Studies on Muon Induction Acceleration and an Objective Lens Design for Transmission Muon Microscope

NASA Astrophysics Data System (ADS)

Artikova, Sayyora; Yoshida, Mitsuhiro; Naito, Fujio

Muon acceleration will be accomplished by a set of induction cells, where each increases the energy of the muon beam by an increment of up to 30 kV. The cells are arranged in a linear way resulting in total accelerating voltage of 300 kV. Acceleration time in the linac is about hundred nanoseconds. Induction field calculation is based on an electrostatic approximation. Beam dynamics in the induction accelerator is investigated and final beam focusing on specimen is realized by designing a pole piece lens.

The DARHT Phase 2 Linac

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

wolf, Zachary R.

2000-09-12

The second phase accelerator for the Dual Axis Hydrodynamic Test facility (DARHT) is designed to provide an electron beam pulse that is 2{mu}s long, 2kA, and 20 MeV in particle energy. The injector provides 3.2 MeV so that the linac need only provide 16.8 MeV. The linac is made with two types of induction accelerator cells. The first block of 8 cells have a 14 in. beam pipe compared to 10 in. in the remaining 80 cells. The other principal difference is that the first 8 cells have reduced volt-sec in their induction cores as a result of a largermore » diameter beam pipe. The cells are designed for very reliable high voltage operation. The insulator is Mycalex. Results from prototype tests are given including results from solenoid measurements. Each cell contains a solenoid for beam transport and a set of x-y correction coils to reduce corkscrew motion. Details of tests to determine RF mode impedances relevant to BBU generation are given. Blocks of cells are separated by intercells some of which contain transport solenoids. The intercells provide vacuum pumping stations as well. Issues of alignment and installation are discussed.« less

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.

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

Investigation of Re-X glass ceramic for acceleration insulating columns

NASA Astrophysics Data System (ADS)

Faltens, A.; Rosenblum, S.

1985-05-01

In an induction linac the accelerating voltage appears along a voltage-graded vacuum insulator column which is a performance limiting and major cost component. Re-X glass ceramic insulators have the long-sought properties of allowing cast-in gradient electrodes, good breakdown characteristics, and compatibility with high vacuum systems. Re-X is a glass ceramic developed by General Electric for use in the manufacture of electrical apparatus, such as vacuum arc interrupters. We have examined vacuum outgassing behavior and voltage breakdown in vacuum and find excellent performance. The housings are in the shape of tubes with type 430 stainless steel terminations. Due to a matched coefficient of thermal expansion between metal and insulator, no vacuum leaks have resulted from any welding operation. The components should be relatively inexpensive to manufacture in large sizes and appear to be a very attractive accelerator column. We are planning to use a standard GE housing in our MBE-4 induction linac.

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.

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.

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.

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.

The ETA-II induction linac as a high-average-power FEL driver

NASA Astrophysics Data System (ADS)

Nexsen, W. E.; Atkinson, D. P.; Barrett, D. M.; Chen, Y.-J.; Clark, J. C.; Griffith, L. V.; Kirbie, H. C.; Newton, M. A.; Paul, A. C.; Sampayan, S.; Throop, A. L.; Turner, W. C.

1990-10-01

The Experimental Test Accelerator II (ETA-II) is the first induction linac designed specifically to FEL requirements. It is primarily intended to demonstrate induction accelerator technology for high-average-power, high-brightness electron beams, and will be used to drive a 140 and 250 GHz microwave FEL for plasma heating experiments in the Microwave Tokamak Experiment (MTX) at LLNL. Its features include high-vacuum design which allows the use of an intrinsically bright dispenser cathode, induction cells designed to minimize BBU growth rate, and careful attention to magnetic alignment to minimize radial sweep due to beam corkscrew. The use of magnetic switches allows high-average-power operation. At present ETA-II is being used to drive 140 GHz plasma heating experiments. These experiments require nominal beam parameters of 6 MeV energy, 2 kA current, 20 ns pulse width and a brightness of 1 × 108 A/(m rad)2 at the wiggler with a pulse repetition frequency (prf) of 0.5 Hz. Future 250 GHz experiments require beam parameters of 10 MeV energy, 3 kA current, 50 ns pulse width and a brightness of 1 × 108 A/(m rad)2 with a 5 kHz prf for 0.5 s. In this paper we discuss the present status of ETA-II parameters and the phased development program necessary to satisfy these future requirements.

Development of a high-power solid-state switch using static induction thyristors for a klystron modulator

NASA Astrophysics Data System (ADS)

Tokuchi, Akira; Kamitsukasa, Fumiyoshi; Furukawa, Kazuya; Kawase, Keigo; Kato, Ryukou; Irizawa, Akinori; Fujimoto, Masaki; Osumi, Hiroki; Funakoshi, Sousuke; Tsutsumi, Ryouta; Suemine, Shoji; Honda, Yoshihide; Isoyama, Goro

2015-01-01

We developed a solid-state switch with static induction thyristors for the klystron modulator of the L-band electron linear accelerator (linac) at the Institute of Scientific and Industrial Research, Osaka University. This switch is designed to have maximum specifications of a holding voltage of 25 kV and a current of 6 kA at the repetition frequency of 10 Hz for forced air cooling. The turn-on time of the switch was measured with a matched resistor to be 270 ns, which is sufficiently fast for the klystron modulator. The switch is retrofitted in the modulator to generate 1.3 GHz RF pulses with durations of either 4 or 8 μs using a 30 MW klystron, and the linac is successfully operated under maximum conditions. This finding demonstrates that the switch can be used as a high-power switch for the modulator. Pulse-to-pulse variations of the klystron voltage are measured to be less than 0.015%, and those of RF power and phase are lower than 0.15% and 0.1°, respectively. These values are significantly smaller than those obtained with a thyratron; hence, the stability of the main RF system is improved. The solid-state switch has been used in normal operation of the linac for more than a year without any serious trouble. Thus, we confirmed the switch's robustness and long-term reliability.

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

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.

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.

The ETA-2 induction linac as a high average power FEL driver

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

Nexsen, W.E.; Atkinson, D.P.; Barrett, D.M.

1989-10-16

The Experimental Test Accelerator-II (ETA-II) is the first induction linac designed specifically to FEL requirements. It primarily is intended to demonstrate induction accelerator technology for high average power, high brightness electron beams, and will be used to drive a 140 and 250 GHz microwave FEL for plasma heating experiments in the Microwave Tokamak Experiment (MTX) at LLNL. Its features include high vacuum design which allows the use of an intrinsically bright dispenser cathode, induction cells designed to minimize BBU growth rate, and careful attention to magnetic alignment to minimize radial sweep due to beam corkscrew. The use of magnetic switchesmore » allows high average power operation. At present ETA-II is being used to drive 140 GHz plasma heating experiments. These experiments require nominal beam parameters of 6 Mev energy, 2kA current, 20ns pulse width and a brightness of 1 {times} 10{sup 8} A/(m-rad){sup 2} at the wiggler with a pulse repetition frequency (PRF) of 0.5 Hz. Future 250 GHz experiments require beam parameters of 10 Mev energy, 3kA current, 50ns pulse width and a brightness of 1 {times} 10{sup 8} A/(m-rad){sup 2} with a 5 kHz PRF for 0.5 sec. In this paper we discuss the present status of ETA-II parameters and the phased development program necessary to satisfy these future requirements. 13 refs., 9 figs., 1 tab.« less

Beam-dynamics driven design of the LHeC energy-recovery linac

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

Pellegrini, Dario; Latina, Andrea; Schulte, Daniel

The LHeC study is a possible upgrade of the LHC that aims at delivering an electron beam for collisions with the existing hadronic beams. The current baseline design for the electron facility consists of a multi-pass superconducting energy-recovery linac operating in a continuous wave mode. Here, we summarize the overall layout of such ERL complex located on the LHC site and introduce the most recent developments. We review of the lattice components, presenting their baseline design along with possible alternatives that aims at improving the overall machine performance. The detector bypass has been designed and integrated into the lattice. Trackingmore » simulations allowed us to verify the high current (~150 mA in the linacs) beam operation required for the LHeC to serve as an Higgs Factory. The impact of single and multi-bunch wake-fields, synchrotron radiation and beam-beam effects has been assessed in this paper.« less

Beam-dynamics driven design of the LHeC energy-recovery linac

DOE PAGES

Pellegrini, Dario; Latina, Andrea; Schulte, Daniel; ...

2015-12-23

The LHeC study is a possible upgrade of the LHC that aims at delivering an electron beam for collisions with the existing hadronic beams. The current baseline design for the electron facility consists of a multi-pass superconducting energy-recovery linac operating in a continuous wave mode. Here, we summarize the overall layout of such ERL complex located on the LHC site and introduce the most recent developments. We review of the lattice components, presenting their baseline design along with possible alternatives that aims at improving the overall machine performance. The detector bypass has been designed and integrated into the lattice. Trackingmore » simulations allowed us to verify the high current (~150 mA in the linacs) beam operation required for the LHeC to serve as an Higgs Factory. The impact of single and multi-bunch wake-fields, synchrotron radiation and beam-beam effects has been assessed in this paper.« less

Principles of Induction Accelerators

NASA Astrophysics Data System (ADS)

Briggs*, Richard J.

The basic concepts involved in induction accelerators are introduced in this chapter. The objective is to provide a foundation for the more detailed coverage of key technology elements and specific applications in the following chapters. A wide variety of induction accelerators are discussed in the following chapters, from the high current linear electron accelerator configurations that have been the main focus of the original developments, to circular configurations like the ion synchrotrons that are the subject of more recent research. The main focus in the present chapter is on the induction module containing the magnetic core that plays the role of a transformer in coupling the pulsed power from the modulator to the charged particle beam. This is the essential common element in all these induction accelerators, and an understanding of the basic processes involved in its operation is the main objective of this chapter. (See [1] for a useful and complementary presentation of the basic principles in induction linacs.)

First demonstration of simultaneous measurement of beam current, beam position, and beam tilt on induction linac using combined B-dot monitor

NASA Astrophysics Data System (ADS)

He, Xiaozhong; Pang, Jian; Chen, Nan; Li, Qin; Dai, Wenhua; Ma, Chaofan; Zhao, Liangchao; Gao, Feng; Dai, Zhiyong

2017-06-01

The authors previously reported that the axial B-dots can be used to directly measure the beam tilt and demonstrated that the axial B-dots are applicable to a coaxial calibration stand. In this study, a combined B-dot monitor composed of four axial B-dot loops and four azimuthal ones is tested for the simultaneous measurement of the time-varying beam current, beam offset, and beam tilt at the output of the injector of the DRAGON-I induction linac. In the experiments, the beam offset and beam tilt at the position of the monitor are proportionally adjusted using a pair of steering coils. Eight waveforms acquired from the B-dot monitor are analyzed to reconstruct the time-varying beam current, beam offset, and beam tilt. The original signals of both the azimuthal B-dot and the axial B-dot ports change significantly with respect to the current applied to the steering coils. The measured beam tilt is linearly dependent on the current applied to the steering coils and agrees well with the measured beam offset.

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 of induction-linac based free-electron laser amplifiers

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

Jong, R.A.; Fawley, W.M.; Scharlemann, E.T.

We describe the modeling of an induction-linac based free-electron laser (IFEL) amplifier for producing multimegawatt levels of microwave power. We have used the Lawrence Livermore National Laboratory (LLNL) free-electron laser simulation code, FRED, and the simulation code for sideband calculations, GINGER for this study. For IFEL amplifiers in the frequency range of interest (200 to 600 GHz), we have devised a wiggler design strategy which incorporates a tapering algorithm that is suitable for free-electron laser (FEL) systems with moderate space-charge effects and that minimizes spontaneous noise growth at frequencies below the fundamental, while enhancing the growth of the signal atmore » the fundamental. In addition, engineering design considerations of the waveguide wall loading and electron beam fill factor in the waveguide set limits on the waveguide dimensions, the wiggler magnet gap spacing, the wiggler period, and the minimum magnetic field strength in the tapered region of the wiggler. As an example, we shall describe an FEL amplifier designed to produce an average power of about 10 MW at a frequency of 280 GHz to be used for electron cyclotron resonance heating of tokamak fusion devices. 17 refs., 4 figs.« less

RF low-level control for the Linac4 H{sup −} source

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

Butterworth, A., E-mail: andrew.butterworth@cern.ch; Grudiev, A.; Lettry, J.

2015-04-08

The H{sup −} source for the Linac4 accelerator at CERN uses an RF driven plasma for the production of H{sup −}. The RF is supplied by a 2 MHz RF tube amplifier with a maximum power output of 100 kW and a pulse duration of up to 2 ms. The low-level RF signal generation and measurement system has been developed using standard CERN controls electronics in the VME form factor. The RF frequency and amplitude reference signals are generated using separate arbitrary waveform generator channels. The frequency and amplitude are both freely programmable over the duration of the RF pulse, which allowsmore » fine-tuning of the excitation. Measurements of the forward and reverse RF power signals are performed via directional couplers using high-speed digitizers, and permit the estimation of the plasma impedance and deposited power via an equivalent circuit model. The low-level RF hardware and software implementations are described, and experimental results obtained with the Linac4 ion sources in the test stand are presented.« less

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.

Fast ferroelectric phase shifters for energy recovery linacs

DOE PAGES

Kazakov, S. Yu; Shchelkunov, S. V.; Yakovlev, V. P.; ...

2010-11-24

Fast phase shifters are described that use a novel barium strontium titanate ceramic that can rapidly change its dielectric constant as an external bias voltage is changed. These phase shifters promise to reduce by ~10 times the power requirements for the rf source needed to drive an energy recovery linac (ERL). Such phase shifters will be coupled with superconducting radiofrequency cavities so as to tune them to compensate for phase instabilities, whether beam-driven or those caused by microphonics. The most promising design is presented, which was successfully cold tested and demonstrated a switching speed of ~30 ns for 77 deg, correspondingmore » to < 0.5 ns per deg of rf phase. As a result, other crucial issues (losses, phase shift values, etc.) are discussed.« less

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

Caspi, S.; Schlueter, R.; Tatchyn, R.

Linac-driven X-Ray Free Electron Lasers (e.g., Linac Coherent Light Sources (LCLSs)), operating on the principle of single-pass saturation in the Self-Amplified Spontaneous Emission (SASE) regime typically require multi-GeV beam energies and undulator lengths in excess of tens of meters to attain sufficient gain in the 1{angstrom}--0.1{angstrom} range. In this parameter regime, the undulator structure must provide: (1) field amplitudes B{sub 0} in excess of 1T within periods of 4cm or less, (2) peak on-axis focusing gradients on the order of 30T/m, and (3) field quality in the 0.1%--0.3% range. In this paper the authors report on designs under consideration formore » a 4.5--1.5 {angstrom} LCLS based on superconducting (SC), hybrid/PM, and pulsed-Cu technologies.« less

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.

The Role of Guided Induction in Paper-Based Data-Driven Learning

ERIC Educational Resources Information Center

Smart, Jonathan

2014-01-01

This study examines the role of guided induction as an instructional approach in paper-based data-driven learning (DDL) in the context of an ESL grammar course during an intensive English program at an American public university. Specifically, it examines whether corpus-informed grammar instruction is more effective through inductive, data-driven…

Induction Linacs and Free Electron Laser Amplifiers

DTIC Science & Technology

1986-03-20

accelerated and the effects of space - charge force is minimized. EMnTANCE-PRESERVING BEAMLINE The beamline (Fig. 5) is designed to preserve the good beam...electrons and pushes them right out of the way leaving a bare ion cloud. With relativistic beams in vacuum, their space charge defocusing is offset by the...suspect, on why charged particle beams cannot be used in space . Now it is a fairly straight- forward extrapolation, already mentioned in Lou Marguet’s

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.

Beam-dynamics driven design of the LHeC energy-recovery linac

NASA Astrophysics Data System (ADS)

Pellegrini, Dario; Latina, Andrea; Schulte, Daniel; Bogacz, S. Alex

2015-12-01

The LHeC is envisioned as a natural upgrade of the LHC that aims at delivering an electron beam for collisions with the existing hadronic beams. The current baseline design for the electron facility consists of a multipass superconducting energy-recovery linac (ERL) operating in a continuous wave mode. The unprecedently high energy of the multipass ERL combined with a stringent emittance dilution budget poses new challenges for the beam optics. Here, we investigate the performances of a novel arc architecture based on a flexible momentum compaction lattice that mitigates the effects of synchrotron radiation while containing the bunch lengthening. Extensive beam-dynamics investigations have been performed with placet2, a recently developed tracking code for recirculating machines. They include the first end-to-end tracking and a simulation of the machine operation with a continuous beam. This paper briefly describes the Conceptual Design Report lattice, with an emphasis on possible and proposed improvements that emerged from the beam-dynamics studies. The detector bypass section has been integrated in the lattice, and its design choices are presented here. The stable operation of the ERL with a current up to ˜150 mA in the linacs has been validated in the presence of single- and multibunch wakefields, synchrotron radiation, and beam-beam effects.

In situ insights into shock-driven reactive flow

NASA Astrophysics Data System (ADS)

Dattelbaum, Dana

2017-06-01

Shock-driven reactions are commonplace. Examples include the detonation of high explosives, shock-driven dissociation of polymers, and transformation of carbon from graphite to diamond phases. The study of shock-driven chemical reactions is important for understanding reaction thresholds, their mechanisms and rates, and associated state sensitivities under the extreme conditions generated by shock compression. Reactions are distinguished by their thermicity - e.g. the volume and enthalpy changes along the reaction coordinate. A survey of the hallmarks of shock-driven reactivity for a variety of simple molecules and polymers will be presented, including benzene, acetylenes and nitriles, and formic acid. Many of the examples will illustrate the nature of the reactive flow through particle velocity wave profiles measured by in situ electromagnetic gauging in gas gun-driven plate impact experiments. General trends will be presented linking molecular moieties, shock temperatures, and reaction state sensitivities. Progress in applying bond-specific diagnostics will also be presented, including time-resolved Raman spectroscopy, and recent results of in situ x-ray diffraction of carbon at the Linac Coherent Light Souce (LCLS) free electron laser.

RF pulse compression for future linear colliders

NASA Astrophysics Data System (ADS)

Wilson, Perry B.

1995-07-01

Future (nonsuperconducting) linear colliders will require very high values of peak rf power per meter of accelerating structure. The role of rf pulse compression in producing this power is examined within the context of overall rf system design for three future colliders at energies of 1.0-1.5 TeV, 5 TeV, and 25 TeV. In order to keep the average AC input power and the length of the accelerator within reasonable limits, a collider in the 1.0-1.5 TeV energy range will probably be built at an x-band rf frequency, and will require a peak power on the order of 150-200 MW per meter of accelerating structure. A 5 TeV collider at 34 GHz with a reasonable length (35 km) and AC input power (225 MW) would require about 550 MW per meter of structure. Two-beam accelerators can achieve peak powers of this order by applying dc pulse compression techniques (induction linac modules) to produce the drive beam. Klystron-driven colliders achieve high peak power by a combination of dc pulse compression (modulators) and rf pulse compression, with about the same overall rf system efficiency (30-40%) as a two-beam collider. A high gain (6.8) three-stage binary pulse compression system with high efficiency (80%) is described, which (compared to a SLED-II system) can be used to reduce the klystron peak power by about a factor of two, or alternatively, to cut the number of klystrons in half for a 1.0-1.5 TeV x-band collider. For a 5 TeV klystron-driven collider, a high gain, high efficiency rf pulse compression system is essential.

