3.6%), respectively. The CLs for Vero4DRT show similar results to that for the general-purpose linac. Conclusion: The independent dose verification for the new linac is clinically available as a secondary check and we performed the check with the similar tolerance level of the general-purpose linac. This research is partially supported by Japan Agency for Medical Research and Development (AMED)« less

SIMULATIONS OF TRANSVERSE STACKING IN THE NSLS-II BOOSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fliller III, R.; Shaftan, T.

2011-03-28

The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The linac needs to deliver 15 nC in 80 - 150 bunches to the booster every minute to achieve current stability goals in the storage ring. This is a very stringent requirement that has not been demonstrated at an operating light source. We have developed a scheme to transversely stack two bunch trains in the NSLS-II booster in order to alleviate the charge requirements on the linac. This scheme has been outlined previously. In this paper we show particle tracking simulations of the tracking scheme.more » We show simulations of the booster ramp with a stacked beam for a variety of lattice errors and injected beam parameters. In all cases the performance of the proposed stacking method is sufficient to reduce the required charge from the linac. For this reason the injection system of the NSLS-II booster is being designed to include this feature. The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The injectors must provide 7.5nC in bunch trains 80-150 bunches long every minute for top off operation of the storage ring. Top off then requires that the linac deliver 15nC of charge once losses in the injector chain are taken into consideration. This is a very stringent requirement that has not been demonstrated at an operating light source. For this reason we have developed a method to transversely stack two bunch trains in the booster while maintaining the charge transport efficiency. This stacking scheme has been discussed previously. In this paper we show the simulations of the booster ramp with a single bunch train in the booster. Then we give a brief overview of the stacking scheme. Following, we show the results of stacking two bunch trains in the booster with varying beam emittances and train separations. The behavior of the beam through the ramp is examined showing that it is possible to stack two bunch trains in the booster.« less

Compact Short-Pulsed Electron Linac Based Neutron Sources for Precise Nuclear Material Analysis

NASA Astrophysics Data System (ADS)

Uesaka, M.; Tagi, K.; Matsuyama, D.; Fujiwara, T.; Dobashi, K.; Yamamoto, M.; Harada, H.

2015-10-01

An X-band (11.424GHz) electron linac as a neutron source for nuclear data study for the melted fuel debris analysis and nuclear security in Fukushima is under development. Originally we developed the linac for Compton scattering X-ray source. Quantitative material analysis and forensics for nuclear security will start several years later after the safe settlement of the accident is established. For the purpose, we should now accumulate more precise nuclear data of U, Pu, etc., especially in epithermal (0.1-10 eV) neutrons. Therefore, we have decided to modify and install the linac in the core space of the experimental nuclear reactor "Yayoi" which is now under the decommission procedure. Due to the compactness of the X-band linac, an electron gun, accelerating tube and other components can be installed in a small space in the core. First we plan to perform the time-of-flight (TOF) transmission measurement for study of total cross sections of the nuclei for 0.1-10 eV energy neutrons. Therefore, if we adopt a TOF line of less than 10m, the o-pulse length of generated neutrons should be shorter than 100 ns. Electronenergy, o-pulse length, power, and neutron yield are ~30 MeV, 100 ns - 1 micros, ~0.4 kW, and ~1011 n/s (~103 n/cm2/s at samples), respectively. Optimization of the design of a neutron target (Ta, W, 238U), TOF line and neutron detector (Ce:LiCAF) of high sensitivity and fast response is underway. We are upgrading the electron gun and a buncher to realize higher current and beam power with a reasonable beam size in order to avoid damage of the neutron target. Although the neutron flux is limited in case of the X-band electron linac based source, we take advantage of its short pulse aspect and availability for nuclear data measurement with a short TOF system. First, we form a tentative configuration in the current experimental room for Compton scattering in 2014. Then, after the decommissioning has been finished, we move it to the "Yayoi" room and perform the operation and measurement.

SU-F-J-143: Initial Assessment of Image Quality of An Integrated MR-Linac System with ACR Phantom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J; Fuller, C; Yung, J

Purpose/Objective(s): To assess the image quality of an integrated MR-Linac system and compare with other MRI systems that are primarily used for diagnostic purposes. Materials/Methods: An ACR MRI quality control (QC) phantom was used to evaluate the image quality of a fully integrated 1.5T MRI-Linac system recently installed at our institution. This system has a new split magnet design which gives the magnetic field strength of 1.5T. All images were acquired with a set of phased-array surface coils which are designed to have minimal attention of radiation beam. The anterior coil rests on a coil holder which keeps the anteriormore » coil’s position consistent for QA purposes. The posterior coil is imbedded in the patient couch. Multiple sets of T1, T2/PD images were acquired using the protocols as prescribed by the ACR on three different dates, ranging 3 months apart. Results: The geometric distortion are within 0.5 mm in the axial scans and within 1mm in the saggital (z-direction) scans. Slice thickness accuracy, image uniformity, ghosting ratio, high contrast detectability are comparable to other 1.5T diagnostic MRI scanners. The low-contrast object detectability are lower comparatively, which is a result of using the body array coil. Additionally, the beam’s-eye-view images (oblique coronal and saggital images) have minimal geometric distortion at all linac gantry angles tested. No observable changes or drift in image quality is found from images acquired 3 month apart. Conclusion: Despite the use of a body array surface coil, the image quality is comparable to that of an 1.5T MRI scanner and is of sufficient quality to pass the ACR MRI accreditation program. The geometric distortion of the MRI system of the integrated MR-Linac is within 1mm for an object size similar to the ACR phantom, sufficient for radiation therapy treatment purpose. The authors received corporate sponsored research grants from Elekta which is the vendor for the MR-Linac evaluated in this study.« less

Watt-Level Continuous-Wave Emission from a Bi-Functional Quantum Cascade Laser/Detector

DTIC Science & Technology

2017-04-18

facet continuous wave emission at 15◦C. Apart from the general performance benets, this enables sensing techiques which rely on continuous wave...record achieved with strained material at this wavelength. Keywords quantum cascade laser, quantum cascade detector, lab- on -a-chip, monolithic integrated...materials, which makes their integration on Si particularly dicult. Heterogeneous integration using transfer techniques allows both single device and wafer

Reasons for Trying E-cigarettes and Risk of Continued Use

PubMed Central

Kong, Grace; Cavallo, Dana A.; Camenga, Deepa R.; Krishnan-Sarin, Suchitra

2016-01-01

BACKGROUND: Longitudinal research is needed to identify predictors of continued electronic cigarette (e-cigarette) use among youth. We expected that certain reasons for first trying e-cigarettes would predict continued use over time (eg, good flavors, friends use), whereas other reasons would not predict continued use (eg, curiosity). METHODS: Longitudinal surveys from middle and high school students from fall 2013 (wave 1) and spring 2014 (wave 2) were used to examine reasons for trying e-cigarettes as predictors of continued e-cigarette use over time. Ever e-cigarette users (n = 340) at wave 1 were categorized into those using or not using e-cigarettes at wave 2. Among those who continued using e-cigarettes, reasons for trying e-cigarettes were examined as predictors of use frequency, measured as the number of days using e-cigarettes in the past 30 days at wave 2. Covariates included age, sex, race, and smoking of traditional cigarettes. RESULTS: Several reasons for first trying e-cigarettes predicted continued use, including low cost, the ability to use e-cigarettes anywhere, and to quit smoking regular cigarettes. Trying e-cigarettes because of low cost also predicted more days of e-cigarette use at wave 2. Being younger or a current smoker of traditional cigarettes also predicted continued use and more frequent use over time. CONCLUSIONS: Regulatory strategies such as increasing cost or prohibiting e-cigarette use in certain places may be important for preventing continued use in youth. In addition, interventions targeting current cigarette smokers and younger students may also be needed. PMID:27503349

Reasons for Trying E-cigarettes and Risk of Continued Use.

PubMed

Bold, Krysten W; Kong, Grace; Cavallo, Dana A; Camenga, Deepa R; Krishnan-Sarin, Suchitra

2016-09-01

Longitudinal research is needed to identify predictors of continued electronic cigarette (e-cigarette) use among youth. We expected that certain reasons for first trying e-cigarettes would predict continued use over time (eg, good flavors, friends use), whereas other reasons would not predict continued use (eg, curiosity). Longitudinal surveys from middle and high school students from fall 2013 (wave 1) and spring 2014 (wave 2) were used to examine reasons for trying e-cigarettes as predictors of continued e-cigarette use over time. Ever e-cigarette users (n = 340) at wave 1 were categorized into those using or not using e-cigarettes at wave 2. Among those who continued using e-cigarettes, reasons for trying e-cigarettes were examined as predictors of use frequency, measured as the number of days using e-cigarettes in the past 30 days at wave 2. Covariates included age, sex, race, and smoking of traditional cigarettes. Several reasons for first trying e-cigarettes predicted continued use, including low cost, the ability to use e-cigarettes anywhere, and to quit smoking regular cigarettes. Trying e-cigarettes because of low cost also predicted more days of e-cigarette use at wave 2. Being younger or a current smoker of traditional cigarettes also predicted continued use and more frequent use over time. Regulatory strategies such as increasing cost or prohibiting e-cigarette use in certain places may be important for preventing continued use in youth. In addition, interventions targeting current cigarette smokers and younger students may also be needed. Copyright © 2016 by the American Academy of Pediatrics.

EFFECTS OF CONTINUOUS-WAVE, PULSED, AND SINUSOIDAL-AMPLITUDE-MODULATED MICROWAVES ON BRAIN ENERGY METABOLISM

EPA Science Inventory

A comparison of the effects of continuous wave, sinusoidal-amplitude modulated, and pulsed square-wave-modulated 591-MHz microwave exposures on brain energy metabolism was made in male Sprague Dawley rats (175-225g). Brain NADH fluorescence, adensine triphosphate (ATP) concentrat...

Passive magnetic shielding in MRI-Linac systems.

PubMed

Whelan, Brendan; Kolling, Stefan; Oborn, Brad M; Keall, Paul

2018-03-26

Passive magnetic shielding refers to the use of ferromagnetic materials to redirect magnetic field lines away from vulnerable regions. An application of particular interest to the medical physics community is shielding in MRI systems, especially integrated MRI-linear accelerator (MRI-Linac) systems. In these systems, the goal is not only to minimize the magnetic field in some volume, but also to minimize the impact of the shield on the magnetic fields within the imaging volume of the MRI scanner. In this work, finite element modelling was used to assess the shielding of a side coupled 6 MV linac and resultant heterogeneity induced within the 30 cm diameter of spherical volume (DSV) of a novel 1 Tesla split bore MRI magnet. A number of different shield parameters were investigated; distance between shield and magnet, shield shape, shield thickness, shield length, openings in the shield, number of concentric layers, spacing between each layer, and shield material. Both the in-line and perpendicular MRI-Linac configurations were studied. By modifying the shield shape around the linac from the starting design of an open ended cylinder, the shielding effect was boosted by approximately 70% whilst the impact on the magnet was simultaneously reduced by approximately 10%. Openings in the shield for the RF port and beam exit were substantial sources of field leakage; however it was demonstrated that shielding could be added around these openings to compensate for this leakage. Layering multiple concentric shield shells was highly effective in the perpendicular configuration, but less so for the in-line configuration. Cautious use of high permeability materials such as Mu-metal can greatly increase the shielding performance in some scenarios. In the perpendicular configuration, magnetic shielding was more effective and the impact on the magnet lower compared with the in-line configuration.

Passive magnetic shielding in MRI-Linac systems

NASA Astrophysics Data System (ADS)

Whelan, Brendan; Kolling, Stefan; Oborn, Brad M.; Keall, Paul

2018-04-01

Passive magnetic shielding refers to the use of ferromagnetic materials to redirect magnetic field lines away from vulnerable regions. An application of particular interest to the medical physics community is shielding in MRI systems, especially integrated MRI-linear accelerator (MRI-Linac) systems. In these systems, the goal is not only to minimize the magnetic field in some volume, but also to minimize the impact of the shield on the magnetic fields within the imaging volume of the MRI scanner. In this work, finite element modelling was used to assess the shielding of a side coupled 6 MV linac and resultant heterogeneity induced within the 30 cm diameter of spherical volume (DSV) of a novel 1 Tesla split bore MRI magnet. A number of different shield parameters were investigated; distance between shield and magnet, shield shape, shield thickness, shield length, openings in the shield, number of concentric layers, spacing between each layer, and shield material. Both the in-line and perpendicular MRI-Linac configurations were studied. By modifying the shield shape around the linac from the starting design of an open ended cylinder, the shielding effect was boosted by approximately 70% whilst the impact on the magnet was simultaneously reduced by approximately 10%. Openings in the shield for the RF port and beam exit were substantial sources of field leakage; however it was demonstrated that shielding could be added around these openings to compensate for this leakage. Layering multiple concentric shield shells was highly effective in the perpendicular configuration, but less so for the in-line configuration. Cautious use of high permeability materials such as Mu-metal can greatly increase the shielding performance in some scenarios. In the perpendicular configuration, magnetic shielding was more effective and the impact on the magnet lower compared with the in-line configuration.

Solid-state pulse modulator using Marx generator for a medical linac electron-gun

NASA Astrophysics Data System (ADS)

Lim, Heuijin; Hyeok Jeong, Dong; Lee, Manwoo; Lee, Mujin; Yi, Jungyu; Yang, Kwangmo; Ro, Sung Chae

2016-04-01

A medical linac is used for the cancer treatment and consists of an accelerating column, waveguide components, a magnetron, an electron-gun, a pulse modulator, and an irradiation system. The pulse modulator based on hydrogen thyratron-switched pulse-forming network is commonly used in linac. As the improvement of the high power semiconductors in switching speed, voltage rating, and current rating, an insulated gate bipolar transistor has become the more popular device used for pulsed power systems. We propose a solid-state pulse modulator to generator high voltage by multi-stacked storage-switch stages based on the Marx generator. The advantage of our modulator comes from the use of two semiconductors to control charging and discharging of the storage capacitor at each stage and it allows to generate the pulse with various amplitudes, widths, and shapes. In addition, a gate driver for two semiconductors is designed to reduce the control channels and to protect the circuits. It is developed for providing the pulsed power to a medical linac electron-gun that requires 25 kV and 1 A as the first application. In order to improve the power efficiency and achieve the compactness modulator, a capacitor charging power supply, a Marx pulse generator, and an electron-gun heater isolated transformer are constructed and integrated. This technology is also being developed to extend the high power pulsed system with > 1 MW and also other applications such as a plasma immersed ion implantation and a micro pulse electrostatic precipitator which especially require variable pulse shape and high repetition rate > 1 kHz. The paper describes the design features and the construction of this solid-state pulse modulator. Also shown are the performance results into the linac electron-gun.

Treatment vault shielding for a flattening filter-free medical linear accelerator

NASA Astrophysics Data System (ADS)

Kry, Stephen F.; Howell, Rebecca M.; Polf, Jerimy; Mohan, Radhe; Vassiliev, Oleg N.

2009-03-01

The requirements for shielding a treatment vault with a Varian Clinac 2100 medical linear accelerator operated both with and without the flattening filter were assessed. Basic shielding parameters, such as primary beam tenth-value layers (TVLs), patient scatter fractions, and wall scatter fractions, were calculated using Monte Carlo simulations of 6, 10 and 18 MV beams. Relative integral target current requirements were determined from treatment planning studies of several disease sites with, and without, the flattening filter. The flattened beam shielding data were compared to data published in NCRP Report No. 151, and the unflattened beam shielding data were presented relative to the NCRP data. Finally, the shielding requirements for a typical treatment vault were determined for a single-energy (6 MV) linac and a dual-energy (6 MV/18 MV) linac. With the exception of large-angle patient scatter fractions and wall scatter fractions, the vault shielding parameters were reduced when the flattening filter was removed. Much of this reduction was consistent with the reduced average energy of the FFF beams. Primary beam TVLs were reduced by 12%, on average, and small-angle scatter fractions were reduced by up to 30%. Head leakage was markedly reduced because less integral target current was required to deliver the target dose. For the treatment vault examined in the current study, removal of the flattening filter reduced the required thickness of the primary and secondary barriers by 10-20%, corresponding to 18 m3 less concrete to shield the single-energy linac and 36 m3 less concrete to shield the dual-energy linac. Thus, a shielding advantage was found when the linac was operated without the flattening filter. This translates into a reduction in occupational exposure and/or the cost and space of shielding.

Treatment vault shielding for a flattening filter-free medical linear accelerator.

PubMed

Kry, Stephen F; Howell, Rebecca M; Polf, Jerimy; Mohan, Radhe; Vassiliev, Oleg N

2009-03-07

The requirements for shielding a treatment vault with a Varian Clinac 2100 medical linear accelerator operated both with and without the flattening filter were assessed. Basic shielding parameters, such as primary beam tenth-value layers (TVLs), patient scatter fractions, and wall scatter fractions, were calculated using Monte Carlo simulations of 6, 10 and 18 MV beams. Relative integral target current requirements were determined from treatment planning studies of several disease sites with, and without, the flattening filter. The flattened beam shielding data were compared to data published in NCRP Report No. 151, and the unflattened beam shielding data were presented relative to the NCRP data. Finally, the shielding requirements for a typical treatment vault were determined for a single-energy (6 MV) linac and a dual-energy (6 MV/18 MV) linac. With the exception of large-angle patient scatter fractions and wall scatter fractions, the vault shielding parameters were reduced when the flattening filter was removed. Much of this reduction was consistent with the reduced average energy of the FFF beams. Primary beam TVLs were reduced by 12%, on average, and small-angle scatter fractions were reduced by up to 30%. Head leakage was markedly reduced because less integral target current was required to deliver the target dose. For the treatment vault examined in the current study, removal of the flattening filter reduced the required thickness of the primary and secondary barriers by 10-20%, corresponding to 18 m(3) less concrete to shield the single-energy linac and 36 m(3) less concrete to shield the dual-energy linac. Thus, a shielding advantage was found when the linac was operated without the flattening filter. This translates into a reduction in occupational exposure and/or the cost and space of shielding.

Volume Changes After Stereotactic LINAC Radiotherapy in Vestibular Schwannoma: Control Rate and Growth Patterns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Langenberg, Rick van de, E-mail: rickvandelangenberg@hotmail.com; Dohmen, Amy J.C.; Bondt, Bert J. de

2012-10-01

Purpose: The purpose of this study was to evaluate the control rate of vestibular schwannomas (VS) after treatment with linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) or radiotherapy (SRT) by using a validated volumetric measuring tool. Volume-based studies on prognosis after LINAC-based SRS or SRT for VS are reported scarcely. In addition, growth patterns and risk factors predicting treatment failure were analyzed. Materials and Methods: Retrospectively, 37 VS patients treated with LINAC based SRS or SRT were analyzed. Baseline and follow-up magnetic resonance imaging scans were analyzed with volume measurements on contrast enhanced T1-weighted magnetic resonance imaging. Absence of intervention aftermore » radiotherapy was defined as 'no additional intervention group, ' absence of radiological growth was defined as 'radiological control group. ' Significant growth was defined as a volume change of 19.7% or more, as calculated in a previous study. Results: The cumulative 4-year probability of no additional intervention was 96.4% {+-} 0.03; the 4-year radiological control probability was 85.4% {+-} 0.1). The median follow-up was 40 months. Overall, shrinkage was seen in 65%, stable VS in 22%, and growth in 13%. In 54% of all patients, transient swelling was observed. No prognostic factors were found regarding VS growth. Previous treatment and SRS were associated with transient swelling significantly. Conclusions: Good control rates are reported for LINAC based SRS or SRT in VS, in which the lower rate of radiological growth control is attributed to the use of the more sensitive volume measurements. Transient swelling after radiosurgery is a common phenomenon and should not be mistaken for treatment failure. Previous treatment and SRS were significantly associated with transient swelling.« less

Infrastructure and equipment for radiation oncology in the Spanish National Health System: analysis of external beam radiotherapy 2015-2020.

PubMed

Rodríguez, A; Algara, M; Monge, D; López-Torrecilla, J; Caballero, F; Morera, R; Escó, R; Pérez-Montero, H; Ferrer, C; Lara, P C

2018-03-01

Planning for radiation oncology requires reliable estimates of both demand for radiotherapy and availability of technological resources. This study compares radiotherapy resources in the 17 regions of the decentralised Spanish National Health System (SNHS). The Sociedad Española de Oncología Radioterápica (SEOR) performed a cross-sectional survey of all Spanish radiation oncology services (ROS) in 2015. We collected data on SNHS radiotherapy units, recording the year of installation, specific features of linear accelerators (LINACs) and other treatment units, and radiotherapeutic techniques implemented by region. Any machine over 10 years old or lacking a multileaf collimator or portal imaging system was considered obsolete. We performed a k-means clustering analysis using the Hartigan-Wong method to test associations between the gross domestic regional product (GDRP), the number of LINACs per million population and the percentage of LINACs over 10 years old. The SNHS controls 72 (61%) of the 118 Spanish ROS and has 180 LINACs, or 72.5% of the total public and private resources. The mean rate of LINACs per million population is 3.9 for public ROS, and 42% (n = 75) of the public accelerators were obsolete in 2015: 61 due to age and 14 due to technological capability. There was considerable regional variation in terms of the number and technological capacity of radiotherapy units; correlation between GRDP and resource availability was moderate. Despite improvements, new investments are still needed to replace obsolete units and increase access to modern radiotherapy. Regular analysis of ROS in each Spanish region is the only strategy for monitoring progress in radiotherapy capacity.

Investigating in-field and out-of-field neutron contamination in high-energy medical linear accelerators based on the treatment factors of field size, depth, beam modifiers, and beam type.

PubMed

Biltekin, Fatih; Yeginer, Mete; Ozyigit, Gokhan

2015-07-01

We analysed the effects of field size, depth, beam modifier and beam type on the amount of in-field and out-of-field neutron contamination for medical linear accelerators (linacs). Measurements were carried out for three high-energy medical linacs of Elekta Synergy Platform, Varian Clinac DHX High Performance and Philips SL25 using bubble detectors. The photo-neutron measurements were taken in the first two linacs with 18 MV nominal energy, whereas the electro-neutrons were measured in the three linacs with 9 MeV, 10 MeV, 15 MeV and 18 MeV. The central neutron doses increased with larger field sizes as a dramatic drop off was observed in peripheral areas. Comparing with the jaws-shaped open-field of 10 × 10 cm, the motorised and physical wedges contributed to neutron contamination at central axis by 60% and 18%, respectively. The similar dose increment was observed in MLC-shaped fields. The contributions of MLCs were in the range of 55-59% and 19-22% in Elekta and Varian linacs comparing with 10 × 10 and 20 × 20 cm open fields shaped by the jaws, respectively. The neutron doses at shallow depths were found to be higher than the doses found at deeper regions. The electro-neutron dose at the 18 MeV energy was higher than the doses at the electron energies of 15 MeV and 9 MeV by a factor of 3 and 50, respectively. The photo- and electro-neutron dose should be taken into consideration in the radiation treatment with high photon and electron energies. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

The LLRF System for the S-Band RF Plants of the FERMI Linac

NASA Astrophysics Data System (ADS)

Fabris, A.; Byrd, J.; D'Auria, G.; Doolittle, L.; Gelmetti, F.; Huang, G.; Jones, J.; Milloch, M.; Predonzani, M.; Ratti, A.; Rohlev, T.; Salom, A.; Serrano, C.; Stettler, M.

2016-04-01

Specifications on electron beam quality for the operation of a linac-based free-electron laser (FEL), as FERMI in Trieste (Italy), impose stringent requirements on the stability of the electromagnetic fields of the accelerating sections. These specifications can be met only with state-of-the-art low-level RF (LLRF) systems based on advanced digital technologies. Design considerations, construction, and performance results of the FERMI digital LLRF are presented in this paper. The stability requirements derived by simulations are better than 0.1% in amplitude and 0.1° S-band in phase. The system installed in the FERMI Linac S-band RF plants has met these specifications and is in operation on a 24-h basis as a user facility. Capabilities of the system allow planning for new developments that are also described here.

Beam dynamic simulation and optimization of the CLIC positron source and the capture linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bayar, C., E-mail: cafer.bayar@cern.ch; CERN, Geneva; Doebert, S., E-mail: Steffen.Doebert@cern.ch

2016-03-25

The CLIC Positron Source is based on the hybrid target composed of a crystal and an amorphous target. Simulations have been performed from the exit of the amorphous target to the end of pre-injector linac which captures and accelerates the positrons to an energy of 200 MeV. Simulations are performed by the particle tracking code PARMELA. The magnetic field of the AMD is represented in PARMELA by simple coils. Two modes are applied in this study. The first one is accelerating mode based on acceleration after the AMD. The second one is decelerating mode based on deceleration in the first acceleratingmore » structure. It is shown that the decelerating mode gives a higher yield for the e{sup +} beam in the end of the Pre-Injector Linac.« less

Novel Imaging Method of Continuous Shear Wave by Ultrasonic Color Flow Mapping

NASA Astrophysics Data System (ADS)

Yamakoshi, Yoshiki; Yamamoto, Atsushi; Yuminaka, Yasushi

Shear wave velocity measurement is a promising method in evaluation of tissue stiffness. Several methods have been developed to measure the shear wave velocity, however, it is difficult to obtain quantitative shear wave image in real-time by low cost system. In this paper, a novel shear wave imaging method for continuous shear wave is proposed. This method uses a color flow imaging which is used in ultrasonic imaging system to obtain shear wave's wavefront map. Two conditions, shear wave frequency condition and shear wave displacement amplitude condition, are required, however, these conditions are not severe restrictions in most applications. Using the proposed method, shear wave velocity of trapezius muscle is measured. The result is consistent with the velocity which is calculated from shear elastic modulus measured by ARFI method.