An exposure-response analysis based on rifampin suggests CYP3A4 induction is driven by AUC: an in vitro investigation.

PubMed

Chang, Cheng; Yang, Xin; Fahmi, Odette A; Riccardi, Keith A; Di, Li; Obach, R Scott

2017-08-01

1. Induction is an important mechanism contributing to drug-drug interactions. It is most commonly evaluated in the human hepatocyte assay over 48-h or 72-h incubation period. However, whether the overall exposure (i.e. Area Under the Curve (AUC) or C ave ) or maximum exposure (i.e. C max ) of the inducer is responsible for the magnitude of subsequent induction has not been thoroughly investigated. Additionally, in vitro induction assays are typically treated as static systems, which could lead to inaccurate induction potency estimation. Hence, European Medicines Agency (EMA) guidance now specifies quantitation of drug levels in the incubation. 2. This work treated the typical in vitro evaluation of rifampin induction as an in vivo system by generating various target engagement profiles, measuring free rifampin concentration over 3 d of incubation and evaluating the impact of these factors on final induction response. 3. This rifampin-based analysis demonstrates that the induction process is driven by time-averaged target engagement (i.e. AUC-driven). Additionally, depletion of rifampin in the incubation medium over 3 d as well as non-specific/specific binding were observed. 4. These findings should help aid the discovery of clinical candidates with minimal induction liability and further expand our knowledge in the quantitative translatability of in vitro induction assays.

Beam commissioning for a superconducting proton linac

NASA Astrophysics Data System (ADS)

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

2016-12-01

To develop the next generation of safe and cleaner nuclear energy, the accelerator-driven subcritical (ADS) system emerges as one of the most attractive technologies. It will be able to transmute the long-lived transuranic radionuclides produced in the reactors of today's nuclear power plants into shorter-lived ones, and also it will provide positive energy output at the same time. The prototype of the Chinese ADS (C-ADS) proton accelerator comprises two injectors and a 1.5 GeV, 10 mA continuous wave (CW) superconducting main linac. The injector scheme II at the C-ADS demo facility inside the Institute of Modern Physics is a 10 MeV CW superconducting linac with a designed beam current of 10 mA, which includes an ECR ion source, a low-energy beam transport line, a 162.5 MHz radio frequency quadrupole accelerator, a medium-energy beam transport line, and a superconducting half wave resonator accelerator section. This demo facility has been successfully operating with an 11 mA, 2.7 MeV CW beam and a 3.9 mA, 4.3 MeV CW beam at different times and conditions since June 2014. The beam power has reached 28 kW, which is the highest record for the same type of linear accelerators. In this paper, the parameters of the test injector II and the progress of the beam commissioning are reported.

Public Data Set: Non-inductively Driven Tokamak Plasmas at Near-Unity βt in the Pegasus Toroidal Experiment

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

Reusch, Joshua A.; Bodner, Grant M.; Bongard, Michael W.

This public data set contains openly-documented, machine readable digital research data corresponding to figures published in J.A. Reusch et al., 'Non-inductively Driven Tokamak Plasmas at Near-Unity βt in the Pegasus Toroidal Experiment,' Phys. Plasmas 25, 056101 (2018).

The Japanese Positron Factory

NASA Astrophysics Data System (ADS)

Okada, S.; Sunaga, H.; Kaneko, H.; Takizawa, H.; Kawasuso, A.; Yotsumoto, K.; Tanaka, R.

1999-06-01

The Positron Factory has been planned at Japan Atomic Energy Research Institute (JAERI). The factory is expected to produce linac-based monoenergetic positron beams having world-highest intensities of more than 1010e+/sec, which will be applied for R&D of materials science, biotechnology and basic physics & chemistry. In this article, results of the design studies are demonstrated for the following essential components of the facilities: 1) Conceptual design of a high-power electron linac with 100 MeV in beam energy and 100 kW in averaged beam power, 2) Performance tests of the RF window in the high-power klystron and of the electron beam window, 3) Development of a self-driven rotating electron-to-positron converter and the performance tests, 4) Proposal of multi-channel beam generation system for monoenergetic positrons, with a series of moderator assemblies based on a newly developed Monte Carlo simulation and the demonstrative experiment, 5) Proposal of highly efficient moderator structures, 6) Conceptual design of a local shield to suppress the surrounding radiation and activation levels.

Surface production dominating Cs-free H- ion source for high intensity and high energy proton accelerators

NASA Astrophysics Data System (ADS)

Ueno, Akira; Ikegami, Kiyoshi; Kondo, Yasuhiro

2004-05-01

A Cs-free negative hydrogen (H-) ion source driven by pulsed arc plasma with a LaB6 filament is being operated for the beam tests of the Japan Proton Accelerator Research Complex (J-PARC) linac. A peak H- current of 38 mA, which exceeds the requirement of the J-PARC first stage, is stably extracted from the ion source with a beam duty factor of 0.9% (360 μs×25 Hz) by principally optimizing the surface condition and shape of the plasma electrode. The sufficiently small emittance of the beam was confirmed by high transmission efficiency (around 90%) through the following 324 MHz 3 MeV J-PARC radio frequency quadrupole linac (M. Ikegami et al., Proc. 2003 Part. Accel. Conf. 2003, p. 1509). The process of the optimization, which confirms the validity of hypothesis that H- ions are produced by surface reaction on a Mo plasma electrode dominantly in the ion source, is presented.

Overview of Mono-Energetic Gamma-Ray Sources and Applications

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

Hartemann, Fred; /LLNL, Livermore; Albert, Felicie

2012-06-25

Recent progress in accelerator physics and laser technology have enabled the development of a new class of tunable gamma-ray light sources based on Compton scattering between a high-brightness, relativistic electron beam and a high intensity laser pulse produced via chirped-pulse amplification (CPA). A precision, tunable Mono-Energetic Gamma-ray (MEGa-ray) source driven by a compact, high-gradient X-band linac is currently under development and construction at LLNL. High-brightness, relativistic electron bunches produced by an X-band linac designed in collaboration with SLAC NAL will interact with a Joule-class, 10 ps, diode-pumped CPA laser pulse to generate tunable {gamma}-rays in the 0.5-2.5 MeV photon energymore » range via Compton scattering. This MEGaray source will be used to excite nuclear resonance fluorescence in various isotopes. Applications include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. The source design, key parameters, and current status are presented, along with important applications, including nuclear resonance fluorescence.« less

Transverse emittance-preserving arc compressor for high-brightness electron beam-based light sources and colliders

NASA Astrophysics Data System (ADS)

Di Mitri, S.; Cornacchia, M.

2015-03-01

Bunch length magnetic compression is used in high-brightness linacs driving free-electron lasers (FELs) and particle colliders to increase the peak current of the injected beam. To date, it is performed in dedicated insertions made of few degrees bending magnets and the compression factor is limited by the degradation of the beam transverse emittance owing to emission of coherent synchrotron radiation (CSR). We reformulate the known concept of CSR-driven optics balance for the general case of varying bunch length and demonstrate, through analytical and numerical results, that a 500 pC charge beam can be time-compressed in a periodic 180 deg arc at 2.4 GeV beam energy and lower, by a factor of up to 45, reaching peak currents of up to 2 kA and with a normalized emittance growth at the 0.1 μ \\text{m} rad level. The proposed solution offers new schemes of beam longitudinal gymnastics; an application to an energy recovery linac driving FEL is discussed.

Experimental benchmark of the NINJA code for application to the Linac4 H- ion source plasma

NASA Astrophysics Data System (ADS)

Briefi, S.; Mattei, S.; Rauner, D.; Lettry, J.; Tran, M. Q.; Fantz, U.

2017-10-01

For a dedicated performance optimization of negative hydrogen ion sources applied at particle accelerators, a detailed assessment of the plasma processes is required. Due to the compact design of these sources, diagnostic access is typically limited to optical emission spectroscopy yielding only line-of-sight integrated results. In order to allow for a spatially resolved investigation, the electromagnetic particle-in-cell Monte Carlo collision code NINJA has been developed for the Linac4 ion source at CERN. This code considers the RF field generated by the ICP coil as well as the external static magnetic fields and calculates self-consistently the resulting discharge properties. NINJA is benchmarked at the diagnostically well accessible lab experiment CHARLIE (Concept studies for Helicon Assisted RF Low pressure Ion sourcEs) at varying RF power and gas pressure. A good general agreement is observed between experiment and simulation although the simulated electron density trends for varying pressure and power as well as the absolute electron temperature values deviate slightly from the measured ones. This can be explained by the assumption of strong inductive coupling in NINJA, whereas the CHARLIE discharges show the characteristics of loosely coupled plasmas. For the Linac4 plasma, this assumption is valid. Accordingly, both the absolute values of the accessible plasma parameters and their trends for varying RF power agree well in measurement and simulation. At varying RF power, the H- current extracted from the Linac4 source peaks at 40 kW. For volume operation, this is perfectly reflected by assessing the processes in front of the extraction aperture based on the simulation results where the highest H- density is obtained for the same power level. In surface operation, the production of negative hydrogen ions at the converter surface can only be considered by specialized beam formation codes, which require plasma parameters as input. It has been demonstrated that this input can be provided reliably by the NINJA code.

TU-H-BRA-05: A System Design for Integration of An Interior MRI and a Linear Accelerator

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

Mao, W; Henry Ford Hospital, Detroit, MI; Wang, G

Purpose: MRI is a highly desirable modality to guide radiation therapy but it is difficult to combine a conventional MRI scanner directly with a linear accelerator (linac). An interior MRI (iMRI) concept has been proposed to acquire MRI images within a small field of view only covering targets and immediate surrounding tissues. The objective of this project is to design an interior MRI system to work with a linac using a magnet to provide a field around 0.2T in a cube of 20cm per side, and perform image reconstruction with a slightly inhomogeneous static magnetic fields. Methods: All the resultsmore » are simulated using a commercially available software package, FARADY. In our design, a ring structure holds the iMRI system and also imbeds a linac treatment head. The ring is synchronized to the linac gantry rotation. Half of the ring is made of steel and becomes a magnetic flux return path (yoke) so that a strong magnetic field will be limited inside the iron circuit and fringe fields will be very weak. In order to increase the static magnetic field homogeneity, special steel magnet boots or tips were simulated. Three curved boots were designed based on two-dimensional curves: arc, parabola and hyperbola. Results: Different boot surfaces modify magnetic field distributions differently. With the same pair of neodymium-iron-boron (NdFeB) magnets, the magnetic induction at the centers are 0.217T, 0.201T, 0.204T, and 0.212T for flat, arc, parabola and hyperbola boots, respectively. The hyperbola boots lead to the most homogeneous results, the static magnetic field deviations are within 0.5% in a cube of 20cm, and can be further improved using shimming techniques. Conclusion: This study supports the concept of an iMRI design. Successful development of iMRI will provide crucial information for tumor delineation in radiation therapy.« less

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.

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.

Data-Driven Learning of Speech Acts Based on Corpora of DVD Subtitles

ERIC Educational Resources Information Center

Kitao, S. Kathleen; Kitao, Kenji

2013-01-01

Data-driven learning (DDL) is an inductive approach to language learning in which students study examples of authentic language and use them to find patterns of language use. This inductive approach to learning has the advantages of being learner-centered, encouraging hypothesis testing and learner autonomy, and helping develop learning skills.…

Beam-return current systems in solar flares

NASA Technical Reports Server (NTRS)

Spicer, D. S.; Sudan, R. N.

1984-01-01

It is demonstrated that the common assumption made in solar flare beam transport theory that the beam-accompanied return current is purely electrostatically driven is incorrect, and that the return current is both electrostatically and inductively driven, in accordance with Lenz's law, with the inductive effects dominating for times greater than a few plasma periods. In addition, it is shown that a beam can only exist in a solar plasma for a finite time which is much smaller than the inductive return current dissipation time. The importance of accounting for the role of the acceleration mechanism in forming the beam is discussed. In addition, the role of return current driven anomalous resistivity and its subsequent anomalous Joule heating during the flare process is elucidated.

Energy saving concepts relating to induction generators

NASA Technical Reports Server (NTRS)

Nola, F. J.

1980-01-01

Energy saving concepts relating to induction generators are presented. The first describes a regenerative scheme using an induction generator as a variable load for prime movers under test is described. A method for reducing losses in induction machines used specifically as wind driven generators is also described.

Investigation of ISIS and Brookhaven National Laboratory ion source electrodes after extended operation

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

Lettry J.; Alessi J.; Faircloth, D.

2012-02-23

Linac4 accelerator of Centre Europeen de Recherches Nucleaires is under construction and a RF-driven H{sup -} ion source is being developed. The beam current requirement for Linac4 is very challenging: 80 mA must be provided. Cesiated plasma discharge ion sources such as Penning or magnetron sources are also potential candidates. Accelerator ion sources must achieve typical reliability figures of 95% and above. Investigating and understanding the underlying mechanisms involved with source failure or ageing is critical when selecting the ion source technology. Plasma discharge driven surface ion sources rely on molybdenum cathodes. Deformation of the cathode surfaces is visible aftermore » extended operation periods. A metallurgical investigation of an ISIS ion source is presented. The origin of the deformation is twofold: Molybdenum sputtering by cesium ions digs few tenths of mm cavities while a growth of molybdenum is observed in the immediate vicinity. The molybdenum growth under hydrogen atmosphere is hard and loosely bound to the bulk. It is, therefore, likely to peel off and be transported within the plasma volume. The observation of the cathode, anode, and extraction electrodes of the magnetron source operated at BNL for two years are presented. A beam simulation of H{sup -}, electrons, and Cs{sup -} ions was performed with the IBSimu code package to qualitatively explain the observations. This paper describes the operation conditions of the ion sources and discusses the metallurgical analysis and beam simulation results.« less

Investigation of ISIS and Brookhaven National Laboratory ion source electrodes after extended operation

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

Lettry, J.; Gerardin, A.; Pereira, H.

2012-02-15

Linac4 accelerator of Centre Europeen de Recherches Nucleaires is under construction and a RF-driven H{sup -} ion source is being developed. The beam current requirement for Linac4 is very challenging: 80 mA must be provided. Cesiated plasma discharge ion sources such as Penning or magnetron sources are also potential candidates. Accelerator ion sources must achieve typical reliability figures of 95% and above. Investigating and understanding the underlying mechanisms involved with source failure or ageing is critical when selecting the ion source technology. Plasma discharge driven surface ion sources rely on molybdenum cathodes. Deformation of the cathode surfaces is visible aftermore » extended operation periods. A metallurgical investigation of an ISIS ion source is presented. The origin of the deformation is twofold: Molybdenum sputtering by cesium ions digs few tenths of mm cavities while a growth of molybdenum is observed in the immediate vicinity. The molybdenum growth under hydrogen atmosphere is hard and loosely bound to the bulk. It is, therefore, likely to peel off and be transported within the plasma volume. The observation of the cathode, anode, and extraction electrodes of the magnetron source operated at BNL for two years are presented. A beam simulation of H{sup -}, electrons, and Cs{sup -} ions was performed with the IBSimu code package to qualitatively explain the observations. This paper describes the operation conditions of the ion sources and discusses the metallurgical analysis and beam simulation results.« less

An overview of beam diagnostic and control systems for 50 MeV AREAL Linac

NASA Astrophysics Data System (ADS)

Sargsyan, A. A.; Amatuni, G. A.; Sahakyan, V. V.; Zanyan, G. S.; Martirosyan, N. W.; Vardanyan, V. V.; Grigoryan, B. A.

2017-03-01

Advanced Research Electron Accelerator Laboratory (AREAL) is an electron linear accelerator project with a laser driven RF gun being constructed at CANDLE Synchrotron Research Institute. After the successful operation of the gun section at 5 MeV, a program of facility energy enhancement up to 50 MeV is launched. In this paper the current status of existing diagnostic and control systems, as well as the results of electron beam parameter measurements are presented. The approaches of intended diagnostic and control systems for the upgrade program are also described.

Principle and experimental investigation of current-driven negative-inductance superconducting quantum interference device

NASA Astrophysics Data System (ADS)

Li, Hao; Liu, Jianshe; Zhang, Yingshan; Cai, Han; Li, Gang; Liu, Qichun; Han, Siyuan; Chen, Wei

2017-03-01

A negative-inductance superconducting quantum interference device (nSQUID) is an adiabatic superconducting logic device with high energy efficiency, and therefore a promising building block for large-scale low-power superconducting computing. However, the principle of the nSQUID is not that straightforward and an nSQUID driven by voltage is vulnerable to common mode noise. We investigate a single nSQUID driven by current instead of voltage, and clarify the principle of the adiabatic transition of the current-driven nSQUID between different states. The basic logic operations of the current-driven nSQUID with proper parameters are simulated by WRspice. The corresponding circuit is fabricated with a 100 A cm-2 Nb-based lift-off process, and the experimental results at low temperature confirm the basic logic operations as a gated buffer.

Feasibility of an XUV FEL Oscillator Driven by a SCRF Linear Accelerator

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

Lumpkin, A. H.; Freund, H. P.; Reinsch, M.

The Advanced Superconducting Test Accelerator (ASTA) facility is currently under construction at Fermi National Accelerator Laboratory. Using a1-ms-long macropulse composed of up to 3000 micropulses, and with beam energies projected from 45 to 800 MeV, the possibility for an extreme ultraviolet (XUV) free-electron laser oscillator (FELO) with the higher energy is evaluated. We have used both GINGER with an oscillator module and the MEDUSA/OPC code to assess FELO saturation prospects at 120 nm, 40 nm, and 13.4 nm. The results support saturation at all of these wavelengths which are also shorter than the demonstrated shortest wavelength record of 176 nmmore » from a storage-ring-based FELO. This indicates linac-driven FELOs can be extended into this XUV wavelength regime previously only reached with single-pass FEL configurations.« less

Mass sensitivity studies for an inductively driven railgun

NASA Astrophysics Data System (ADS)

Scanlon, J. J., III; Young, A. F.

1991-01-01

Those areas which result in substantial system mass reductions for an HPG (homopolar generator) driven EML (electromagnetic launcher) are identified. Sensitivity studies are performed by varying launch mass, peak acceleration, launcher efficiency, inductance gradient, injection velocity, barrel mass per unit length, fuel tankage and pump estimates, and component energy and power densities. Two major contributors to the system mass are the allowed number of shots per barrel versus the number required for the mission, and the barrel length. The effects of component performance parameters, such as friction coefficient, injection velocity, ablation coefficient, rail resistivity, armature voltage, peak acceleration, and inductance gradient on these two areas, are addressed.

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

Physics design of a 10 MeV injector test stand for an accelerator-driven subcritical system

NASA Astrophysics Data System (ADS)

Yan, Fang; Pei, Shilun; Geng, Huiping; Meng, Cai; Zhao, Yaliang; Sun, Biao; Cheng, Peng; Yang, Zheng; Ouyang, Huafu; Li, Zhihui; Tang, Jingyu; Wang, Jianli; Sui, Yefeng; Dai, Jianping; Sha, Peng; Ge, Rui

2015-05-01

The 10 MeV accelerator-driven subcritical system (ADS) Injector I test stand at Institute of High Energy Physics (IHEP) is a testing facility dedicated to demonstrate one of the two injector design schemes [Injector Scheme-I, which works at 325 MHz], for the ADS project in China. The injector is composed of two parts, the linac part and the beam dump line. The former is designed on the basis of 325 MHz four-vane type copper structure radio frequency quadrupole and superconducting (SC) spoke cavities with β =0.12 . The latter is designed to transport the beam coming out of the SC section of the linac to the beam dump, where the beam transverse profile is fairly enlarged and unformed to simplify the beam target design. The SC section consists of two cryomodules with 14 β =0.12 Spoke cavities, 14 solenoid and 14 BPMs in total. The first challenge in the physics design comes from the necessary space required for the cryomodule separation where the periodical lattice is destroyed at a relatively lower energy of ˜5 MeV . Another challenge is the beam dump line design, as it will be the first beam dump line being built by using a step field magnet for the transverse beam expansion and uniformity in the world. This paper gives an overview of the physics design study together with the design principles and machine construction considerations. The results of an optimized design, fabrication status and end to end simulations including machine errors are presented.

OSIRIS and SOMBRERO Inertial Fusion Power Plant Designs, Volume 2: Designs, Assessments, and Comparisons

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

Meier, W. R.; Bieri, R. L.; Monsler, M. J.

1992-03-01

This is a comprehensive design study of two Inertial Fusion Energy (IFE) electric power plants. Conceptual designs are presented for a fusion reactor (called Osiris) using an induction-linac heavy-ion beam driver, and another (called SOMBRERO) using a KrF laser driver. The designs covered all aspects of IFE power plants, including the chambers, heat transport and power conversion systems, balance-of-plant facilities, target fabrication, target injection and tracking, as well as the heavy-ion and KrF drivers. The point designs were assessed and compared in terms of their environmental & safety aspects, reliability and availability, economics, and technology development needs.

Post-acceleration of laser driven protons with a compact high field linac

NASA Astrophysics Data System (ADS)

Sinigardi, Stefano; Londrillo, Pasquale; Rossi, Francesco; Turchetti, Giorgio; Bolton, Paul R.

2013-05-01

We present a start-to-end 3D numerical simulation of a hybrid scheme for the acceleration of protons. The scheme is based on a first stage laser acceleration, followed by a transport line with a solenoid or a multiplet of quadrupoles, and then a post-acceleration section in a compact linac. Our simulations show that from a laser accelerated proton bunch with energy selection at ~ 30MeV, it is possible to obtain a high quality monochromatic beam of 60MeV with intensity at the threshold of interest for medical use. In the present day experiments using solid targets, the TNSA mechanism describes accelerated bunches with an exponential energy spectrum up to a cut-off value typically below ~ 60MeV and wide angular distribution. At the cut-off energy, the number of protons to be collimated and post-accelerated in a hybrid scheme are still too low. We investigate laser-plasma acceleration to improve the quality and number of the injected protons at ~ 30MeV in order to assure efficient post-acceleration in the hybrid scheme. The results are obtained with 3D PIC simulations using a code where optical acceleration with over-dense targets, transport and post-acceleration in a linac can all be investigated in an integrated framework. The high intensity experiments at Nara are taken as a reference benchmarks for our virtual laboratory. If experimentally confirmed, a hybrid scheme could be the core of a medium sized infrastructure for medical research, capable of producing protons for therapy and x-rays for diagnosis, which complements the development of all optical systems.

Nuclear Methods for Transmutation of Nuclear Waste: Problems, Perspextives, Cooperative Research - Proceedings of the International Workshop

NASA Astrophysics Data System (ADS)

Khankhasayev, Zhanat B.; Kurmanov, Hans; Plendl, Mikhail Kh.

1996-12-01

The Table of Contents for the full book PDF is as follows: * Preface * I. Review of Current Status of Nuclear Transmutation Projects * Accelerator-Driven Systems — Survey of the Research Programs in the World * The Los Alamos Accelerator-Driven Transmutation of Nuclear Waste Concept * Nuclear Waste Transmutation Program in the Czech Republic * Tentative Results of the ISTC Supported Study of the ADTT Plutonium Disposition * Recent Neutron Physics Investigations for the Back End of the Nuclear Fuel Cycle * Optimisation of Accelerator Systems for Transmutation of Nuclear Waste * Proton Linac of the Moscow Meson Factory for the ADTT Experiments * II. Computer Modeling of Nuclear Waste Transmutation Methods and Systems * Transmutation of Minor Actinides in Different Nuclear Facilities * Monte Carlo Modeling of Electro-nuclear Processes with Nonlinear Effects * Simulation of Hybrid Systems with a GEANT Based Program * Computer Study of 90Sr and 137Cs Transmutation by Proton Beam * Methods and Computer Codes for Burn-Up and Fast Transients Calculations in Subcritical Systems with External Sources * New Model of Calculation of Fission Product Yields for the ADTT Problem * Monte Carlo Simulation of Accelerator-Reactor Systems * III. Data Basis for Transmutation of Actinides and Fission Products * Nuclear Data in the Accelerator Driven Transmutation Problem * Nuclear Data to Study Radiation Damage, Activation, and Transmutation of Materials Irradiated by Particles of Intermediate and High Energies * Radium Institute Investigations on the Intermediate Energy Nuclear Data on Hybrid Nuclear Technologies * Nuclear Data Requirements in Intermediate Energy Range for Improvement of Calculations of ADTT Target Processes * IV. Experimental Studies and Projects * ADTT Experiments at the Los Alamos Neutron Science Center * Neutron Multiplicity Distributions for GeV Proton Induced Spallation Reactions on Thin and Thick Targets of Pb and U * Solid State Nuclear Track Detector and Radiochemical Studies on the Transmutation of Nuclei Using Relativistic Heavy Ions * Experimental and Theoretical Study of Radionuclide Production on the Electronuclear Plant Target and Construction Materials Irradiated by 1.5 GeV and 130 MeV Protons * Neutronics and Power Deposition Parameters of the Targets Proposed in the ISTC Project 17 * Multicycle Irradiation of Plutonium in Solid Fuel Heavy-Water Blanket of ADS * Compound Neutron Valve of Accelerator-Driven System Sectioned Blanket * Subcritical Channel-Type Reactor for Weapon Plutonium Utilization * Accelerator Driven Molten-Fluoride Reactor with Modular Heat Exchangers on PB-BI Eutectic * A New Conception of High Power Ion Linac for ADTT * Pions and Accelerator-Driven Transmutation of Nuclear Waste? * V. Problems and Perspectives * Accelerator-Driven Transmutation Technologies for Resolution of Long-Term Nuclear Waste Concerns * Closing the Nuclear Fuel-Cycle and Moving Toward a Sustainable Energy Development * Workshop Summary * List of Participants

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.

Inductive tuners for microwave driven discharge lamps

DOEpatents

Simpson, James E.

1999-01-01

An RF powered electrodeless lamp utilizing an inductive tuner in the waveguide which couples the RF power to the lamp cavity, for reducing reflected RF power and causing the lamp to operate efficiently.

A fully-implicit Particle-In-Cell Monte Carlo Collision code for the simulation of inductively coupled plasmas

NASA Astrophysics Data System (ADS)

Mattei, S.; Nishida, K.; Onai, M.; Lettry, J.; Tran, M. Q.; Hatayama, A.

2017-12-01

We present a fully-implicit electromagnetic Particle-In-Cell Monte Carlo collision code, called NINJA, written for the simulation of inductively coupled plasmas. NINJA employs a kinetic enslaved Jacobian-Free Newton Krylov method to solve self-consistently the interaction between the electromagnetic field generated by the radio-frequency coil and the plasma response. The simulated plasma includes a kinetic description of charged and neutral species as well as the collision processes between them. The algorithm allows simulations with cell sizes much larger than the Debye length and time steps in excess of the Courant-Friedrichs-Lewy condition whilst preserving the conservation of the total energy. The code is applied to the simulation of the plasma discharge of the Linac4 H- ion source at CERN. Simulation results of plasma density, temperature and EEDF are discussed and compared with optical emission spectroscopy measurements. A systematic study of the energy conservation as a function of the numerical parameters is presented.

Improvements on the accuracy of beam bugs

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

Chen, Y.J.; Fessenden, T.

1998-08-17

At LLNL resistive wall monitors are used to measure the current and position used on ETA-II show a droop in signal due to a fast redistribution time constant of the signals. This paper presents the analysis and experimental test of the beam bugs used for beam current and position measurements in and after the fast kicker. It concludes with an outline of present and future changes that can be made to improve the accuracy of these beam bugs. of intense electron beams in electron induction linacs and beam transport lines. These, known locally as ''beam bugs'', have been used throughoutmore » linear induction accelerators as essential diagnostics of beam current and location. Recently, the development of a fast beam kicker has required improvement in the accuracy of measuring the position of beams. By picking off signals at more than the usual four positions around the monitor, beam position measurement error can be greatly reduced. A second significant source of error is the mechanical variation of the resistor around the bug.« less

Improvements on the accuracy of beam bugs

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

Chen, Y J; Fessenden, T

1998-09-02

At LLNL resistive wall monitors are used to measure the current and position used on ETA-II show a droop in signal due to a fast redistribution time constant of the signals. This paper presents the analysis and experimental test of the beam bugs used for beam current and position measurements in and after the fast kicker. It concludes with an outline of present and future changes that can be made to improve the accuracy of these beam bugs. of intense electron beams in electron induction linacs and beam transport lines. These, known locally as "beam bugs", have been used throughoutmore » linear induction accelerators as essential diagnostics of beam current and location. Recently, the development of a fast beam kicker has required improvement in the accuracy of measuring the position of beams. By picking off signals at more than the usual four positions around the monitor, beam position measurement error can be greatly reduced. A second significant source of error is the mechanical variation of the resistor around the bug.« less

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.

Practice and Policy to Enhance Student Induction and Transition: A Case Study of Institution-Wide Change

ERIC Educational Resources Information Center

Alsford, Sally; Rose, Christine

2014-01-01

This case study gives an analytical account of institutional development in induction provision. Driven by student experience concerns, a London post-1992 University set up an "enhanced induction project" to provide a more integrated, personalised approach through more coordinated processes. In a large, diverse context, university-wide…

Injector Beam Dynamics for a High-Repetition Rate 4th-Generation Light Source

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

Papadopoulos, C. F.; Corlett, J.; Emma, P.

2013-05-20

We report on the beam dynamics studies and optimization methods for a high repetition rate (1 MHz) photoinjector based on a VHF normal conducting electron source. The simultaneous goals of beamcompression and reservation of 6-dimensional beam brightness have to be achieved in the injector, in order to accommodate a linac driven FEL light source. For this, a parallel, multiobjective optimization algorithm is used. We discuss the relative merits of different injector design points, as well as the constraints imposed on the beam dynamics by technical considerations such as the high repetition rate.

Compensating effect of the coherent synchrotron radiation in bunch compressors

NASA Astrophysics Data System (ADS)

Jing, Yichao; Hao, Yue; Litvinenko, Vladimir N.

2013-06-01

Typical bunch compression for a high-gain free-electron laser (FEL) requires a large compression ratio. Frequently, this compression is distributed in multiple stages along the beam transport line. However, for a high-gain FEL driven by an energy recovery linac (ERL), compression must be accomplished in a single strong compressor located at the beam line’s end; otherwise the electron beam would be affected severely by coherent synchrotron radiation (CSR) in the ERL’s arcs. In such a scheme, the CSR originating from the strong compressors could greatly degrade the quality of the electron beam. In this paper, we present our design for a bunch compressor that will limit the effect of CSR on the e-beam’s quality. We discuss our findings from a study of such a compressor, and detail its potential for an FEL driven by a multipass ERL developed for the electron-Relativistic Heavy Ion Collider.

FLASH free-electron laser single-shot temporal diagnostic: terahertz-field-driven streaking.

PubMed

Ivanov, Rosen; Liu, Jia; Brenner, Günter; Brachmanski, Maciej; Düsterer, Stefan

2018-01-01

The commissioning of a terahertz-field-driven streak camera installed at the free-electron laser (FEL) FLASH at DESY in Hamburg, being able to deliver photon pulse duration as well as arrival time information with ∼10 fs resolution for each single XUV FEL pulse, is reported. Pulse durations between 300 fs and <15 fs have been measured for different FLASH FEL settings. A comparison between the XUV pulse arrival time and the FEL electron bunch arrival time measured at the FLASH linac section exhibits a correlation width of 20 fs r.m.s., thus demonstrating the excellent operation stability of FLASH. In addition, the terahertz-streaking setup was operated simultaneously to an alternative method to determine the FEL pulse duration based on spectral analysis. FLASH pulse duration derived from simple spectral analysis is in good agreement with that from terahertz-streaking measurement.

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

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

Free electron lasers driven by linear induction accelerators: High power radiation sources

NASA Technical Reports Server (NTRS)

Orzechowski, T. J.

1989-01-01

The technology of Free Electron Lasers (FELs) and linear induction accelerators (LIAs) is addressed by outlining the following topics: fundamentals of FELs; basic concepts of linear induction accelerators; the Electron Laser Facility (a microwave FEL); PALADIN (an infrared FEL); magnetic switching; IMP; and future directions (relativistic klystrons). This presentation is represented by viewgraphs only.

Study of Collective Beam Effects in Energy Recovery Linac Driven Free Electron Lasers

NASA Astrophysics Data System (ADS)

Hall, Christpher C.

Collective beam effects such as coherent synchrotron radiation (CSR) and longitudinal space charge (LSC) can degrade the quality of high-energy electron beams used for applications such as free-electron lasers (FELs). The advent of energy recovery linac (ERL)-based FELs brings exciting possibilities for very high-average current FELs that can operate with greater efficiency. However, due to the structure of ERLs, they may be even more susceptible to CSR. It is therefore necessary that these collective beam effects be well understood if future ERL-based designs are to be successful. The Jefferson Laboratory ERL driven IR FEL provides an ideal test-bed for looking at how CSR impacts the electron beam. Due to its novel design we can easily test how CSR's impact on the beam varies as a function of compression within the machine. In this work we will look at measurements of both average energy loss and energy spectrum fragmentation as a function of bunch compression. These results are compared to particle tracking simulations including a 1D CSR model and, in general, good agreement is seen between simulation and measurement. Of particular interest is fragmentation of the energy spectrum that is observed due to CSR and LSC. We will also show how this fragmentation develops and how it can be mitigated through use of the sextupoles in the JLab FEL. Finally, a more complete 2D model is used to simulate CSR-beam interaction. Due to the parameters of the experiment it is expected that a 2D CSR model would yield different results than the 1D CSR model. However, excellent agreement is seen between the two CSR model results.

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.

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

Advanced Compton scattering light source R&D at LLNL

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

Albert, F; Anderson, S G; Anderson, G

2010-02-16

We report the design and current status of a monoenergetic laser-based Compton scattering 0.5-2.5 MeV {gamma}-ray source. Previous nuclear resonance fluorescence results and future linac and laser developments for the source are presented. At MeV photon energies relevant for nuclear processes, Compton scattering light sources are attractive because of their relative compactness and improved brightness above 100 keV, compared to typical 4th generation synchrotrons. Recent progress in accelerator physics and laser technology have enabled the development of a new class of tunable Mono-Energetic Gamma-Ray (MEGa-Ray) light sources based on Compton scattering between a high-brightness, relativistic electron beam and a highmore » intensity laser pulse produced via chirped-pulse amplification (CPA). A new precision, tunable gamma-ray source driven by a compact, high-gradient X-band linac is currently under development and construction at LLNL. High-brightness, relativistic electron bunches produced by an X-band linac designed in collaboration with SLAC will interact with a Joule-class, 10 ps, diode-pumped CPA laser pulse to generate tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range via Compton scattering. Based on the success of the previous Thomson-Radiated Extreme X-rays (T-REX) Compton scattering source at LLNL, the source will be used to excite nuclear resonance fluorescence lines in various isotopes; applications include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. After a brief presentation of successful nuclear resonance fluorescence (NRF) experiments done with T-REX, the new source design, key parameters, and current status are presented.« less

Reactive Power Compensating System.

DOEpatents

Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.

1985-01-04

The circuit was designed for the specific application of wind-driven induction generators. It has great potential for application in any situation where a varying reactive power load is present, such as with induction motors or generators, or for transmission network compensation.

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

Overtaking collision effects in a cw double-pass proton linac

DOE PAGES

Tao, Yue; Qiang, Ji; Hwang, Kilean

2017-12-22

The recirculating superconducting proton linac has the advantage of reducing the number of cavities in the accelerator and the corresponding construction and operational costs. Beam dynamics simulations were done recently in a double-pass recirculating proton linac using a single proton beam bunch. For continuous wave (cw) operation, the high-energy proton bunch during the second pass through the linac will overtake and collide with the low-energy bunch during the first pass at a number of locations of the linac. These collisions might cause proton bunch emittance growth and beam quality degradation. Here, we study the collisional effects due to Coulomb space-chargemore » forces between the high-energy bunch and the low-energy bunch. Our results suggest that these effects on the proton beam quality would be small and might not cause significant emittance growth or beam blowup through the linac. A 10 mA, 500 MeV cw double-pass proton linac is feasible without using extra hardware for phase synchronization.« less

Overtaking collision effects in a cw double-pass proton linac

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

Tao, Yue; Qiang, Ji; Hwang, Kilean

The recirculating superconducting proton linac has the advantage of reducing the number of cavities in the accelerator and the corresponding construction and operational costs. Beam dynamics simulations were done recently in a double-pass recirculating proton linac using a single proton beam bunch. For continuous wave (cw) operation, the high-energy proton bunch during the second pass through the linac will overtake and collide with the low-energy bunch during the first pass at a number of locations of the linac. These collisions might cause proton bunch emittance growth and beam quality degradation. Here, we study the collisional effects due to Coulomb space-chargemore » forces between the high-energy bunch and the low-energy bunch. Our results suggest that these effects on the proton beam quality would be small and might not cause significant emittance growth or beam blowup through the linac. A 10 mA, 500 MeV cw double-pass proton linac is feasible without using extra hardware for phase synchronization.« 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.

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

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.

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.

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.

Laser Cooling for Heavy-Ion Fusion (HIF)

NASA Astrophysics Data System (ADS)

Ho, D. D.-M.; Brandon, S.; Lee, Y.

1997-05-01

A critical requirement for HIF is the ability to focus space-charge dominated beams onto a millimeter-size spot. However, chromatic aberration can result in a substantial fraction of the beam ions falling outside the spot radius. Because of the space-charge force, correcting the chromatic aberration using sextupoles is impractical. Success in laser cooling of low-current ion beams in storage rings leads us to explore the application of laser cooling to HIF. Basic scheme: After the beams have been accelerated to the desired energy by the recirculating induction linac, we let the beams coast around at constant energy. For efficient interaction between the laser and the beam ions, we use Ba+ beams. We use two lasers to pump the transitions in the Ba+ for generating the laser force FL. There is also an auxiliary force Fa, which is in the opposition direction of FL, provided by the induction cores. The momentum spread along the beam can be compressed by FL and Fa. We will present preliminary PIC simulations using the PIC code CONDOR. Potential difficulties caused by velocity space instabilities will be discussed.

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

High-explosive driven crowbar switch

DOEpatents

Dike, Robert S.; Kewish, Jr., Ralph W.

1976-01-13

The disclosure relates to a compact explosive driven switch for use as a low resistance, low inductance crowbar switch. A high-explosive charge extrudes a deformable conductive metallic plate through a polyethylene insulating layer to achieve a hard current contact with a supportive annular conductor.

Energy partitioning in an inductively driven rail gun

NASA Technical Reports Server (NTRS)

Sen, K. K.; Ray, P. K.