Design of a Tunable, Room Temperature, Continuous-Wave Terahertz Source and Detector using Silicon Waveguides

DTIC Science & Technology

2008-01-30

that will use conventional diode- or hotomultiplier-tube-based optical detectors , which are xtremely sensitive . . HEATING AND FREE-CARRIER IMITATIONS...CONTRACT NUMBER IN-HOUSE Design of a tunable, room temperature, continuous-wave terahertz source and detector using silicon waveguides 5b. GRANT...B 261Design of a tunable, room temperature, continuous-wave terahertz source and detector using silicon waveguides T. Baehr-Jones,1,* M. Hochberg,1,3

Freak Waves In The Ocean A~é­ We Need Continuous Measurements!

NASA Astrophysics Data System (ADS)

Liu, P.; Teng, C.; Mori, N.

Freak waves, sometimes also known as rogue waves, are a particular kind of ocean waves that displays a singular, unexpected, and unusually high wave profile with an extraordinarily large and steep trough or crest. The existence of freak waves has be- come widely accepted while it always poses severe hazard to the navy fleets, merchant marines, offshore structures, and virtually all oceanic ventures. Multitudes of seagoing vessels and mariners have encountered freak waves over the years, many had resulted in disasters. The emerging interest in freak waves and the quest to grasp an understand- ing of the phenomenon have inspired numerous theoretical conjectures in recent years. But the practical void of actual field observation on freak waves renders even the well- developed theories remain unverified. Furthermore, the present wave measurement systems, which have been in practice for the last 5 decades, are not at all designed to capture freak waves. We wish therefore to propose and petition to all oceanic scientist and engineers to consider undertaking an unprecedented but technologically feasible practice of making continuous and uninterrupted wave measurements. As freak waves can happen anywhere in the ocean and at anytime, the continuous and uninterrupted measurements at a fixed station would certainly be warranted to document the occur- rence of freak waves, if present, and thus lead to basic realizations of the underlying driving mechanisms.

Advanced Photon Source accelerator ultrahigh vacuum guide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, C.; Noonan, J.

1994-03-01

In this document the authors summarize the following: (1) an overview of basic concepts of ultrahigh vacuum needed for the APS project, (2) a description of vacuum design and calculations for major parts of APS, including linac, linac waveguide, low energy undulator test line, positron accumulator ring (PAR), booster synchrotron ring, storage ring, and insertion devices, and (3) cleaning procedures of ultrahigh vacuum (UHV) components presently used at APS.

Radiation Surveys of the Naval Postgraduate School LINAC.

DTIC Science & Technology

1992-06-01

personnel dosimetry at the NPS LINAC. This will result in the reduction of the TLD measured neutron dose evaluation for personnel. Accession For NTIS F. A...29 ix Figure 16: Average TLD NECF for electron energy and slit width co m b inatio ns...values obtained at 90 MeV electron energy, or NECFfmal = 0.341 ± 0.015 TABLE 5: AVERAGE TLD NEUTRON ENERGY CORRECTION FACTORS Electron Energy S lit

The CSU Accelerator and FEL Facility

NASA Astrophysics Data System (ADS)

Biedron, Sandra; Milton, Stephen; D'Audney, Alex; Edelen, Jonathan; Einstein, Josh; Harris, John; Hall, Chris; Horovitz, Kahren; Martinez, Jorge; Morin, Auralee; Sipahi, Nihan; Sipahi, Taylan; Williams, Joel

2014-03-01

The Colorado State University (CSU) Accelerator Facility will include a 6-MeV L-Band electron linear accelerator (linac) with a free-electron laser (FEL) system capable of producing Terahertz (THz) radiation, a laser laboratory, a microwave test stand, and a magnetic test stand. The photocathode drive linac will be used in conjunction with a hybrid undulator capable of producing THz radiation. Details of the systems used in CSU Accelerator Facility are discussed.

Analysis of HOM Problems in the C-ADS Main Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Burn; Ng, King Yuen

2017-05-18

Excitation of higher-order modes (HOMs) in superconducting cavities may severely affect the operation of the main linac in the Chinese Accelerator Driven System (CADS). Preliminary analysis is made on the effects of beam dynamic, which includes possible longitudinal and transverse emittance enlargements, as well as the possibility of beam breakup. Suggestions are given for further investigation. Comparison is made between the C-ADS and the Fermilab Project X.

Wakefields in SLAC linac collimators

DOE PAGES

Novokhatski, A.; Decker, F. -J.; Smith, H.; ...

2014-12-02

When a beam travels near collimator jaws, it gets an energy loss and a transverse kick due to the backreaction of the beam field diffracted from the jaws. The effect becomes very important for an intense short bunch when a tight collimation of the background beam halo is required. In the Linac Coherent Light Source at SLAC a collimation system is used to protect the undulators from radiation due to particles in the beam halo. The halo is most likely formed from gun dark current or dark current in some of the accelerating sections. However, collimators are also responsible formore » the generation of wake fields. The wake field effect from the collimators not only brings an additional energy jitter and change in the trajectory of the beam, but it also rotates the beam on the phase plane, which consequently leads to a degradation of the performance of the Free Electron Laser at the Linac Coherent Light Source. In this paper, we describe a model of the wake field radiation in the SLAC linac collimators. We use the results of a numerical simulation to illustrate the model. Based on the model, we derive simple formulas for the bunch energy loss and the average kick. We also present results from experimental measurements that confirm our model.« less

Effect of high current electron beam in a 30 MeV radio frequency linac for neutron-time-of-flight applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nayak, B., E-mail: biswaranjan.nayak1@gmail.com; Acharya, S.; Rajawat, R. K.

2016-01-15

A high power pulsed radio frequency electron linac is designed by BARC, India to accelerate 30 MeV, 10 A, 10 ns beam for neutron-time-of-flight applications. It will be used as a neutron generator and will produce ∼10{sup 12}–10{sup 13} n/s. It is essential to reduce the beam instability caused by space charge effect and the beam cavity interaction. In this paper, the wakefield losses in the accelerating section due to bunch of RMS (Root mean square) length 2 mm (at the gun exit) is analysed. Loss and kick factors are numerically calculated using CST wakefield solver. Both the longitudinal and transverse wake potentialsmore » are incorporated in beam dynamics code ELEGANT to find the transverse emittance growth of the beam propagating through the linac. Beam loading effect is examined by means of numerical computation carried out in ASTRA code. Beam break up start current has been estimated at the end of the linac which arises due to deflecting modes excited by the high current beam. At the end, transverse beam dynamics of such high current beam has been analysed.« less

Spiraling contaminant electrons increase doses to surfaces outside the photon beam of an MRI-linac with a perpendicular magnetic field

NASA Astrophysics Data System (ADS)

Hackett, S. L.; van Asselen, B.; Wolthaus, J. W. H.; Bluemink, J. J.; Ishakoglu, K.; Kok, J.; Lagendijk, J. J. W.; Raaymakers, B. W.

2018-05-01

The transverse magnetic field of an MRI-linac sweeps contaminant electrons away from the radiation beam. Films oriented perpendicular to the magnetic field and 5 cm from the radiation beam edge show a projection of the divergent beam, indicating that contaminant electrons spiral along magnetic field lines and deposit dose on surfaces outside the primary beam perpendicular to the magnetic field. These spiraling contaminant electrons (SCE) could increase skin doses to protruding regions of the patient along the cranio-caudal axis. This study investigated doses from SCE for an MRI-linac comprising a 7 MV linac and a 1.5 T MRI scanner. Surface doses to films perpendicular to the magnetic field and 5 cm from the radiation beam edge showed increased dose within the projection of the primary beam, whereas films parallel to the magnetic field and 5 cm from the beam edge showed no region of increased dose. However, the dose from contaminant electrons is absorbed within a few millimeters. For large fields, the SCE dose is within the same order of magnitude as doses from scattered and leakage photons. Doses for both SCE and scattered photons decrease rapidly with decreasing beam size and increasing distance from the beam edge.

Multipass Steering: A Reference Implementation

NASA Astrophysics Data System (ADS)

Hennessey, Michael; Tiefenback, Michael

2015-10-01

We introduce a reference implementation of a protocol to compute corrections that bring all beams in one of the CEBAF linear accelerators (linac) to axis, including, with a larger tolerance, the lowest energy pass using measured beam trajectory data. This method relies on linear optics as representation of the system; we treat beamline perturbations as magnetic field errors localized to regions between cryomodules, providing the same transverse momentum kick to each beam. We produce a vector of measured beam position data with which we left-multiply the pseudo-inverse of a coefficient array, A, that describes the transport of the beam through the linac using parameters that include the magnetic offsets of the quadrupole magnets, the instrumental offsets of the BPMs, and the beam initial conditions. This process is repeated using a reduced array to produce values that can be applied to the available correcting magnets and beam initial conditions. We show that this method is effective in steering the beam to a straight axis along the linac by using our values in elegant, the accelerator simulation program, on a model of the linac in question. The algorithms in this reference implementation provide a tool for systematic diagnosis and cataloging of perturbations in the beam line. Supported by Jefferson Lab, Old Dominion University, NSF, DOE.

Bi-directional ultrasonic wave coupling to FBGs in continuously bonded optical fiber sensing.

PubMed

Wee, Junghyun; Hackney, Drew; Bradford, Philip; Peters, Kara

2017-09-01

Fiber Bragg grating (FBG) sensors are typically spot-bonded onto the surface of a structure to detect ultrasonic waves in laboratory demonstrations. However, to protect the rest of the optical fiber from any environmental damage during real applications, bonding the entire length of fiber, called continuous bonding, is commonly done. In this paper, we investigate the impact of continuously bonding FBGs on the measured Lamb wave signal. In theory, the ultrasonic wave signal can bi-directionally transfer between the optical fiber and the plate at any adhered location, which could potentially produce output signal distortion for the continuous bonding case. Therefore, an experiment is performed to investigate the plate-to-fiber and fiber-to-plate signal transfer, from which the signal coupling coefficient of each case is theoretically estimated based on the experimental data. We demonstrate that the two coupling coefficients are comparable, with the plate-to-fiber case approximately 19% larger than the fiber-to-plate case. Finally, the signal waveform and arrival time of the output FBG responses are compared between the continuous and spot bonding cases. The results indicate that the resulting Lamb wave signal output is only that directly detected at the FBG location; however, a slight difference in signal waveform is observed between the two bonding configurations. This paper demonstrates the practicality of using continuously bonded FBGs for ultrasonic wave detection in structural health monitoring (SHM) applications.

Continuous Wavelet Transform Analysis of Acceleration Signals Measured from a Wave Buoy

PubMed Central

Chuang, Laurence Zsu-Hsin; Wu, Li-Chung; Wang, Jong-Hao

2013-01-01

Accelerometers, which can be installed inside a floating platform on the sea, are among the most commonly used sensors for operational ocean wave measurements. To examine the non-stationary features of ocean waves, this study was conducted to derive a wavelet spectrum of ocean waves and to synthesize sea surface elevations from vertical acceleration signals of a wave buoy through the continuous wavelet transform theory. The short-time wave features can be revealed by simultaneously examining the wavelet spectrum and the synthetic sea surface elevations. The in situ wave signals were applied to verify the practicality of the wavelet-based algorithm. We confirm that the spectral leakage and the noise at very-low-frequency bins influenced the accuracies of the estimated wavelet spectrum and the synthetic sea surface elevations. The appropriate thresholds of these two factors were explored. To study the short-time wave features from the wave records, the acceleration signals recorded from an accelerometer inside a discus wave buoy are analysed. The results from the wavelet spectrum show the evidence of short-time nonlinear wave events. Our study also reveals that more surface profiles with higher vertical asymmetry can be found from short-time nonlinear wave with stronger harmonic spectral peak. Finally, we conclude that the algorithms of continuous wavelet transform are practical for revealing the short-time wave features of the buoy acceleration signals. PMID:23966188

A Wave-Optics Approach to Paraxial Geometrical Laws Based on Continuity at Boundaries

ERIC Educational Resources Information Center

Linares, J.; Nistal, M. C.

2011-01-01

We present a derivation of the paraxial geometrical laws starting from a wave-optics approach, in particular by using simple continuity conditions of paraxial spherical waves at boundaries (discontinuities) between optical media. Paraxial geometrical imaging and magnification laws, under refraction and reflection at boundaries, are derived for…

Penetration of magnetosonic waves into the plasmasphere observed by the Van Allen Probes

DOE PAGES

Xiao, Fuliang; Zhou, Qinghua; He, Yihua; ...

2015-09-11

During the small storm on 14–15 April 2014, Van Allen Probe A measured a continuously distinct proton ring distribution and enhanced magnetosonic (MS) waves along its orbit outside the plasmapause. Inside the plasmasphere, strong MS waves were still present but the distinct proton ring distribution was falling steeply with distance. We adopt a sum of subtracted bi-Maxwellian components to model the observed proton ring distribution and simulate the wave trajectory and growth. MS waves at first propagate toward lower L shells outside the plasmasphere, with rapidly increasing path gains related to the continuous proton ring distribution. The waves then graduallymore » cross the plasmapause into the deep plasmasphere, with almost unchanged path gains due to the falling proton ring distribution and higher ambient density. These results present the first report on how MS waves penetrate into the plasmasphere with the aid of the continuous proton ring distributions during weak geomagnetic activities.« less

Directed search for continuous gravitational waves from the Galactic center

NASA Astrophysics Data System (ADS)

Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Adhikari, R. X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O. D.; Ajith, P.; Allen, B.; Allocca, A.; Amador Ceron, E.; Amariutei, D.; Anderson, R. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Areeda, J.; Ast, S.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Austin, L.; Aylott, B. E.; Babak, S.; Baker, P. T.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barker, D.; Barnum, S. H.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Behnke, B.; Bejger, M.; Beker, M. G.; Bell, A. S.; Bell, C.; Belopolski, I.; Bergmann, G.; Berliner, J. M.; Bertolini, A.; Bessis, D.; Betzwieser, J.; Beyersdorf, P. T.; Bhadbhade, T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Blom, M.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogan, C.; Bond, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Bose, S.; Bosi, L.; Bowers, J.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brannen, C. A.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brückner, F.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calderón Bustillo, J.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Castiglia, A.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chu, Q.; Chua, S. S. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Colombini, M.; Constancio, M., Jr.; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Coulon, J.-P.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Dal Canton, T.; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; Debreczeni, G.; Degallaix, J.; Del Pozzo, W.; Deleeuw, E.; Deléglise, S.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; DeRosa, R.; DeSalvo, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; Díaz, M.; Dietz, A.; Dmitry, K.; Donovan, F.; Dooley, K. L.; Doravari, S.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edwards, M.; Effler, A.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Endrőczi, G.; Essick, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fang, Q.; Farr, B.; Farr, W.; Favata, M.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R.; Flaminio, R.; Foley, E.; Foley, S.; Forsi, E.; Forte, L. A.; Fotopoulos, N.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P.; Fyffe, M.; Gair, J.; Gammaitoni, L.; Garcia, J.; Garufi, F.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; Gergely, L.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Goßler, S.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Griffo, C.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hall, B.; Hall, E.; Hammer, D.; Hammond, G.; Hanke, M.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Heefner, J.; Heidmann, A.; Heintze, M.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Horrom, T.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hu, Y.; Hua, Z.; Huang, V.; Huerta, E. A.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Iafrate, J.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Iyer, B. R.; Izumi, K.; Jacobson, M.; James, E.; Jang, H.; Jang, Y. J.; Jaranowski, P.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; K, Haris; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kasprzack, M.; Kasturi, R.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kaufman, K.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kéfélian, F.; Keitel, D.; Kelley, D. B.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, B. K.; Kim, C.; Kim, K.; Kim, N.; Kim, W.; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J.; Koehlenbeck, S.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kremin, A.; Kringel, V.; Krishnan, B.; Królak, A.; Kucharczyk, C.; Kudla, S.; Kuehn, G.; Kumar, A.; Kumar, P.; Kumar, R.; Kurdyumov, R.; Kwee, P.; Landry, M.; Lantz, B.; Larson, S.; Lasky, P. D.; Lawrie, C.; Lazzarini, A.; Le Roux, A.; Leaci, P.; Lebigot, E. O.; Lee, C.-H.; Lee, H. K.; Lee, H. M.; Lee, J.; Lee, J.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levine, B.; Lewis, J. B.; Lhuillier, V.; Li, T. G. F.; Lin, A. C.; Littenberg, T. B.; Litvine, V.; Liu, F.; Liu, H.; Liu, Y.; Liu, Z.; Lloyd, D.; Lockerbie, N. A.; Lockett, V.; Lodhia, D.; Loew, K.; Logue, J.; Lombardi, A. L.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J.; Luan, J.; Lubinski, M. J.; Lück, H.; Lundgren, A. P.; Macarthur, J.; Macdonald, E.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magana-Sandoval, F.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Manca, G. M.; Mandel, I.; Mandic, V.; Mangano, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Martinelli, L.; Martynov, D.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; May, G.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; Meacher, D.; Meadors, G. D.; Mehmet, M.; Meidam, J.; Meier, T.; Melatos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Mikhailov, E. E.; Milano, L.; Miller, J.; Minenkov, Y.; Mingarelli, C. M. F.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mohan, M.; Mohapatra, S. R. P.; Mokler, F.; Moraru, D.; Moreno, G.; Morgado, N.; Mori, T.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nagy, M. F.; Nanda Kumar, D.; Nardecchia, I.; Nash, T.; Naticchioni, L.; Nayak, R.; Necula, V.; Neri, I.; Newton, G.; Nguyen, T.; Nishida, E.; Nishizawa, A.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E.; Nuttall, L. K.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oppermann, P.; O'Reilly, B.; Ortega Larcher, W.; O'Shaughnessy, R.; Osthelder, C.; Ottaway, D. J.; Ottens, R. S.; Ou, J.; Overmier, H.; Owen, B. J.; Padilla, C.; Pai, A.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Paoletti, R.; Papa, M. A.; Paris, H.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Pedraza, M.; Peiris, P.; Penn, S.; Perreca, A.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pierro, V.; Pinard, L.; Pindor, B.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Poeld, J.; Poggiani, R.; Poole, V.; Poux, C.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Quintero, E.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Raja, S.; Rajalakshmi, G.; Rakhmanov, M.; Ramet, C.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Robertson, N. A.; Robinet, F.; Rocchi, A.; Roddy, S.; Rodriguez, C.; Rodruck, M.; Roever, C.; Rolland, L.; Rollins, J. G.; Romano, J. D.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Salemi, F.; Sammut, L.; Sandberg, V.; Sanders, J.; Sannibale, V.; Santiago-Prieto, I.; Saracco, E.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schreiber, E.; Schuette, D.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siellez, K.; Siemens, X.; Sigg, D.; Simakov, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G. R.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Soden, K.; Son, E. J.; Sorazu, B.; Souradeep, T.; Sperandio, L.; Staley, A.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stevens, D.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szeifert, G.; Tacca, M.; Talukder, D.; Tang, L.; Tanner, D. B.; Tarabrin, S. P.; Taylor, R.; ter Braack, A. P. M.; Thirugnanasambandam, M. P.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C. V.; Torrie, C. I.; Travasso, F.; Traylor, G.; Tse, M.; Ugolini, D.; Unnikrishnan, C. S.; Vahlbruch, H.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Heijningen, J.; van Veggel, A. A.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Verma, S.; Vetrano, F.; Viceré, A.; Vincent-Finley, R.; Vinet, J.-Y.; Vitale, S.; Vlcek, B.; Vo, T.; Vocca, H.; Vorvick, C.; Vousden, W. D.; Vrinceanu, D.; Vyachanin, S. P.; Wade, A.; Wade, L.; Wade, M.; Waldman, S. J.; Walker, M.; Wallace, L.; Wan, Y.; Wang, J.; Wang, M.; Wang, X.; Wanner, A.; Ward, R. L.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Wibowo, S.; Wiesner, K.; Wilkinson, C.; Williams, L.; Williams, R.; Williams, T.; Willis, J. L.; Willke, B.; Wimmer, M.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yancey, C. C.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yum, H.; Yvert, M.; Zadrożny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, F.; Zhang, L.; Zhao, C.; Zhu, H.; Zhu, X. J.; Zotov, N.; Zucker, M. E.; Zweizig, J.

2013-11-01

We present the results of a directed search for continuous gravitational waves from unknown, isolated neutron stars in the Galactic center region, performed on two years of data from LIGO’s fifth science run from two LIGO detectors. The search uses a semicoherent approach, analyzing coherently 630 segments, each spanning 11.5 hours, and then incoherently combining the results of the single segments. It covers gravitational wave frequencies in a range from 78 to 496 Hz and a frequency-dependent range of first-order spindown values down to -7.86×10-8Hz/s at the highest frequency. No gravitational waves were detected. The 90% confidence upper limits on the gravitational wave amplitude of sources at the Galactic center are ˜3.35×10-25 for frequencies near 150 Hz. These upper limits are the most constraining to date for a large-parameter-space search for continuous gravitational wave signals.

Electromagnetic induction and radiation-induced abnormality of wave propagation in excitable media

NASA Astrophysics Data System (ADS)

Ma, Jun; Wu, Fuqiang; Hayat, Tasawar; Zhou, Ping; Tang, Jun

2017-11-01

Continuous wave emitting from sinus node of the heart plays an important role in wave propagating among cardiac tissue, while the heart beating can be terminated when the target wave is broken into turbulent states by electromagnetic radiation. In this investigation, local periodical forcing is applied on the media to induce continuous target wave in the improved cardiac model, which the effect of electromagnetic induction is considered by using magnetic flux, then external electromagnetic radiation is imposed on the media. It is found that target wave propagation can be blocked to stand in a local area and the excitability of media is suppressed to approach quiescent but homogeneous state when electromagnetic radiation is imposed on the media. The sampled time series for membrane potentials decrease to quiescent state due to the electromagnetic radiation. It could accounts for the mechanism of abnormality in heart failure exposed to continuous electromagnetic field.

Recent searches for continuous gravitational waves

NASA Astrophysics Data System (ADS)

Riles, Keith

2017-12-01

Gravitational wave astronomy opened dramatically in September 2015 with the LIGO discovery of a distant and massive binary black hole coalescence. The more recent discovery of a binary neutron star merger, followed by a gamma ray burst (GRB) and a kilonova, reinforces the excitement of this new era, in which we may soon see other sources of gravitational waves, including continuous, nearly monochromatic signals. Potential continuous wave (CW) sources include rapidly spinning galactic neutron stars and more exotic possibilities, such as emission from axion Bose Einstein “clouds” surrounding black holes. Recent searches in Advanced LIGO data are presented, and prospects for more sensitive future searches are discussed.

TM 4: Beam through the Main Linac Cryomodule

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartnik, A.

2017-06-14

On May 15th 2017, the CBETA project reached the major funding milestone, “Beam through the MLC.” For this test, the team had to successfully accelerate the electron beam to 6 MeV in the Injector Cryomodule (ICM), and then to a final energy of 12 MeV in the Main Linac Cryomodule (MLC). The MLC contains six superconducting accelerating cavities; for this initial test only a single cavity was powered.

Using the Malthus programme to predict the recruitment of patients to MR-linac research trials in prostate and lung cancer.

PubMed

Sanderson, Benjamin; McWilliam, Alan; Faivre-Finn, Corinne; Kirkby, Norman Francis; Jena, Rajesh; Mee, Thomas; Choudhury, Ananya

2017-01-01

In this study, we used evidence-based mathematical modelling to predict the patient cohort for MR-linac to assess its feasibility in a time of austerity. We discuss our results and the implications of evidence-based radiotherapy demand modelling tools such as Malthus on the implementation of new technology and value-based healthcare. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Performance of the 2 × 4-cell superconducting linac module for the THz-FEL facility

NASA Astrophysics Data System (ADS)

Kui, Zhou; Chenglong, Lao; Dai, Wu; Xing, Luo; Jianxin, Wang; Dexin, Xiao; Lijun, Shan; Tianhui, He; Xuming, Shen; Sifen, Lin; Linde, Yang; Hanbin, Wang; Xingfan, Yang; Ming, Li; Xiangyang, Lu

2018-07-01

A high average power THz radiation facility has been developed by the China Academy of Engineering Physics. It is the first CW THz user facility based on superconducting accelerator technology in China. The superconducting linac module, which contains two 4-cell 1.3 GHz TESLA-like superconducting radio frequency cavities, is a major component of this facility. The expected electron energy gain is 6-8 MeV with a field gradient of 8-10 MV/m. The design and fabrication of the linac module is complete. This paper discusses its assembly and results from cyromodule tests and beam commissioning. At 2 K, the cryomodule works smoothly and stably. Both cavities have achieved effective field gradients of 10 MV/m. In beam loading experiments, 8 MeV, 5 mA electron beams with an energy spread less than 0.2% have been produced, which satisfies our requirements.

Electron Accelerators for Research at the Frontiers of Nuclear Physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartline, Beverly; Grunder, Hermann

1986-10-01

Electron accelerators for the frontiers of nuclear physics must provide high duty factor (gte 80) for coincidence measurements; few-hundred-MeV through few-GeV energy for work in the nucleonic, hadronic, and confinement regimes; energy resolution of ~ 10 -4; and high current (gte 100 zA). To fulfill these requirements new machines and upgrades of existing ones are being planned or constructed. Representative microtron-based facilities are the upgrade of MAMI at the University of Mainz (West Germany), the proposed two-stage cascade microtron at the University of Illinois (U.S.A.), and the three-stage Troitsk ``polytron'' (USSR). Representative projects to add pulse stretcher rings to existingmore » linacs are the upgrades at MIT-Bates (U.S.A.) and at NIKHEF-K (Netherlands). Recent advances in superconducting rf technology, especially in cavity design and fabrication, have made large superconducting cw linacs become feasible. Recirculating superconducting cw linacs are under construc« less

Linear accelerator radiosurgery for arteriovenous malformations: Updated literature review.