1984-01-01

The equations describing the performance of an inductively driven rail are analyzed numerically. Friction between the projectile and rails is included through an empirical formulation. The equations are applied to the experiment of Rashleigh and Marshall to obtain an estimate of energy distribution in rail guns as a function of time. It is found that only 15 percent of energy delivered by the inductor to the gun is transformed into the kinetic energy of the projectile. This study provides an insight into the nature of nonlinear coupling involved in the electromechanical interactions in a rail gun.

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.

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

Design and Calibration of an RF Actuator for Low-Level RF Systems

NASA Astrophysics Data System (ADS)

Geng, Zheqiao; Hong, Bo

2016-02-01

X-ray free electron laser (FEL) machines like the Linac Coherent Light Source (LCLS) at SLAC require high-quality electron beams to generate X-ray lasers for various experiments. Digital low-level RF (LLRF) systems are widely used to control the high-power RF klystrons to provide a highly stable RF field in accelerator structures for beam acceleration. Feedback and feedforward controllers are implemented in LLRF systems to stabilize or adjust the phase and amplitude of the RF field. To achieve the RF stability and the accuracy of the phase and amplitude adjustment, low-noise and highly linear RF actuators are required. Aiming for the upgrade of the S-band Linac at SLAC, an RF actuator is designed with an I/Qmodulator driven by two digital-to-analog converters (DAC) for the digital LLRF systems. A direct upconversion scheme is selected for RF actuation, and an on-line calibration algorithm is developed to compensate the RF reference leakage and the imbalance errors in the I/Q modulator, which may cause significant phase and amplitude actuation errors. This paper presents the requirements on the RF actuator, the design of the hardware, the calibration algorithm, and the implementation in firmware and software and the test results at LCLS.

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.

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.

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.

Radiobiological effectiveness of laser accelerated electrons in comparison to electron beams from a conventional linear accelerator.

PubMed

Laschinsky, Lydia; Baumann, Michael; Beyreuther, Elke; Enghardt, Wolfgang; Kaluza, Malte; Karsch, Leonhard; Lessmann, Elisabeth; Naumburger, Doreen; Nicolai, Maria; Richter, Christian; Sauerbrey, Roland; Schlenvoigt, Hans-Peter; Pawelke, Jörg

2012-01-01

The notable progress in laser particle acceleration technology promises potential medical application in cancer therapy through compact and cost effective laser devices that are suitable for already existing clinics. Previously, consequences on the radiobiological response by laser driven particle beams characterised by an ultra high peak dose rate have to be investigated. Therefore, tumour and non-malignant cells were irradiated with pulsed laser accelerated electrons at the JETI facility for the comparison with continuous electrons of a conventional therapy LINAC. Dose response curves were measured for the biological endpoints clonogenic survival and residual DNA double strand breaks. The overall results show no significant differences in radiobiological response for in vitro cell experiments between laser accelerated pulsed and clinical used electron beams. These first systematic in vitro cell response studies with precise dosimetry to laser driven electron beams represent a first step toward the long term aim of the application of laser accelerated particles in radiotherapy.

1.5-GW S-band relativistic klystron amplifier

NASA Astrophysics Data System (ADS)

Ferguson, Patrick E.

1992-04-01

There is a strong symbiotic relationship between a developing technology and its applications. New technologies can generate applications previously either unrealizable or impractical. Conversely, applications can demand the development of new technological capability. Examples of both types of development can be found in the evolution of HPM. The high power and energy output made possible by HPM have created a technology driven interest in directed energy weapons and short pulse radar. On the other hand, the requirements for heating of fusion plasmas have resulted in an application driven program to develop high average power microwave devices. In this paper we address these and other applications such as RF electron linacs, laser pumping, and beaming of power. Emerging applications, such as ionispheric modification and environmental cleanup, are also touched upon. The approach of this paper will be to review each application separately and then compare the requirements of the applications in terms of the power, frequency and other key requirements necessary for HPM to usefully address the application.

Development of fundamental power coupler for C-ADS superconducting elliptical cavities

NASA Astrophysics Data System (ADS)

Gu, Kui-Xiang; Bing, Feng; Pan, Wei-Min; Huang, Tong-Ming; Ma, Qiang; Meng, Fan-Bo

2017-06-01

5-cell elliptical cavities have been selected for the main linac of the China Accelerator Driven sub-critical System (C-ADS) in the medium energy section. According to the design, each cavity should be driven with radio frequency (RF) energy up to 150 kW by a fundamental power coupler (FPC). As the cavities work with high quality factor and high accelerating gradient, the coupler should keep the cavity from contamination in the assembly procedure. To fulfil the requirements, a single-window coaxial type coupler was designed with the capabilities of handling high RF power, class 10 clean room assembly, and heat load control. This paper presents the coupler design and gives details of RF design, heat load optimization and thermal analysis as well as multipacting simulations. In addition, a primary high power test has been performed and is described in this paper. Supported by China ADS Project (XDA03020000) and National Natural Science Foundation of China (11475203)

Beam dynamics study of a 30 MeV electron linear accelerator to drive a neutron source

NASA Astrophysics Data System (ADS)

Kumar, Sandeep; Yang, Haeryong; Kang, Heung-Sik

2014-02-01

An experimental neutron facility based on 32 MeV/18.47 kW electron linac has been studied by means of PARMELA simulation code. Beam dynamics study for a traveling wave constant gradient electron accelerator is carried out to reach the preferential operation parameters (E = 30 MeV, P = 18 kW, dE/E < 12.47% for 99% particles). The whole linac comprises mainly E-gun, pre-buncher, buncher, and 2 accelerating columns. A disk-loaded, on-axis-coupled, 2π/3-mode type accelerating rf cavity is considered for this linac. After numerous optimizations of linac parameters, 32 MeV beam energy is obtained at the end of the linac. As high electron energy is required to produce acceptable neutron flux. The final neutron flux is estimated to be 5 × 1011 n/cm2/s/mA. Future development will be the real design of a 30 MeV electron linac based on S band traveling wave.

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.

Low-energy beam transport studies supporting the spallation neutron source 1-MW beam operation.

PubMed

Han, B X; Kalvas, T; Tarvainen, O; Welton, R F; Murray, S N; Pennisi, T R; Santana, M; Stockli, M P

2012-02-01

The H(-) injector consisting of a cesium enhanced RF-driven ion source and a 2-lens electrostatic low-energy beam transport (LEBT) system supports the spallation neutron source 1 MW beam operation with ∼38 mA beam current in the linac at 60 Hz with a pulse length of up to ∼1.0 ms. In this work, two important issues associated with the low-energy beam transport are discussed: (1) inconsistent dependence of the post-radio frequency quadrupole accelerator beam current on the ion source tilt angle and (2) high power beam losses on the LEBT electrodes under some off-nominal conditions compromising their reliability.

Simulations of inertial confinement fusion driven by a novel synchrotron-radiation-based x-ray igniter

NASA Astrophysics Data System (ADS)

Shlyaptsev, Vyacheslav N.; Tatchyn, Roman O.

2004-01-01

The advantages and challenges of using a powerful x-ray source for the fast ignition of compressed Inertial Confinement Fusion (ICF) targets have been considered. The requirements for such a source together with the optics to focus the x-rays onto compressed DT cores lead to a conceptual design based on Energy Recovery Linacs (ERLs) and long wigglers to produce x-ray pulses with the appropriate phase space properties. A comparative assessment of the parameters of the igniter system indicates that the technologies for building it, although expensive, are physically achievable. Our x-ray fast ignition (XFI) scheme requires substantially smaller energy for the initiation of nuclear fusion reactions than other methods.

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).

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.

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

Process simulations for the LCLS-II cryogenic systems

NASA Astrophysics Data System (ADS)

Ravindranath, V.; Bai, H.; Heloin, V.; Fauve, E.; Pflueckhahn, D.; Peterson, T.; Arenius, D.; Bevins, M.; Scanlon, C.; Than, R.; Hays, G.; Ross, M.

2017-12-01

Linac Coherent Light Source II (LCLS-II), a 4 GeV continuous-wave (CW) superconducting electron linear accelerator, is to be constructed in the existing two mile Linac facility at the SLAC National Accelerator Laboratory. The first light from the new facility is scheduled to be in 2020. The LCLS-II Linac consists of thirty-five 1.3 GHz and two 3.9 GHz superconducting cryomodules. The Linac cryomodules require cryogenic cooling for the super-conducting niobium cavities at 2.0 K, low temperature thermal intercept at 5.5-7.5 K, and a thermal shield at 35-55 K. The equivalent 4.5 K refrigeration capacity needed for the Linac operations range from a minimum of 11 kW to a maximum of 24 kW. Two cryogenic plants with 18 kW of equivalent 4.5 K refrigeration capacity will be used for supporting the Linac cryogenic cooling requirements. The cryogenic plants are based on the Jefferson Lab’s CHL-II cryogenic plant design which uses the “Floating Pressure” design to support a wide variation in the cooling load. In this paper, the cryogenic process for the integrated LCLS-II cryogenic system and the process simulation for a 4.5 K cryoplant in combination with a 2 K cold compressor box, and the Linac cryomodules are described.

High dose-per-pulse electron beam dosimetry: Usability and dose-rate independence of EBT3 Gafchromic films.

PubMed

Jaccard, Maud; Petersson, Kristoffer; Buchillier, Thierry; Germond, Jean-François; Durán, Maria Teresa; Vozenin, Marie-Catherine; Bourhis, Jean; Bochud, François O; Bailat, Claude

2017-02-01

The aim of this study was to assess the suitability of Gafchromic EBT3 films for reference dose measurements in the beam of a prototype high dose-per-pulse linear accelerator (linac), capable of delivering electron beams with a mean dose-rate (Ḋ m ) ranging from 0.07 to 3000 Gy/s and a dose-rate in pulse (Ḋ p ) of up to 8 × 10 6 Gy/s. To do this, we evaluated the overall uncertainties in EBT3 film dosimetry as well as the energy and dose-rate dependence of their response. Our dosimetric system was composed of EBT3 Gafchromic films in combination with a flatbed scanner and was calibrated against an ionization chamber traceable to primary standard. All sources of uncertainties in EBT3 dosimetry were carefully analyzed using irradiations at a clinical radiotherapy linac. Energy dependence was investigated with the same machine by acquiring and comparing calibration curves for three different beam energies (4, 8 and 12 MeV), for doses between 0.25 and 30 Gy. Ḋ m dependence was studied at the clinical linac by changing the pulse repetition frequency (f) of the beam in order to vary Ḋ m between 0.55 and 4.40 Gy/min, while Ḋ p dependence was probed at the prototype machine for Ḋ p ranging from 7 × 10 3 to 8 × 10 6 Gy/s. Ḋ p dependence was first determined by studying the correlation between the dose measured by films and the charge of electrons measured at the exit of the machine by an induction torus. Furthermore, we compared doses from the films to independently calibrated thermo-luminescent dosimeters (TLD) that have been reported as being dose-rate independent up to such high dose-rates. We report that uncertainty below 4% (k = 2) can be achieved in the dose range between 3 and 17 Gy. Results also demonstrated that EBT3 films did not display any detectable energy dependence for electron beam energies between 4 and 12 MeV. No Ḋ m dependence was found either. In addition, we obtained excellent consistency between films and TLDs over the entire Ḋ p range attainable at the prototype linac confirming the absence of any dose-rate dependence within the investigated range (7 × 10 3 to 8 × 10 6 Gy/s). This aspect was further corroborated by the linear relationship between the dose-per-pulse (D p ) measured by films and the charge per pulse (C p ) measured at the prototype linac exit. Our study shows that the use of EBT3 Gafchromic films can be extended to reference dosimetry in pulsed electron beams with a very high dose rate. The measurement results are associated with an overall uncertainty below 4% (k = 2) and are dose-rate and energy independent. © 2016 American Association of Physicists in Medicine.

Kinetic modeling of x-ray laser-driven solid Al plasmas via particle-in-cell simulation

NASA Astrophysics Data System (ADS)

Royle, R.; Sentoku, Y.; Mancini, R. C.; Paraschiv, I.; Johzaki, T.

2017-06-01

Solid-density plasmas driven by intense x-ray free-electron laser (XFEL) radiation are seeded by sources of nonthermal photoelectrons and Auger electrons that ionize and heat the target via collisions. Simulation codes that are commonly used to model such plasmas, such as collisional-radiative (CR) codes, typically assume a Maxwellian distribution and thus instantaneous thermalization of the source electrons. In this study, we present a detailed description and initial applications of a collisional particle-in-cell code, picls, that has been extended with a self-consistent radiation transport model and Monte Carlo models for photoionization and K L L Auger ionization, enabling the fully kinetic simulation of XFEL-driven plasmas. The code is used to simulate two experiments previously performed at the Linac Coherent Light Source investigating XFEL-driven solid-density Al plasmas. It is shown that picls-simulated pulse transmissions using the Ecker-Kröll continuum-lowering model agree much better with measurements than do simulations using the Stewart-Pyatt model. Good quantitative agreement is also found between the time-dependent picls results and those of analogous simulations by the CR code scfly, which was used in the analysis of the experiments to accurately reproduce the observed K α emissions and pulse transmissions. Finally, it is shown that the effects of the nonthermal electrons are negligible for the conditions of the particular experiments under investigation.

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

Efficiency optimization of class-D biomedical inductive wireless power transfer systems by means of frequency adjustment.

PubMed

Schormans, Matthew; Valente, Virgilio; Demosthenous, Andreas

2015-01-01

Inductive powering for implanted medical devices is a commonly employed technique, that allows for implants to avoid more dangerous methods such as the use of transcutaneous wires or implanted batteries. However, wireless powering in this way also comes with a number of difficulties and conflicting requirements, which are often met by using designs based on compromise. In particular, one aspect common to most inductive power links is that they are driven with a fixed frequency, which may not be optimal depending on factors such as coupling and load. In this paper, a method is proposed in which an inductive power link is driven by a frequency that is maintained at an optimum value f(opt), to ensure that the link is in resonance. In order to maintain this resonance, a phase tracking technique is employed at the primary side of the link; this allows for compensation of changes in coil separation and load. The technique is shown to provide significant improvements in maintained secondary voltage and efficiency for a range of loads when the link is overcoupled.

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.

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

Three-dimensional particle simulation of heavy-ion fusion beams

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

Friedman, A.; Grote, D.P.; Haber, I.

1992-07-01

The beams in a heavy-ion-beam-driven inertial fusion (HIF) accelerator are collisionless, nonneutral plasmas, confined by applied magnetic and electric fields. These space-charge-dominated beams must be focused onto small (few mm) spots at the fusion target, and so preservation of a small emittance is crucial. The nonlinear beam self-fields can lead to emittance growth, and so a self-consistent field description is needed. To this end, a multidimensional particle simulation code, WARP (Friedman {ital et} {ital al}., Part. Accel. {bold 37}-{bold 38}, 131 (1992)), has been developed and is being used to study the transport of HIF beams. The code's three-dimensional (3-D)more » package combines features of an accelerator code and a particle-in-cell plasma simulation. Novel techniques allow it to follow beams through many accelerator elements over long distances and around bends. This paper first outlines the algorithms employed in WARP. A number of applications and corresponding results are then presented. These applications include studies of: beam drift-compression in a misaligned lattice of quadrupole focusing magnets; beam equilibria, and the approach to equilibrium; and the MBE-4 experiment ({ital AIP} {ital Conference} {ital Proceedings} 152 (AIP, New York, 1986), p. 145) recently concluded at Lawrence Berkeley Laboratory (LBL). Finally, 3-D simulations of bent-beam dynamics relevant to the planned Induction Linac Systems Experiments (ILSE) (Fessenden, Nucl. Instrum. Methods Plasma Res. A {bold 278}, 13 (1989)) at LBL are described. Axially cold beams are observed to exhibit little or no root-mean-square emittance growth at midpulse in transiting a (sharp) bend. Axially hot beams, in contrast, do exhibit some emittance growth.« 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.

Design and experiments of RF transverse focusing in S-Band, 1 MeV standing wave linac

NASA Astrophysics Data System (ADS)

Mondal, J.; Chandan, Shiv; Parashar, S.; Bhattacharjee, D.; Tillu, A. R.; Tiwari, R.; Jayapraksh, D.; Yadav, V.; Banerjee, S.; Choudhury, N.; Ghodke, S. R.; Dixit, K. P.; Nimje, V. T.

2015-09-01

S-Band standing wave (SW) linacs in the range of 1-10 MeV have many potential industrial applications world wide. In order to mitigate the industrial requirement it is required to reduce the overall size and weight of the system. On this context a 2856 M Hz, 1 Me V, bi-periodic on axis coupled self transverse focused SW linac has been designed and tested. The RF phase focusing is achieved by introducing an asymmetric field distribution in the first cell of the 1 MeV linac. The pulsed electron beam of 40 keV, 650 mA and 5 μs duration is injected from a LaB6 thermionic gun. This paper presents the structure design, beam dynamics simulation, fabrication and experimental results of the 1 MeV auto-focusing SW linac.

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

Fourth Generation Light Sources

NASA Astrophysics Data System (ADS)

Winick, Herman

1997-05-01

Concepts and designs are now being developed at laboratories around the world for light sources with performance levels that exceed present sources, including the very powerful and successful third generation synchrotron radiation sources that have come on line in the past few years. Workshops (M. Cornacchia and H. Winick (eds), Workshop on Fourth Generation Light Sources, Feb. 24-27, 1992, SSRL Report 92/02) (J.-L. Laclare (ed), ICFA Workshop on Fourth Generation Light Sources, Jan. 22-25, 1996, ESRF Report) have been held to review directions for future sources. A main thrust is to increase the brightness and coherence of the radiation using storage rings with lower electron-beam emittance or free-electron lasers (FELs). In the infra-red part of the spectrum very high brightness and coherence is already provided by FEL user facilities driven by linacs and storage rings. It now appears possible to extend FEL operation to the VUV, soft X-ray and even hard X-ray spectral range, to wavelengths down to the angstrom range, using high energy linacs equipped with high-brightness rf photoinjectors and bunch-length compressors. R&D to develop such sources is in progress at BNL, DESY, KEK, SLAC and other laboratories. In the absence of mirrors to form optical cavities, short wavelengths are reached in FEL systems in which a high peak current, low-emittance electron beam becomes bunch-density modulated at the optical wavelength in a single pass through a long undulator by self-amplified spontaneous emission (SASE); i.e.; startup from noise. A proposal to use the last kilometer of the three kilometer SLAC linac (the first two kilometers will be used for injection to the PEP II B-Factory) to provide 15 GeV electron beams to reach 1.5 Angstroms by SASE in a 100 m long undulator is in preparation.

Aerospace induction motor actuators driven from a 20-kHz power link

NASA Technical Reports Server (NTRS)

Hansen, Irving G.

1990-01-01

Aerospace electromechanical actuators utilizing induction motors are under development in sizes up to 40 kW. While these actuators have immediate application to the Advanced Launch System (ALS) program, several potential applications are currently under study including the Advanced Aircraft Program. Several recent advances developed for the Space Station Freedom have allowed induction motors to be selected as a first choice for such applications. Among these technologies are bi-directional electronics and high frequency power distribution techniques. Each of these technologies are discussed with emphasis on their impact upon induction motor operation.

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.

Applications of the Strategic Defense Initiative's compact accelerators

NASA Technical Reports Server (NTRS)

Montanarelli, Nick; Lynch, Ted

1991-01-01

The Strategic Defense Initiative's (SDI) investment in particle accelerator technology for its directed energy weapons program has produced breakthroughs in the size and power of new accelerators. These accelerators, in turn, have produced spinoffs in several areas: the radio frequency quadrupole linear accelerator (RFQ linac) was recently incorporated into the design of a cancer therapy unit at the Loma Linda University Medical Center, an SDI-sponsored compact induction linear accelerator may replace Cobalt-60 radiation and hazardous ethylene-oxide as a method for sterilizing medical products, and other SDIO-funded accelerators may be used to produce the radioactive isotopes oxygen-15, nitrogen-13, carbon-11, and fluorine-18 for positron emission tomography (PET). Other applications of these accelerators include bomb detection, non-destructive inspection, decomposing toxic substances in contaminated ground water, and eliminating nuclear waste.

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.

Development and evaluation of yeast-based GFP and luciferase reporter assays for chemical-induced genotoxicity and oxidative damage.

PubMed

Suzuki, Hajime; Sakabe, Takahiro; Hirose, Yuu; Eki, Toshihiko

2017-01-01

We aimed to develop the bioassays for genotixicity and/or oxidative damage using the recombinant yeast. A genotoxicity assay was developed using recombinant Saccharomyces cerevisiae strain BY4741 with a green fluorescent protein (GFP) reporter plasmid, driven by the DNA damage-responsive RNR3 promoter. Enhanced fluorescence induction was observed in DNA repair-deficient strains treated with methyl methanesulfonate, but not with hydrogen peroxide. A GFP reporter yeast strain driven by the oxidative stress-responsive TRX2 promoter was newly developed to assess oxidative damage, but fluorescence was poorly induced by oxidants. In place of GFP, yeast strains with luciferase gene reporter plasmids (luc2 and luc2CP, encoding stable and unstable luciferase, respectively) were prepared. Transient induction of luciferase activity was clearly detected only in a TRX2 promoter-driven luc2CP reporter strain within 90 min of oxidant exposure. However, luciferase was strongly induced by hydroxyurea in the RNR3 promoter-driven luc2 and GFP reporter strains over 8 h after the exposure, suggesting that the RNR3 promoter is continuously upregulated by DNA damage, whereas the TRX2 promoter is transiently activated by oxidative agents. Luciferase activity levels were also increased in a TRX2-promoter-driven luc2CP reporter strain treated with tert-butyl hydroperoxide and menadione and weakly induced with diamide and diethyl maleate. Weakly enhanced luciferase activity induction was detected in the sod1Δ, sod2Δ, and rad27Δ strains treated with hydrogen peroxide compared with that in the wild-type strain. In conclusion, tests using GFP and stable luciferase reporters are useful for genotoxicity, and oxidative damage can be clearly detected by assay with an unstable luciferase reporter.

Unlearning Overgenerated "Be" through Data-Driven Learning in the Secondary EFL Classroom

ERIC Educational Resources Information Center

Moon, Soyeon; Oh, Sun-Young

2018-01-01

This paper reports on the cognitive and affective benefits of data-driven learning (DDL), in which Korean EFL learners at the secondary level notice and unlearn their "overgenerated 'be'" by comparing native English-speaker and learner corpora with guided induction. To select the target language item and compile learner-corpus-based…

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.

Non-inductive current driven by Alfvén waves in solar coronal loops

NASA Astrophysics Data System (ADS)

Elfimov, A. G.; de Azevedo, C. A.; de Assis, A. S.

1996-08-01

It has been shown that Alfvén waves can drive non-inductive current in solar coronal loops via collisional or collisionless damping. Assuming that all the coronal-loop density of dissipated wave power (W= 10-3 erg cm-3 s-1), which is necessary to keep the plasma hot, is due to Alfvén wave electron heating, we have estimated the axial current density driven by Alfvén waves to be ≈ 103 105 statA cm-2. This current can indeed support the quasi-stationary equilibrium and stability of coronal loops and create the poloidal magnetic field up to B θ≈1-5 G.

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.

Biodosimetry of heavy ions by interphase chromosome painting

NASA Astrophysics Data System (ADS)

Durante, M.; Kawata, T.; Nakano, T.; Yamada, S.; Tsujii, H.

1998-11-01

We report measurements of chromosomal aberrations in peripheral blood lymphocytes from cancer patients undergoing radiotherapy treatment. Patients with cervix or esophageal cancer were treated with 10 MV X-rays produced at a LINAC accelerator, or high-energy carbon ions produced at the HIMAC accelerator at the National Institute for Radiological Sciences (NIRS) in Chiba. Blood samples were obtained before, during, and after the radiation treatment. Chromosomes were prematurely condensed by incubation in calyculin A. Aberrations in chromosomes 2 and 4 were scored after fluorescence in situ hybridization with whole-chromosome probes. Pre-treatment samples were exposed in vitro to X-rays, individual dose-response curves for the induction of chromosomal aberrations were determined, and used as calibration curves to calculate the effective whole-body dose absorbed during the treatment. This calculated dose, based on the calibration curve relative to the induction of reciprocal exchanges, has a sharp increase after the first few fractions of the treatment, then saturates at high doses. Although carbon ions are 2-3 times more effective than X-rays in tumor sterilization, the effective dose was similar to that of X-ray treatment. However, the frequency of complex-type chromosomal exchanges was much higher for patients treated with carbon ions than X-ray.

Numerical simulation of electromagnetic fields and impedance of CERN LINAC4 H(-) source taking into account the effect of the plasma.

PubMed

Grudiev, A; Lettry, J; Mattei, S; Paoluzzi, M; Scrivens, R

2014-02-01

Numerical simulation of the CERN LINAC4 H(-) source 2 MHz RF system has been performed taking into account a realistic geometry from 3D Computer Aided Design model using commercial FEM high frequency simulation code. The effect of the plasma has been added to the model by the approximation of a homogenous electrically conducting medium. Electric and magnetic fields, RF power losses, and impedance of the circuit have been calculated for different values of the plasma conductivity. Three different regimes have been found depending on the plasma conductivity: (1) Zero or low plasma conductivity results in RF electric field induced by the RF antenna being mainly capacitive and has axial direction; (2) Intermediate conductivity results in the expulsion of capacitive electric field from plasma and the RF power coupling, which is increasing linearly with the plasma conductivity, is mainly dominated by the inductive azimuthal electric field; (3) High conductivity results in the shielding of both the electric and magnetic fields from plasma due to the skin effect, which reduces RF power coupling to plasma. From these simulations and measurements of the RF power coupling on the CERN source, a value of the plasma conductivity has been derived. It agrees well with an analytical estimate calculated from the measured plasma parameters. In addition, the simulated and measured impedances with and without plasma show very good agreement as well demonstrating validity of the plasma model used in the RF simulations.

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.

The Fusion Gain Analysis of the Inductively Driven Liner Compression Based Fusion

NASA Astrophysics Data System (ADS)

Shimazu, Akihisa; Slough, John

2016-10-01

An analytical analysis of the fusion gain expected in the inductively driven liner compression (IDLC) based fusion is conducted to identify the fusion gain scaling at various operating conditions. The fusion based on the IDLC is a magneto-inertial fusion concept, where a Field-Reversed Configuration (FRC) plasmoid is compressed via the inductively-driven metal liner to drive the FRC to fusion conditions. In the past, an approximate scaling law for the expected fusion gain for the IDLC based fusion was obtained under the key assumptions of (1) D-T fuel at 5-40 keV, (2) adiabatic scaling laws for the FRC dynamics, (3) FRC energy dominated by the pressure balance with the edge magnetic field at the peak compression, and (4) the liner dwell time being liner final diameter divided by the peak liner velocity. In this study, various assumptions made in the previous derivation is relaxed to study the change in the fusion gain scaling from the previous result of G ml1 / 2 El11 / 8 , where ml is the liner mass and El is the peak liner kinetic energy. The implication from the modified fusion gain scaling on the performance of the IDLC fusion reactor system is also explored.

PV Array Driven Adjustable Speed Drive for a Lunar Base Heat Pump

NASA Technical Reports Server (NTRS)

Domijan, Alexander, Jr.; Buchh, Tariq Aslam

1995-01-01

A study of various aspects of Adjustable Speed Drives (ASD) is presented. A summary of the relative merits of different ASD systems presently in vogue is discussed. The advantages of using microcomputer based ASDs is now widely understood and accepted. Of the three most popular drive systems, namely the Induction Motor Drive, Switched Reluctance Motor Drive and Brushless DC Motor Drive, any one may be chosen. The choice would depend on the nature of the application and its requirements. The suitability of the above mentioned drive systems for a photovoltaic array driven ASD for an aerospace application are discussed. The discussion is based on the experience of the authors, various researchers and industry. In chapter 2 a PV array power supply scheme has been proposed, this scheme will have an enhanced reliability in addition to the other known advantages of the case where a stand alone PV array is feeding the heat pump. In chapter 3 the results of computer simulation of PV array driven induction motor drive system have been included. A discussion on these preliminary simulation results have also been included in this chapter. Chapter 4 includes a brief discussion on various control techniques for three phase induction motors. A discussion on different power devices and their various performance characteristics is given in Chapter 5.

Tuner control system of Spoke012 SRF cavity for C-ADS injector I

NASA Astrophysics Data System (ADS)

Liu, Na; Sun, Yi; Wang, Guang-Wei; Mi, Zheng-Hui; Lin, Hai-Ying; Wang, Qun-Yao; Liu, Rong; Ma, Xin-Peng

2016-09-01

A new tuner control system for spoke superconducting radio frequency (SRF) cavities has been developed and applied to cryomodule I of the C-ADS injector I at the Institute of High Energy Physics, Chinese Academy of Sciences. We have successfully implemented the tuner controller based on Programmable Logic Controller (PLC) for the first time and achieved a cavity tuning phase error of ±0.7° (about ±4 Hz peak to peak) in the presence of electromechanical coupled resonance. This paper presents preliminary experimental results based on the PLC tuner controller under proton beam commissioning. Supported by Proton linac accelerator I of China Accelerator Driven sub-critical System (Y12C32W129)

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.

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.

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

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

Designs and Plans for MAIZE: a 1 MA LTD-Driven Z-Pinch

NASA Astrophysics Data System (ADS)

Gilgenbach, R. M.; Gomez, M. R.; Zier, J.; Tang, W.; French, D. M.; Hoff, B. W.; Jordan, N.; Cruz, E.; Lau, Y. Y.; Fowler-Guzzardo, T.; Meisel, J.; Mazarakis, M. G.; Cuneo, M. E.; Johnston, M. D.; Mehlhorn, T. A.; Kim, A. A.; Sinebryukhov, V. A.

2007-11-01

We present designs and experimental plans of the first 1 MA z-pinch in the USA to be driven by a Linear Transformer Driver (LTD). The Michigan Accelerator for Inductive Z-pinch Experiments, (MAIZE), is based on the LTD developed at the Institute for High Current Electronics, utilizing 80 capacitors and 40 spark gap switches to deliver a 1 MA, 100 kV pulse with <100 ns risetime. Designs will be presented of a low-inductance MITL terminated in a wire-array z-pinch. Initial, planned experiments will evaluate the LTD driving time-changing inductance of imploding 4-16 wire-array z-pinches. Wire ablation dynamics, axial-correlations and instability development will be explored. *This work was supported by U. S. DoE through Sandia National Laboratories award number 240985 to the University of Michigan. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Simultaneous integrated boost therapy of carcinoma of the hypopharynx/larynx with and without flattening filter - a treatment planning and dosimetry study.

PubMed

Dobler, Barbara; Obermeier, Tina; Hautmann, Matthias G; Khemissi, Amine; Koelbl, Oliver

2017-07-05

The aim of this study was to investigate if the flattening filter free (FFF) irradiation mode of a linear accelerator (linac) is advantageous as compared to the flat beam (FF) irradiation mode in intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for carcinoma of the hypopharynx / larynx. Four treatment plans were created for each of 10 patients for an Elekta Synergy linac with Agility collimating device, a dual arc VMAT and a nine field step and shoot IMRT each with and without flattening filter. Plan quality was compared considering target coverage and dose to the organs at risk. All plans were verified by a 2D-ionization-chamber-array and delivery times were compared. Peripheral point doses were determined as a measure of second cancer risk. The Wilcoxon test was used for statistical analysis with a significance level of 0.05. Plan quality was similar for all four treatment plans without statistically significant differences of clinical relevance. The clinical goals were met in all plans for the PTV-SIB (V 95%  > 95%), the spinal cord (D 1ccm  < 45 Gy) and the brain stem (D 1ccm  < 48 Gy). For the parotids, the goal of D 50%  < 30 Gy was met in 70% and 60% of the plans for the left and right parotid respectively, and the V 95% of the SIB reached an average of 94%. Delivery times were similar for FF and FFF and significantly decreased by around 70% for VMAT as compared to IMRT. Peripheral doses were significantly reduced by 18% in FFF mode as compared to FF and by 26% for VMAT as compared to IMRT. Lowest peripheral doses were found for VMAT FFF, followed by VMAT FF. The FFF mode of a linear accelerator is advantageous for the treatment of hypopharynx/larynx carcinoma only with respect to reduction of second cancer induction in peripheral organs for the combination of Elekta Synergy linacs and Oncentra® External Beam v4.5 treatment planning system. This might be of interest in a therapy with curative intent.

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.

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.

A beamline systems model for Accelerator-Driven Transmutation Technology (ADTT) facilities

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

Todd, A.M.M.; Paulson, C.C.; Peacock, M.A.

1995-10-01

A beamline systems code, that is being developed for Accelerator-Driven Transmutation Technology (ADTT) facility trade studies, is described. The overall program is a joint Grumman, G.H. Gillespie Associates (GHGA) and Los Alamos National Laboratory effort. The GHGA Accelerator Systems Model (ASM) has been adopted as the framework on which this effort is based. Relevant accelerator and beam transport models from earlier Grumman systems codes are being adapted to this framework. Preliminary physics and engineering models for each ADTT beamline component have been constructed. Examples noted include a Bridge Coupled Drift Tube Linac (BCDTL) and the accelerator thermal system. A decisionmore » has been made to confine the ASM framework principally to beamline modeling, while detailed target/blanket, balance-of-plant and facility costing analysis will be performed externally. An interfacing external balance-of-plant and facility costing model, which will permit the performance of iterative facility trade studies, is under separate development. An ABC (Accelerator Based Conversion) example is used to highlight the present models and capabilities.« less

A beamline systems model for Accelerator-Driven Transmutation Technology (ADTT) facilities

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

Todd, Alan M. M.; Paulson, C. C.; Peacock, M. A.

1995-09-15

A beamline systems code, that is being developed for Accelerator-Driven Transmutation Technology (ADTT) facility trade studies, is described. The overall program is a joint Grumman, G. H. Gillespie Associates (GHGA) and Los Alamos National Laboratory effort. The GHGA Accelerator Systems Model (ASM) has been adopted as the framework on which this effort is based. Relevant accelerator and beam transport models from earlier Grumman systems codes are being adapted to this framework. Preliminary physics and engineering models for each ADTT beamline component have been constructed. Examples noted include a Bridge Coupled Drift Tube Linac (BCDTL) and the accelerator thermal system. Amore » decision has been made to confine the ASM framework principally to beamline modeling, while detailed target/blanket, balance-of-plant and facility costing analysis will be performed externally. An interfacing external balance-of-plant and facility costing model, which will permit the performance of iterative facility trade studies, is under separate development. An ABC (Accelerator Based Conversion) example is used to highlight the present models and capabilities.« less

Reversible beam heater for suppression of microbunching instability by transverse gradient undulators

NASA Astrophysics Data System (ADS)

Liu, Tao; Qin, Weilun; Wang, Dong; Huang, Zhirong

2017-08-01

The microbunching instability driven by beam collective effects in a linear accelerator of a free-electron laser (FEL) facility significantly degrades the electron beam quality and FEL performance. A conventional method to suppress this instability is to introduce an additional uncorrelated energy spread by laser-electron interaction, which has been successfully operated in the Linac Coherent Light Source and Fermi@Elettra, etc. Some other ideas are recently proposed to suppress the instability without increasing energy spread, which could benefit the seeded FEL schemes. In this paper, we propose a reversible electron beam heater using two transverse gradient undulators to suppress the microbunching instability. This scheme introduces both an energy spread increase and a transverse-to-longitudinal phase space coupling, which suppress the microbunching instabilities driven by both longitudinal space charge and coherent synchrotron radiation before and within the system. Finally the induced energy spread increase and emittance growth are reversed. Theoretical analysis and numerical simulations are presented to verify the feasibility of the scheme and indicate the capability to improve the seeded FEL radiation performance.

Reversible beam heater for suppression of microbunching instability by transverse gradient undulators

DOE PAGES

Liu, Tao; Qin, Weilun; Wang, Dong; ...

2017-08-02

The microbunching instability driven by beam collective effects in a linear accelerator of a free-electron laser (FEL) facility significantly degrades the electron beam quality and FEL performance. A conventional method to suppress this instability is to introduce an additional uncorrelated energy spread by laser-electron interaction, which has been successfully operated in the Linac Coherent Light Source and Fermi@Elettra, etc. Some other ideas are recently proposed to suppress the instability without increasing energy spread, which could benefit the seeded FEL schemes. In this paper, we propose a reversible electron beam heater using two transverse gradient undulators to suppress the microbunching instability.more » This scheme introduces both an energy spread increase and a transverse-to-longitudinal phase space coupling, which suppress the microbunching instabilities driven by both longitudinal space charge and coherent synchrotron radiation before and within the system. Finally the induced energy spread increase and emittance growth are reversed. In conclusion, theoretical analysis and numerical simulations are presented to verify the feasibility of the scheme and indicate the capability to improve the seeded FEL radiation performance.« less

rf improvements for Spallation Neutron Source H- ion sourcea)

NASA Astrophysics Data System (ADS)

Kang, Y. W.; Fuja, R.; Goulding, R. H.; Hardek, T.; Lee, S.-W.; McCarthy, M. P.; Piller, M. C.; Shin, K.; Stockli, M. P.; Welton, R. F.

2010-02-01

The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering ˜38 mA H- beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

rf improvements for Spallation Neutron Source H- ion source.

PubMed

Kang, Y W; Fuja, R; Goulding, R H; Hardek, T; Lee, S-W; McCarthy, M P; Piller, M C; Shin, K; Stockli, M P; Welton, R F

2010-02-01

The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering approximately 38 mA H(-) beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

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.

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

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.

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.

Resonant excitation of high order modes in the 3.9 GHz cavity of the Linac Coherent Light Source

DOE PAGES

Lunin, A.; Khabiboulline, T.; Solyak, N.; ...

2018-02-06

Construction of the Linac Coherent Light Source II (LCLS-II) is underway for the world’s first hard x-ray free-electron laser. A central part of the LCLS-II project is a 4 GeV superconducting radio frequency electron linac that will operate in the continuous wave (cw) mode. The linac is segmented into four sections named as L0, L1, L2, and L3. Two 3.9 GHz cryomodules, each housing of eight third-harmonic cavities similar to the cavities developed for the European X-ray Free Electron Laser (XFEL), will be used in section L1 of the linac for linearizing the longitudinal beam profile. Here in this paper, we presentmore » a study of trapped high order modes (HOMs) excited by a cw electron beam in the third-harmonic cavities of the LCLS-II linac. A detailed comparison of the original XFEL design and the LCLS-II design with a modified end group is performed in order to estimate the effect of a reduced beam pipe aperture on the efficiency of HOM damping. Furthermore, we apply a statistical analysis of the eigenmode spectrum for the estimation of the probability of resonant HOM losses and influence of HOMs on beam dynamics.« less

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.