PubMed

Yahya, S; Heyes, G; Nightingale, P; Lamin, S; Chavda, S; Geh, I; Spooner, D; Cruickshank, G; Sanghera, P

2017-04-01

Arteriovenous malformations (AVMs) are the leading causing of intra-cerebral haemorrhage. Stereotactic radiosurgery (SRS) is an established treatment for arteriovenous malformations (AVM) and commonly delivered using Gamma Knife within dedicated radiosurgery units. Linear accelerator (LINAC) SRS is increasingly available however debate remains over whether it offers an equivalent outcome. The aim of this project is to evaluate the outcomes using LINAC SRS for AVMs used within a UK neurosciences unit and review the literature to aid decision making across various SRS platforms. Results have shown comparability across platforms and strongly supports that an adapted LINAC based SRS facility within a dynamic regional neuro-oncology department delivers similar outcomes (in terms of obliteration and toxicity) to any other dedicated radio-surgical platform. Locally available facilities can facilitate discussion between options however throughput will inevitably be lower than centrally based dedicated national radiosurgery units. Copyright © 2016. Published by Elsevier Ltd.

In modern linacs monitor units should be defined in water at 10 cm depth rather than at dmax.

PubMed

Van den Heuvel, Frank; Wu, Qiuwen; Cai, Jing

2018-05-28

Thanks to the widely adopted guidelines such as AAPM TG-51 1 and IAEA TRS-398 2 , linac calibration has become more consistent and accurate around the globe than previously. Modern linac photon beams are often calibrated in water at 10 cm depth, and configured such that 1 monitor unit (MU) corresponds to 1 cGy at the depth of maximum dose, (d max) . However, such configuration is not without limitations. Some think it is unnecessarily complex and prone to errors, and believe that defining MU at 10 cm is more appropriate. Others think that change of MU definition can cause confusion and possibly serious consequences without any real benefit. This is the premise debated in this month's Point/Counterpoint. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Assessment of Alternative RF Linac Structures for APT

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

The APT program has been examining both normal and superconducting variants of the APT linac for the past two years. A decision on which of the two will be the selected technology will depend upon several considerations including the results of ongoing feasibility experiments, the performance and overall attractiveness of each of the design concepts, and an assessment of the system-level features of both alternatives. The primary objective of the Assessment of Alternative RF Linac Structures for APT study reported herein was to assess and compare, at the system-level, the performance, capital and life cycle costs, reliability/availability/maintainability (RAM) and manufacturingmore » schedules of APT RF linear accelerators based upon both superconducting and normal conducting technologies. A secondary objective was to perform trade studies to explore opportunities for system optimization, technology substitution and alternative growth pathways and to identify sensitivities to design uncertainties.« less

Development of a combined feed forward-feedback system for an electron Linac

NASA Astrophysics Data System (ADS)

Meier, E.; Biedron, S. G.; LeBlanc, G.; Morgan, M. J.; Wu, J.

2009-10-01

This paper describes the results of an advanced control algorithm for the stabilization of electron beam energy in a Linac. The approach combines a conventional Proportional-Integral (PI) controller with a neural network (NNET) feed forward algorithm; it utilizes the robustness of PI control and the ability of a feed forward system in order to exert control over a wider range of frequencies. The NNET is trained to recognize jitter occurring in the phase and voltage of one of the klystrons, based on a record of these parameters, and predicts future energy deviations. A systematic approach is developed to determine the optimal NNET parameters that are then applied to the Australian Synchrotron Linac. The system's capability to fully cancel multi-frequency jitter is demonstrated. The NNET system is then augmented with the PI algorithm, and further jitter attenuation is achieved when the NNET is not operating optimally.

Development of a novel optimization tool for electron linacs inspired by artificial intelligence techniques in video games

NASA Astrophysics Data System (ADS)

Meier, E.; Biedron, S. G.; LeBlanc, G.; Morgan, M. J.

2011-03-01

This paper reports the results of an advanced algorithm for the optimization of electron beam parameters in Free Electron Laser (FEL) Linacs. In the novel approach presented in this paper, the system uses state of the art developments in video games to mimic an operator's decisions to perform an optimization task when no prior knowledge, other than constraints on the actuators is available. The system was tested for the simultaneous optimization of the energy spread and the transmission of the Australian Synchrotron Linac. The proposed system successfully increased the transmission of the machine from 90% to 97% and decreased the energy spread of the beam from 1.04% to 0.91%. Results of a control experiment performed at the new FERMI@Elettra FEL is also reported, suggesting the adaptability of the scheme for beam-based control.

Compact injector with alternating phase focusing-interdigital H-mode linac and superconducting electron cyclotron resonance ion source for heavy ion cancer therapy

NASA Astrophysics Data System (ADS)

Hayashizaki, Noriyosu; Hattori, Toshiyuki; Matsui, Shinjiro; Tomizawa, Hiromitsu; Yoshida, Toru; Isokawa, Katsushi; Kitagawa, Atsushi; Muramatsu, Masayuki; Yamada, Satoru; Okamura, Masahiro

2000-02-01

We have researched a compact medical accelerator with low investment and running cost for the popularization of heavy ion cancer therapy. As the first step, the compact injector system has been investigated for a Heavy Ion Medical Accelerator in Chiba at National Institute of Radiological Sciences. The proposed new injector system consists of a 6 MeV/u interdigital H-mode (IH) linac of 3.1 m long and a 18 GHz superconducting electron cyclotron resonance (ECR) (SC-ECR) ion source. The IH linac with high power efficiency is appropriate to a medical and industrial injector system. Its beam trajectory was simulated and a prototype has been constructed. The SC-ECR ion source has been designed to realize lightweight and low power consumption and the mirror field distribution was estimated.

Hierarchical multistage MCMC follow-up of continuous gravitational wave candidates

NASA Astrophysics Data System (ADS)

Ashton, G.; Prix, R.

2018-05-01

Leveraging Markov chain Monte Carlo optimization of the F statistic, we introduce a method for the hierarchical follow-up of continuous gravitational wave candidates identified by wide-parameter space semicoherent searches. We demonstrate parameter estimation for continuous wave sources and develop a framework and tools to understand and control the effective size of the parameter space, critical to the success of the method. Monte Carlo tests of simulated signals in noise demonstrate that this method is close to the theoretical optimal performance.

Continuous monitoring of prostate position using stereoscopic and monoscopic kV image guidance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevens, M. Tynan R.; Parsons, Dave D.; Robar, James L.

2016-05-15

Purpose: To demonstrate continuous kV x-ray monitoring of prostate motion using both stereoscopic and monoscopic localizations, assess the spatial accuracy of these techniques, and evaluate the dose delivered from the added image guidance. Methods: The authors implemented both stereoscopic and monoscopic fiducial localizations using a room-mounted dual oblique x-ray system. Recently developed monoscopic 3D position estimation techniques potentially overcome the issue of treatment head interference with stereoscopic imaging at certain gantry angles. To demonstrate continuous position monitoring, a gold fiducial marker was placed in an anthropomorphic phantom and placed on the Linac couch. The couch was used as a programmablemore » translation stage. The couch was programmed with a series of patient prostate motion trajectories exemplifying five distinct categories: stable prostate, slow drift, persistent excursion, transient excursion, and high frequency excursions. The phantom and fiducial were imaged using 140 kVp, 0.63 mAs per image at 1 Hz for a 60 s monitoring period. Both stereoscopic and monoscopic 3D localization accuracies were assessed by comparison to the ground-truth obtained from the Linac log file. Imaging dose was also assessed, using optically stimulated luminescence dosimeter inserts in the phantom. Results: Stereoscopic localization accuracy varied between 0.13 ± 0.05 and 0.33 ± 0.30 mm, depending on the motion trajectory. Monoscopic localization accuracy varied from 0.2 ± 0.1 to 1.1 ± 0.7 mm. The largest localization errors were typically observed in the left–right direction. There were significant differences in accuracy between the two monoscopic views, but which view was better varied from trajectory to trajectory. The imaging dose was measured to be between 2 and 15 μGy/mAs, depending on location in the phantom. Conclusions: The authors have demonstrated the first use of monoscopic localization for a room-mounted dual x-ray system. Three-dimensional position estimation from monoscopic imaging permits continuous, uninterrupted intrafraction motion monitoring even in the presence of gantry rotation, which may block kV sources or imagers. This potentially allows for more accurate treatment delivery, by ensuring that the prostate does not deviate substantially from the initial setup position.« less

Neuronal Networks in Children with Continuous Spikes and Waves during Slow Sleep

ERIC Educational Resources Information Center

Siniatchkin, Michael; Groening, Kristina; Moehring, Jan; Moeller, Friederike; Boor, Rainer; Brodbeck, Verena; Michel, Christoph M.; Rodionov, Roman; Lemieux, Louis; Stephani, Ulrich

2010-01-01

Epileptic encephalopathy with continuous spikes and waves during slow sleep is an age-related disorder characterized by the presence of interictal epileptiform discharges during at least greater than 85% of sleep and cognitive deficits associated with this electroencephalography pattern. The pathophysiological mechanisms of continuous spikes and…

TU-H-BRA-03: Performance of a Clinical Gridded Electron Gun in Magnetic Fields: Implications for MRI-Linac Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whelan, B; Keall, P; Bazalova-Carter, M

Purpose: Recent advances towards MRI Linac radiotherapy have motivated a wide range of studies characterizing electromagnetic interactions between the two devices. One of the most sensitive components is the linac electron gun. To data, only non gridded (diode) guns have been investigated however, most linac vendors utilize gridded (triode) guns, which enable efficient and robust beam gating. The purpose of this study was to develop a realistic model of a gridded gun used clinically, and to characterize its performance in magnetic fields. Methods: The gridded electron gun used on Varian high energy machines was measured using 3D laser scanning quotedmore » as accurate to 0.1mm. Based on the scane, a detailed CAD mode was developed. From this, key geometry was extracted and a FEM model was developed (Opera/SCALA). Next, the high voltage (HV), grid voltage, and emission current were read from six dose matched TrueBeam linacs for the 6X, 10X and 15X photon modes (0 B-field). The mean values were used to represent each mode, which was simulated I constant magnetic fields from 0–200G in-line, and 0–35G perpendicular. Results: Experimentally measured HV, grid voltage, and emission current from 6X, 10X and 15X modes were respectively: 15±.03kV, 10±.08kV, 11±.03kV; 93±7V, 41±3V, and 70±6V; 327±27mA, 129±10mA, and 214±19mA. The error in simulated emission current of each mode was 3%,6%, and 3%. For in-line fields, 50% beam loss occurred at 114, 96, and 97G; for perpendicular; at 12, 13 and 14G. Sensitivity for a given geometry is primarily determined by HV setting. Conclusion: Future MRI-Linac systems will almost certainly use gridded guns. We present the first model of a clinical gridded gun, and match the experimental emission current to within 6% across three different operating modes. This clinical gun shows increased sensitivity to magnetic fields than previous work,and different modes show different sensitivity.« less

SU-F-J-149: Beam and Cryostat Scatter Characteristics of the Elekta MR-Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duglio, M; Towe, S; Roberts, D

2016-06-15

Purpose: The Elekta MR-Linac combines a digital linear accelerator system with a 1.5T Philips MRI machine. This study aimed to determine key characteristic information regarding the MR-Linac beam and in particular it evaluated the effect of the MR cryostat on the out of field scatter dose. Methods: Tissue phantom ratios, profiles and depth doses were acquired in plastic water with an IC-profiler or with an MR compatible water tank using multiple system configurations (Full (B0= 1.5T), Full (B0=0T) and No cryostat). Additionally, an in-house CAD based Monte Carlo code based on Penelope was used to provide comparative data. Results: Withmore » the cryostat in place and B0=0T, the measured TPR for the MR Linac system was 0.702, indicating an energy of around 7MV. Without the cryostat, the measured TPR was 0.669. For the Full (B0=0T) case, out of field dose at a depth of 10 cm in the isocentric plane, 5 cm from the field edge was 0.8%, 3.1% and 5.4% for 3×3 cm{sup 2}, 10×10 cm{sup 2} and 20×20 cm{sup 2} fields respectively.The out of field dose (averaged between 5 cm and 10 cm beyond the field edges) in the “with cryostat” case is 0.78% (absolute difference) higher than without the cryostat for clinically relevant field sizes (i.e. 10×10 cm{sup 2}) and comparable to measured conventional 6MV treatment beams at a depth of 10 cm (within 0.1% between 5 cm and 6 cm from field edge). At dose maximum and at 5 cm from the field edge, the “with cryostat” out of field scatter for a 10×10 cm{sup 2} field is 1.5% higher than “without cryostat', with a modest increase (0.9%) compared to Agility 6MV in the same conditions. Conclusion: The study has presented typical characteristics of the MR-Linac beam and determined that out of field dose is comparable to conventional treatment beams. All authors are employed by Elekta Ltd., who are developing an MR-Linac.« less

Dosimetry quality audit of high energy photon beams in greek radiotherapy centers.

PubMed

Hourdakis, Constantine J; Boziari, A

2008-04-01

Dosimetry quality audits and intercomparisons in radiotherapy centers is a useful tool in order to enhance the confidence for an accurate therapy and to explore and dissolve discrepancies in dose delivery. This is the first national comprehensive study that has been carried out in Greece. During 2002--2006 the Greek Atomic Energy Commission performed a dosimetry quality audit of high energy external photon beams in all (23) Greek radiotherapy centers, where 31 linacs and 13 Co-60 teletherapy units were assessed in terms of their mechanical performance characteristics and relative and absolute dosimetry. The quality audit in dosimetry of external photon beams took place by means of on-site visits, where certain parameters of the photon beams were measured, calculated and assessed according to a specific protocol and the IAEA TRS 398 dosimetry code of practice. In each radiotherapy unit (Linac or Co-60), certain functional parameters were measured and the results were compared to tolerance values and limits. Doses in water under reference and non reference conditions were measured and compared to the stated values. Also, the treatment planning systems (TPS) were evaluated with respect to irradiation time calculations. The results of the mechanical tests, dosimetry measurements and TPS evaluation have been presented in this work and discussed in detail. This study showed that Co-60 units had worse performance mechanical characteristics than linacs. 28% of all irradiation units (23% of linacs and 42% of Co-60 units) exceeded the acceptance limit at least in one mechanical parameter. Dosimetry accuracy was much worse in Co60 units than in linacs. 61% of the Co60 units exhibited deviations outside +/-3% and 31% outside +/-5%. The relevant percentages for the linacs were 24% and 7% respectively. The results were grouped for each hospital and the sources of errors (functional and human) have been investigated and discussed in details. This quality audit proved to be a useful tool for the improvement of quality in radiotherapy. It succeeded to disseminate the IAEA TRS-398 protocol in nearly all radiotherapy centers achieving homogenization and consistency of dosimetry within the country. Also, it detected discrepancies in dosimetry and provided guidance and recommendations to eliminate sources of errors. Finally, it proved that quality assurance programs, periodic quality control tests, maintenance and service play an important role for achieving accuracy and safe operation in radiotherapy.

SU-G-JeP2-09: Minimal Skin Dose Increase in Longitudinal Rotating Biplanar Linac-MR Systems: Examination of Radiation Energy and Flattening Filter Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fallone, B; Keyvanloo, A; Burke, B

Purpose: To quantify increase in entrance skin-dose due to magnetic fields of the Alberta longitudinal linac-MR by examining the effect of radiation energy and flattening filter, using Monte Carlo calculations and accurate 3-D models of the magnetic field. Methods: The 3-D magnetic fields generated by the bi-planar Linac-MR are calculated with FEM using Opera-3D. BEAMnrc simulates the particle phase-space in the presence of the rapidly decaying fringe field of 0.5T MRI assembled with a Varian 600C linac with an isocentre distance of 130 cm for 6 MV and 10 MV beams. Skin doses are calculated at an average depth ofmore » 70 µm using DOSXYZnrc with varying SSDs and field sizes. Furthermore, flattening filters are reshaped to compensate for the significant drop in dose rate due to increased SAD of 130 cm and skin-doses are evaluated. Results: The confinement effect of the MRI fringe field on the contaminant electrons is minimal. For SSDs of 100 – 120 cm the increase in skin dose is ∼6% – 19% and ∼1% – 9% for the 6 and 10 MV beams, respectively. For 6MV, skin dose increases from ∼10.5% to 1.5%. for field-size increases of 5×5 cm2 to 20×20 cm2. For 10 MV, skin dose increases by ∼6% for a 5×5 cm2 field, and decreases by ∼1.5% for a 20×20 cm2 field. The reshaped flattening filter increases the dose rate from 355 MU/min to 529 MU/min (6 MV) or 604 MU/min (10 MV), while the skin-dose increases by only an additional ∼2.6% (all percent increases in skin dose are relative to Dmax). Conclusion: There is minimal increase in the entrance skin dose and minimal/no decrease in the dose rate of the Alberta longitudinal linac-MR system. There is even lower skin-dose increase at 10 MV. Funding: Alberta Innovates - Health Solutions (AIHS) Conflict of Interest: Fallone is a co-founder and CEO of MagnetTx Oncology Solutions (under discussions to license Alberta bi-planar linac MR for commercialization)« less

Beam characterisation of the 1.5 T MRI-linac

NASA Astrophysics Data System (ADS)

Woodings, S. J.; Bluemink, J. J.; de Vries, J. H. W.; Niatsetski, Y.; van Veelen, B.; Schillings, J.; Kok, J. G. M.; Wolthaus, J. W. H.; Hackett, S. L.; van Asselen, B.; van Zijp, H. M.; Pencea, S.; Roberts, D. A.; Lagendijk, J. J. W.; Raaymakers, B. W.

2018-04-01

As a prerequisite for clinical treatments it was necessary to characterize the Elekta 1.5 T MRI-linac 7 MV FFF radiation beam. Following acceptance testing, beam characterization data were acquired with Semiflex 3D (PTW 31021), microDiamond (PTW 60019), and Farmer-type (PTW 30013 and IBA FC65-G) detectors in an Elekta 3D scanning water phantom and a PTW 1D water phantom. EBT3 Gafchromic film and ion chamber measurements in a buildup cap were also used. Special consideration was given to scan offsets, detector effective points of measurement and avoiding air gaps. Machine performance has been verified and the system satisfied the relevant beam requirements of IEC60976. Beam data were acquired for field sizes between 1  ×  1 and 57  ×  22 cm2. New techniques were developed to measure percentage depth dose (PDD) curves including the electron return effect at beam exit, which exhibits an electron-type practical range of cm. The Lorentz force acting on the secondary charged particles creates an asymmetry in the crossline profiles with an average shift of  +0.24 cm. For a 10  ×  10 cm2 beam, scatter from the cryostat contributes 1% of the dose at isocentre. This affects the relative output factors, scatter factors and beam profiles, both in-field and out-of-field. The average 20%–80% penumbral width measured for small fields with a microDiamond detector at 10 cm depth is 0.50 cm. MRI-linac penumbral widths are very similar to that of the Elekta Agility linac MLC, as is the near-surface dose PDD(0.2 cm)  =  57%. The entrance surface dose is  ∼36% of . Cryostat transmission is quantified for inclusion within the treatment planning system. As a result, the 1.5 T MRI-linac 7 MV FFF beam has been characterised for the first time and is suitable for clinical use. This was a key step towards the first clinical treatments with the MRI-linac, which were delivered at University Medical Center Utrecht in May 2017 (Raaymakers et al 2017 Phys. Med. Biol. 62 L41–50).

Design study of the CEPC booster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chuang

2014-12-10

Design study of the CEPC booster is reported. The booster provides 120 GeV beams for the collider with topup injection frequency of 0.1 Hz. To save cost, energy of the linac injector for the booster is chosen as 6GeV, corresponding to the magnetic field of 30 Gs. In this paper, lattice of the booster is described; the low injection energy issues are studied; beam transfer from linac to booster and from booster to collider are discussed.

Low Level RF Control for the PIP-II Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edelen, J. P.; Chase, B. E.; Cullerton, E.

The PIP-II accelerator is a proposed upgrade to the Fermilab accelerator complex that will replace the existing, 400 MeV room temperature LINAC with an 800 MeV superconducting LINAC. Part of this upgrade includes a new injection scheme into the booster that levies tight requirements on the LLRF control system for the cavities. In this paper we discuss the challenges of the PIP-II accelerator and the present status of the LLRF system for this project.

BEAM DYNAMICS STUDIES OF A HIGH-REPETITION RATE LINAC-DRIVER FOR A 4TH GENERATION LIGHT SOURCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ventturini, M.; Corlett, J.; Emma, P.

2012-05-18

We present recent progress toward the design of a super-conducting linac driver for a high-repetition rate FEL-based soft x-ray light source. The machine is designed to accept beams generated by the APEX photo-cathode gun operating with MHz-range repetition rate and deliver them to an array of SASE and seeded FEL beamlines. We review the current baseline design and report results of beam dynamics studies.

Biomedical user facility at the 400-MeV Linac at Fermilab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu, W.T.

1993-12-01

In this paper, general requirements are discussed on a biomedical user facility at the Fermilab`s 400-MeV Linac, which meets the needs of biology and biophysics experiments, and a conceptual design and typical operations requirements of the facility is presented. It is assumed that no human patient treatment will take place in this facility. If human patients were treated, much greater attention would have to be paid to safeguarding the patients.

Design for simultaneous acceleration of stable and unstable beams in a superconducting heavy-ion linear accelerator for RISP

NASA Astrophysics Data System (ADS)

Kim, Jongwon; Son, Hyock-Jun; Park, Young-Ho

2017-11-01

The post-accelerator of isotope separation on-line (ISOL) system for rare isotope science project (RISP) is a superconducting linear accelerator (SC-linac) with a DC equivalent voltage of around 160 MV. An isotope beam extracted from the ISOL is in a charge state of 1+ and its charge state is increased to n+ by charge breeding with an electron beam ion source (EBIS). The charge breeding takes tens of ms and the pulse width of extracted beam from the EBIS is tens of μs, which operates at up to 30 Hz. Consequently a large portion of radio frequency (rf) time of the post SC-linac is unused. The post-linac is equipped also with an electron cyclotron resonance (ECR) ion source for stable ion acceleration. Thanks to the large phase acceptance of SC-linac, it is possible to accelerate simultaneously both stable and radioisotope ions with a similar charge to mass ratio by sharing rf time. This operation scheme is implemented for RISP with the addition of an electric chopper and magnetic kickers. The facility will be capable of providing the users of the ISOL and in-flight fragmentation (IF) systems with different beams simultaneously, which would help nuclear science users in obtaining a beam time as high-precision measurements often need long hours.

Tumour regression of uveal melanoma after ruthenium-106 brachytherapy or stereotactic radiotherapy with gamma knife or linear accelerator.

PubMed

Georgopoulos, Michael; Zehetmayer, Martin; Ruhswurm, Irene; Toma-Bstaendig, Sabine; Ségur-Eltz, Nikolaus; Sacu, Stefan; Menapace, Rupert

2003-01-01

This study assesses differences in relative tumour regression and internal acoustic reflectivity after 3 methods of radiotherapy for uveal melanoma: (1) brachytherapy with ruthenium-106 radioactive plaques (RU), (2) fractionated high-dose gamma knife stereotactic irradiation in 2-3 fractions (GK) or (3) fractionated linear-accelerator-based stereotactic teletherapy in 5 fractions (Linac). Ultrasound measurements of tumour thickness and internal reflectivity were performed with standardised A scan pre-operatively and 3, 6, 9, 12, 18, 24 and 36 months postoperatively. Of 211 patients included in the study, 111 had a complete 3-year follow-up (RU: 41, GK: 37, Linac: 33). Differences in tumour thickness and internal reflectivity were assessed with analysis of variance, and post hoc multiple comparisons were calculated with Tukey's honestly significant difference test. Local tumour control was excellent with all 3 methods (>93%). At 36 months, relative tumour height reduction was 69, 50 and 30% after RU, GK and Linac, respectively. In all 3 treatment groups, internal reflectivity increased from about 30% initially to 60-70% 3 years after treatment. Brachytherapy with ruthenium-106 plaques results in a faster tumour regression as compared to teletherapy with gamma knife or Linac. Internal reflectivity increases comparably in all 3 groups. Besides tumour growth arrest, increasing internal reflectivity is considered as an important factor indicating successful treatment. Copyright 2003 S. Karger AG, Basel

SU-E-T-267: Construction and Evaluation of a Neutron Wall to Shield a 15 MV Linac in a Low-Energy Vault.

PubMed

Speiser, M; Hager, F; Foster, R; Solberg, T

2012-06-01

To design and quantify the shielding efficacy of an inner Borated Polyethylene (BPE)wall for a 15 MV linac in a low energy vault. A Varian TrueBeam linac with a maximum photon energy of 15 MV was installed in asmaller, preexisting vault. This vault originally housed a low-energy machine and did not havesufficient maze length recommended for neutron attenuation. Effective dose rate calculationswere performed using the Modified Kersey's Method as detailed in NCRP Report No. 151 andfound to be unacceptably high. An initial survey following the machine installation confirmedthese calculations. Rather than restrict the linac beam energy to 10 MV, BPE was investigatedas a neutron moderating addition. An inner wall and door were planned and constructed using4'×8'×1″ thick 5% BPE sheets. The resulting door and wall had 2″ of BPE; conduits and ductwork were also redesigned and shielded. A survey was conducted following construction of thewall. The vault modification reduced the expected effective dose at the vault door from 36.23to 0.010 mSv/week. As specific guidelines for vault modification are lacking, this project quantitativelydemonstrates the potential use of BPE for vault modification. Such modifications may provide alow-cost shielding solution to allow for the use of high energy modes in smaller treatment vaults. © 2012 American Association of Physicists in Medicine.