Resonant excitation of high order modes in the 3.9 GHz cavity of the Linac Coherent Light Source

NASA Astrophysics Data System (ADS)

Lunin, A.; Khabiboulline, T.; Solyak, N.; Sukhanov, A.; Yakovlev, V.

2018-02-01

Construction of the Linac Coherent Light Source II (LCLS-II) is underway for the world's first hard x-ray free-electron laser. A central part of the LCLS-II project is a 4 GeV superconducting radio frequency electron linac that will operate in the continuous wave (cw) mode. The linac is segmented into four sections named as L 0 , L 1 , L 2 , and L 3 . Two 3.9 GHz cryomodules, each housing of eight third-harmonic cavities similar to the cavities developed for the European X-ray Free Electron Laser (XFEL), will be used in section L 1 of the linac for linearizing the longitudinal beam profile. In this paper, we present a study of trapped high order modes (HOMs) excited by a cw electron beam in the third-harmonic cavities of the LCLS-II linac. A detailed comparison of the original XFEL design and the LCLS-II design with a modified end group is performed in order to estimate the effect of a reduced beam pipe aperture on the efficiency of HOM damping. Furthermore, we apply a statistical analysis of the eigenmode spectrum for the estimation of the probability of resonant HOM losses and influence of HOMs on beam dynamics.

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

No Evidence That Gratitude Enhances Neural Performance Monitoring or Conflict-Driven Control

PubMed Central

Saunders, Blair; He, Frank F. H.; Inzlicht, Michael

2015-01-01

It has recently been suggested that gratitude can benefit self-regulation by reducing impulsivity during economic decision making. We tested if comparable benefits of gratitude are observed for neural performance monitoring and conflict-driven self-control. In a pre-post design, 61 participants were randomly assigned to either a gratitude or happiness condition, and then performed a pre-induction flanker task. Subsequently, participants recalled an autobiographical event where they had felt grateful or happy, followed by a post-induction flanker task. Despite closely following existing protocols, participants in the gratitude condition did not report elevated gratefulness compared to the happy group. In regard to self-control, we found no association between gratitude—operationalized by experimental condition or as a continuous predictor—and any control metric, including flanker interference, post-error adjustments, or neural monitoring (the error-related negativity, ERN). Thus, while gratitude might increase economic patience, such benefits may not generalize to conflict-driven control processes. PMID:26633830

No Evidence That Gratitude Enhances Neural Performance Monitoring or Conflict-Driven Control.

PubMed

Saunders, Blair; He, Frank F H; Inzlicht, Michael

2015-01-01

It has recently been suggested that gratitude can benefit self-regulation by reducing impulsivity during economic decision making. We tested if comparable benefits of gratitude are observed for neural performance monitoring and conflict-driven self-control. In a pre-post design, 61 participants were randomly assigned to either a gratitude or happiness condition, and then performed a pre-induction flanker task. Subsequently, participants recalled an autobiographical event where they had felt grateful or happy, followed by a post-induction flanker task. Despite closely following existing protocols, participants in the gratitude condition did not report elevated gratefulness compared to the happy group. In regard to self-control, we found no association between gratitude--operationalized by experimental condition or as a continuous predictor--and any control metric, including flanker interference, post-error adjustments, or neural monitoring (the error-related negativity, ERN). Thus, while gratitude might increase economic patience, such benefits may not generalize to conflict-driven control processes.

Simplifying Causal Complexity: How Interactions between Modes of Causal Induction and Information Availability Lead to Heuristic-Driven Reasoning

ERIC Educational Resources Information Center

Grotzer, Tina A.; Tutwiler, M. Shane

2014-01-01

This article considers a set of well-researched default assumptions that people make in reasoning about complex causality and argues that, in part, they result from the forms of causal induction that we engage in and the type of information available in complex environments. It considers how information often falls outside our attentional frame…

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

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

Data-Intensive Science Meets Inquiry-Driven Pedagogy: Interactive Big Data Exploration, Threshold Concepts, and Liminality

NASA Astrophysics Data System (ADS)

Ramachandran, R.; Nair, U. S.; Word, A.

2014-12-01

Threshold concepts in any discipline are the core concepts an individual must understand in order to master a discipline. By their very nature, these concepts are troublesome, irreversible, integrative, bounded, discursive, and reconstitutive. Although grasping threshold concepts can be extremely challenging for each learner as s/he moves through stages of cognitive development relative to a given discipline, the learner's grasp of these concepts determines the extent to which s/he is prepared to work competently and creatively within the field itself. The movement of individuals from a state of ignorance of these core concepts to one of mastery occurs not along a linear path but in iterative cycles of knowledge creation and adjustment in liminal spaces - conceptual spaces through which learners move from the vaguest awareness of concepts to mastery, accompanied by understanding of their relevance, connectivity, and usefulness relative to questions and constructs in a given discipline. With the explosive growth of data available in atmospheric science, driven largely by satellite Earth observations and high-resolution numerical simulations, paradigms such as that of data-intensive science have emerged. These paradigm shifts are based on the growing realization that current infrastructure, tools and processes will not allow us to analyze and fully utilize the complex and voluminous data that is being gathered. In this emerging paradigm, the scientific discovery process is driven by knowledge extracted from large volumes of data. In this presentation, we contend that this paradigm naturally lends to inquiry-driven pedagogy where knowledge is discovered through inductive engagement with large volumes of data rather than reached through traditional, deductive, hypothesis-driven analyses. In particular, data-intensive techniques married with an inductive methodology allow for exploration on a scale that is not possible in the traditional classroom with its typical problem sets and static, limited data samples. In addition, we identify existing gaps and possible solutions for addressing the infrastructure and tools as well as a pedagogical framework through which to implement this inductive approach.

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.

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 ...

OVERVIEW OF MONO-ENERGETIC GAMMA-RAY SOURCES & APPLICATIONS

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

Hartemann, F V; Albert, F; Anderson, G G

2010-05-18

Recent progress in accelerator physics and laser technology have enabled the development of a new class of tunable gamma-ray light sources based on Compton scattering between a high-brightness, relativistic electron beam and a high intensity laser pulse produced via chirped-pulse amplification (CPA). A precision, tunable Mono-Energetic Gamma-ray (MEGa-ray) source driven by a compact, high-gradient X-band linac is currently under development and construction at LLNL. High-brightness, relativistic electron bunches produced by an X-band linac designed in collaboration with SLAC NAL will interact with a Joule-class, 10 ps, diode-pumped CPA laser pulse to generate tunable {gamma}-rays in the 0.5-2.5 MeV photon energymore » range via Compton scattering. This MEGa-ray source will be used to excite nuclear resonance fluorescence in various isotopes. Applications include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. The source design, key parameters, and current status are presented, along with important applications, including nuclear resonance fluorescence. In conclusion, we have optimized the design of a high brightness Compton scattering gamma-ray source, specifically designed for NRF applications. Two different parameters sets have been considered: one where the number of photons scattered in a single shot reaches approximately 7.5 x 10{sup 8}, with a focal spot size around 8 {micro}m; in the second set, the spectral brightness is optimized by using a 20 {micro}m spot size, with 0.2% relative bandwidth.« less

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

Research and development toward a 4.5-1.5 Å linac coherent light source (LCLS) at SLAC

NASA Astrophysics Data System (ADS)

Tatchyn, R.; Arthur, J.; Baltay, M.; Bane, K.; Boyce, R.; Cornacchia, M.; Cremer, T.; Fisher, A.; Hahn, S.-J.; Hernandez, M.; Loew, G.; Miller, R.; Nelson, W. R.; Nuhn, H.-D.; Palmer, D.; Paterson, J.; Raubenheimer, T.; Weaver, J.; Wiedemann, H.; Winick, H.; Pellegrini, C.; Travish, G.; Scharlemann, E. T.; Caspi, S.; Fawley, W.; Halbach, K.; Kim, K.-J.; Schlueter, R.; Xie, M.; Meyerhofer, D.; Bonifacio, R.; De Salvo, L.

1996-02-01

In recent years significant studies have been initiated on the feasibility of utilizing a portion of the 3 km S-band accelerator at SLAC to drive a short wavelength (4.5-1.5 Å) Linac Coherent Light Source (LCLS), a Free-Electron Laser (FEL) operating in the Self-Amplified Spontaneous Emission (SASE) regime. Electron beam requirements for single-pass saturation in a minimal time include: 1) a peak current in the 7 kA range, 2) a relative energy spread of <0.05%, and 3) a transverse emittance, ɛ [rad-m], approximating the diffraction-limit condition ɛ = {λ}/{4π}, where λ[m] is the output wavelength. Requirements on the insertion device include field error levels of 0.02% for keeping the electron bunch centered on and in phase with the amplified photons, and a focusing beta of 8 m/rad for inhibiting the dilution of its transverse density. Although much progress has been made in developing individual components and beam-processing techniques necessary for LCLS operation down to ˜20 Å, a substantial amount of research and development is still required in a number of theoretical and experimental areas leading to the construction and operation of a 4.5-1.5 Å LCLS. In this paper we report on a research and development program underway and in planning at SLAC for addressing critical questions in these areas. These include the construction and operation of a linac test stand for developing laser-driven photocathode rf guns with normalized emittances approaching 1 mm-mrad; development of advanced beam compression, stability, and emittance control techniques at multi-GeV energies; the construction and operation of a FEL Amplifier Test Experiment (FATE) for theoretical and experimental studies of SASE at IR wavelengths; an undulator development program to investigate superconducting, hybrid/permanent magnet (hybrid/PM), and pulsed-Cu technologies; theoretical and computational studies of high-gain FEL physics and LCLS component designs; development of X-ray optics and instrumentation for extracting, modulating, and delivering photons to experimental users; and the study and development of scientific experiments made possible by the source properties of the LCLS.

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

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.

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

Schlossberg, David J.; Bodner, Grant M.; Bongard, Michael W.

This public data set contains openly-documented, machine readable digital research data corresponding to figures published in D.J. Schlossberg et al., 'Non-Inductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta,' Phys. Rev. Lett. 119, 035001 (2017).

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.

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.

Composite synchronization of three eccentric rotors driven by induction motors in a vibrating system

NASA Astrophysics Data System (ADS)

Kong, Xiangxi; Chen, Changzheng; Wen, Bangchun

2018-03-01

This paper addresses the problem of composite synchronization of three eccentric rotors (ERs) driven by induction motors in a vibrating system. The composite synchronous motion of three ERs is composed of the controlled synchronous motion of two ERs and the self-synchronous motion of the third ER. Combining an adaptive sliding mode control (ASMC) algorithm with a modified master-slave control structure, the controllers are designed to implement controlled synchronous motion of two ERs with zero phase difference. Based on Lyapunov stability theorem and Barbalat's lemma, the stability of the designed controllers is verified. On basis of controlled synchronization of two ERs, self-synchronization of the third ER is introduced to implement composite synchronous motion of three ERs. The feasibility of the proposed composite synchronization method is analyzed by numerical method. The effects of motor and structure parameters on composite synchronous motion are discussed. Experiments on a vibrating test bench driven by three ERs are operated to validate the effectiveness of the proposed composite synchronization method, including a comparison with self-synchronization method.

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.

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.

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

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.

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.

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.

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.

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.

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.

Fuzzy inductive reasoning: a consolidated approach to data-driven construction of complex dynamical systems

NASA Astrophysics Data System (ADS)

Nebot, Àngela; Mugica, Francisco

2012-10-01

Fuzzy inductive reasoning (FIR) is a modelling and simulation methodology derived from the General Systems Problem Solver. It compares favourably with other soft computing methodologies, such as neural networks, genetic or neuro-fuzzy systems, and with hard computing methodologies, such as AR, ARIMA, or NARMAX, when it is used to predict future behaviour of different kinds of systems. This paper contains an overview of the FIR methodology, its historical background, and its evolution.

Experimental observation of the inductive electric field and related plasma nonuniformity in high frequency capacitive discharge

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

Ahn, S. K.; Chang, H. Y.

To elucidate plasma nonuniformity in high frequency capacitive discharges, Langmuir probe and B-dot probe measurements were carried out in the radial direction in a cylindrical capacitive discharge driven at 90 MHz with argon pressures of 50 and 400 mTorr. Through the measurements, a significant inductive electric field (i.e., time-varying magnetic field) was observed at the radial edge, and it was found that the inductive electric field creates strong plasma nonuniformity at high pressure operation. The plasma nonuniformity at high pressure operation is physically similar to the E-H mode transition typically observed in inductive discharges. This result agrees well with themore » theories of electromagnetic effects in large area and/or high frequency capacitive discharges.« less

Modernization of gas-turbine engines with high-frequency induction motors

NASA Astrophysics Data System (ADS)

Abramovich, B. N.; Sychev, Yu A.; Kuznetsov, P. A.

2018-03-01

Main tendencies of growth of electric energy consumption in general and mining industries were analyzed in the paper. A key role of electric drive in this process was designated. A review about advantages and disadvantages of unregulated gearboxes with mechanical units that are commonly used in domestically produced gas-turbine engines was made. This review allows one to propose different gas-turbine engines modernization schemes with the help of PWM-driven high-frequency induction motors. Induction motors with the double rotor winding were examined. A simulation of high-frequency induction motors with double rotor windings in Matlab-Simulink software was carried out based on equivalent circuit parameters. Obtained characteristics of new motors were compared with serially produced analogues. After the simulation, results were implemented in the real prototype.

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

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.

High resolution x-ray Thomson scattering measurements from cryogenic hydrogen jets using the linac coherent light source

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

Fletcher, L. B., E-mail: lbfletch@slac.stanford.edu; Galtier, E.; Gamboa, E. J.

2016-11-15

We present the first spectrally resolved measurements of x-rays scattered from cryogenic hydrogen jets in the single photon counting limit. The 120 Hz capabilities of the LCLS, together with a novel hydrogen jet design [J. B. Kim et al., Rev. Sci. Instrum. (these proceedings)], allow for the ability to record a near background free spectrum. Such high-dynamic-range x-ray scattering measurements enable a platform to study ultra-fast, laser-driven, heating dynamics of hydrogen plasmas. This measurement has been achieved using two highly annealed pyrolytic graphite crystal spectrometers to spectrally resolve 5.5 keV x-rays elastically and inelastically scattered from cryogenic hydrogen and focusedmore » on Cornell-SLAC pixel array detectors [S. Herrmann et al., Nucl. Instrum. Methods Phys. Res., Sect. A 718, 550 (2013)].« less

How similar are recognition memory and inductive reasoning?

PubMed

Hayes, Brett K; Heit, Evan

2013-07-01

Conventionally, memory and reasoning are seen as different types of cognitive activities driven by different processes. In two experiments, we challenged this view by examining the relationship between recognition memory and inductive reasoning involving multiple forms of similarity. A common study set (members of a conjunctive category) was followed by a test set containing old and new category members, as well as items that matched the study set on only one dimension. The study and test sets were presented under recognition or induction instructions. In Experiments 1 and 2, the inductive property being generalized was varied in order to direct attention to different dimensions of similarity. When there was no time pressure on decisions, patterns of positive responding were strongly affected by property type, indicating that different types of similarity were driving recognition and induction. By comparison, speeded judgments showed weaker property effects and could be explained by generalization based on overall similarity. An exemplar model, GEN-EX (GENeralization from EXamples), could account for both the induction and recognition data. These findings show that induction and recognition share core component processes, even when the tasks involve flexible forms of similarity.

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.

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.

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.

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.

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

Present developments and status of electron sources for high power gyrotron tubes and free electron masers

NASA Astrophysics Data System (ADS)

Thumm, M.

1997-02-01

Gyrotron oscillators are mainly used as high power mm-wave sources for start-up, electron cyclotron heating (ECH) and diagnostics of magnetically confined plasmas for controlled thermonuclear fusion research. 140 GHz (110 GHz) gyrotrons with output power Pout = 0.55 MW (0.93 MW), pulse length τ = 3.0 s (2.0 s) and efficiency η = 40% (38%) are commercially available. Total efficiencies around 50% have been achieved using single-stage depressed collectors. Diagnostic gyrotrons deliver Pout = 40 kW with τ = 40 μs at frequencies up to 650 GHz ( η≥4%). Recently, gyrotron oscillators have also been successfully used in materials processing, for example sintering of high performance, structural and functional ceramics. Such technological applications require gyrotrons with f≥24 GHz, Pout = 10-100 kW, CW, η≥30%. This paper reports on recent achievements in the development of very high power mm-wave gyrotron oscillators for long pulse or CW operation. In addition a short overview of the present development status of gyrotrons for technological applications, gyroklystron amplifiers, gyro-TWT amplifiers, cyclotron autoresonance masers (CARMs) and free electron masers (FEMs) is given. The most impressive FEM output parameters are: Pout = 2GW, τ = 20 ns, η = 13% at 140 GHz (LLNL) and Pout = 15 kW, τ = 20 μs, η = 5% in the range from 120 to 900 GHz (UCSB). In gyro-devices, magnetron injection guns (MIGs) operating in the temperature limited current regime have thus far been used most successfully. Diode guns as well as triode guns with a modulating anode are employed. Tests of a MIG operated under space-charge limited conditions have been not very successful. Electrostatic CW FEMs are driven by thermionic Pierce guns whereas pulsed high power devices employ many types of accelerators as drivers for example pulse-line accelerators, microtrons and induction or rf linacs, using field and photo emission cathodes.

Coaxial Helicity Injection experiments in NSTX*

NASA Astrophysics Data System (ADS)

Raman, R.; Jarboe, T. R.; Gates, D.; Mueller, D.; Schaffer, M. J.; Maqueda, R.; Nelson, B. A.; Menard, J.; Soukhanovskii, V.; Paul, S.; Jardin, S.; Skinner, C. H.; Sabbagh, S.; Paoletti, F.; Stutman, D.; Lao, L.; Nagata, M.

2001-10-01

Coaxial helicity injection (CHI) can potentially eliminate inductive startup and thus the induction solenoid in spherical tori (ST), thereby greatly improving the ST fusion concept. CHI experiments on NSTX have produced 360 kA of toroidal current using about 25 kA of injector current. These have been produced in the preferred 'narrow flux foot print' condition in pulses that were sustained for 300 ms. A rotating n=1 mode, previously observed in optimized discharges on smaller STs driven by CHI and deemed necessary for transporting edge driven current to the interior of the discharge, has been observed for the first time in NSTX CHI discharges. The flux utilization efficiency continues to be high, approaching 100%. EFIT and TSC codes are being used to assess flux closure. This work is supported by the US DOE contract numbers: DE-AC02-76CH03073 and DE-AC05-00R22725.

Using a theory-driven conceptual framework in qualitative health research.

PubMed

Macfarlane, Anne; O'Reilly-de Brún, Mary

2012-05-01

The role and merits of highly inductive research designs in qualitative health research are well established, and there has been a powerful proliferation of grounded theory method in the field. However, tight qualitative research designs informed by social theory can be useful to sensitize researchers to concepts and processes that they might not necessarily identify through inductive processes. In this article, we provide a reflexive account of our experience of using a theory-driven conceptual framework, the Normalization Process Model, in a qualitative evaluation of general practitioners' uptake of a free, pilot, language interpreting service in the Republic of Ireland. We reflect on our decisions about whether or not to use the Model, and describe our actual use of it to inform research questions, sampling, coding, and data analysis. We conclude with reflections on the added value that the Model and tight design brought to our research.