Beam dynamics pre-study for the RFQ of SPPC p-Linac

NASA Astrophysics Data System (ADS)

Liu, Jing; Lu, Yuanrong; Li, Haipeng; Su, Jiancang; Liu, Xiaolong

2018-02-01

A proton-proton collider at center-of-mass energy of more than 70 TeV is the second stage of the CEPC-SPPC program. As proposed, the SPPC injector chain will use a 1.2 GeV p-Linac and three synchrotrons of 10 GeV p-RCS, 180 GeV MSS and 2.1 TeV SS. Peking University is responsible for the preliminary conceptual design of the room temperature part of SPPC p-Linac. This paper is focusing on the beam dynamics studies performed with respect to the 325 MHz RFQ. As the first accelerator structure after the ion source and the front-end of the whole SPPC, RFQ plays an important role in the beam initial transverse focusing and longitudinal bunching. Based on the New Four Section Procedure strategy, as well as the matched and Equipartitioning design method, a 3 MeV RFQ designed by Parmteq code will be introduced. The cavity length of RFQ is 3.6 m and the transmission efficiency is 98%. In this design scheme, the 40 mA proton beam from the 50 keV ion source is accelerated to 3 MeV in 3.8 m length, which achieves a sixty times energy gain. The results of the analyses show that the RFQ design is reliable and meets all the SPPC p-Linac requirements well.

Comparison between the TRS-398 code of practice and the TG-51 dosimetry protocol for flattening filter free beams

NASA Astrophysics Data System (ADS)

Lye, J. E.; Butler, D. J.; Oliver, C. P.; Alves, A.; Lehmann, J.; Gibbons, F. P.; Williams, I. M.

2016-07-01

Dosimetry protocols for external beam radiotherapy currently in use, such as the IAEA TRS-398 and AAPM TG-51, were written for conventional linear accelerators. In these accelerators, a flattening filter is used to produce a beam which is uniform at water depths where the ionization chamber is used to measure the absorbed dose. Recently, clinical linacs have been implemented without the flattening filter, and published theoretical analysis suggested that with these beams a dosimetric error of order 0.6% could be expected for IAEA TRS-398, because the TPR20,10 beam quality index does not accurately predict the stopping power ratio (water to air) for the softer flattening-filter-free (FFF) beam spectra. We measured doses on eleven FFF linacs at 6 MV and 10 MV using both dosimetry protocols and found average differences of 0.2% or less. The expected shift due to stopping powers was not observed. We present Monte Carlo k Q calculations which show a much smaller difference between FFF and flattened beams than originally predicted. These results are explained by the inclusion of the added backscatter plates and build-up filters used in modern clinical FFF linacs, compared to a Monte Carlo model of an FFF linac in which the flattening filter is removed and no additional build-up or backscatter plate is added.

MO-FG-BRA-01: 4D Monte Carlo Simulations for Verification of Dose Delivered to a Moving Anatomy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gholampourkashi, S; Cygler, J E.; The Ottawa Hospital Cancer Centre, Ottawa, ON

Purpose: To validate 4D Monte Carlo (MC) simulations of dose delivery by an Elekta Agility linear accelerator to a moving phantom. Methods: Monte Carlo simulations were performed using the 4DdefDOSXYZnrc/EGSnrc user code which samples a new geometry for each incident particle and calculates the dose in a continuously moving anatomy. A Quasar respiratory motion phantom with a lung insert containing a 3 cm diameter tumor was used for dose measurements on an Elekta Agility linac with the phantom in stationary and moving states. Dose to the center of tumor was measured using calibrated EBT3 film and the RADPOS 4D dosimetrymore » system. A VMAT plan covering the tumor was created on the static CT scan of the phantom using Monaco V.5.10.02. A validated BEAMnrc model of our Elekta Agility linac was used for Monte Carlo simulations on stationary and moving anatomies. To compare the planned and delivered doses, linac log files recorded during measurements were used for the simulations. For 4D simulations, deformation vectors that modeled the rigid translation of the lung insert were generated as input to the 4DdefDOSXYZnrc code as well as the phantom motion trace recorded with RADPOS during the measurements. Results: Monte Carlo simulations and film measurements were found to agree within 2mm/2% for 97.7% of points in the film in the static phantom and 95.5% in the moving phantom. Dose values based on film and RADPOS measurements are within 2% of each other and within 2σ of experimental uncertainties with respect to simulations. Conclusion: Our 4D Monte Carlo simulation using the defDOSXYZnrc code accurately calculates dose delivered to a moving anatomy. Future work will focus on more investigation of VMAT delivery on a moving phantom to improve the agreement between simulation and measurements, as well as establishing the accuracy of our method in a deforming anatomy. This work was supported by the Ontario Consortium of Adaptive Interventions in Radiation Oncology (OCAIRO), funded by the Ontario Research Fund Research Excellence program.« less

Dedicated linear accelerator radiosurgery for trigeminal neuralgia: a single-center experience in 179 patients with varied dose prescriptions and treatment plans.

PubMed

Smith, Zachary A; Gorgulho, Alessandra A; Bezrukiy, Nikita; McArthur, David; Agazaryan, Nzhde; Selch, Michael T; De Salles, Antonio A F

2011-09-01

Dedicated linear accelerator radiosurgery (D-LINAC) has become an important treatment for trigeminal neuralgia (TN). Although the use of gamma knife continues to be established, few large series exist using D-LINAC. The authors describe their results, comparing the effects of varied target and dose regimens. Between August 1995 and January 2008, 179 patients were treated with D-LINAC radiosurgery. Ten patients (5.58%) had no clinical follow-up. The median age was 74.0 years (range, 32-90 years). A total of 39 patients had secondary or atypical pain, and 130 had idiopathic TN. Initially, 28 patients received doses between 70 and 85 Gy, with the 30% isodose line (IDL) touching the brainstem. Then, using 90 Gy, 82 consecutive patients were treated with a 30% IDL and 59 patients with a 50% IDL tangential to the pons. Of 169 patients, 134 (79.3%) experienced significant relief at a mean of 28.8 months (range, 5-142 months). Average time to relief was 1.92 months (range, immediate to 6 months). A total of 31 patients (19.0%) had recurrent pain at 13.5 months. Of 87 patients with idiopathic TN without prior procedures, 79 (90.8%) had initial relief. Among 28 patients treated with 70 Gy and 30% IDL, 18 patients (64.3%) had significant relief, and 10 (35.7%) had numbness. Of the patients with 90 Gy and 30% IDL at the brainstem, 59 (79.0%) had significant relief and 48.9% had numbness. Among 59 consecutive patients with similar dose but the 50% isodoseline at the brainstem, 49 patients (88.0%) had excellent/good relief. Numbness, averaging 2.49 on a subjective scale of 1 to 5, was experienced by 49.7% of the patients, Increased radiation dose and volume of brainstem irradiation may improve clinical outcomes with the trade-off of trigeminal dysfunction. Further study of the implications of dose and target are needed to optimize outcomes and to minimize complications. Published by Elsevier Inc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swapan Chattopadhyay

Hurricane Isabel was at category five--the most violent on the Saffir-Simpson scale of hurricane strength--when it began threatening the central Atlantic seaboard of the US. Over the course of several days, precautions against the extreme weather conditions were taken across the Jefferson Lab site in south-east Virginia. On 18 September 2003, when Isabel struck North Carolina's Outer Banks and moved northward, directly across the region around the laboratory, the storm was still quite destructive, albeit considerably reduced in strength. The flood surge and trees felled by wind substantially damaged or even devastated buildings and homes, including many belonging to Jeffersonmore » Lab staff members. For the laboratory itself, Isabel delivered an unplanned and severe challenge in another form: a power outage that lasted nearly three-and-a-half days, and which severely tested the robustness of Jefferson Lab's two superconducting machines, the Continuous Electron Beam Accelerator Facility (CEBAF) and the superconducting radiofrequency ''driver'' accelerator of the laboratory's free-electron laser. Robustness matters greatly for science at a time when microwave superconducting linear accelerators (linacs) are not only being considered, but in some cases already being built for projects such as neutron sources, rare-isotope accelerators, innovative light sources and TeV-scale electron-positron linear colliders. Hurricane Isabel interrupted a several-week-long maintenance shutdown of CEBAF, which serves nuclear and particle physics and represents the world's pioneering large-scale implementation of superconducting radiofrequency (SRF) technology. The racetrack-shaped machine is actually a pair of 500-600 MeV SRF linacs interconnected by recirculation arc beamlines. CEBAF delivers simultaneous beams at up to 6 GeV to three experimental halls. An imminent upgrade will double the energy to 12 GeV and add an extra hall for ''quark confinement'' studies. On a smaller scale, Jefferson Lab's original kilowatt-scale infrared free-electron laser (FEL) is ''driven'' by a high-current cousin of CEBAF, a 70 MeV SRF linac with a high-current injector. The FEL serves multidisciplinary science and technology as the world's highest-average-power source of tunable coherent infrared light. An upgrade to 10 kW is in commissioning--as it was when Isabel began threatening.« less

Dedicated Linear Accelerator Radiosurgery for Trigeminal Neuralgia: A Single-Center Experience in 179 Patients With Varied Dose Prescriptions and Treatment Plans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Zachary A.; Gorgulho, Alessandra A.; Bezrukiy, Nikita

2011-09-01

Purpose: Dedicated linear accelerator radiosurgery (D-LINAC) has become an important treatment for trigeminal neuralgia (TN). Although the use of gamma knife continues to be established, few large series exist using D-LINAC. The authors describe their results, comparing the effects of varied target and dose regimens. Methods and Materials: Between August 1995 and January 2008, 179 patients were treated with D-LINAC radiosurgery. Ten patients (5.58%) had no clinical follow-up. The median age was 74.0 years (range, 32-90 years). A total of 39 patients had secondary or atypical pain, and 130 had idiopathic TN. Initially, 28 patients received doses between 70 andmore » 85 Gy, with the 30% isodose line (IDL) touching the brainstem. Then, using 90 Gy, 82 consecutive patients were treated with a 30% IDL and 59 patients with a 50% IDL tangential to the pons. Results: Of 169 patients, 134 (79.3%) experienced significant relief at a mean of 28.8 months (range, 5-142 months). Average time to relief was 1.92 months (range, immediate to 6 months). A total of 31 patients (19.0%) had recurrent pain at 13.5 months. Of 87 patients with idiopathic TN without prior procedures, 79 (90.8%) had initial relief. Among 28 patients treated with 70 Gy and 30% IDL, 18 patients (64.3%) had significant relief, and 10 (35.7%) had numbness. Of the patients with 90 Gy and 30% IDL at the brainstem, 59 (79.0%) had significant relief and 48.9% had numbness. Among 59 consecutive patients with similar dose but the 50% isodoseline at the brainstem, 49 patients (88.0%) had excellent/good relief. Numbness, averaging 2.49 on a subjective scale of 1 to 5, was experienced by 49.7% of the patients, Conclusions: Increased radiation dose and volume of brainstem irradiation may improve clinical outcomes with the trade-off of trigeminal dysfunction. Further study of the implications of dose and target are needed to optimize outcomes and to minimize complications.« less

Relaxation oscillation suppression in continuous-wave intracavity optical parametric oscillators.

PubMed

Stothard, David J M; Dunn, Malcolm H

2010-01-18

We report a solution to the long standing problem of the occurrence of spontaneous and long-lived bursts of relaxation oscillations which occur when a continuous-wave optical parametric oscillator is operated within the cavity of the parent pump-laser. By placing a second nonlinear crystal within the pump-wave cavity for the purpose of second-harmonic-generation of the pump-wave the additional nonlinear loss thereby arising due to up-conversion effectively suppresses the relaxation oscillations with very little reduction in down-converted power.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oborn, B. M.; Kolling, S.; Metcalfe, P. E.

Purpose: A potential side effect of inline MRI-linac systems is electron contamination focusing causing a high skin dose. In this work, the authors reexamine this prediction for an open bore 1 T MRI system being constructed for the Australian MRI-Linac Program. The efficiency of an electron contamination deflector (ECD) in purging electron contamination from the linac head is modeled, as well as the impact of a helium gas region between the deflector and phantom surface for lowering the amount of air-generated contamination. Methods: Magnetic modeling of the 1 T MRI was used to generate 3D magnetic field maps both withmore » and without the presence of an ECD located immediately below the MLC’s. Forty-seven different ECD designs were modeled and for each the magnetic field map was imported into Geant4 Monte Carlo simulations including the linac head, ECD, and a 30 × 30 × 30 cm{sup 3} water phantom located at isocenter. For the first generation system, the x-ray source to isocenter distance (SID) will be 160 cm, resulting in an 81.2 cm long air gap from the base of the ECD to the phantom surface. The first 71.2 cm was modeled as air or helium gas, with the latter encased between two windows of 50 μm thick high density polyethlyene. 2D skin doses (at 70 μm depth) were calculated across the phantom surface at 1 × 1 mm{sup 2} resolution for 6 MV beams of field size of 5 × 5, 10 × 10, and 20 × 20 cm{sup 2}. Results: The skin dose was predicted to be of similar magnitude as the generic systems modeled in previous work, 230% to 1400% ofD {sub max} for 5 × 5 to 20 × 20 cm{sup 2}, respectively. Inclusion of the ECD introduced a nonuniformity to the MRI imaging field that ranged from ∼20 to ∼140 ppm while the net force acting on the ECD ranged from ∼151 N to ∼1773 N. Various ECD designs were 100% efficient at purging the electron contamination into the ECD magnet banks; however, a small percentage were scattered back into the beam and continued to the phantom surface. Replacing a large portion of the extended air-column between the ECD and phantom surface with helium gas is a key element as it significantly minimized the air-generated contamination. When using an optimal ECD and helium gas region, the 70 μm skin dose is predicted to increase moderately inside a small hot spot over that of the case with no magnetic field present for the jaw defined square beams examined here. These increases include from 12% to 40% of D {sub max} for 5 × 5 cm{sup 2}, 18% to 55% of D {sub max} for 10 × 10 cm{sup 2}, and from 23% to 65% of D {sub max} for 20 × 20 cm{sup 2}. Conclusions: Coupling an efficient ECD and helium gas region below the MLCs in the 160 cm isocenter MRI-linac system is predicted to ameliorate the impact electron contamination focusing has on skin dose increases. An ECD is practical as its impact on the MRI imaging distortion is correctable, and the mechanical forces acting on it manageable from an engineering point of view.« less

Impact of the MLC on the MRI field distortion of a prototype MRI-linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kolling, Stefan; Keall, Paul; Oborn, Brad

2013-12-15

Purpose: To cope with intrafraction tumor motion, integrated MRI-linac systems for real-time image guidance are currently under development. The multileaf collimator (MLC) is a key component in every state-of-the-art radiotherapy treatment system, allowing for accurate field shaping and tumor tracking. This work quantifies the magnetic impact of a widely used MLC on the MRI field homogeneity for such a modality.Methods: The finite element method was employed to model a MRI-linac assembly comprised of a 1.0 T split-bore MRI magnet and the key ferromagnetic components of a Varian Millennium 120 MLC, namely, the leaves and motors. Full 3D magnetic field maps ofmore » the system were generated. From these field maps, the peak-to-peak distortion within the MRI imaging volume was evaluated over a 30 cm diameter sphere volume (DSV) around the isocenter and compared to a maximum preshim inhomogeneity of 300 μT. Five parametric studies were performed: (1) The source-to-isocenter distance (SID) was varied from 100 to 200 cm, to span the range of a compact system to that with lower magnetic coupling. (2) The MLC model was changed from leaves only to leaves with motors, to determine the contribution to the total distortion caused by MLC leaves and motors separately. (3) The system was configured in the inline or perpendicular orientation, i.e., the linac treatment beam was oriented parallel or perpendicular to the magnetic field direction. (4) The treatment field size was varied from 0 × 0 to 20×20 cm{sup 2}, to span the range of clinical treatment fields. (5) The coil currents were scaled linearly to produce magnetic field strengths B{sub 0} of 0.5, 1.0, and 1.5 T, to estimate how the MLC impact changes with B{sub 0}.Results: (1) The MLC-induced MRI field distortion fell continuously with increasing SID. (2) MLC leaves and motors were found to contribute to the distortion in approximately equal measure. (3) Due to faster falloff of the fringe field, the field distortion was generally smaller in the perpendicular beam orientation. The peak-to-peak DSV distortion was below 300 μT at SID≥130 cm (perpendicular) and SID≥140 cm (inline) for the 1.0 T design. (4) The simulation of different treatment fields was identified to cause dynamic changes in the field distribution. However, the estimated residual distortion was below 1.2 mm geometric distortion at SID≥120 cm (perpendicular) and SID≥130 cm (inline) for a 10 mT/m frequency-encoding gradient. (5) Due to magnetic saturation of the MLC materials, the field distortion remained constant at B{sub 0}>1.0 T.Conclusions: This work shows that the MRI field distortions caused by the MLC cannot be ignored and must be thoroughly investigated for any MRI-linac system. The numeric distortion values obtained for our 1.0 T magnet may vary for other magnet designs with substantially different fringe fields, however the concept of modest increases in the SID to reduce the distortion to a shimmable level is generally applicable.« less

High-precision terahertz frequency modulated continuous wave imaging method using continuous wavelet transform

NASA Astrophysics Data System (ADS)

Zhou, Yu; Wang, Tianyi; Dai, Bing; Li, Wenjun; Wang, Wei; You, Chengwu; Wang, Kejia; Liu, Jinsong; Wang, Shenglie; Yang, Zhengang

2018-02-01

Inspired by the extensive application of terahertz (THz) imaging technologies in the field of aerospace, we exploit a THz frequency modulated continuous-wave imaging method with continuous wavelet transform (CWT) algorithm to detect a multilayer heat shield made of special materials. This method uses the frequency modulation continuous-wave system to catch the reflected THz signal and then process the image data by the CWT with different basis functions. By calculating the sizes of the defects area in the final images and then comparing the results with real samples, a practical high-precision THz imaging method is demonstrated. Our method can be an effective tool for the THz nondestructive testing of composites, drugs, and some cultural heritages.

Continuity Conditions on Schrodinger Wave Functions at Discontinuities of the Potential.

ERIC Educational Resources Information Center

Branson, David

1979-01-01

Several standard arguments which attempt to show that the wave function and its derivative must be continuous across jump discontinuities of the potential are reviewed and their defects discussed. (Author/HM)

Applications of High Intensity Proton Accelerators

NASA Astrophysics Data System (ADS)

Raja, Rajendran; Mishra, Shekhar

2010-06-01

Superconducting radiofrequency linac development at Fermilab / S. D. Holmes -- Rare muon decay experiments / Y. Kuno -- Rare kaon decays / D. Bryman -- Muon collider / R. B. Palmer -- Neutrino factories / S. Geer -- ADS and its potential / J.-P. Revol -- ADS history in the USA / R. L. Sheffield and E. J. Pitcher -- Accelerator driven transmutation of waste: high power accelerator for the European ADS demonstrator / J. L. Biarrotte and T. Junquera -- Myrrha, technology development for the realisation of ADS in EU: current status & prospects for realisation / R. Fernandez ... [et al.] -- High intensity proton beam production with cyclotrons / J. Grillenberger and M. Seidel -- FFAG for high intensity proton accelerator / Y. Mori -- Kaon yields for 2 to 8 GeV proton beams / K. K. Gudima, N. V. Mokhov and S. I. Striganov -- Pion yield studies for proton driver beams of 2-8 GeV kinetic energy for stopped muon and low-energy muon decay experiments / S. I. Striganov -- J-Parc accelerator status and future plans / H. Kobayashi -- Simulation and verification of DPA in materials / N. V. Mokhov, I. L. Rakhno and S. I. Striganov -- Performance and operational experience of the CNGS facility / E. Gschwendtner -- Particle physics enabled with super-conducting RF technology - summary of working group 1 / D. Jaffe and R. Tschirhart -- Proton beam requirements for a neutrino factory and muon collider / M. S. Zisman -- Proton bunching options / R. B. Palmer -- CW SRF H linac as a proton driver for muon colliders and neutrino factories / M. Popovic, C. M. Ankenbrandt and R. P. Johnson -- Rapid cycling synchrotron option for Project X / W. Chou -- Linac-based proton driver for a neutrino factory / R. Garoby ... [et al.] -- Pion production for neutrino factories and muon colliders / N. V. Mokhov ... [et al.] -- Proton bunch compression strategies / V. Lebedev -- Accelerator test facility for muon collider and neutrino factory R&D / V. Shiltsev -- The superconducting RF linac for muon collider and neutrino factory - summary of working group 2 / J. Galambos, R. Garoby and S. Geer -- Prospects for a very high power CW SRF linac / R. A. Rimmer -- Indian accelerator program for ADS applications / V. C. Sahni and P. Singh -- Ion accelerator activities at VECC (particularly, operating at low temperature) / R. K. Bhandari -- Chinese efforts in high intensity proton accelerators / S. Fu, J. Wang and S. Fang -- ADSR activity in the UK / R. J. Barlow -- ADS development in Japan / K. Kikuchi -- Project-X, SRF, and very large power stations / C. M. Ankenbrandt, R. P. Johnson and M. Popovic -- Power production and ADS / R. Raja -- Experimental neutron source facility based on accelerator driven system / Y. Gohar -- Transmutation mission / W. S. Yang -- Safety performance and issues / J. E. Cahalan -- Spallation target design for accelerator-driven systems / Y. Gohar -- Design considerations for accelerator transmutation of waste system / W. S. Yang -- Japan ADS program / T. Sasa -- Overview of members states' and IAEA activities in the field of Accelerator Driven Systems (ADS) / A. Stanculescu -- Linac for ADS applications - accelerator technologies / R. W. Garnett and R. L. Sheffield -- SRF linacs and accelerator driven sub-critical systems - summary working groups 3 & 4 / J. Delayen -- Production of Actinium-225 via high energy proton induced spallation of Thorium-232 / J. Harvey ... [et al.] -- Search for the electric dipole moment of Radium-225 / R. J. Holt, Z.-T. Lu and R. Mueller -- SRF linac and material science and medicine - summary of working group 5 / J. Nolen, E. Pitcher and H. Kirk.

Picture of the global field of quasi-monochromatic gravity waves observed by stratospheric balloons and MST radars

NASA Technical Reports Server (NTRS)

Yamanaka, M. D.

1989-01-01

In MAP observations, it was found that: (1) gravity waves in selected or filtered portions of data are fit for monochromatic structures, whereas (2) those in fully continuous and resolved observations take universal continuous spectra. It is possible to explain (2) by dispersion of quasi-monochromatic (or slowly varying) wave packets observed locally as (1), since the medium atmosphere is unsteady and nonuniform. Complete verification of the wave-mean flow interactions by tracking individual wave packets seems hopeless, because the wave induced flow cannot be distinguished from the basic flow independent of the waves. Instead, the primitive picture is looked at before MAP, that is, the atmosphere is just like an entertainment stage illuminated by cocktail lights of quasi-monochromatic gravity waves. The wave parameters are regarded as functions of time and spatial coordinates. The observational evidences (1) and (2) suggest that the wave parameter field is rather homogeneous, which can be explained by interference of quasi-monochromatic wave packets.

A novel electron accelerator for MRI-Linac radiotherapy.

PubMed

Whelan, Brendan; Gierman, Stephen; Holloway, Lois; Schmerge, John; Keall, Paul; Fahrig, Rebecca

2016-03-01

MRI guided radiotherapy is a rapidly growing field; however, current electron accelerators are not designed to operate in the magnetic fringe fields of MRI scanners. As such, current MRI-Linac systems require magnetic shielding, which can degrade MR image quality and limit system flexibility. The purpose of this work was to develop and test a novel medical electron accelerator concept which is inherently robust to operation within magnetic fields for in-line MRI-Linac systems. Computational simulations were utilized to model the accelerator, including the thermionic emission process, the electromagnetic fields within the accelerating structure, and resulting particle trajectories through these fields. The spatial and energy characteristics of the electron beam were quantified at the accelerator target and compared to published data for conventional accelerators. The model was then coupled to the fields from a simulated 1 T superconducting magnet and solved for cathode to isocenter distances between 1.0 and 2.4 m; the impact on the electron beam was quantified. For the zero field solution, the average current at the target was 146.3 mA, with a median energy of 5.8 MeV (interquartile spread of 0.1 MeV), and a spot size diameter of 1.5 mm full-width-tenth-maximum. Such an electron beam is suitable for therapy, comparing favorably to published data for conventional systems. The simulated accelerator showed increased robustness to operation in in-line magnetic fields, with a maximum current loss of 3% compared to 85% for a conventional system in the same magnetic fields. Computational simulations suggest that replacing conventional DC electron sources with a RF based source could be used to develop medical electron accelerators which are robust to operation in in-line magnetic fields. This would enable the development of MRI-Linac systems with no magnetic shielding around the Linac and reduce the requirements for optimization of magnetic fringe field, simplify design of the high-field magnet, and increase system flexibility.