Dynamic Performance of Subway Vehicle with Linear Induction Motor System

NASA Astrophysics Data System (ADS)

Wu, Pingbo; Luo, Ren; Hu, Yan; Zeng, Jing

The light rail vehicle with Linear Induction Motor (LIM) bogie, which is a new type of urban rail traffic tool, has the advantages of low costs, wide applicability, low noise, simple maintenance and better dynamic behavior. This kind of vehicle, supported and guided by the wheel and rail, is not driven by the wheel/rail adhesion force, but driven by the electromagnetic force between LIM and reaction plate. In this paper, three different types of suspensions and their characteristic are discussed with considering the interactions both between wheel and rail and between LIM and reaction plate. A nonlinear mathematical model of the vehicle with LIM bogie is set up by using the software SIMPACK, and the electromechanical model is also set up on Simulink roof. Then the running behavior of the LIM vehicle is simulated, and the influence of suspension on the vehicle dynamic performance is investigated.

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.

Inductive detection of fieldlike and dampinglike ac inverse spin-orbit torques in ferromagnet/normal-metal bilayers

NASA Astrophysics Data System (ADS)

Berger, Andrew J.; Edwards, Eric R. J.; Nembach, Hans T.; Karenowska, Alexy D.; Weiler, Mathias; Silva, Thomas J.

2018-03-01

Functional spintronic devices rely on spin-charge interconversion effects, such as the reciprocal processes of electric field-driven spin torque and magnetization dynamics-driven spin and charge flow. Both dampinglike and fieldlike spin-orbit torques have been observed in the forward process of current-driven spin torque and dampinglike inverse spin-orbit torque has been well studied via spin pumping into heavy metal layers. Here, we demonstrate that established microwave transmission spectroscopy of ferromagnet/normal metal bilayers under ferromagnetic resonance can be used to inductively detect the ac charge currents driven by the inverse spin-charge conversion processes. This technique relies on vector network analyzer ferromagnetic resonance (VNA-FMR) measurements. We show that in addition to the commonly extracted spectroscopic information, VNA-FMR measurements can be used to quantify the magnitude and phase of all ac charge currents in the sample, including those due to spin pumping and spin-charge conversion. Our findings reveal that Ni80Fe20/Pt bilayers exhibit both dampinglike and fieldlike inverse spin-orbit torques. While the magnitudes of both the dampinglike and fieldlike inverse spin-orbit torque are of comparable scale to prior reported values for similar material systems, we observed a significant dependence of the dampinglike magnitude on the order of deposition. This suggests interface quality plays an important role in the overall strength of the dampinglike spin-to-charge conversion.

Inductive storage for quasi-steady MPD thrusters

NASA Technical Reports Server (NTRS)

Clark, K. E.

1978-01-01

Experiments in which a quasi-steady MPD thruster is driven by a large inductor demonstrate the feasibility of using inductive energy storage to couple an intermittent high power plasma thruster to a lower power steady state supply, such as a thermionic converter. Switching between inductor charging and MPD thrusting phases of the current cycle occurs smoothly, with the voltage spike generated during switching sufficient to initiate the arc discharge in the thruster without an auxiliary starting circuit. Further, the current waveforms delivered by the inductor are of a shape suitable for the quasi-steady thrusting process, and they agree with analytical estimates, indicating that the interaction between the thruster impedance and the inductive source is dynamically stable.

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.

An Efficient Fuzzy Controller Design for Parallel Connected Induction Motor Drives

NASA Astrophysics Data System (ADS)

Usha, S.; Subramani, C.

2018-04-01

Generally, an induction motors are highly non-linear and has a complex time varying dynamics. This makes the speed control of an induction motor a challenging issue in the industries. But, due to the recent trends in the power electronic devices and intelligent controllers, the speed control of the induction motor is achieved by including non-linear characteristics also. Conventionally a single inverter is used to run one induction motor in industries. In the traction applications, two or more inductions motors are operated in parallel to reduce the size and cost of induction motors. In this application, the parallel connected induction motors can be driven by a single inverter unit. The stability problems may introduce in the parallel operation under low speed operating conditions. Hence, the speed deviations should be reduce with help of suitable controllers. The speed control of the parallel connected system is performed by PID controller and fuzzy logic controller. In this paper the speed response of the induction motor for the rating of IHP, 1440 rpm, and 50Hz with these controller are compared in time domain specifications. The stability analysis of the system also performed under low speed using matlab platform. The hardware model is developed for speed control using fuzzy logic controller which exhibited superior performances over the other controller.

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.

A superconducting CW-LINAC for heavy ion acceleration at GSI

NASA Astrophysics Data System (ADS)

Barth, Winfried; Aulenbacher, Kurt; Basten, Markus; Dziuba, Florian; Gettmann, Viktor; Miski-Oglu, Maksym; Podlech, Holger; Yaramyshev, Stepan

2017-03-01

Recently the Universal Linear Accelerator (UNILAC) serves as a powerful high duty factor (25%) heavy ion beam accelerator for the ambitious experiment program at GSI. Beam time availability for SHE (Super Heavy Element)-research will be decreased due to the limitation of the UNILAC providing Uranium beams with an extremely high peak current for FAIR simultaneously. To keep the GSI-SHE program competitive on a high level and even beyond, a standalone superconducting continuous wave (100% duty factor) LINAC in combination with the upgraded GSI High Charge State injector is envisaged. In preparation for this, the first LINAC section (financed by HIM and GSI) will be tested with beam in 2017, demonstrating the future experimental capabilities. Further on the construction of an extended cryo module comprising two shorter Crossbar-H cavities is foreseen to test until end of 2017. As a final R&D step towards an entire LINAC three advanced cryo modules, each comprising two CH cavities, should be built until 2019, serving for first user experiments at the Coulomb barrier.

Design study of a radio-frequency quadrupole for high-intensity beams

NASA Astrophysics Data System (ADS)

Bahng, Jungbae; Kim, Eun-San; Choi, Bong-Hyuk

2017-07-01

The Rare isotope Accelerator Of Newness (RAON) heavy-ion accelerator has been designed for the Rare Isotope Science Project (RISP) in Korea. The RAON will produce heavy-ion beams from 660-MeV-proton to 200-MeV/u-uranium with continuous wave (CW) power of 400 kW to support research in various scientific fields. Its system consists of an ECR ion source, LEBTs with 10 keV/u, CW RFQ accelerator with 81.25 MHz and 500 keV/u, a MEBT system, and a SC linac. In detail, the driver linac system consists of a Quarter Wave Resonator (QWR) section with 81.25 MHz and a Half Wave Resonator (HWR) section with 162.5 MHz, Linac-1, and a Spoke Cavity section with 325 MHz, Linac-2. These linacs have been designed to optimize the beam parameters to meet the required design goals. At the same time, a light-heavy ion accelerator with high-intensity beam, such as proton, deuteron, and helium beams, is required for experiments. In this paper, we present the design study of the high intensity RFQ for a deuteron beam with energies from 30 keV/u to 1.5 MeV/u and currents in the mA range. This system is composed of an Penning Ionization Gauge ion source, short LEBT with a RF deflector, and shared SC Linac. In order to increase acceleration efficiency in a short length with low cost, the 2nd harmonic of 162.5 MHz is applied as the operation frequency in the D+ RFQ design. The D+ RFQ is designed with 4.97 m, 1.52 bravery factor. Since it operates with 2nd harmonic frequency, the beam should be 50% of the duty factor while the cavity should be operated in CW mode, to protect the downstream linac system. We focus on avoiding emittance growth by the space-charge effect and optimizing the RFQ to achieve a high transmission and low emittance growth. Both the RFQ beam dynamics study and RFQ cavity design study for two and three dimensions will be discussed. Supported by Korea University Future Research Grant

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

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.

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.

Analytical study of beam handling and emittance control

NASA Astrophysics Data System (ADS)

Thompson, James R.; Sloan, M. L.

1993-12-01

The thrust of our research on beam handling and emittance control was to explore how one might design high current electron accelerators, with the preservation of high beam quality designed as the primary design consideration. We considered high current, induction linacs in the parameter class of the ETA/ATA accelerators at LLNL, but with improvements to the accelerator gap design and other features to permit a significant increase in the deliverable beam brightness. Our approach for beam quality control centered on the use of solenoidal magnetic focusing through such induction accelerators, together with gently-shaped (adiabatic) acceleration gaps. This approach offers several tools for the control of beam quality. The strength and axial variation in the solenoidal magnetic field may be designed, as may the length and shape of the acceleration gaps, the loading of the gaps, and the axial spacing from gap to gap. This research showed that each of these design features may individually be optimized to contribute to improved beam quality control, and by exploiting these features, it appears feasible to produce high current, high energy electron beams possessing breakthrough beam quality and brightness. Applications which have been technologically unachievable may for the first time become possible. One such application is the production of high performance free electron lasers at very short wavelengths, extending down to the optical (less than 1 micron) regime.

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

A survey of the three-dimensional high Reynolds number transonic wind tunnel

NASA Technical Reports Server (NTRS)

Takashima, K.; Sawada, H.; Aoki, T.

1982-01-01

The facilities for aerodynamic testing of airplane models at transonic speeds and high Reynolds numbers are surveyed. The need for high Reynolds number testing is reviewed, using some experimental results. Some approaches to high Reynolds number testing such as the cryogenic wind tunnel, the induction driven wind tunnel, the Ludwieg tube, the Evans clean tunnel and the hydraulic driven wind tunnel are described. The level of development of high Reynolds number testing facilities in Japan is discussed.

FGF-mediated mesoderm induction involves the Src-family kinase Laloo.

PubMed

Weinstein, D C; Marden, J; Carnevali, F; Hemmati-Brivanlou, A

1998-08-27

During embryogenesis, inductive interactions underlie the development of much of the body plan. In Xenopus laevis, factors secreted from the vegetal pole induce mesoderm in the adjacent marginal zone; members of both the transforming growth factor-beta (TGF-beta) and fibroblast growth factor (FGF) ligand families seem to have critical roles in this process. Here we report the identification and characterization of laloo, a novel participant in the signal transduction cascade linking extracellular, mesoderm-inducing signals to the nucleus, where alteration of cell fate is driven by changes in gene expression. Overexpression of laloo, a member of the Src-related gene family, in Xenopus embryos gives rise to ectopic posterior structures that frequently contain axial tissue. Laloo induces mesoderm in Xenopus ectodermal explants; this induction is blocked by reagents that disrupt the FGF signalling pathway. Conversely, expression of a dominant-inhibitory Laloo mutant blocks mesoderm induction by FGF and causes severe posterior truncations in vivo. This work provides the first evidence that a Src-related kinase is involved in vertebrate mesoderm induction.

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.

Production of low-Z ions in the Dresden superconducting electron ion beam source for medical particle therapy.

PubMed

Zschornack, G; Schwan, A; Ullmann, F; Grossmann, F; Ovsyannikov, V P; Ritter, E

2012-02-01

We report on experiments with a new superconducting electron beam ion source (EBIS-SC), the Dresden EBIS-SC, with the objective to meet the main requirements for their application in particle-therapy facilities. Synchrotrons as well as innovative accelerator concepts, such as high-gradient linacs which are driven by a large-current cyclotron (CYCLINACS) and direct drive RF linear accelerators may benefit from the advantages of EBISs in regard to their functional principle. First experimental studies of the production of low-Z ions such as H(+), H(2)(+), H(3)(+), C(4+), and C(6+) are presented. Particular attention is paid to the ion output, i.e., the number of ions per pulse and per second, respectively. Important beam parameters in this context are, among others, ion pulse shaping, pulse repetition rates, beam emittance, and ion energy spread.

Real-Time Phase Correction Based on FPGA in the Beam Position and Phase Measurement System

NASA Astrophysics Data System (ADS)

Gao, Xingshun; Zhao, Lei; Liu, Jinxin; Jiang, Zouyi; Hu, Xiaofang; Liu, Shubin; An, Qi

2016-12-01

A fully digital beam position and phase measurement (BPPM) system was designed for the linear accelerator (LINAC) in Accelerator Driven Sub-critical System (ADS) in China. Phase information is obtained from the summed signals from four pick-ups of the Beam Position Monitor (BPM). Considering that the delay variations of different analog circuit channels would introduce phase measurement errors, we propose a new method to tune the digital waveforms of four channels before summation and achieve real-time error correction. The process is based on the vector rotation method and implemented within one single Field Programmable Gate Array (FPGA) device. Tests were conducted to evaluate this correction method and the results indicate that a phase correction precision better than ± 0.3° over the dynamic range from -60 dBm to 0 dBm is achieved.

High resolution x-ray Thomson scattering measurements from cryogenic hydrogen jets using the linac coherent light source

DOE PAGES

Fletcher, L. B.; Zastrau, U.; Galtier, E.; ...

2016-08-15

Here, we present the first spectrally resolved measurements of x-rays scattered from cryogenic hydrogen jets in the single photon counting limit. The 120 Hz capabilities of the LCLS, together with a novel hydrogen jet design [J. B. Kim et al., Rev. Sci. Instrum. (these proceedings)], allow for the ability to record a near background free spectrum. Such high-dynamic-range x-ray scattering measurements enable a platform to study ultra-fast, laser-driven, heating dynamics of hydrogen plasmas. This measurement has been achieved using two highly annealed pyrolytic graphite crystal spectrometers to spectrally resolve 5.5 keV x-rays elastically and inelastically scattered from cryogenic hydrogen andmore » focused on Cornell-SLAC pixel array detectors [S. Herrmann et al., Nucl. Instrum. Methods Phys. Res., Sect. A 718, 550 (2013)].« less

Optical pulse evolution in the Stanford free-electron laser and in a tapered wiggler

NASA Technical Reports Server (NTRS)

Colson, W. B.

1982-01-01

The Stanford free electron laser (FEL) oscillator is driven by a series of electron pulses from a high-quality superconducting linear accelerator (LINAC). The electrons pass through a transverse and nearly periodic magnetic field, a 'wiggler', to oscillate and amplify a superimposed optical pulse. The rebounding optical pulse must be closely synchronized with the succession of electron pulses from the accelerator, and can take on a range of structures depending on the precise degree of synchronism. Small adjustments in desynchronism can make the optical pulse either much shorter or longer than the electron pulse, and can cause significant subpulse structure. The oscillator start-up from low level incoherent fields is discussed. The effects of desynchronism on coherent pulse propagation are presented and compared with recent Stanford experiments. The same pulse propagation effects are studied for a magnet design with a tapered wavelength in which electrons are trapped in the ponderomotive potential.

Effects of Cascaded Voltage Collapse and Protection of Many Induction Machine Loads upon Load Characteristics Viewed from Bulk Transmission System

NASA Astrophysics Data System (ADS)

Kumano, Teruhisa

As known well, two of the fundamental processes which give rise to voltage collapse in power systems are the on load tap changers of transformers and dynamic characteristics of loads such as induction machines. It has been well established that, comparing among these two, the former makes slower collapse while the latter makes faster. However, in realistic situations, the load level of each induction machine is not uniform and it is well expected that only a part of loads collapses first, followed by collapse process of each load which did not go into instability during the preceding collapses. In such situations the over all equivalent collapse behavior viewed from bulk transmission level becomes somewhat different from the simple collapse driven by one aggregated induction machine. This paper studies the process of cascaded voltage collapse among many induction machines by time simulation, where load distribution on a feeder line is modeled by several hundreds of induction machines and static impedance loads. It is shown that in some cases voltage collapse really cascades among induction machines, where the macroscopic load dynamics viewed from upper voltage level makes slower collapse than expected by the aggregated load model. Also shown is the effects of machine protection of induction machines, which also makes slower collapse.

Push-pull switching power amplifier

NASA Technical Reports Server (NTRS)

Cuk, Slobodan M. (Inventor)

1980-01-01

A true push-pull switching power amplifier is disclosed utilizing two dc-to-dc converters. Each converter is comprised of two inductances, one inductance in series with a DC source and the other inductor in series with the output load, and an electrical energy transferring device with storage capability, namely storage capacitance, with suitable switching means between the inductances to obtain DC level conversion, where the switching means allows bidirectional current (and power) flow, and the switching means of one dc-to-dc converter is driven by the complement of a square-wave switching signal for the other dc-to-dc converter for true push-pull operation. For reduction of current ripple, the inductances in each of the two converters may be coupled, and with proper design of the coupling, the ripple can be reduced to zero at either the input or the output, but preferably the output.

Multiple beam induction accelerators for heavy ion fusion

NASA Astrophysics Data System (ADS)

Seidl, Peter A.; Barnard, John J.; Faltens, Andris; Friedman, Alex; Waldron, William L.

2014-01-01

Induction accelerators are appealing for heavy-ion driven inertial fusion energy (HIF) because of their high efficiency and their demonstrated capability to accelerate high beam current (≥10 kA in some applications). For the HIF application, accomplishments and challenges are summarized. HIF research and development has demonstrated the production of single ion beams with the required emittance, current, and energy suitable for injection into an induction linear accelerator. Driver scale beams have been transported in quadrupole channels of the order of 10% of the number of quadrupoles of a driver. We review the design and operation of induction accelerators and the relevant aspects of their use as drivers for HIF. We describe intermediate research steps that would provide the basis for a heavy-ion research facility capable of heating matter to fusion relevant temperatures and densities, and also to test and demonstrate an accelerator architecture that scales well to a fusion power plant.

Low pressure EGR system having full range capability

DOEpatents

Easley, Jr., William Lanier; Milam, David Michael; Roozenboom, Stephan Donald; Bond, Michael Steven; Kapic, Amir

2009-09-22

An exhaust treatment system for an engine is disclosed and may have an air induction circuit, an exhaust circuit, and an exhaust recirculation circuit. The air induction circuit may be configured to direct air into the engine. The exhaust circuit may be configured to direct exhaust from the engine and include a turbine driven by the exhaust, a particulate filter disposed in series with and downstream of the turbine, and a catalytic device disposed in series with and downstream of the particulate filter. The exhaust recirculation circuit may be configured to selectively redirect at least some of the exhaust from between the particulate filter and the catalytic device to the air induction circuit. The catalytic device is selected to create backpressure within the exhaust circuit sufficient to ensure that, under normal engine operating conditions above low idle, exhaust can flow into the air induction circuit without throttling of the air.

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.

Compact compressive arc and beam switchyard for energy recovery linac-driven ultraviolet free electron lasers

NASA Astrophysics Data System (ADS)

Akkermans, J. A. G.; Di Mitri, S.; Douglas, D.; Setija, I. D.

2017-08-01

High gain free electron lasers (FELs) driven by high repetition rate recirculating accelerators have received considerable attention in the scientific and industrial communities in recent years. Cost-performance optimization of such facilities encourages limiting machine size and complexity, and a compact machine can be realized by combining bending and bunch length compression during the last stage of recirculation, just before lasing. The impact of coherent synchrotron radiation (CSR) on electron beam quality during compression can, however, limit FEL output power. When methods to counteract CSR are implemented, appropriate beam diagnostics become critical to ensure that the target beam parameters are met before lasing, as well as to guarantee reliable, predictable performance and rapid machine setup and recovery. This article describes a beam line for bunch compression and recirculation, and beam switchyard accessing a diagnostic line for EUV lasing at 1 GeV beam energy. The footprint is modest, with 12 m compressive arc diameter and ˜20 m diagnostic line length. The design limits beam quality degradation due to CSR both in the compressor and in the switchyard. Advantages and drawbacks of two switchyard lines providing, respectively, off-line and on-line measurements are discussed. The entire design is scalable to different beam energies and charges.