A novel electron accelerator for MRI-Linac radiotherapy

PubMed Central

Whelan, Brendan; Gierman, Stephen; Holloway, Lois; Schmerge, John; Keall, Paul; Fahrig, Rebecca

2016-01-01

Purpose: MRI guided radiotherapy is a rapidly growing field; however, current electron accelerators are not designed to operate in the magnetic fringe fields of MRI scanners. As such, current MRI-Linac systems require magnetic shielding, which can degrade MR image quality and limit system flexibility. The purpose of this work was to develop and test a novel medical electron accelerator concept which is inherently robust to operation within magnetic fields for in-line MRI-Linac systems. Methods: Computational simulations were utilized to model the accelerator, including the thermionic emission process, the electromagnetic fields within the accelerating structure, and resulting particle trajectories through these fields. The spatial and energy characteristics of the electron beam were quantified at the accelerator target and compared to published data for conventional accelerators. The model was then coupled to the fields from a simulated 1 T superconducting magnet and solved for cathode to isocenter distances between 1.0 and 2.4 m; the impact on the electron beam was quantified. Results: For the zero field solution, the average current at the target was 146.3 mA, with a median energy of 5.8 MeV (interquartile spread of 0.1 MeV), and a spot size diameter of 1.5 mm full-width-tenth-maximum. Such an electron beam is suitable for therapy, comparing favorably to published data for conventional systems. The simulated accelerator showed increased robustness to operation in in-line magnetic fields, with a maximum current loss of 3% compared to 85% for a conventional system in the same magnetic fields. Conclusions: Computational simulations suggest that replacing conventional DC electron sources with a RF based source could be used to develop medical electron accelerators which are robust to operation in in-line magnetic fields. This would enable the development of MRI-Linac systems with no magnetic shielding around the Linac and reduce the requirements for optimization of magnetic fringe field, simplify design of the high-field magnet, and increase system flexibility. PMID:26936713

Visual Analysis of the Daily QA Results of Photon and Electron Beams of a Trilogy Linac over a Five-year Period

PubMed Central

Chan, Maria F.; Li, Qiongge; Tang, Xiaoli; Li, Xiang; Li, Jingdong; Tang, Grace; Hunt, Margie A.; Deasy, Joseph O.

2016-01-01

Data visualization technique was applied to analyze the daily QA results of photon and electron beams. Special attention was paid to any trend the beams might display. A Varian Trilogy Linac equipped with dual photon energies and five electron energies was commissioned in early 2010. Daily Linac QA tests including the output constancy, beam flatness and symmetry (radial and transverse directions) were performed with an ionization chamber array device (QA BeamChecker Plus, Standard Imaging). The data of five years were collected and analyzed. For each energy, the measured data were exported and processed for visual trending using an in-house Matlab program. These daily data were cross-correlated with the monthly QA and annual QA results, as well as the preventive maintenance records. Majority of the output were within 1% of variation, with a consistent positive/upward drift for all seven energies (~+0.25% per month). The baseline of daily device is reset annually right after the TG-51 calibration. This results in a sudden drop of the output. On the other hand, the large amount of data using the same baseline exhibits a sinusoidal behavior (cycle = 12 months; amplitude = 0.8%, 0.5% for photons, electrons, respectively) on symmetry and flatness when normalization of baselines is accounted for. The well known phenomenon of new Linac output drift was clearly displayed. This output drift was a result of the air leakage of the over-pressurized sealed monitor chambers for the specific vendor. Data visualization is a new trend in the era of big data in radiation oncology research. It allows the data to be displayed visually and therefore more intuitive. Based on the visual display from the past, the physicist might predict the trend of the Linac and take actions proactively. It also makes comparisons, alerts failures, and potentially identifies causalities. PMID:27547595

SU-C-19A-05: Treatment Chairs for Modern Radiation Therapy Treatments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Court, L; Fullen, D; Tharp, K

2014-06-15

Purpose: Treating patients in a seated position has potential advantages including improved comfort, increased lung volume, and reduced respiratory motion. We compared chair designs for head and neck, thoracic and breast patients for use with either IGRT linacs or a proposed low-cost fixed horizontal beam-line machine. Methods: Three treatment chairs were designed and constructed. Two of the chairs are based on a massage-chair, with the patient angled slightly forwards and knee rests used to minimize intra-fraction slouch. The third chair design is more conventional; the patient is angled backwards, with indexed positioning devices and the ability to attach thermoplastic masks.more » Patient geometries, including PTV location and patient sizes, were extracted from 137 CTs of past patients were used to model the probability of collision between the patient and the linac for various seated positions. All chairs were designed around the weight limits for couches on our linacs. At the time of writing we have just received IRB approval for imaging studies to evaluate comfort, and intra- and interfraction reproducibility. Results: The geometric analysis showed that head and neck patients and thoracic patients could be treated without collision. However, there is very limited space between the patient and the treatment/imaging devices, so careful design of the chair is essential. The position of the treatment target and extended arm positioning means that this is a particular concern for thoracic and breast patients. This was demonstrated for one of the prototype chairs designed for breast treatment where the arm holders would collide with the kV detector. The extra clearance of a dedicated fixed-beam linac would overcome these difficulties. Intra- and inter-fraction reproducibility results will be presented at the meeting. Conclusion: To take advantage of the clinical advantages of seated treatments, appropriate treatment chairs are needed. A dedicate fixed-beam linac may enable more options. This work was partially funded by Varian Medical Systems.« less

SU-E-T-06: A Comparison of IMRT Treatment of Esophageal Carcinoma in Elekta-Precise and Varian23EX Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, W; Fan, X; Qiu, R

2014-06-01

Purpose: To compare and analyze the characteristics of static intensity-modulated radiotherapy (IMRT) plans designed on Elekta and Varian Linac in different esophageal cancer(EC), exploring advantages and disadvantages of different vendor Linac, thus can be better serve for clinical. Methods: Twenty-four patients with EC were selected, including 6 cases located in the cervical, upper, middle and the lower thorax, respectively. Two IMRT plans were generated with the Oncentra planning system: in Elekta and Varian Linac, prescription dose of 60Gy in 30 fractions to the PTV. We examined the dose-volume histogram parameters of PTV and the organs at risk (OAR) such asmore » lungs, spinal cord and heart, and additional Monitor units(MU), treatment time, Homogeneity index(HI), Conformity index(CI) and Gamma index comparisons were performed. Results: All plans resulted in abundant dose coverage of PTV for EC of different locations. The doses to PTV, HI and OAR in Elekta plans were not statistically different in comparison with Varian plans, with the following exceptions: in cervical, upper and lower thoracic EC the PTV's CI, and in middle thorax EC PTV's D2, D50, V105 and PTV-average were better in Elekta plans than in Varian plans. In the cervical, upper and the middle thorax EC, treatment time were significantly decreased in Varian plans as against Elekta plans, while in the lower thoracic EC treatment time were no striking difference. MUs and gamma index were similar between the two Linac plans. Conclusion: For the the middle thorax EC Varian plans is better than Elekta plans, not only in treatment time but in the PTV dose; while for the lower thorax EC Elekta plans is the first choice for better CI; for the other part of the EC usually Elekta plans can increase the CI, while Varian plans can reduce treatment time, can be selected according to the actual situation of the patient treatment.« less

The Relationship of Dysthymia, Minor Depression, and Gender to Changes in Smoking for Current and Former Smokers: Longitudinal Evaluation in the U.S. Population

PubMed Central

Weinberger, Andrea H.; Pilver, Corey E.; Desai, Rani A.; Mazure, Carolyn M.; McKee, Sherry A.

2012-01-01

BACKGROUND Although data clearly link major depression and smoking, little is known about the association between dysthymia and minor depression and smoking behavior. The current study examined changes in smoking over three years for current and former smokers with and without dysthymia and minor depression. METHODS Participants who were current or former daily cigarette smokers at Wave 1 of the National Epidemiologic Survey on Alcohol and Related Conditions and completed the Wave 2 assessment were included in these analyses (n=11,973; 46% female). Analyses examined the main and gender-specific effects of current dysthymia, lifetime dysthymia, and minor depression (a single diagnostic category that denoted current and or lifetime prevalence) on continued smoking for Wave 1 current daily smokers and continued abstinence for Wave 1 former daily smokers. RESULTS Wave 1 current daily smokers with current dysthymia (OR=2.13, 95% CI=1.23, 3.70) or minor depression (OR=1.53, 95% CI=1.07, 2.18) were more likely than smokers without the respective diagnosis to report continued smoking at Wave 2. Wave 1 former daily smokers with current dysthymia (OR=0.44, 95% CI=0.20, 0.96) and lifetime dysthymia (OR=0.37, 95% CI=0.15, 0.91) were less likely than those without the diagnosis to remain abstinent from smoking at Wave 2. The gender-by-diagnosis interactions were not significant, suggesting that the impact of dysthymia and minor depression on smoking behavior is similar among men and women. CONCLUSIONS Current dysthymia and minor depression are associated with a greater likelihood of continued smoking; current and lifetime dysthymia are associated with a decreased likelihood of continued smoking abstinence. PMID:22809897

The relationship of dysthymia, minor depression, and gender to changes in smoking for current and former smokers: longitudinal evaluation in the U.S. population.

PubMed

Weinberger, Andrea H; Pilver, Corey E; Desai, Rani A; Mazure, Carolyn M; McKee, Sherry A

2013-01-01

Although data clearly link major depression and smoking, little is known about the association between dysthymia and minor depression and smoking behavior. The current study examined changes in smoking over 3 years for current and former smokers with and without dysthymia and minor depression. Participants who were current or former daily cigarette smokers at Wave 1 of the National Epidemiologic Survey on Alcohol and Related Conditions and completed the Wave 2 assessment were included in these analyses (n=11,973; 46% female). Analyses examined the main and gender-specific effects of current dysthymia, lifetime dysthymia, and minor depression (a single diagnostic category that denoted current and/or lifetime prevalence) on continued smoking for Wave 1 current daily smokers and continued abstinence for Wave 1 former daily smokers. Wave 1 current daily smokers with current dysthymia (OR=2.13, 95% CI=1.23, 3.70) or minor depression (OR=1.53, 95% CI=1.07, 2.18) were more likely than smokers without the respective diagnosis to report continued smoking at Wave 2. Wave 1 former daily smokers with current dysthymia (OR=0.44, 95% CI=0.20, 0.96) and lifetime dysthymia (OR=0.37, 95% CI=0.15, 0.91) were less likely than those without the diagnosis to remain abstinent from smoking at Wave 2. The gender-by-diagnosis interactions were not significant, suggesting that the impact of dysthymia and minor depression on smoking behavior is similar among men and women. Current dysthymia and minor depression are associated with a greater likelihood of continued smoking; current and lifetime dysthymia are associated with a decreased likelihood of continued smoking abstinence. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Science Requirements and Conceptual Design for a Polarized Medium Energy Electron-Ion Collider at Jlab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abeyratne, S; Ahmed, S; Barber, D

2012-08-01

Researchers have envisioned an electron-ion collider with ion species up to heavy ions, high polarization of electrons and light ions, and a well-matched center-of-mass energy range as an ideal gluon microscope to explore new frontiers of nuclear science. In its most recent Long Range Plan, the Nuclear Science Advisory Committee (NSAC) of the US Department of Energy and the National Science Foundation endorsed such a collider in the form of a 'half-recommendation.' As a response to this science need, Jefferson Lab and its user community have been engaged in feasibility studies of a medium energy polarized electron-ion collider (MEIC), cost-effectivelymore » utilizing Jefferson Lab's already existing Continuous Electron Beam Accelerator Facility (CEBAF). In close collaboration, this community of nuclear physicists and accelerator scientists has rigorously explored the science case and design concept for this envisioned grand instrument of science. An electron-ion collider embodies the vision of reaching the next frontier in Quantum Chromodynamics - understanding the behavior of hadrons as complex bound states of quarks and gluons. Whereas the 12 GeV Upgrade of CEBAF will map the valence-quark components of the nucleon and nuclear wave functions in detail, an electron-ion collider will determine the largely unknown role sea quarks play and for the first time study the glue that binds all atomic nuclei. The MEIC will allow nuclear scientists to map the spin and spatial structure of quarks and gluons in nucleons, to discover the collective effects of gluons in nuclei, and to understand the emergence of hadrons from quarks and gluons. The proposed electron-ion collider at Jefferson Lab will collide a highly polarized electron beam originating from the CEBAF recirculating superconducting radiofrequency (SRF) linear accelerator (linac) with highly polarized light-ion beams or unpolarized light- to heavy-ion beams from a new ion accelerator and storage complex. Since the very beginning, the design studies at Jefferson Lab have focused on achieving high collider performance, particularly ultrahigh luminosities up to 10{sup 34} cm{sup -2}s{sup -1} per detector with large acceptance, while maintaining high polarization for both the electron and light-ion beams. These are the two key performance requirements of a future electron-ion collider facility as articulated by the NSAC Long Range Plan. In MEIC, a new ion complex is designed specifically to deliver ion beams that match the high bunch repetition and highly polarized electron beam from CEBAF. During the last two years, both development of the science case and optimization of the machine design point toward a medium-energy electron-ion collider as the topmost goal for Jefferson Lab. The MEIC, with relatively compact collider rings, can deliver a luminosity above 10{sup 34} cm{sup -2}s{sup -1} at a center-of-mass energy up to 65 GeV. It offers an electron energy up to 11 GeV, a proton energy up to 100 GeV, and corresponding energies per nucleon for heavy ions with the same magnetic rigidity. This design choice balances the scope of the science program, collider capabilities, accelerator technology innovation, and total project cost. An energy upgrade could be implemented in the future by adding two large collider rings housed in another large tunnel to push the center-of-mass energy up to or exceeding 140 GeV. After careful consideration of an alternative electron energy recovery linac on ion storage ring approach, a ring-ring collider scenario at high bunch repetition frequency was found to offer fully competitive performance while eliminating the uncertainties of challenging R&D on ampere-class polarized electron sources and many-pass energy-recovery linacs (ERLs). The essential new elements of an MEIC facility at Jefferson Lab are an electron storage ring and an entirely new, modern ion acceleration and storage complex. For the high-current electron collider ring, the upgraded 12 GeV CEBAF SRF linac will serve as a full-energy injector, and, if needed, provide top-off refilling. The CEBAF fixed-target nuclear physics program can be simultaneously operated since the filling time of the electron ring is very short. The ion complex for MEIC consists of sources for polarized light ions and unpolarized light to heavy ions, an SRF ion linac with proton energy up to 280 MeV, a 3 GeV prebooster synchrotron, a large booster synchrotron for proton energy up to 20 GeV, and a medium-energy collider ring with energy up to 100 GeV. The ion complex can accelerate other species of ions with corresponding energies at each accelerating stage. There are three collision points planned for MEIC. Two of them are for collisions with medium-energy ions; the third is for low energy ion beams stored in a dedicated low-energy compact storage ring, as a possible follow-on project.« less

Critical analysis of industrial electron accelerators

NASA Astrophysics Data System (ADS)

Korenev, S.

2004-09-01

The critical analysis of electron linacs for industrial applications (degradation of PTFE, curing of composites, modification of materials, sterlization and others) is considered in this report. Main physical requirements for industrial electron accelerators consist in the variations of beam parameters, such as kinetic energy and beam power. Questions for regulation of these beam parameters are considered. The level of absorbed dose in the irradiated product and throughput determines the main parameters of electron accelerator. The type of ideal electron linac for industrial applications is discussed.

Optical laser systems at the Linac Coherent Light Source

DOE PAGES

Minitti, Michael P.; Robinson, Joseph S.; Coffee, Ryan N.; ...

2015-04-22

Ultrafast optical lasers play an essential role in exploiting the unique capabilities of recently commissioned X-ray free-electron laser facilities such as the Linac Coherent Light Source (LCLS). Pump–probe experimental techniques reveal ultrafast dynamics in atomic and molecular processes and reveal new insights in chemistry, biology, material science and high-energy-density physics. This manuscript describes the laser systems and experimental methods that enable cutting-edge optical laser/X-ray pump–probe experiments to be performed at LCLS.

Design of Linear Accelerator (LINAC) tanks for proton therapy via Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) approaches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castellano, T.; De Palma, L.; Laneve, D.

2015-07-01

A homemade computer code for designing a Side- Coupled Linear Accelerator (SCL) is written. It integrates a simplified model of SCL tanks with the Particle Swarm Optimization (PSO) algorithm. The computer code main aim is to obtain useful guidelines for the design of Linear Accelerator (LINAC) resonant cavities. The design procedure, assisted via the aforesaid approach seems very promising, allowing future improvements towards the optimization of actual accelerating geometries. (authors)

Symposium on electron linear accelerators in honor of Richard B. Neal's 80th birthday: Proceedings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siemann, R.H.

The papers presented at the conference are: (1) the construction of SLAC and the role of R.B. Neal; (2) symposium speech; (3) lessons learned from the SLC; (4) alternate approaches to future electron-positron linear colliders; (5) the NLC technical program; (6) advanced electron linacs; (7) medical uses of linear accelerators; (8) linac-based, intense, coherent X-ray source using self-amplified spontaneous emission. Selected papers have been indexed separately for inclusion in the Energy Science and Technology Database.

SYNCHROTRON RADIATION, FREE ELECTRON LASER, APPLICATION OF NUCLEAR TECHNOLOGY, ETC.: Study on the characteristics of linac based THz light source

NASA Astrophysics Data System (ADS)

Zhu, Xiong-Wei; Wang, Shu-Hong; Chen, Sen-Yu

2009-10-01

There are many methods based on linac for THz radiation production. As one of the options for the Beijing Advanced Light, an ERL test facility is proposed for THz radiation. In this test facility, there are 4 kinds of methods to produce THz radiation: coherent synchrotron radiation (CSR), synchrotron radiation (SR), low gain FEL oscillator, and high gain SASE FEL. In this paper, we study the characteristics of the 4 kinds of THz light sources.

2-micrometer continuous wave laser treatment for multiple non-muscle-invasive bladder cancer with intravesical instillation of epirubicin.

PubMed

Liu, Haitao; Xue, Song; Ruan, Yuan; Sun, Xiaowen; Han, Bangmin; Xia, Shujie

2011-01-01

We have reported the efficacy and safety of 2-micrometer continuous wave laser resection of non-muscle-invasive bladder tumor (NMIVBC) (World J Urology 2010;28:157-161). In this study, we evaluated the use of 2-micrometer continuous wave laser resection in combination with intravesical instillation of epirubicin for the treatment of multiple NMIVBC. From September 2007 to April 2008, sixty patients with multiple NMIVBC were included in this study (44 cases of low grade papillary urothelial carcinoma, 10 cases of high grade papillary urothelial carcinoma, and six cases of papillary urothelial neoplasm with low malignant potential). Imaging examinations including pelvic computer tomography (CT) and intravenous urography showed no extravesical extension, lymphatic metastasis or any lesions of upper urinary tract. All patients received 2-micrometer continuous wave laser therapy under continuous epidural anesthesia, and intravesical chemotherapy with epirubicin 1 week later (intravesical instillation weekly for 8 weeks, followed by monthly maintenance to 12 months). Totally 211 tumors in 60 patients were successfully removed with 2-micrometer continuous wave laser. The mean operation time was 48 minutes per patient (ranged 20-90 minutes) and 13.6 minutes per tumor (range 5-25 minutes). No obturator nerve reflection or bladder perforation occurred during the procedure. All patients finished 12 months of intravesical chemotherapy without severe complications. The mean followed-up time was 23 months. Tumor recurrences were found in 13 patients (22%). The combination of 2-micrometer continuous wave laser and intravesical chemotherapy is feasible, safe, and efficacious for the treatment of multiple NMIVBC. Copyright © 2011 Wiley-Liss, Inc.

Characteristics of GeV Electron Bunches Accelerated by Intense Lasers in Vacuum

NASA Astrophysics Data System (ADS)

Wang, P. X.; Ho, Y. K.; Kong, Q.; Yuan, X. Q.; Cao, N.; Feng, L.

This paper studies the characteristics of GeV electron bunches driven by ultra-intense lasers in vacuum based on the mechanism of capture and violent acceleration scenario [CAS, see, e.g. J. X. Wang et al., Phys. Rev. E58, 6575 (1998)], which shows an interesting prospect of becoming a new principle of laser-driven accelerators. It has been found that the accelerated GeV electron bunch is a macro-pulse composed of a lot of micro-pulses, which is analogous to the structure of the bunches produced by conventional linacs. The macro-pulse corresponds to the duration of the laser pulse while the micro-pulse corresponds to the periodicity of the laser wave. Therefore, provided that the incoming electron bunch with comparable sizes as that of the laser pulse synchronously impinges on the laser pulse, the total fraction of electrons captured and accelerated to GeV energy can reach more than 20%. These results demonstrate that the mechanisms of CAS is a relatively effective accelerator mechanism.

A new THz/Far-IR beamline at the Jefferson Lab ERL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neil, George; Williams, Gwyn

2003-08-01

Multiparticle coherent synchrotron emitted by sub-picosecond bunches of electrons in an energy recovering linac, (ERL), at 75 MHz, yield average powers of ~ 100 watts, even for beam currents of 10 mA.This is 10,000 times higher than typical table-top systems.We describe a new ERL facility under construction at Jefferson Lab, and a new THz extraction system and beamline.We also present theoretical calculations.Potential applications of this exciting new source include driving new non-linear phenomena, performing pump-probe studies of dynamical properties of novel materials, and studying molecular vibrations and rotations, low frequency protein motions, phonons, superconductor bandgaps, electronic scattering, collective electronic excitationsmore » (e.g., charge density waves), and spintronics.This work was supported by the US Department of Energy, the Office of Naval Research and the Commonwealth of Virginia.G.L. Carr, M.C. Martin, W.R. McKinney, K. Jordan, G.R. Neil and G.P. Wi« less

Bent crystal spectrometer for both frequency and wavenumber resolved x-ray scattering at a seeded free-electron laser.

PubMed

Zastrau, Ulf; Fletcher, Luke B; Förster, Eckhart; Galtier, Eric Ch; Gamboa, Eliseo; Glenzer, Siegfried H; Heimann, Philipp; Marschner, Heike; Nagler, Bob; Schropp, Andreas; Wehrhan, Ortrud; Lee, Hae Ja

2014-09-01

We present a cylindrically curved GaAs x-ray spectrometer with energy resolution ΔE/E = 1.1 × 10(-4) and wave-number resolution of Δk/k = 3 × 10(-3), allowing plasmon scattering at the resolution limits of the Linac Coherent Light Source (LCLS) x-ray free-electron laser. It spans scattering wavenumbers of 3.6 to 5.2/Å in 100 separate bins, with only 0.34% wavenumber blurring. The dispersion of 0.418 eV/13.5 μm agrees with predictions within 1.3%. The reflection homogeneity over the entire wavenumber range was measured and used to normalize the amplitude of scattering spectra. The proposed spectrometer is superior to a mosaic highly annealed pyrolytic graphite spectrometer when the energy resolution needs to be comparable to the LCLS seeded bandwidth of 1 eV and a significant range of wavenumbers must be covered in one exposure.

RF study and 3-D simulations of a side-coupling thermionic RF-gun

NASA Astrophysics Data System (ADS)

Rimjaem, S.; Kusoljariyakul, K.; Thongbai, C.

2014-02-01

A thermionic RF-gun for generating ultra-short electron bunches was optimized, developed and used as a source at a linac-based THz radiation research laboratory of the Plasma and Beam Physics Research Facility, Chiang Mai University, Thailand. The RF-gun is a π/2-mode standing wave structure, which consists of two S-band accelerating cells and a side-coupling cavity. The 2856 MHz RF wave is supplied from an S-band klystron to the gun through the waveguide input-port at the cylindrical wall of the second cell. A fraction of the RF power is coupled from the second cell to the first one via a side-coupling cavity. Both the waveguide input-port and the side-coupling cavity lead to an asymmetric geometry of the gun. RF properties and electromagnetic field distributions inside the RF-gun were studied and numerically simulated by using computer codes SUPERFISH 7.19 and CST Microwave Studio 2012©. RF characterizations and tunings of the RF-gun were performed to ensure the reliability of the gun operation. The results from 3D simulations and measurements are compared and discussed in this paper. The influence of asymmetric field distributions inside the RF-gun on the electron beam properties was investigated via 3D beam dynamics simulations. A change in the coupling-plane of the side-coupling cavity is suggested to improve the gun performance.

Plasma production for electron acceleration by resonant plasma wave

NASA Astrophysics Data System (ADS)

Anania, M. P.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Croia, M.; Curcio, A.; Di Giovenale, D.; Di Pirro, G. P.; Filippi, F.; Ghigo, A.; Lollo, V.; Pella, S.; Pompili, R.; Romeo, S.; Ferrario, M.

2016-09-01

Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (10-100 GV/m), enabling acceleration of electrons to GeV energy in few centimeter. However, the quality of the electron bunches accelerated with this technique is still not comparable with that of conventional accelerators (large energy spread, low repetition rate, and large emittance); radiofrequency-based accelerators, in fact, are limited in accelerating field (10-100 MV/m) requiring therefore hundred of meters of distances to reach the GeV energies, but can provide very bright electron bunches. To combine high brightness electron bunches from conventional accelerators and high accelerating fields reachable with plasmas could be a good compromise allowing to further accelerate high brightness electron bunches coming from LINAC while preserving electron beam quality. Following the idea of plasma wave resonant excitation driven by a train of short bunches, we have started to study the requirements in terms of plasma for SPARC_LAB (Ferrario et al., 2013 [1]). In particular here we focus on hydrogen plasma discharge, and in particular on the theoretical and numerical estimates of the ionization process which are very useful to design the discharge circuit and to evaluate the current needed to be supplied to the gas in order to have full ionization. Eventually, the current supplied to the gas simulated will be compared to that measured experimentally.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yewondwossen, M; Robar, J; Parsons, D

Purpose: During radiotherapy treatment, lung tumors can display substantial respiratory motion. This motion usually necessitates enlarged treatment margins to provide full tumour coverage. Unfortunately, these margins limit the dose that can be prescribed for tumour control and cause complications to normal tissue. Options for real-time methods of direct detection of tumour position, and particularly those that obviate the need for inserted fiducial markers, are limited. We propose a method of tumor tracking without implanted fiducial markers using a novel fast switching-target that toggles between a FFF copper/tungsten therapy mode and a FFF low-Z target mode for imaging. In this workmore » we demonstrate proof-of-concept of this new technology. Methods: The prototype includes two targets: i) a FFF copper/tungsten target equivalent to that in the Varian 2100 EX 6 MV, and ii) a low-Z (carbon) target with a thickness of 110% of continuous slowing down approximation range (CSDA) at 7 MeV. The two targets can be exchanged with a custom made linear slide and motor-driven actuator. The usefulness of the switching-target concept is demonstrated through experimental BEV Planar images acquired with continual treatment and imaging at a user-defined period. Results: The prototype switching-target demonstrates that two recent advances in linac technology (FFF target for therapy and low-Z target) can be combined with synergy. The switching-target approach offers the capacity for rapid switching between treatment and high-contrast imaging modes, allowing intrafractional tracking, as demonstrated in this work with dynamic breathing phantom. By using a single beam-line, the design is streamlined and may obviate the need for an auxiliary imaging system (e.g., kV OBI.) Conclusion: This switching-target approach is a feasible combination of two current advances in linac technology (FFF target for therapy and a FFF low-Z target) allowing new options in on-line IGRT.« less

Wave function continuity and the diagonal Born-Oppenheimer correction at conical intersections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meek, Garrett A.; Levine, Benjamin G., E-mail: levine@chemistry.msu.edu

2016-05-14

We demonstrate that though exact in principle, the expansion of the total molecular wave function as a sum over adiabatic Born-Oppenheimer (BO) vibronic states makes inclusion of the second-derivative nonadiabatic energy term near conical intersections practically problematic. In order to construct a well-behaved molecular wave function that has density at a conical intersection, the individual BO vibronic states in the summation must be discontinuous. When the second-derivative nonadiabatic terms are added to the Hamiltonian, singularities in the diagonal BO corrections (DBOCs) of the individual BO states arise from these discontinuities. In contrast to the well-known singularities in the first-derivative couplingsmore » at conical intersections, these singularities are non-integrable, resulting in undefined DBOC matrix elements. Though these singularities suggest that the exact molecular wave function may not have density at the conical intersection point, there is no physical basis for this constraint. Instead, the singularities are artifacts of the chosen basis of discontinuous functions. We also demonstrate that continuity of the total molecular wave function does not require continuity of the individual adiabatic nuclear wave functions. We classify nonadiabatic molecular dynamics methods according to the constraints placed on wave function continuity and analyze their formal properties. Based on our analysis, it is recommended that the DBOC be neglected when employing mixed quantum-classical methods and certain approximate quantum dynamical methods in the adiabatic representation.« less

Wave function continuity and the diagonal Born-Oppenheimer correction at conical intersections

NASA Astrophysics Data System (ADS)

Meek, Garrett A.; Levine, Benjamin G.

2016-05-01

We demonstrate that though exact in principle, the expansion of the total molecular wave function as a sum over adiabatic Born-Oppenheimer (BO) vibronic states makes inclusion of the second-derivative nonadiabatic energy term near conical intersections practically problematic. In order to construct a well-behaved molecular wave function that has density at a conical intersection, the individual BO vibronic states in the summation must be discontinuous. When the second-derivative nonadiabatic terms are added to the Hamiltonian, singularities in the diagonal BO corrections (DBOCs) of the individual BO states arise from these discontinuities. In contrast to the well-known singularities in the first-derivative couplings at conical intersections, these singularities are non-integrable, resulting in undefined DBOC matrix elements. Though these singularities suggest that the exact molecular wave function may not have density at the conical intersection point, there is no physical basis for this constraint. Instead, the singularities are artifacts of the chosen basis of discontinuous functions. We also demonstrate that continuity of the total molecular wave function does not require continuity of the individual adiabatic nuclear wave functions. We classify nonadiabatic molecular dynamics methods according to the constraints placed on wave function continuity and analyze their formal properties. Based on our analysis, it is recommended that the DBOC be neglected when employing mixed quantum-classical methods and certain approximate quantum dynamical methods in the adiabatic representation.

Wave function continuity and the diagonal Born-Oppenheimer correction at conical intersections.

PubMed

Meek, Garrett A; Levine, Benjamin G

2016-05-14

We demonstrate that though exact in principle, the expansion of the total molecular wave function as a sum over adiabatic Born-Oppenheimer (BO) vibronic states makes inclusion of the second-derivative nonadiabatic energy term near conical intersections practically problematic. In order to construct a well-behaved molecular wave function that has density at a conical intersection, the individual BO vibronic states in the summation must be discontinuous. When the second-derivative nonadiabatic terms are added to the Hamiltonian, singularities in the diagonal BO corrections (DBOCs) of the individual BO states arise from these discontinuities. In contrast to the well-known singularities in the first-derivative couplings at conical intersections, these singularities are non-integrable, resulting in undefined DBOC matrix elements. Though these singularities suggest that the exact molecular wave function may not have density at the conical intersection point, there is no physical basis for this constraint. Instead, the singularities are artifacts of the chosen basis of discontinuous functions. We also demonstrate that continuity of the total molecular wave function does not require continuity of the individual adiabatic nuclear wave functions. We classify nonadiabatic molecular dynamics methods according to the constraints placed on wave function continuity and analyze their formal properties. Based on our analysis, it is recommended that the DBOC be neglected when employing mixed quantum-classical methods and certain approximate quantum dynamical methods in the adiabatic representation.

The local nanohertz gravitational-wave landscape from supermassive black hole binaries

NASA Astrophysics Data System (ADS)

Mingarelli, Chiara M. F.; Lazio, T. Joseph W.; Sesana, Alberto; Greene, Jenny E.; Ellis, Justin A.; Ma, Chung-Pei; Croft, Steve; Burke-Spolaor, Sarah; Taylor, Stephen R.

2017-12-01

Supermassive black hole binary systems form in galaxy mergers and reside in galactic nuclei with large and poorly constrained concentrations of gas and stars. These systems emit nanohertz gravitational waves that will be detectable by pulsar timing arrays. Here we estimate the properties of the local nanohertz gravitational-wave landscape that includes individual supermassive black hole binaries emitting continuous gravitational waves and the gravitational-wave background that they generate. Using the 2 Micron All-Sky Survey, together with galaxy merger rates from the Illustris simulation project, we find that there are on average 91 ± 7 continuous nanohertz gravitational-wave sources, and 7 ± 2 binaries that will never merge, within 225 Mpc. These local unresolved gravitational-wave sources can generate a departure from an isotropic gravitational-wave background at a level of about 20 per cent, and if the cosmic gravitational-wave background can be successfully isolated, gravitational waves from at least one local supermassive black hole binary could be detected in 10 years with pulsar timing arrays.

The Status of Turkish Accelerator Center Test Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yavas, Oe.

2007-04-23

Recently, conceptual design of Turkic Accelerator Center (TAC) proposal was completed. Main goal of this proposal is a charm factory that consists of a linac-ring type electron-positron collider. In addition, synchrotron radiation from the positron ring and free electron laser from the electron linac are proposed. The project related with this proposal has been accepted by Turkish government. It is planned that the Technical Design Report of TAC will have been written in next three years. In this period, an infrared oscillator free electron laser (IR FEL) will be constructed as a test facility for TAC. 20 and 50 MeVmore » electron energies will be used to obtain infra red free electron laser. The main parameters of the electron linac, the optical cavities and the free electron laser were determined. The possible use of obtained laser beam in basic and applied research areas such as biotechnology, nanotechnology, semiconductors and photo chemistry were stated.« less

Status Report on the CEBAF IR and UV FELs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leemann, Christoph; Bisognano, Joseph; Douglas, David

1993-07-01

The CEBAF five pass recirculating, superconducting linac, being developed as a high power electron source for nuclear physics, is also an ideal FEL driver.The 45 MeV front end linac is presently operational with a CW (low peak current) nuclear physics gun and has met all CEBAF performance specifications including low emittance and energy spread (< 1 * 10^-4). Progress will be reported in commissioning.This experience leads to predictions of excellent FEL performance.Initial designs reported last year have been advanced.Using the output of a high charge DC photoemission gun under development with a 6 cm period wiggler produces kilowatt output powersmore » in the 3.6 to 17 micrometer range in the fundamental.Third harmonic operation extends IR performance down to 1.2 micrometer.Beam at energies up to 400 MeV from the first full CEBAF linac will interact in a similar but longer wiggler to yield kilowatt UV light production at wavelengths as short as 0.15 micrometers.Full power FEL« less

1 MeV, 10 kW DC electron accelerator for industrial applications

NASA Astrophysics Data System (ADS)

Nayak, B.; Acharya, S.; Bhattacharjee, D.; Bakhtsingh, R. I.; Rajan, R.; Sharma, D. K.; Dewangan, S.; Sharma, V.; Patel, R.; Tiwari, R.; Benarjee, S.; Srivastava, S. K.

2016-03-01

Several modern applications of radiation processing like medical sterilization, rubber vulcanization, polymerization, cross-linking and pollution control from thermal power stations etc. require D.C. electron accelerators of energy ranging from a few hundred keVs to few MeVs and power from a few kilowatts to hundreds of kilowatts. To match these requirements, a 3 MeV, 30 kW DC electron linac has been developed at BARC, Mumbai and current operational experience of 1 MeV, 10 kW beam power will be described in this paper. The LINAC composed mainly of Electron Gun, Accelerating Tubes, Magnets, High Voltage source and provides 10 kW beam power at the Ti beam window stably after the scanning section. The control of the LINAC is fully automated. Here Beam Optics study is carried out to reach the preferential parameters of Accelerating as well as optical elements. Beam trials have been conducted to find out the suitable operation parameters of the system.

Linac cryogenic distribution system maintenance and upgrades at JLab

NASA Astrophysics Data System (ADS)

Dixon, K.; Wright, M.; Ganni, V.

2014-01-01

The Central Helium Liquefier (CHL) distribution system to the CEBAF and FEL linacs at Jefferson Lab (JLab) experienced a planned warm up during the late summer and fall of 2012 for the first time after its commissioning in 1991. Various maintenance and modifications were performed to support high beam availability to the experimental users, meet 10 CFR 851 requirements for pressure systems, address operational issues, and prepare the cryogenic interfaces for the high-gradient cryomodules needed for the 12 GeV upgrade. Cryogenic maintenance and installation work had to be coordinated with other activities in the linacs and compete for manpower from other department installation activities. With less than a quarter of the gas storage capacity available to handle the boil-off from the more than 40 cryomodules, 35,000 Nm3 of helium was re-liquefied and shipped to a vendor via a liquid tanker trailer. Nearly 200 u-tubes had to be removed and stored while seals were replaced on related equipment such as vacuum pump outs, bayonet isolation and process valves.

Electron beam energy and bunch length feed forward control studies using an artificial neural network at the Linac coherent light source

NASA Astrophysics Data System (ADS)

Meier, E.; Biedron, S. G.; LeBlanc, G.; Morgan, M. J.; Wu, J.

2009-11-01

This paper describes the results of an advanced control algorithm for the stabilization of electron beam energy in a Linac. The approach combines a conventional Proportional-Integral (PI) controller with a neural network (NNET) feed forward algorithm; it utilizes the robustness of PI control and the ability of a feed forward system in order to exert control over a wider range of frequencies. The NNET is trained to recognize jitter occurring in the phase and voltage of one of the klystrons, based on a record of these parameters, and predicts future energy deviations. A systematic approach is developed to determine the optimal NNET parameters that are then applied to the Australian Synchrotron Linac. The system's capability to fully cancel multi-frequency jitter is demonstrated. The NNET system is then augmented with the PI algorithm, and further jitter attenuation is achieved when the NNET is not operating optimally.

Modeling of neutrals in the Linac4 H- ion source plasma: Hydrogen atom production density profile and Hα intensity by collisional radiative model

NASA Astrophysics Data System (ADS)

Yamamoto, T.; Shibata, T.; Ohta, M.; Yasumoto, M.; Nishida, K.; Hatayama, A.; Mattei, S.; Lettry, J.; Sawada, K.; Fantz, U.

2014-02-01

To control the H0 atom production profile in the H- ion sources is one of the important issues for the efficient and uniform surface H- production. The purpose of this study is to construct a collisional radiative (CR) model to calculate the effective production rate of H0 atoms from H2 molecules in the model geometry of the radio-frequency (RF) H- ion source for Linac4 accelerator. In order to validate the CR model by comparison with the experimental results from the optical emission spectroscopy, it is also necessary for the model to calculate Balmer photon emission rate in the source. As a basic test of the model, the time evolutions of H0 production and the Balmer Hα photon emission rate are calculated for given electron energy distribution functions in the Linac4 RF H- ion source. Reasonable test results are obtained and basis for the detailed comparisons with experimental results have been established.

First experience with carbon stripping foils for the 160 MeV H- injection into the CERN PSB

NASA Astrophysics Data System (ADS)

Weterings, Wim; Bracco, Chiara; Jorat, Louise; Noulibos, Remy; van Trappen, Pieter

2018-05-01

160 MeV H- beam will be delivered from the new CERN linear accelerator (Linac4) to the Proton Synchrotron Booster (PSB), using a H- charge-exchange injection system. A 200 µg/cm2 carbon stripping foil will convert H- into protons by stripping off the electrons. The H- charge-exchange injection principle will be used for the first time in the CERN accelerator complex and involves many challenges. In order to gain experience with the foil changing mechanism and the very fragile foils, in 2016, prior to the installation in the PSB, a stripping foil test stand has been installed in the Linac4 transfer line. In addition, parts of the future PSB injection equipment are also temporarily installed in the Linac4 transfer line for tests with a 160 MeV H- commissioning proton beam. This paper describes the foil changing mechanism and control system, summarizes the practical experience of gluing and handling these foils and reports on the first results with beam.

Improved ultrasonic TV images achieved by use of Lamb-wave orientation technique

NASA Technical Reports Server (NTRS)

Berger, H.

1967-01-01

Lamb-wave sample orientation technique minimizes the interference from standing waves in continuous wave ultrasonic television imaging techniques used with thin metallic samples. The sample under investigation is oriented such that the wave incident upon it is not normal, but slightly angled.

An analysis of the gradient-induced electric fields and current densities in human models when situated in a hybrid MRI-LINAC system

NASA Astrophysics Data System (ADS)

Liu, Limei; Trakic, Adnan; Sanchez-Lopez, Hector; Liu, Feng; Crozier, Stuart

2014-01-01

MRI-LINAC is a new image-guided radiotherapy treatment system that combines magnetic resonance imaging (MRI) with a linear accelerator (LINAC) in a single unit. One drawback is that the pulsing of the split gradient coils of the system induces an electric field and currents in the patient which need to be predicted and evaluated for patient safety. In this novel numerical study the in situ electric fields and associated current densities were evaluated inside tissue-accurate male and female human voxel models when a number of different split-geometry gradient coils were operated. The body models were located in the MRI-LINAC system along the axial and radial directions in three different body positions. Each model had a region of interest (ROI) suitable for image-guided radiotherapy. The simulation results show that the amplitudes and distributions of the field and current density induced by different split x-gradient coils were similar with one another in the ROI of the body model, but varied outside of the region. The fields and current densities induced by a split classic coil with the surface unconnected showed the largest deviation from those given by the conventional non-split coils. Another finding indicated that the distributions of the peak current densities varied when the body position, orientation or gender changed, while the peak electric fields mainly occurred in the skin and fat tissues.

The future of image-guided radiotherapy-is image everything?

PubMed

Noble, David J; Burnet, Neil G

2018-05-17

MR-based image-guided (IG) radiotherapy via all-in-one MR treatment units (MR-linacs) is one of the hottest topics in contemporary radiotherapy research. From ingenious engineering solutions to complex physical problems, researchers have developed machines with the promise of superior image quality, and all the advantages this may confer. Benefits include better tumour visualisation, online adaptation and the potential for image biomarker-based personalised RT. However, it is important to remember that the technical challenges are real. In many instances, they are skillfully managed rather than abolished, a point illustrated by the wide variety of MR-linac designs. The proposed benefits also deserve careful inspection. Better visibility of the primary tumour on an IG scan cannot be bad, but does not automatically equate to better IG, which often depends on a more generalised match to daily anatomy. MR-linac will undoubtedly be a rich milieu to search for IMBs, but these will need to be carefully validated, and similar work with CT-based biomarkers using existing, cheaper, and more widely available hardware is currently ongoing. Online adaptation is an attractive concept, but practicalities are complex, and more work is required to understand which patients will benefit from plan adaptation, and when. Finally, the issue of cost cannot be overlooked, nor can the research community's responsibilities to global healthcare inequalities. MR-linac is an exciting and ingenious technology, which merits both investment and research. It may not, however, have the future to itself.

Automatic detection of MLC relative position errors for VMAT using the EPID-based picket fence test

NASA Astrophysics Data System (ADS)

Christophides, Damianos; Davies, Alex; Fleckney, Mark

2016-12-01

Multi-leaf collimators (MLCs) ensure the accurate delivery of treatments requiring complex beam fluences like intensity modulated radiotherapy and volumetric modulated arc therapy. The purpose of this work is to automate the detection of MLC relative position errors  ⩾0.5 mm using electronic portal imaging device-based picket fence tests and compare the results to the qualitative assessment currently in use. Picket fence tests with and without intentional MLC errors were measured weekly on three Varian linacs. The picket fence images analysed covered a time period ranging between 14-20 months depending on the linac. An algorithm was developed that calculated the MLC error for each leaf-pair present in the picket fence images. The baseline error distributions of each linac were characterised for an initial period of 6 months and compared with the intentional MLC errors using statistical metrics. The distributions of median and one-sample Kolmogorov-Smirnov test p-value exhibited no overlap between baseline and intentional errors and were used retrospectively to automatically detect MLC errors in routine clinical practice. Agreement was found between the MLC errors detected by the automatic method and the fault reports during clinical use, as well as interventions for MLC repair and calibration. In conclusion the method presented provides for full automation of MLC quality assurance, based on individual linac performance characteristics. The use of the automatic method has been shown to provide early warning for MLC errors that resulted in clinical downtime.

Direct megavoltage photon calibration service in Australia

PubMed Central

Ramanathan, G.; Oliver, C.; Cole, A.; Lye, J.; Harty, P. D.; Wright, T.; Webb, D. V.; Followill, D. S.

2014-01-01

The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) maintains the Australian primary standard of absorbed dose. Until recently, the standard was used to calibrate ionisation chambers only in 60Co gamma rays. These chambers are then used by radiotherapy clinics to determine linac output, using a correction factor (kQ) to take into account the different spectra of 60Co and the linac. Over the period 2010–2013, ARPANSA adapted the primary standard to work in megavoltage linac beams, and has developed a calibration service at three photon beams (6, 10 and 18 MV) from an Elekta Synergy linac. We describe the details of the new calibration service, the method validation and the use of the new calibration factors with the International Atomic Energy Agency’s TRS-398 dosimetry Code of Practice. The expected changes in absorbed dose measurements in the clinic when shifting from 60Co to the direct calibration are determined. For a Farmer chamber (model 2571), the measured chamber calibration coefficient is expected to be reduced by 0.4, 1.0 and 1.1 % respectively for these three beams when compared to the factor derived from 60Co. These results are in overall agreement with international absorbed dose standards and calculations by Muir and Rogers in 2010 of kQ factors using Monte Carlo techniques. The reasons for and against moving to the new service are discussed in the light of the requirements of clinical dosimetry. PMID:25146559

Intra-coil interactions in split gradient coils in a hybrid MRI-LINAC system

NASA Astrophysics Data System (ADS)

Tang, Fangfang; Freschi, Fabio; Sanchez Lopez, Hector; Repetto, Maurizio; Liu, Feng; Crozier, Stuart

2016-04-01

An MRI-LINAC system combines a magnetic resonance imaging (MRI) system with a medical linear accelerator (LINAC) to provide image-guided radiotherapy for targeting tumors in real-time. In an MRI-LINAC system, a set of split gradient coils is employed to produce orthogonal gradient fields for spatial signal encoding. Owing to this unconventional gradient configuration, eddy currents induced by switching gradient coils on and off may be of particular concern. It is expected that strong intra-coil interactions in the set will be present due to the constrained return paths, leading to potential degradation of the gradient field linearity and image distortion. In this study, a series of gradient coils with different track widths have been designed and analyzed to investigate the electromagnetic interactions between coils in a split gradient set. A driving current, with frequencies from 100 Hz to 10 kHz, was applied to study the inductive coupling effects with respect to conductor geometry and operating frequency. It was found that the eddy currents induced in the un-energized coils (hereby-referred to as passive coils) positively correlated with track width and frequency. The magnetic field induced by the eddy currents in the passive coils with wide tracks was several times larger than that induced by eddy currents in the cold shield of cryostat. The power loss in the passive coils increased with the track width. Therefore, intra-coil interactions should be included in the coil design and analysis process.

Characterization of the a-Si EPID in the unity MR-linac for dosimetric applications.

PubMed

Torres-Xirau, I; Olaciregui-Ruiz, I; Baldvinsson, G; Mijnheer, B J; van der Heide, U A; Mans, A

2018-01-09

Electronic portal imaging devices (EPIDs) are frequently used in external beam radiation therapy for dose verification purposes. The aim of this study was to investigate the dose-response characteristics of the EPID in the Unity MR-linac (Elekta AB, Stockholm, Sweden) relevant for dosimetric applications under clinical conditions. EPID images and ionization chamber (IC) measurements were used to study the effects of the magnetic field, the scatter generated in the MR housing reaching the EPID, and inhomogeneous attenuation from the MR housing. Dose linearity and dose rate dependencies were also determined. The magnetic field strength at EPID level did not exceed 10 mT, and dose linearity and dose rate dependencies proved to be comparable to that on a conventional linac. Profiles of fields, delivered with and without the magnetic field, were indistinguishable. The EPID center had an offset of 5.6 cm in the longitudinal direction, compared to the beam central axis, meaning that large fields in this direction will partially fall outside the detector area and not be suitable for verification. Beam attenuation by the MRI scanner and the table is gantry angle dependent, presenting a minimum attenuation of 67% relative to the 90° measurement. Repeatability, observed over two months, was within 0.5% (1 SD). In order to use the EPID for dosimetric applications in the MR-linac, challenges related to the EPID position, scatter from the MR housing, and the inhomogeneous, gantry angle-dependent attenuation of the beam will need to be solved.

Characterization of the a-Si EPID in the unity MR-linac for dosimetric applications

NASA Astrophysics Data System (ADS)

Torres-Xirau, I.; Olaciregui-Ruiz, I.; Baldvinsson, G.; Mijnheer, B. J.; van der Heide, U. A.; Mans, A.

2018-01-01

Electronic portal imaging devices (EPIDs) are frequently used in external beam radiation therapy for dose verification purposes. The aim of this study was to investigate the dose-response characteristics of the EPID in the Unity MR-linac (Elekta AB, Stockholm, Sweden) relevant for dosimetric applications under clinical conditions. EPID images and ionization chamber (IC) measurements were used to study the effects of the magnetic field, the scatter generated in the MR housing reaching the EPID, and inhomogeneous attenuation from the MR housing. Dose linearity and dose rate dependencies were also determined. The magnetic field strength at EPID level did not exceed 10 mT, and dose linearity and dose rate dependencies proved to be comparable to that on a conventional linac. Profiles of fields, delivered with and without the magnetic field, were indistinguishable. The EPID center had an offset of 5.6 cm in the longitudinal direction, compared to the beam central axis, meaning that large fields in this direction will partially fall outside the detector area and not be suitable for verification. Beam attenuation by the MRI scanner and the table is gantry angle dependent, presenting a minimum attenuation of 67% relative to the 90° measurement. Repeatability, observed over two months, was within 0.5% (1 SD). In order to use the EPID for dosimetric applications in the MR-linac, challenges related to the EPID position, scatter from the MR housing, and the inhomogeneous, gantry angle-dependent attenuation of the beam will need to be solved.

Experimental studies of a continuous-wave HF(DF) confocal unstable resonator. Interim report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chodzko, R.A.; Cross, E.F.; Durran, D.A.

1976-05-03

A series of experiments were performed on a continuous-wave HF(DF) multiline edge-coupled confocal unstable resonator at The Aerospace Corporation MESA facility. Experimental techniques were developed to measure remotely (from a blockhouse) the output power, the near-field intensity distribution, the spatially resolved spectral content of the near field, and the far-field power distribution. A new technique in which a variable aperture calorimeter absorbing scraper (VACAS) was used for measuring the continuous-wave output power from an unstable resonator with variable-mode geometry and without the use of an output coupling mirror was developed. (GRA)

Noninvasive estimation of cardiac systolic function using continuous-wave Doppler echocardiography in dogs with experimental mitral regurgitation.

PubMed

Asano, K; Masui, Y; Masuda, K; Fujinaga, T

2002-01-01

To evaluate the feasibility of noninvasive estimation of cardiac systolic function using transthoracic continuous-wave Doppler echocardiography in dogs with mitral regurgitation. Seven mongrel dogs with experimental mitral regurgitation were used. Left ventriculography and measurement of pulmonary capillary wedge pressure were performed under inhalational anaesthesia. A micromanometer-tipped catheter was placed into the left ventricle and transthoracic echocardiography was carried out. The peak rate of left ventricular pressure rise (peak dP/dt) was derived simultaneously by continuous-wave Doppler and manometer measurements. The Doppler-derived dP/dt was compared with the catheter-measured peak dP/dt in the dogs. Classification of the severity of mitral regurgitation in the dogs was as follows: 1+, 2 dogs; 2+, 1 dog; 3+, 2 dogs; 4+, 1 dog; and not examined, 1 dog. We were able to derive dP/dt from the transthoracic continuous-wave Doppler echocardiography in all dogs. Doppler-derived dP/dt had a significant correlation with the catheter-measured peak dP/dt (r = 0.90, P < 0.0001). It was demonstrated that transthoracic continuous-wave Doppler echocardiography is a feasible method of noninvasive estimation of cardiac systolic function in dogs with experimental mitral regurgitation and may have clinical usefulness in canine patients with spontaneous mitral regurgitation.

Dynamic response analysis of surrounding rock under the continuous blasting seismic wave

NASA Astrophysics Data System (ADS)

Gao, P. F.; Zong, Q.; Xu, Y.; Fu, J.

2017-10-01

The blasting vibration that is caused by blasting excavation will generate a certain degree of negative effect on the stability of surrounding rock in underground engineering. A dynamic response analysis of surrounding rock under the continuous blasting seismic wave is carried out to optimize blasting parameters and guide underground engineering construction. Based on the theory of wavelet analysis, the reconstructed signals of each layer of different frequency bands are obtained by db8 wavelet decomposition. The difference of dynamic response of the continuous blasting seismic wave at a certain point caused by different blasting sources is discussed. The signal in the frequency band of natural frequency of the surrounding rock shows a certain degree of amplification effect deduced from the dynamic response characteristics of the surrounding rock under the influence of continuous blasting seismic wave. Continuous blasting operations in a fixed space will lead to the change of internal structure of the surrounding rock. It may result in the decline of natural frequency of the whole surrounding rock and it is also harmful for the stability of the surrounding rock.

Time-Frequency-Wavenumber Analysis of Surface Waves Using the Continuous Wavelet Transform

NASA Astrophysics Data System (ADS)

Poggi, V.; Fäh, D.; Giardini, D.

2013-03-01

A modified approach to surface wave dispersion analysis using active sources is proposed. The method is based on continuous recordings, and uses the continuous wavelet transform to analyze the phase velocity dispersion of surface waves. This gives the possibility to accurately localize the phase information in time, and to isolate the most significant contribution of the surface waves. To extract the dispersion information, then, a hybrid technique is applied to the narrowband filtered seismic recordings. The technique combines the flexibility of the slant stack method in identifying waves that propagate in space and time, with the resolution of f- k approaches. This is particularly beneficial for higher mode identification in cases of high noise levels. To process the continuous wavelet transform, a new mother wavelet is presented and compared to the classical and widely used Morlet type. The proposed wavelet is obtained from a raised-cosine envelope function (Hanning type). The proposed approach is particularly suitable when using continuous recordings (e.g., from seismological-like equipment) since it does not require any hardware-based source triggering. This can be subsequently done with the proposed method. Estimation of the surface wave phase delay is performed in the frequency domain by means of a covariance matrix averaging procedure over successive wave field excitations. Thus, no record stacking is necessary in the time domain and a large number of consecutive shots can be used. This leads to a certain simplification of the field procedures. To demonstrate the effectiveness of the method, we tested it on synthetics as well on real field data. For the real case we also combine dispersion curves from ambient vibrations and active measurements.

A full-wave Helmholtz model for continuous-wave ultrasound transmission.

PubMed

Huttunen, Tomi; Malinen, Matti; Kaipio, Jari P; White, Phillip Jason; Hynynen, Kullervo

2005-03-01

A full-wave Helmholtz model of continuous-wave (CW) ultrasound fields may offer several attractive features over widely used partial-wave approximations. For example, many full-wave techniques can be easily adjusted for complex geometries, and multiple reflections of sound are automatically taken into account in the model. To date, however, the full-wave modeling of CW fields in general 3D geometries has been avoided due to the large computational cost associated with the numerical approximation of the Helmholtz equation. Recent developments in computing capacity together with improvements in finite element type modeling techniques are making possible wave simulations in 3D geometries which reach over tens of wavelengths. The aim of this study is to investigate the feasibility of a full-wave solution of the 3D Helmholtz equation for modeling of continuous-wave ultrasound fields in an inhomogeneous medium. The numerical approximation of the Helmholtz equation is computed using the ultraweak variational formulation (UWVF) method. In addition, an inverse problem technique is utilized to reconstruct the velocity distribution on the transducer which is used to model the sound source in the UWVF scheme. The modeling method is verified by comparing simulated and measured fields in the case of transmission of 531 kHz CW fields through layered plastic plates. The comparison shows a reasonable agreement between simulations and measurements at low angles of incidence but, due to mode conversion, the Helmholtz model becomes insufficient for simulating ultrasound fields in plates at large angles of incidence.

Investigation of fundamental limits to beam brightness available from photoinjectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bazarov, Ivan

2015-07-09

The goal of this project was investigation of fundamental limits to beam brightness available from photoinjectors. This basic research in accelerator physics spanned over 5 years aiming to extend the fundamental understanding of high average current, low emittance sources of relativistic electrons based on photoemission guns, a necessary prerequisite for a new generation of coherent X-ray synchrotron radiation facilities based on continuous duty superconducting linacs. The program focused on two areas critical to making advances in the electron source performance: 1) the physics of photocathodes for the production of low emittance electrons and 2) control of space charge forces inmore » the immediate vicinity to the cathode via 3D laser pulse shaping.« less

Epileptic encephalopathy with continuous spike-waves during sleep: the need for transition from childhood to adulthood medical care appears to be related to etiology.

PubMed

de Saint-Martin, Anne; Rudolf, Gabrielle; Seegmuller, Caroline; Valenti-Hirsch, Maria Paola; Hirsch, Edouard

2014-08-01

Epileptic encephalopathy with continuous diffuse spike-waves during slow-wave sleep (ECSWS) presents clinically with infrequent nocturnal focal seizures, atypical absences related to secondary bilateral synchrony, negative myoclonia, and atonic and rare generalized tonic-clonic seizures. The unique electroencephalography (EEG) pattern found in ECSWS consists of continuous, diffuse, bilateral spike-waves during slow-wave sleep. Despite the eventual disappearance of clinical seizures and EEG abnormalities by adolescence, the prognosis is guarded in most cases because of neuropsychological and behavioral deficits. ECSWS has a heterogeneous etiology (genetic, structural, and unknown). Because epilepsy and electroencephalography (EEG) abnormalities in epileptic encephalopathy with continuous diffuse spike-waves during slow-wave sleep (ECSWS) are self-limited and age related, the need for ongoing medical care and transition to adult care might be questioned. For adolescents in whom etiology remains unknown (possibly genetic) and who experience the disappearance of seizures and EEG abnormalities, there is rarely need for long-term neurologic follow-up, because often a relatively normal cognitive and social evolution follows. However, the majority of patients with structural and possibly "genetic syndromic" etiologies will have persistent cognitive deficits and will need suitable socioeducative care. Therefore, the transition process in ECSWS will depend mainly on etiology and its related features (epileptic active phase duration, and cognitive and behavioral evolution) and revolve around neuropsychological and social support rather than medical and pharmacologic follow-up. Wiley Periodicals, Inc. © 2014 International League Against Epilepsy.

PIP-II Cryogenic System and the Evolution of Superfluid Helium Cryogenic Plant Specifications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakravarty, Anindya; Rane, Tejas; Klebaner, Arkadiy

2017-01-01

PIP-II cryogenic system: Superfluid Helium Cryogenic Plant (SHCP) and Cryogenic Distribution System (CDS) connecting the SHCP and the SC Linac (25 cryomodules) PIP-II Cryogenic System Static and dynamic heat loads for the SC Linac and static load of CDS listed out Simulation study carried out to compute SHe flow requirements for each cryomodule Comparison between the flow requirements of the cryomodules for the CW and pulsed modes of operation presented From computed heat load and pressure drop values, SHCP basic specifications evolved.

Beam energy spread in FERMI@elettra gun and linac induced by intrabeam scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zholents, Alexander A; Zholents, Alexander A; Zolotorev, Max S.

Intrabeam scattering (IBS) of electrons in the pre-cathode area in the electron guns know in the literature as Boersh effect is responsible for a growth of the electron beam energy spread there. Albeit most visible within the electron gun where the electron beam density is large and the energy spread is small, the IBS acts all along the entire electron beam pass through the Linac. In this report we calculate the energy spread induced by IBS in the FERMI@elettra electron gun.

Generation of whistler waves by continuous HF heating of the upper ionosphere

NASA Astrophysics Data System (ADS)

Vartanyan, A.; Milikh, G. M.; Eliasson, B. E.; Sharma, A.; Chang, C.; Parrot, M.; Papadopoulos, K.

2013-12-01

We report observations of VLF waves by the DEMETER satellite overflying the HAARP facility during ionospheric heating experiments. The detected VLF waves were in the range 8-17 kHz and coincided with times of continuous heating. The experiments indicate whistler generation due to conversion of artificial lower hybrid waves to whistlers on small scale field-aligned plasma density striations. The observations are compared with theoretical models, taking into account both linear and nonlinear processes. Implications of the mode conversion technique on VLF generation with subsequent injection into the radiation belts to trigger particle precipitation are discussed.

Room temperature continuous wave, monolithic tunable THz sources based on highly efficient mid-infrared quantum cascade lasers

PubMed Central

Lu, Quanyong; Wu, Donghai; Sengupta, Saumya; Slivken, Steven; Razeghi, Manijeh

2016-01-01

A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν ~ 1–5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06–4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers. PMID:27009375

Results of an all-sky high-frequency Einstein@Home search for continuous gravitational waves in LIGO's fifth science run

NASA Astrophysics Data System (ADS)

Singh, Avneet; Papa, Maria Alessandra; Eggenstein, Heinz-Bernd; Zhu, Sylvia; Pletsch, Holger; Allen, Bruce; Bock, Oliver; Maschenchalk, Bernd; Prix, Reinhard; Siemens, Xavier

2016-09-01

We present results of a high-frequency all-sky search for continuous gravitational waves from isolated compact objects in LIGO's fifth science run (S5) data, using the computing power of the Einstein@Home volunteer computing project. This is the only dedicated continuous gravitational wave search that probes this high-frequency range on S5 data. We find no significant candidate signal, so we set 90% confidence level upper limits on continuous gravitational wave strain amplitudes. At the lower end of the search frequency range, around 1250 Hz, the most constraining upper limit is 5.0 ×10-24, while at the higher end, around 1500 Hz, it is 6.2 ×10-24. Based on these upper limits, and assuming a fiducial value of the principal moment of inertia of 1038 kg m2 , we can exclude objects with ellipticities higher than roughly 2.8 ×10-7 within 100 pc of Earth with rotation periods between 1.3 and 1.6 milliseconds.

Room temperature continuous wave, monolithic tunable THz sources based on highly efficient mid-infrared quantum cascade lasers.

PubMed

Lu, Quanyong; Wu, Donghai; Sengupta, Saumya; Slivken, Steven; Razeghi, Manijeh

2016-03-24

A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν~1-5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06-4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers.

Understanding Rossby wave trains forced by the Indian Ocean Dipole

NASA Astrophysics Data System (ADS)

McIntosh, Peter C.; Hendon, Harry H.

2018-04-01

Convective variations over the tropical Indian Ocean associated with ENSO and the Indian Ocean Dipole force a Rossby wave train that appears to emanate poleward and eastward to the south of Australia and which causes climate variations across southern Australia and more generally throughout the Southern Hemisphere extratropics. However, during austral winter, the subtropical jet that extends from the eastern Indian Ocean into the western Pacific at Australian latitudes should effectively prohibit continuous propagation of a stationary Rossby wave from the tropics into the extratropics because the meridional gradient of mean absolute vorticity goes to zero on its poleward flank. The observed wave train indeed exhibits strong convergence of wave activity flux upon encountering this region of vanishing vorticity gradient and with some indication of reflection back into the tropics, indicating the continuous propagation of the stationary Rossby wave train from low to high latitudes is inhibited across the south of Australia. However, another Rossby wave train appears to emanate upstream of Australia on the poleward side of the subtropical jet and propagates eastward along the waveguide of the eddy-driven (sub-polar) jet into the Pacific sector of the Southern Ocean. This combination of evanescent wave train from the tropics and eastward propagating wave train emanating from higher latitudes upstream of Australia gives the appearance of a continuous Rossby wave train propagating from the tropical Indian Ocean into higher southern latitudes. The extratropical Rossby wave source on the poleward side of the subtropical jet stems from induced changes in transient eddy activity in the main storm track of the Southern Hemisphere. During austral spring, when the subtropical jet weakens, the Rossby wave train emanating from Indian Ocean convection is explained more traditionally by direct dispersion from divergence forcing at low latitudes.

Propagation characteristics of ultrasonic guided waves in continuously welded rail

NASA Astrophysics Data System (ADS)

Yao, Wenqing; Sheng, Fuwei; Wei, Xiaoyuan; Zhang, Lei; Yang, Yuan

2017-07-01

Rail defects cause numerous railway accidents. Trains are derailed and serious consequences often occur. Compared to traditional bulk wave testing, ultrasonic guided waves (UGWs) can provide larger monitoring ranges and complete coverage of the waveguide cross-section. These advantages are of significant importance for the non-destructive testing (NDT) of the continuously welded rail, and the technique is therefore widely used in high-speed railways. UGWs in continuous welded rail (CWR) and their propagation characteristics have been discussed in this paper. Finite element methods (FEMs) were used to accomplish a vibration modal analysis, which is extended by a subsequent dispersion analysis. Wave structure features were illustrated by displacement profiles. It was concluded that guided waves have the ability to detect defects in the rail via choice of proper mode and frequency. Additionally, thermal conduction that is caused by temperature variation in the rail is added into modeling and simulation. The results indicated that unbalanced thermal distribution may lead to the attenuation of UGWs in the rail.

SU-E-T-354: Efficient and Enhanced QA Testing of Linear Accelerators Using a Real-Time Beam Monitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, J; Farrokhkish, M; Norrlinger, B

2015-06-15

Purpose: To investigate the feasibility of performing routine QA tests of linear accelerators (Linac) using the Integral Quality Monitoring (IQM) system. The system, consisting of a 1-D sensitivity gradient large area ion-chamber mounted at the collimator, allows automatic collection and analysis of beam data. Methods: The IQM was investigated to perform several QA constancy tests, similar to those recommended by AAPM TG142, of a Linac including: beam output, MLC calibration, beam symmetry, relative dose factor (RDF), dose linearity, output as a function of gantry angle and dose rate. All measurements by the IQM system accompanied a reference measurement using amore » conventional dosimetry system and were performed on an Elekta Infinity Linac with Agility MLC. The MLC calibration check is done using a Picket-Fence type 2×10cm{sup 2} field positioned at different off-axis locations along the chamber gradient. Beam symmetry constancy values are established by signals from an 4×4cm{sup 2} aperture located at various off-axis positions; the sensitivity of the test was determined by the changes in the signals in response to a tilt in the beam. The data for various square field sizes were used to develop a functional relationship with RDF. Results: The IQM tracked the beam output well within 1% of the reference ion-chamber readings. The Picket-Fence type field test detected a 1mm shift error of one MLC bank. The system was able to detect 2.5% or greater beam asymmetry. The IQM results for all other QA tests were found to agree with the reference values to within 0.5%. Conclusion: It was demonstrated that the IQM system can effectively monitor the Linac performance parameters for the purpose of routine QA constancy tests. With minimum user interactions a comprehensive set of tests can be performed efficiently, allowing frequent monitoring of the Linac. The presenting author’s salary is funded by the manufacturer of the QA device. All the other authors have financial interests with the commercialization of this QA device.« less

TH-E-BRE-09: TrueBeam Monte Carlo Absolute Dose Calculations Using Monitor Chamber Backscatter Simulations and Linac-Logged Target Current

DOE Office of Scientific and Technical Information (OSTI.GOV)

A, Popescu I; Lobo, J; Sawkey, D

2014-06-15

Purpose: To simulate and measure radiation backscattered into the monitor chamber of a TrueBeam linac; establish a rigorous framework for absolute dose calculations for TrueBeam Monte Carlo (MC) simulations through a novel approach, taking into account the backscattered radiation and the actual machine output during beam delivery; improve agreement between measured and simulated relative output factors. Methods: The ‘monitor backscatter factor’ is an essential ingredient of a well-established MC absolute dose formalism (the MC equivalent of the TG-51 protocol). This quantity was determined for the 6 MV, 6X FFF, and 10X FFF beams by two independent Methods: (1) MC simulationsmore » in the monitor chamber of the TrueBeam linac; (2) linac-generated beam record data for target current, logged for each beam delivery. Upper head MC simulations used a freelyavailable manufacturer-provided interface to a cloud-based platform, allowing use of the same head model as that used to generate the publicly-available TrueBeam phase spaces, without revealing the upper head design. The MC absolute dose formalism was expanded to allow direct use of target current data. Results: The relation between backscatter, number of electrons incident on the target for one monitor unit, and MC absolute dose was analyzed for open fields, as well as a jaw-tracking VMAT plan. The agreement between the two methods was better than 0.15%. It was demonstrated that the agreement between measured and simulated relative output factors improves across all field sizes when backscatter is taken into account. Conclusion: For the first time, simulated monitor chamber dose and measured target current for an actual TrueBeam linac were incorporated in the MC absolute dose formalism. In conjunction with the use of MC inputs generated from post-delivery trajectory-log files, the present method allows accurate MC dose calculations, without resorting to any of the simplifying assumptions previously made in the TrueBeam MC literature. This work has been partially funded by Varian Medical Systems.« less

Performance of a Novel Repositioning Head Frame for Gamma Knife Perfexion and Image-Guided Linac-Based Intracranial Stereotactic Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruschin, Mark, E-mail: Mark.Ruschin@rmp.uhn.on.c; Department of Radiation Oncology, University of Toronto, Toronto; Nayebi, Nazanin

2010-09-01

Purpose: To evaluate the geometric positioning and immobilization performance of a vacuum bite-block repositioning head frame (RHF) system for Perfexion (PFX-SRT) and linac-based intracranial image-guided stereotactic radiotherapy (SRT). Methods and Materials: Patients with intracranial tumors received linac-based image-guided SRT using the RHF for setup and immobilization. Three hundred thirty-three fractions of radiation were delivered in 12 patients. The accuracy of the RHF was estimated for linac-based SRT with online cone-beam CT (CBCT) and for PFX-SRT with a repositioning check tool (RCT) and offline CBCT. The RCT's ability to act as a surrogate for anatomic position was estimated through comparison tomore » CBCT image matching. Immobilization performance was evaluated daily with pre- and postdose delivery CBCT scans and RCT measurements. Results: The correlation coefficient between RCT- and CBCT-reported displacements was 0.59, 0.75, 0.79 (Right, Superior, and Anterior, respectively). For image-guided linac-based SRT, the mean three-dimensional (3D) setup error was 0.8 mm with interpatient ({Sigma}) and interfraction ({sigma}) variations of 0.1 and 0.4 mm, respectively. For PFX-SRT, the initial, uncorrected mean 3D positioning displacement in stereotactic coordinates was 2.0 mm, with {Sigma} = 1.1 mm and {sigma} = 0.8 mm. Considering only RCT setups <1mm (PFX action level) the mean 3D positioning displacement reduced to 1.3 mm, with {Sigma} = 0.9 mm and {sigma} = 0.4 mm. The largest contributing systematic uncertainty was in the superior-inferior direction (mean displacement = -0.5 mm; {Sigma} = 0.9 mm). The largest mean rotation was 0.6{sup o} in pitch. The mean 3D intrafraction motion was 0.4 {+-} 0.3 mm. Conclusion: The RHF provides excellent immobilization for intracranial SRT and PFX-SRT. Some small systematic uncertainties in stereotactic positioning exist and must be considered when generating PFX-SRT treatment plans. The RCT provides reasonable surrogacy for internal anatomic displacement.« less

Thermal limits on MV x-ray production by bremsstrahlung targets in the context of novel linear accelerators.

PubMed

Wang, Jinghui; Trovati, Stefania; Borchard, Philipp M; Loo, Billy W; Maxim, Peter G; Fahrig, Rebecca

2017-12-01

To study the impact of target geometrical and linac operational parameters, such as target material and thickness, electron beam size, repetition rate, and mean current on the ability of the radiotherapy treatment head to deliver high-dose-rate x-ray irradiation in the context of novel linear accelerators capable of higher repetition rates/duty cycle than conventional clinical linacs. The depth dose in a water phantom without a flattening filter and heat deposition in an x-ray target by 10 MeV pulsed electron beams were calculated using the Monte-Carlo code MCNPX, and the transient temperature behavior of the target was simulated by ANSYS. Several parameters that affect both the dose distribution and temperature behavior were investigated. The target was tungsten with a thickness ranging from 0 to 3 mm and a copper heat remover layer. An electron beam with full width at half maximum (FWHM) between 0 and3 mm and mean current of 0.05-2 mA was used as the primary beam at repetition rates of 100, 200, 400, and 800 Hz. For a 10 MeV electron beam with FWHM of 1 mm, pulse length of 5 μs, by using a thin tungsten target with thickness of 0.2 mm instead of 1 mm, and by employing a high repetition rate of 800 Hz instead of 100 Hz, the maximum dose rate delivered can increase two times from 0.57 to 1.16 Gy/s. In this simple model, the limiting factor on dose rate is the copper heat remover's softening temperature, which was considered to be 500°C in our study. A high dose rate can be obtained by employing thin targets together with high repetition rate electron beams enabled by novel linac designs, whereas the benefit of thin targets is marginal at conventional repetition rates. Next generation linacs used to increase dose rate need different target designs compared to conventional linacs. © 2017 American Association of Physicists in Medicine.

Characterization of a prototype MR-compatible Delta4 QA system in a 1.5 tesla MR-linac

NASA Astrophysics Data System (ADS)

de Vries, J. H. W.; Seravalli, E.; Houweling, A. C.; Woodings, S. J.; van Rooij, R.; Wolthaus, J. W. H.; Lagendijk, J. J. W.; Raaymakers, B. W.

2018-01-01

To perform patient plan quality assurance (QA) on a newly installed MR-linac (MRL) it is necessary to have an MR-compatible QA device. An MR compatible device (MR-Delta4) has been developed together with Scandidos AB (Uppsala, Sweden). The basic characteristics of the detector response, such as short-term reproducibility, dose linearity, field size dependency, dose rate dependency, dose-per-pulse dependency and angular dependency, were investigated for the clinical Delta4-PT as well as for the MR compatible version. All tests were performed with both devices on a conventional linac and the MR compatible device was tested on the MRL as well. No statistically significant differences were found in the short-term reproducibility (<0.1%), dose linearity (⩽0.5%), field size dependency (<2.0% for field sizes larger than 5  ×  5 cm2), dose rate dependency (<1.0%) or angular dependency for any phantom/linac combination. The dose-per-pulse dependency (<0.8%) was found to be significantly different between the two devices. This difference can be explained by the fact that the diodes in the clinical Delta4-PT were irradiated with a much larger dose than the MR-Delta4-PT ones. The absolute difference between the devices (<0.5%) was found to be small, so no clinical impact is expected. For both devices, the results were consistent with the characteristics of the Delta4-PT device reported in the literature (Bedford et al 2009 Phys. Med. Biol. 54 N167-76 Sadagopan et al 2009 J. Appl. Clin. Med. Phys. 10 2928). We found that the characteristics of the MR compatible Delta4 phantom were found to be comparable to the clinically used one. Also, the found characteristics do not differ from the previously reported characteristics of the commercially available non-MR compatible Delta4-PT phantom. Therefore, the MR compatible Delta4 prototype was found to be safe and effective for use in the 1.5 tesla magnetic field of the Elekta MR-linac

SU-E-T-228: The Beauty and the Beast: Transition from Film/paper Charts to Paperless Environment with a New TrueBeam/ARIA System in a Small Community Hospital on a Tight Budget.

PubMed

Chu, K; Rasmussen, B

2012-06-01

To review the issues a physicist may encounter in a community hospital during the transition from film/paper charts to a paperless environment with ARIA and a TrueBeam LINAC. With a lean budget, it was necessary for the physics group to take on the project management responsibilities in order save costs. This work highlights the lessons learned during the planning and execution of our project. Like many hospitals around the county, our hospital was caught in the economic downturn and was unable to provide all of the capital necessary to upgrade to the radiation oncology department. However, with the support of the hospital foundation, a total of $6M was secured for new LINAC, ARIA and CT simulator. To save costs on facilities and computers, it was necessary for the physics group to be involved in creating architectural drawings for shielding calculations, finding a vendor to remove the old linac, assisting the foundation to raise money, submission of the 'Certificate of Need' approval with the state, negotiation with vendors, IT infrastructure, reviews with the general contractor and vendor's project team, and ultimately writing the commissioning reports for the new systems as well as developing new policies and procedures. During a period of 4 months, the old LINAC was removed, facility renovations made, the TrueBeam linac was installed, accepted, and commissioned and first patients were treated. In addition, we transitioned from a film/paper environment to a paperless environment. However, this was very stressful for staff and it may be advisable to stage such a project over a longer period of time. There was also significant lost revenue (∼$2M) during downtime of construction, installation, and commissioning. The radiation oncology department was upgraded (The Beauty) on a tight budget but at the cost of added stress (The Beast) to the staff. © 2012 American Association of Physicists in Medicine.

Radio frequency noise from an MLC: a feasibility study of the use of an MLC for linac-MR systems.

PubMed

Lamey, M; Yun, J; Burke, B; Rathee, S; Fallone, B G

2010-02-21

Currently several groups are actively researching the integration of a megavoltage teletherapy unit with magnetic resonance (MR) imaging for real-time image-guided radiotherapy. The use of a multileaf collimator (MLC) for intensity-modulated radiotherapy for linac-MR units must be investigated. The MLC itself will likely reside in the fringe field of the MR and the motors will produce radio frequency (RF) noise. The RF noise power spectral density from a Varian 52-leaf MLC motor, a Varian Millennium MLC motor and a brushless fan motor has been measured as a function of the applied magnetic field using a near field probe set. For the Varian 52-leaf MLC system, the RF noise produced by 13 of 52 motors is studied as a function of distance from the MLC. Data are reported in the frequency range suitable for 0.2-1.5 T linac-MR systems. Below 40 MHz the Millennium MLC motor tested showed more noise than the Varian 52-leaf motor or the brushless fan motor. The brushless motor showed a small dependence on the applied magnetic field. Images of a phantom were taken by the prototype linac-MR system with the MLC placed in close proximity to the magnet. Several orientations of the MLC in both shielded and non-shielded configurations were studied. For the case of a non-shielded MLC and associated cables, the signal-to-noise ratio (SNR) was reduced when 13 of 52 MLC leaves were moved during imaging. When the MLC and associated cables were shielded, the measured SNR of the images with 13 MLC leaves moving was experimentally the same as the SNR of the stationary MLC image. When the MLC and cables are shielded, subtraction images acquired with and without MLC motion contains no systematic signal. This study illustrates that the small RF noise produced by functioning MLC motors can be effectively shielded to avoid SNR degradation. A functioning MLC can be incorporated into a linac-MR unit.

Radio frequency noise from an MLC: a feasibility study of the use of an MLC for linac-MR systems

PubMed Central

Lamey, M; Yun, J; Burke, B; Rathee, S; Fallone, B G

2010-01-01

Currently several groups are actively researching the integration of a megavoltage teletherapy unit with magnetic resonance (MR) imaging for real-time image-guided radiotherapy. The use of a multileaf collimator (MLC) for intensity-modulated radiotherapy for linac-MR units must be investigated. The MLC itself will likely reside in the fringe field of the MR and the motors will produce radio frequency (RF) noise. The RF noise power spectral density from a Varian 52-leaf MLC motor, a Varian Millennium MLC motor and a brushless fan motor has been measured as a function of the applied magnetic field using a near field probe set. For the Varian 52-leaf MLC system, the RF noise produced by 13 of 52 motors is studied as a function of distance from the MLC. Data are reported in the frequency range suitable for 0.2–1.5 T linac-MR systems. Below 40 MHz the Millennium MLC motor tested showed more noise than the Varian 52-leaf motor or the brushless fan motor. The brushless motor showed a small dependence on the applied magnetic field. Images of a phantom were taken by the prototype linac-MR system with the MLC placed in close proximity to the magnet. Several orientations of the MLC in both shielded and non-shielded configurations were studied. For the case of a non-shielded MLC and associated cables, the signal-to-noise ratio (SNR) was reduced when 13 of 52 MLC leaves were moved during imaging. When the MLC and associated cables were shielded, the measured SNR of the images with 13 MLC leaves moving was experimentally the same as the SNR of the stationary MLC image. When the MLC and cables are shielded, subtraction images acquired with and without MLC motion contains no systematic signal. This study illustrates that the small RF noise produced by functioning MLC motors can be effectively shielded to avoid SNR degradation. A functioning MLC can be incorporated into a linac-MR unit. PMID:20090187

SU-E-J-200: Operation of An Electron Accelerator On An Integrated MR-Linac System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harasimowicz, J; Roberts, D; Shinton, I

2015-06-15

Purpose: An integrated MRI guided radiotherapy system poses a challenge of operating a linear accelerator in the presence of a magnetic field as the magnetic force acting on the electrons could Result in radiation source displacement and subsequent reduction of dose output. It was the purpose of this work to test the performance of a linac in the presence of a 1.5T MRI system. Methods: The first experimental MRI guided radiotherapy system at UMC-Utrecht consisting of an Elekta linac rotating around a 1.5T Magnex magnet was examined. A passive magnetic shield was simulated, designed and installed to reduce the influencemore » of the MRI magnet stray field on the electron beamline. The B field inside the shield was measured as a function of gantry angle and measurements of dose rate constancy upon gantry rotation were performed. Results: The magnitude of the magnetic field on the electron beam path without the shield was as high as 70G. It varied by up to 15G with gantry rotation due to the presence of metal beams in the bunker floor which resulted in dose output drop of up to 70% at certain gantry angles. With the prototype shield, field magnitude was reduced to well below 0.5G everywhere along the electron beam path. Field variation with gantry rotation was decreased to below 0.2G and enabled dose output of the linac to be recovered at all gantry angles. The homogeneity of the field inside the MRI magnet has not been compromised. Conclusion: It was demonstrated that the influence of the 1.5T magnet and the bunker design on the linac operation has been minimised. The performance will be further improved on the Elekta Atlantic system which incorporates a newly developed and optimised Philips magnet design and bunker construction. J Harasimowicz, D Roberts, I Shinton and S Sund are employed by Elekta Limited Crawley, H Wang and M Zhong are employed by Elekta Beijing Medical Systems Co. Ltd., J Overweg is employed by Philips Technologie GmbH Forschungslaboratorien.« less

Energy-Recovery Linacs for Commercial Radioisotope Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Rolland Paul

Most radioisotopes are produced by nuclear reactors or positive ion accelerators, which are expensive to construct and to operate. Photonuclear reactions using bremsstrahlung photon beams from less-expensive electron linacs can generate isotopes of critical interest, but much of the beam energy in a conventional electron linac is dumped at high energy, making unwanted radioactivation. The largest part of this radioactivation may be completely eliminated by applying energy recovery linac technology to the problem with an additional benefit that the energy cost to produce a given amount of isotope is reduced. Consequently, a Superconducting Radio Frequency (SRF) Energy Recovery Linac (ERL)more » is a path to a more diverse and reliable domestic supply of short-lived, high-value, high-demand isotopes at a cost lower than that of isotopes produced by reactors or positive-ion accelerators. A Jefferson Lab approach to this problem involves a thin photon production radiator, which allows the electron beam to recirculate through rf cavities so the beam energy can be recovered while the spent electrons are extracted and absorbed at a low enough energy to minimize unwanted radioactivation. The thicker isotope photoproduction target is not in the beam. MuPlus, with Jefferson Lab and Niowave, proposed to extend this ERL technology to the commercial world of radioisotope production. In Phase I we demonstrated that 1) the ERL advantage for producing radioisotopes is at high energies (~100 MeV), 2) the range of acceptable radiator thickness is narrow (too thin and there is no advantage relative to other methods and too thick means energy recovery is too difficult), 3) using optics techniques developed under an earlier STTR for collider low beta designs greatly improves the fraction of beam energy that can be recovered (patent pending), 4) many potentially useful radioisotopes can be made with this ERL technique that have never before been available in significant commercial quantities. We developed a plan for the Phase II project that started with a Conceptual Design Report (CDR) based on the results of the Phase I studies and concluded with a Technical Design Report (TDR) for a facility to make isotopes that are most attractive based on market analyses.« less

TH-CD-BRA-09: Towards Absolute Dose Measurement in MRI-Linac and Gamma-Knife: Design and Construction of An MR-Compatible Water Calorimeter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Entezari, N; Sarfehnia, A; Renaud, J

Purpose: The purpose of this work is to design and optimize a portable Water Calorimeter (WC) for use in a commercial MRI-linac and Gamma-knife in addition to conventional radiotherapy linacs. Water calorimeters determine absorbed dose to water at a point by measuring radiation-induced temperature rise of the volume (the two are related by the medium specific heat capacity). In this formalism, one important correction factor is heat transfer correction k-ht. It compensates for heat gain/loss due to conductive and convective effects, and is numerically calculated as ratio of temperature rise in the absence of heat loss to that in themore » presence of heat loss. Operating at 4°C ensures convection is minimal. Methods: A commercial finite element software was used to evaluate several WC designs with different insulation materials and thicknesses; channels allowing coolant to travel around WC (to sustain WC at 4°C) were modeled, and worst-case scenario variation in the temperature of the coolant was simulated for optimization purposes (2.6 mK/s). Additionally, several calorimeter vessel design parameters (front/back glass thickness/separation, diameter) were also simulated and optimized. Optimization is based on minimizing long term calorimeter drift (24h) as well as variation and magnitude of k-ht. Results: The final selected WC design reached a modest drift of 11µK/s after 15h for the worst-case coolant temperature variation. This design consists of coolant channels being encompassed on both sides by cryogel insulation. For the MRI-linac beam, glass thickness plays the largest effect on k-ht with variation of upto 0.6% in the first run for thicknesses ranging between 0.5–1.7mm. Subsequent runs vary only within 0.1% with glass thickness. Other factors such as vessel radius and top/bottom glass separation have sub 0.1% effects on k-ht. Conclusion: An MR-safe 4°C stagnant WC appropriate for dosimetry in MRI-linac and Gamma-Knife was designed, optimized, and construction is nearly completed. NSERC Discovery Grant RGPIN-435608.« less

TU-H-BRA-07: Design, Construction, and Installation of An Experimental Beam Line for the Development of MRI-Linac Compatible Electron Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whelan, B; Keall, P; Holloway, L

Purpose: MRI guided radiation therapy (MRIgRT) is a rapidly growing field; however, Linac operation in MRI fringe fields represents an ongoing challenge. We have previously shown in-silico that Linacs could be redesigned to function in the in-line orientation with no magnetic shielding by adopting an RF-gun configuration. Other authors have also published insilico studies of Linac operation in magnetic fields; however to date no experimental validation data is published. This work details the design, construction, and installation of an experimental beam line to validate our in-silico results. Methods: An RF-gun comprising 1.5 accelerating cells and capable of generating electron energiesmore » up to 3.2MeV is used. The experimental apparatus was designed to monitor both beam current (toroid current monitor), spot size (two phosphor screens with viewports), and generate peak magnetic fields of at least 1000G (three variable current electromagnetic coils). Thermal FEM simulations were developed to ensure coil temperature remained within 100degC. Other design considerations included beam disposal, vacuum maintenance, radiation shielding, earthquake safety, and machine protection interlocks. Results: The beam line has been designed, built, and installed in a radiation shielded bunker. Water cooling, power supplies, thermo-couples, cameras, and radiation shielding have been successfully connected and tested. Interlock testing, vacuum processing, and RF processing have been successfully completed. The first beam on is expected within weeks. The coil heating simulations show that with care, peak fields of up to 1200G (320G at cathode) can be produced using 40A current, which is well within the fields expected for MRI-Linac systems. The maximum coil temperature at this current was 84degC after 6 minutes. Conclusion: An experimental beam line has been constructed and installed at SLAC in order to experimentally characterise RF gun performance in in-line magnetic fields, validate in-silico design work, and provide the first published experimental data relating to accelerator functionality for MRIgRT.« less

Distinguishing transient signals and instrumental disturbances in semi-coherent searches for continuous gravitational waves with line-robust statistics

NASA Astrophysics Data System (ADS)

Keitel, David

2016-05-01

Non-axisymmetries in rotating neutron stars emit quasi-monochromatic gravitational waves. These long-duration ‘continuous wave’ signals are among the main search targets of ground-based interferometric detectors. However, standard detection methods are susceptible to false alarms from instrumental artefacts that resemble a continuous-wave signal. Past work [Keitel, Prix, Papa, Leaci and Siddiqi 2014, Phys. Rev. D 89 064023] showed that a Bayesian approach, based on an explicit model of persistent single-detector disturbances, improves robustness against such artefacts. Since many strong outliers in semi-coherent searches of LIGO data are caused by transient disturbances that last only a few hours or days, I describe in a recent paper [Keitel D 2015, LIGO-P1500159] how to extend this approach to cover transient disturbances, and demonstrate increased sensitivity in realistic simulated data. Additionally, neutron stars could emit transient signals which, for a limited time, also follow the continuous-wave signal model. As a pragmatic alternative to specialized transient searches, I demonstrate how to make standard semi-coherent continuous-wave searches more sensitive to transient signals. Focusing on the time-scale of a single segment in the semi-coherent search, Bayesian model selection yields a simple detection statistic without a significant increase in computational cost. This proceedings contribution gives a brief overview of both works.

Intracranial stereotactic radiosurgery with an adapted linear accelerator vs. robotic radiosurgery: Comparison of dosimetric treatment plan quality.

PubMed

Treuer, Harald; Hoevels, Moritz; Luyken, Klaus; Visser-Vandewalle, Veerle; Wirths, Jochen; Kocher, Martin; Ruge, Maximilian

2015-06-01

Stereotactic radiosurgery with an adapted linear accelerator (linac-SRS) is an established therapy option for brain metastases, benign brain tumors, and arteriovenous malformations. We intended to investigate whether the dosimetric quality of treatment plans achieved with a CyberKnife (CK) is at least equivalent to that for linac-SRS with circular or micromultileaf collimators (microMLC). A random sample of 16 patients with 23 target volumes, previously treated with linac-SRS, was replanned with CK. Planning constraints were identical dose prescription and clinical applicability. In all cases uniform optimization scripts and inverse planning objectives were used. Plans were compared with respect to coverage, minimal dose within target volume, conformity index, and volume of brain tissue irradiated with ≥ 10 Gy. Generating the CK plan was unproblematic with simple optimization scripts in all cases. With the CK plans, coverage, minimal target volume dosage, and conformity index were significantly better, while no significant improvement could be shown regarding the 10 Gy volume. Multiobjective comparison for the irradiated target volumes was superior in the CK plan in 20 out of 23 cases and equivalent in 3 out of 23 cases. Multiobjective comparison for the treated patients was superior in the CK plan in all 16 cases. The results clearly demonstrate the superiority of the irradiation plan for CK compared to classical linac-SRS with circular collimators and microMLC. In particular, the average minimal target volume dose per patient, increased by 1.9 Gy, and at the same time a 14% better conformation index seems to be an improvement with clinical relevance.

Neutron production from flattening filter free high energy medical linac: A Monte Carlo study

NASA Astrophysics Data System (ADS)

Najem, M. A.; Abolaban, F. A.; Podolyák, Z.; Spyrou, N. M.

2015-11-01

One of the problems arising from using a conventional linac at high energy (>8 MV) is the production of neutrons. One way to reduce neutron production is to remove the flattening filter (FF). The main purpose of this work was to study the effect of FF removal on neutron fluence and neutron dose equivalent inside the treatment room at different photon beam energies. Several simulations based on Monte Carlo techniques were carried out in order to calculate the neutron fluence at different locations in the treatment room from different linac energies with and without a FF. In addition, a step-and-shoot intensity modulated radiotherapy (SnS IMRT) for prostate cancer was modelled using the 15 MV photon beam with and without a FF on a water phantom to calculate the neutron dose received in a full treatment. The results obtained show a significant drop-off in neutrons fluence and dose equivalent when the FF was removed. For example, the neutron fluence was decreased by 54%, 76% and 75% for 10, 15 and 18 MV, respectively. This can decrease the neutron dose to the patient as well as reduce the shielding cost of the treatment room. The neutron dose equivalent of the SnS IMRT for prostate cancer was reduced significantly by 71.3% when the FF was removed. It can be concluded that the flattening filter removal from the head of the linac could reduce the risk of causing secondary cancers and the shielding cost of radiotherapy treatment rooms.

Statistical process control for electron beam monitoring.

PubMed

López-Tarjuelo, Juan; Luquero-Llopis, Naika; García-Mollá, Rafael; Quirós-Higueras, Juan David; Bouché-Babiloni, Ana; Juan-Senabre, Xavier Jordi; de Marco-Blancas, Noelia; Ferrer-Albiach, Carlos; Santos-Serra, Agustín

2015-07-01

To assess the electron beam monitoring statistical process control (SPC) in linear accelerator (linac) daily quality control. We present a long-term record of our measurements and evaluate which SPC-led conditions are feasible for maintaining control. We retrieved our linac beam calibration, symmetry, and flatness daily records for all electron beam energies from January 2008 to December 2013, and retrospectively studied how SPC could have been applied and which of its features could be used in the future. A set of adjustment interventions designed to maintain these parameters under control was also simulated. All phase I data was under control. The dose plots were characterized by rising trends followed by steep drops caused by our attempts to re-center the linac beam calibration. Where flatness and symmetry trends were detected they were less-well defined. The process capability ratios ranged from 1.6 to 9.3 at a 2% specification level. Simulated interventions ranged from 2% to 34% of the total number of measurement sessions. We also noted that if prospective SPC had been applied it would have met quality control specifications. SPC can be used to assess the inherent variability of our electron beam monitoring system. It can also indicate whether a process is capable of maintaining electron parameters under control with respect to established specifications by using a daily checking device, but this is not practical unless a method to establish direct feedback from the device to the linac can be devised. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Intra-coil interactions in split gradient coils in a hybrid MRI-LINAC system.

PubMed

Tang, Fangfang; Freschi, Fabio; Sanchez Lopez, Hector; Repetto, Maurizio; Liu, Feng; Crozier, Stuart

2016-04-01

An MRI-LINAC system combines a magnetic resonance imaging (MRI) system with a medical linear accelerator (LINAC) to provide image-guided radiotherapy for targeting tumors in real-time. In an MRI-LINAC system, a set of split gradient coils is employed to produce orthogonal gradient fields for spatial signal encoding. Owing to this unconventional gradient configuration, eddy currents induced by switching gradient coils on and off may be of particular concern. It is expected that strong intra-coil interactions in the set will be present due to the constrained return paths, leading to potential degradation of the gradient field linearity and image distortion. In this study, a series of gradient coils with different track widths have been designed and analyzed to investigate the electromagnetic interactions between coils in a split gradient set. A driving current, with frequencies from 100 Hz to 10 kHz, was applied to study the inductive coupling effects with respect to conductor geometry and operating frequency. It was found that the eddy currents induced in the un-energized coils (hereby-referred to as passive coils) positively correlated with track width and frequency. The magnetic field induced by the eddy currents in the passive coils with wide tracks was several times larger than that induced by eddy currents in the cold shield of cryostat. The power loss in the passive coils increased with the track width. Therefore, intra-coil interactions should be included in the coil design and analysis process. Copyright © 2016 Elsevier Inc. All rights reserved.

Clinical impact of dosimetric changes for volumetric modulated arc therapy in log file-based patient dose calculations.

PubMed

Katsuta, Yoshiyuki; Kadoya, Noriyuki; Fujita, Yukio; Shimizu, Eiji; Matsunaga, Kenichi; Matsushita, Haruo; Majima, Kazuhiro; Jingu, Keiichi

2017-10-01

A log file-based method cannot detect dosimetric changes due to linac component miscalibration because log files are insensitive to miscalibration. Herein, clinical impacts of dosimetric changes on a log file-based method were determined. Five head-and-neck and five prostate plans were applied. Miscalibration-simulated log files were generated by inducing a linac component miscalibration into the log file. Miscalibration magnitudes for leaf, gantry, and collimator at the general tolerance level were ±0.5mm, ±1°, and ±1°, respectively, and at a tighter tolerance level achievable on current linac were ±0.3mm, ±0.5°, and ±0.5°, respectively. Re-calculations were performed on patient anatomy using log file data. Changes in tumor control probability/normal tissue complication probability from treatment planning system dose to re-calculated dose at the general tolerance level was 1.8% on planning target volume (PTV) and 2.4% on organs at risk (OARs) in both plans. These changes at the tighter tolerance level were improved to 1.0% on PTV and to 1.5% on OARs, with a statistically significant difference. We determined the clinical impacts of dosimetric changes on a log file-based method using a general tolerance level and a tighter tolerance level for linac miscalibration and found that a tighter tolerance level significantly improved the accuracy of the log file-based method. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Technical Note: A Feasibility Study of Using the Flat Panel Detector on Linac for the kV X-ray Generator Test.

PubMed

Cai, Bin; Dolly, Steven; Kamal, Gregory; Yaddanapudi, Sridhar; Sun, Baozhou; Goddu, S Murty; Mutic, Sasa; Li, Hua

2018-04-28

To investigate the feasibility of using kV flat panel detector on linac for consistency evaluations of kV X-ray generator performance. An in-house designed aluminum (Al) array phantom with six 9×9 cm 2 square regions having various thickness was proposed and used in this study. Through XML script-driven image acquisition, kV images with various acquisition settings were obtained using the kV flat panel detector. Utilizing pre-established baseline curves, the consistency of X-ray tube output characteristics including tube voltage accuracy, exposure accuracy and exposure linearity were assessed through image quality assessment metrics including ROI mean intensity, ROI standard deviation (SD) and noise power spectrums (NPS). The robustness of this method was tested on two linacs for a three-month period. With the proposed method, tube voltage accuracy can be verified through conscience check with a 2% tolerance and 2 kVp intervals for forty different kVp settings. The exposure accuracy can be tested with a 4% consistency tolerance for three mAs settings over forty kVp settings. The exposure linearity tested with three mAs settings achieved a coefficient of variation (CV) of 0.1. We proposed a novel approach that uses the kV flat panel detector available on linac for X-ray generator test. This approach eliminates the inefficiencies and variability associated with using third party QA detectors while enabling an automated process. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

MO-D-BRB-02: SBRT Treatment Planning and Delivery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Y.

2016-06-15

Increased use of SBRT and hypofractionation in radiation oncology practice has posted a number of challenges to medical physicist, ranging from planning, image-guided patient setup and on-treatment monitoring, to quality assurance (QA) and dose delivery. This symposium is designed to provide current knowledge necessary for the safe and efficient implementation of SBRT in various linac platforms, including the emerging digital linacs equipped with high dose rate FFF beams. Issues related to 4D CT, PET and MRI simulations, 3D/4D CBCT guided patient setup, real-time image guidance during SBRT dose delivery using gated/un-gated VMAT/IMRT, and technical advancements in QA of SBRT (inmore » particular, strategies dealing with high dose rate FFF beams) will be addressed. The symposium will help the attendees to gain a comprehensive understanding of the SBRT workflow and facilitate their clinical implementation of the state-of-art imaging and planning techniques. Learning Objectives: Present background knowledge of SBRT, describe essential requirements for safe implementation of SBRT, and discuss issues specific to SBRT treatment planning and QA. Update on the use of multi-dimensional and multi-modality imaging for reliable guidance of SBRT. Discuss treatment planning and QA issues specific to SBRT. Provide a comprehensive overview of emerging digital linacs and summarize the key geometric and dosimetric features of the new generation of linacs for substantially improved SBRT. NIH/NCI; Varian Medical Systems; F. Yin, Duke University has a research agreement with Varian Medical Systems. In addition to research grant, I had a technology license agreement with Varian Medical Systems.« less

Semi-continuous detection of mercury in gases

DOEpatents

Granite, Evan J [Wexford, PA; Pennline, Henry W [Bethel Park, PA

2011-12-06

A new method for the semi-continuous detection of heavy metals and metalloids including mercury in gaseous streams. The method entails mass measurement of heavy metal oxides and metalloid oxides with a surface acoustic wave (SAW) sensor having an uncoated substrate. An array of surface acoustic wave (SAW) sensors can be used where each sensor is for the semi-continuous emission monitoring of a particular heavy metal or metalloid.

Long-term, correlated emittance decrease in intense, high-brightness induction linacs

NASA Astrophysics Data System (ADS)

Carlsten, Bruce E.

1999-09-01

Simulations of high-brightness induction linacs often show a slow, long-term emittance decrease as the beam is matched from the electron gun into the linac. Superimposed on this long-term decrease are rapid emittance oscillations. These effects can be described in terms of correlations in the beam's radial phase space. The rapid emittance oscillations are due to transverse plasma oscillations, which stay nearly in phase for different radial positions within the beam. The initial emittance, just after the electron gun, is dominated by nonlinear focusing within the gun introduced by the anode exit hole. Due to the large space-charge force of an intense electron beam, the focusing of the beam through the matching section introduces an effective nonlinear force (from the change in the particles' potential energies) which counteracts the nonlinearities from the electron gun, leading to an average, long-term emittance decrease. Not all of the initial nonlinearity is removed by the matching procedure, and there are important consequences both for emittance measurements using solenoid focal length scans and for focusing the electron beam to a target.

Design and development of a radio frequency quadrupole linac postaccelerator for the Variable Energy Cyclotron Center rare ion beam project.

PubMed

Dechoudhury, S; Naik, V; Mondal, M; Chatterjee, A; Pandey, H K; Mandi, T K; Bandyopadhyay, A; Karmakar, P; Bhattacharjee, S; Chouhan, P S; Ali, S; Srivastava, S C L; Chakrabarti, A

2010-02-01

A four-rod type heavy-ion radio frequency quadrupole (RFQ) linac has been designed, constructed, and tested for the rare ion beam (RIB) facility project at VECC. Designed for cw operation, this RFQ is the first postaccelerator in the RIB beam line. It will accelerate A/q < or = 14 heavy ions coming from the ion source to the energy of around 100 keV/u for subsequent acceleration in a number of Interdigital H-Linac. Operating at a resonance frequency of 37.83 MHz, maximum intervane voltage of around 54 kV will be needed to achieve the final energy over a vane length of 3.12 m for a power loss of 35 kW. In the first beam tests, transmission efficiency of about 90% was measured at the QQ focus after the RFQ for O(5+) beam. In this article the design of the RFQ including the effect of vane modulation on the rf characteristics and results of beam tests will be presented.

Modulators for the S-band test linac at DESY

NASA Astrophysics Data System (ADS)

Bieler, M.; Choroba, S.; Hameister, J.; Lewin, H.-Ch.

1995-07-01

The development of adequate modulators for high peak power klystrons is one of the focus points for linear collider R&D programs. For the DESY/THD S-band linear collider study 150 MW rf-pulse power at 50 Hz repetition rate and 3 μs pulse duration is required [1]. Two different modulator schemes are under investigation. One is the conventional line type pulser, using a pulse forming network and a step up transformer, the other one is a hard tube pulser, using a dc power source at the full klystron voltage and a switch tube. This paper is focused on the modulator development for the S-band Test Linac at DESY. After a short overview over the test linac and a brief description of the 150 MW S-band klystron the circuitry of the line type pulse (LTP) is given. A hard tube pulser (HTP), which switches the high voltage directly from a storage capacitor to the klystron, has been built up at DESY. Circuitry and the results of the commissioning of the switch tube are reported.