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

Noninductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta

DOE PAGES

Schlossberg, David J.; Bodner, Grant M.; Bongard, Michael W.; ...

2017-07-01

Access to and characterization of sustained, toroidally confined plasmas with a very high plasma-to-magnetic pressure ratio (β t), low internal inductance, high elongation, and nonsolenoidal current drive is a central goal of present tokamak plasma research. Stable access to this desirable parameter space is demonstrated in plasmas with ultralow aspect ratio and high elongation. Local helicity injection provides nonsolenoidal sustainment, low internal inductance, and ion heating. Equilibrium analyses indicate β t up to ~100% with a minimum |B| well spanning up to ~50% of the plasma volume.

Modelling high frequency phenomena in the rotor of induction motors under no-load test conditions

NASA Astrophysics Data System (ADS)

Boglietti, Aldo; Bottauscio, Oriano; Chiampi, Mario; Lazzari, Mario

2003-01-01

The paper aims to deep the electromagnetic phenomena in the rotor of induction motors produced during the no-load test by the high-order harmonics of the spatial distribution of magnetic flux. The analysis is carried out by a flux driven finite element procedure, which can take into account the hysteresis of magnetic material, the induced currents in rotor cage and the eddy currents in the laminations. The computed results, including losses and local waveforms of electrical and magnetic quantities, are finally discussed.

Prostate organogenesis: tissue induction, hormonal regulation and cell type specification

PubMed Central

Toivanen, Roxanne

2017-01-01

Prostate organogenesis is a complex process that is primarily mediated by the presence of androgens and subsequent mesenchyme-epithelial interactions. The investigation of prostate development is partly driven by its potential relevance to prostate cancer, in particular the apparent re-awakening of key developmental programs that occur during tumorigenesis. However, our current knowledge of the mechanisms that drive prostate organogenesis is far from complete. Here, we provide a comprehensive overview of prostate development, focusing on recent findings regarding sexual dimorphism, bud induction, branching morphogenesis and cellular differentiation. PMID:28400434

Noninductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta.

PubMed

Schlossberg, D J; Bodner, G M; Bongard, M W; Burke, M G; Fonck, R J; Perry, J M; Reusch, J A

2017-07-21

Access to and characterization of sustained, toroidally confined plasmas with a very high plasma-to-magnetic pressure ratio (β_{t}), low internal inductance, high elongation, and nonsolenoidal current drive is a central goal of present tokamak plasma research. Stable access to this desirable parameter space is demonstrated in plasmas with ultralow aspect ratio and high elongation. Local helicity injection provides nonsolenoidal sustainment, low internal inductance, and ion heating. Equilibrium analyses indicate β_{t} up to ∼100% with a minimum |B| well spanning up to ∼50% of the plasma volume.

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.

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.

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

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.

Ion energy spread and current measurements of the rf-driven multicusp ion source

NASA Astrophysics Data System (ADS)

Lee, Y.; Gough, R. A.; Kunkel, W. B.; Leung, K. N.; Perkins, L. T.; Pickard, D. S.; Sun, L.; Vujic, J.; Williams, M. D.; Wutte, D.

1997-03-01

Axial energy spread and useful beam current of positive ion beams have been carried out using a radio frequency (rf)-driven multicusp ion source. Operating the source with a 13.56 MHz induction discharge, the axial energy spread is found to be approximately 3.2 eV. The extractable beam current of the rf-driven source is found to be comparable to that of filament-discharge sources. With a 0.6 mm diameter extraction aperture, a positive hydrogen ion beam current density of 80 mA/cm2 can be obtained at a rf input power of 2.5 kW. The expected source lifetime is much longer than that of filament discharges.

Coaxial fast metal-to-metal switch for high current.

PubMed

Boissady, C; Rioux-Damidau, F

1978-11-01

A fast mechanical switch of coaxial configuration, driven by a magnetic field, is described. It presents a low inductance (6 nH), a low resistance (3 muOmega) and delay-times of 25 micros with a jitter of 0.08 micros.

Maxillary-driven simultaneous maxillo-mandibular distraction for hemifacial microsomia.

PubMed

Nakajima, Hideo; Sakamoto, Yoshiaki; Tamada, Ikkei; Ogata, Hisao; Kishi, Kazuo; Sakamoto, Teruo

2011-12-01

We treat hemifacial microsomia with a combination of surgery and orthodontic treatment during the growth period, resulting in early improvement in facial asymmetry and the induction of normal growth. We previously used gradual distraction of the mandibular ramus for Pruzansky's type II classification (Pruzansky, 1969). In type II cases, the maxilla should also be treated actively as, using this technique, improvement of the occlusal plane is difficult to achieve, resulting in a cross bite and difficulties in post-operative orthodontic treatment-especially in older patients. Morphologically, the mandibular angle region of the operative side is flat, and the angle of the mouth remains elevated. We performed mandibular-driven simultaneous maxillo-mandibular distraction while the occlusion was maintained using intermaxillary anchorage. However, mandibular-driven distraction tended to elongate the face because the mandible only elongated downwards and the mandibular ramus did not reach the glenoid. Furthermore, external distraction devices produce significant distress for patients until removal of the device and cause scars on the face. We developed a new internal distraction device with a variable angle and performed maxillary-driven simultaneous maxillo-mandibular distraction using this device. The result was morphologically satisfactory and solved the above problems. Because the patient was in the growth period, careful follow-up and induction to normal growth were important while the inferior growth of the affected side was monitored. Copyright © 2010 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Induction of appropriate Th-cell phenotypes: cellular decision-making in heterogeneous environments.

PubMed

van den Ham, H-J; Andeweg, A C; de Boer, R J

2013-11-01

Helper T (Th)-cell differentiation is a key event in the development of the adaptive immune response. By the production of a range of cytokines, Th cells determine the type of immune response that is raised against an invading pathogen. Th cells can adopt many different phenotypes, and Th-cell phenotype decision-making is crucial in mounting effective host responses. This review discusses the different Th-cell phenotypes that have been identified and how Th cells adopt a particular phenotype. The regulation of Th-cell phenotypes has been studied extensively using mathematical models, which have explored the role of regulatory mechanisms such as autocrine cytokine signalling and cross-inhibition between self-activating transcription factors. At the single cell level, Th responses tend to be heterogeneous, but corrections can be made soon after T-cell activation. Although pathogens and the innate immune system provide signals that direct the induction of Th-cell phenotypes, these instructive mechanisms could be easily subverted by pathogens. We discuss that a model of success-driven feedback would select the most appropriate phenotype for clearing a pathogen. Given the heterogeneity in the induction phase of the Th response, such a success-driven feedback loop would allow the selection of effective Th-cell phenotypes while terminating incorrect responses. © 2013 John Wiley & Sons Ltd.

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.

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

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.

Radiobiological Effectiveness of Ultrashort Laser-Driven Electron Bunches: Micronucleus Frequency, Telomere Shortening and Cell Viability.

PubMed

Andreassi, Maria Grazia; Borghini, Andrea; Pulignani, Silvia; Baffigi, Federica; Fulgentini, Lorenzo; Koester, Petra; Cresci, Monica; Vecoli, Cecilia; Lamia, Debora; Russo, Giorgio; Panetta, Daniele; Tripodi, Maria; Gizzi, Leonida A; Labate, Luca

2016-09-01

Laser-driven electron accelerators are capable of producing high-energy electron bunches in shorter distances than conventional radiofrequency accelerators. To date, our knowledge of the radiobiological effects in cells exposed to electrons using a laser-plasma accelerator is still very limited. In this study, we compared the dose-response curves for micronucleus (MN) frequency and telomere length in peripheral blood lymphocytes exposed to laser-driven electron pulse and X-ray radiations. Additionally, we evaluated the effects on cell survival of in vitro tumor cells after exposure to laser-driven electron pulse compared to electron beams produced by a conventional radiofrequency accelerator used for intraoperative radiation therapy. Blood samples from two different donors were exposed to six radiation doses ranging from 0 to 2 Gy. Relative biological effectiveness (RBE) for micronucleus induction was calculated from the alpha coefficients for electrons compared to X rays (RBE = alpha laser/alpha X rays). Cell viability was monitored in the OVCAR-3 ovarian cancer cell line using trypan blue exclusion assay at day 3, 5 and 7 postirradiation (2, 4, 6, 8 and 10 Gy). The RBE values obtained by comparing the alpha values were 1.3 and 1.2 for the two donors. Mean telomere length was also found to be reduced in a significant dose-dependent manner after irradiation with both electrons and X rays in both donors studied. Our findings showed a radiobiological response as mirrored by the induction of micronuclei and shortening of telomere as well as by the reduction of cell survival in blood samples and cancer cells exposed in vitro to laser-generated electron bunches. Additional studies are needed to improve preclinical validation of the radiobiological characteristics and efficacy of laser-driven electron accelerators in the future.

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

Numerical Modeling and Testing of an Inductively-Driven and High-Energy Pulsed Plasma Thrusters

NASA Technical Reports Server (NTRS)

Parma, Brian

2004-01-01

Pulsed Plasma Thrusters (PPTs) are advanced electric space propulsion devices that are characterized by simplicity and robustness. They suffer, however, from low thrust efficiencies. This summer, two approaches to improve the thrust efficiency of PPTs will be investigated through both numerical modeling and experimental testing. The first approach, an inductively-driven PPT, uses a double-ignition circuit to fire two PPTs in succession. This effectively changes the PPTs configuration from an LRC circuit to an LR circuit. The LR circuit is expected to provide better impedance matching and improving the efficiency of the energy transfer to the plasma. An added benefit of the LR circuit is an exponential decay of the current, whereas a traditional PPT s under damped LRC circuit experiences the characteristic "ringing" of its current. The exponential decay may provide improved lifetime and sustained electromagnetic acceleration. The second approach, a high-energy PPT, is a traditional PPT with a variable size capacitor bank. This PPT will be simulated and tested at energy levels between 100 and 450 joules in order to investigate the relationship between efficiency and energy level. Arbitrary Coordinate Hydromagnetic (MACH2) code is used. The MACH2 code, designed by the Center for Plasma Theory and Computation at the Air Force Research Laboratory, has been used to gain insight into a variety of plasma problems, including electric plasma thrusters. The goals for this summer include numerical predictions of performance for both the inductively-driven PPT and high-energy PFT, experimental validation of the numerical models, and numerical optimization of the designs. These goals will be met through numerical and experimental investigation of the PPTs current waveforms, mass loss (or ablation), and impulse bit characteristics.

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

Role of the nuclear xenobiotic receptors CAR and PXR in induction of cytochromes P450 by non-dioxinlike polychlorinated biphenyls in cultured rat hepatocytes

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

Gährs, Maike; Roos, Robert; Andersson, Patrik L.

Polychlorinated biphenyls (PCBs) are among the most ubiquitously detectable ‘persistent organic pollutants’. In contrast to ‘dioxinlike’ (DL) PCBs, less is known about the molecular mode of action of the larger group of the ‘non-dioxinlike’ (NDL) PCBs. Owing to the life-long exposure of the human population, a carcinogenic, i.e., tumor-promoting potency of NDL-PCBs has to be considered in human risk assessment. A major problem in risk assessment of NDL-PCBs is dioxin-like impurities that can occur in commercially available NDL-PCB standards. In the present study, we analyzed the induction of CYP2B1 and CYP3A1 in primary rat hepatocytes using a number of highlymore » purified NDL-PCBs with various degrees of chlorination and substitution patterns. Induction of these enzymes is mediated by the nuclear xenobiotic receptors CAR (Constitutive androstane receptor) and PXR (Pregnane X receptor). For CYP2B1 induction, concentration–response analysis revealed a very narrow window of EC{sub 50} estimates, being in the range of 1–4 μM for PCBs 28 and 52, and between 0.4 and 1 μM for PCBs 101, 138, 153 and 180. CYP3A1 induction was less sensitive to NDL-PCBs, the most pronounced induction being achieved at 100 μM with the higher chlorinated congeners. Using okadaic acid and small interfering RNAs targeting CAR and PXR, we could demonstrate that CAR plays a major role and PXR a minor role in NDL-PCB-driven induction of CYPs, both effects showing no stringent structure–activity relationship. As the only obvious relevant determinant, the degree of chlorination was found to be positively correlated with the inducing potency of the congeners. - Highlights: • We analyzed six highly purified NDL-PCBs for CYP2B1 and CYP3A1 expression. • CAR plays a major, PXR a minor role in NDL-PCB-driven induction of CYPs. • The degree of chlorination seems to be the major parameter for the inducing potency. • There exists a competition between CAR and PXR. • Activated PXR may antagonize CAR binding to the CYP2B1 promoter.« less

The status of normal conducting RF (NCRF) guns, a summary of the ERL2005 workshop

NASA Astrophysics Data System (ADS)

Dowell, David H.; Lewellen, John W.; Nguyen, Dinh; Rimmer, Robert

2006-02-01

The 32nd Advanced ICFA Beam Dynamics Workshop on Energy Recovering Linacs (ERL2005) was held at Jefferson Laboratory, March 20-23, 2005. A wide range of ERL-related topics were presented and discussed in several working groups with Working Group 1 concentrating upon the physics and technology issues for DC, superconducting RF (SRF) and normal conducting RF (NCRF) guns. This paper summarizes the NCRF gun talks and reviews the status of NCRF gun technology. It begins with the presentations made on the subject of low-frequency, high-duty factor guns most appropriate for ERLs. One such gun at 433 MHz was demonstrated at 25%DF in 1992, while the CW and much improved version is currently being constructed at 700 MHz for LANL. In addition, the idea of combining the NCRF gun with a SRF linac booster was presented and is described in this paper. There was also a talk on high-field guns typically used for SASE-free electron lasers. In particular, the DESY coaxial RF feed design provides rotationally symmetric RF fields and greater flexibility in the placement of the focusing magnetic field. While in the LCLS approach, the symmetric fields are obtained with a dual RF feed and racetrack cell shape. Although these guns cannot be operated at high-duty factor, they do produce the best quality beams. With these limitations in mind, a section with material not presented at the workshop has been included in the paper. This work describes a re-entrant approach which may allow NCRF guns to operate with simultaneously increased RF fields and duty factors. And finally, a novel proposal describing a high-duty factor, two-frequency RF gun using a field emission source instead of a laser driven photocathode was also presented.

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

Hartemann, F V; Albert, F; Anderson, S G

Nuclear photonics is an emerging field of research requiring new tools, including high spectral brightness, tunable gamma-ray sources; high photon energy, ultrahigh-resolution crystal spectrometers; and novel detectors. This presentation focuses on the precision linac technology required for Compton scattering gamma-ray light sources, and on the optimization of the laser and electron beam pulse format to achieve unprecedented spectral brightness. Within this context, high-gradient X-band technology will be shown to offer optimal performance in a compact package, when used in conjunction with the appropriate pulse format, and photocathode illumination and interaction laser technologies. The nascent field of nuclear photonics is enabledmore » by the recent maturation of new technologies, including high-gradient X-band electron acceleration, robust fiber laser systems, and hyper-dispersion CPA. Recent work has been performed at LLNL to demonstrate isotope-specific detection of shielded materials via NRF using a tunable, quasi-monochromatic Compton scattering gamma-ray source operating between 0.2 MeV and 0.9 MeV photon energy. This technique is called Fluorescence Imaging in the Nuclear Domain with Energetic Radiation (or FINDER). This work has, among other things, demonstrated the detection of {sup 7}Li shielded by Pb, utilizing gamma rays generated by a linac-driven, laser-based Compton scattering gamma-ray source developed at LLNL. Within this context, a new facility is currently under construction at LLNL, with the goal of generating tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range, at a repetition rate of 120 Hz, and with a peak brightness in the 10{sup 20} photons/(s x mm{sup 2} x mrad{sup 2} x 0.1% bw).« less

Extending the Constant Power Speed Range of the Brushless DC Motor through Dual Mode Inverter Control -- Part II: Laboratory Proof-of-Principle

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

Lawler, J.S.

2001-10-29

Previous theoretical work has shown that when all loss mechanisms are neglected the constant power speed range (CPSR) of a brushless dc motor (BDCM) is infinite when the motor is driven by the dual-mode inverter control (DMIC) [1,2]. In a physical drive, losses, particularly speed-sensitive losses, will limit the CPSR to a finite value. In this paper we report the results of laboratory testing of a low-inductance, 7.5-hp BDCM driven by the DMIC. The speed rating of the test motor rotor limited the upper speed of the testing, and the results show that the CPSR of the test machine ismore » greater than 6:1 when driven by the DMIC. Current wave shape, peak, and rms values remained controlled and within rating over the entire speed range. The laboratory measurements allowed the speed-sensitive losses to be quantified and incorporated into computer simulation models, which then accurately reproduce the results of lab testing. The simulator shows that the limiting CPSR of the test motor is 8:1. These results confirm that the DMIC is capable of driving low-inductance BDCMs over the wide CPSR that would be required in electric vehicle applications.« less

Non-inductively driven tokamak plasmas at near-unity βt in the Pegasus toroidal experiment

NASA Astrophysics Data System (ADS)

Reusch, J. A.; Bodner, G. M.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Pachicano, J. L.; Perry, J. M.; Pierren, C.; Rhodes, A. T.; Richner, N. J.; Rodriguez Sanchez, C.; Schlossberg, D. J.; Weberski, J. D.

2018-05-01

A major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance ℓi, high elongation κ, and high toroidal and normalized beta ( βt and βN) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low ℓi. The low aspect ratio ( R0/a ˜1.2 ) of Pegasus allows access to high κ and high normalized plasma currents ( IN=Ip/a BT>14 ). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high βt plasmas. Equilibrium analyses indicate that βt up to ˜100% is achieved. These high βt discharges disrupt at the ideal no-wall β limit at βN˜7.

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.

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.

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.

Tuning the Magnetic Transport of an Induction LINAC using Emittance

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

Houck, T L; Brown, C G; Ong, M M

2006-08-11

The Lawrence Livermore National Laboratory Flash X-Ray (FXR) machine is a linear induction accelerator used to produce a nominal 18 MeV, 3 kA, 65 ns pulse width electron beam for hydrodynamic radiographs. A common figure of merit for this type of radiographic machine is the x-ray dose divided by the spot area on the bremsstrahlung converter where a higher FOM is desired. Several characteristics of the beam affect the minimum attainable x-ray spot size. The most significant are emittance (chaotic transverse energy), chromatic aberration (energy variation), and beam motion (transverse instabilities and corkscrew motion). FXR is in the midst ofmore » a multi-year optimization project to reduce the spot size. This paper describes the effort to reduce beam emittance by adjusting the fields of the transport solenoids and position of the cathode. If the magnetic transport is not correct, the beam will be mismatched and undergo envelope oscillations increasing the emittance. We measure the divergence and radius of the beam in a drift section after the accelerator by imaging the optical transition radiation (OTR) and beam envelope on a foil. These measurements are used to determine an emittance. Relative changes in the emittance can be quickly estimated from the foil measurements allowing for an efficient, real-time study. Once an optimized transport field is determined, the final focus can be adjusted and the new x-ray spot measured. A description of the diagnostics and analysis is presented.« less

Simulation of RF power and multi-cusp magnetic field requirement for H- ion sources

NASA Astrophysics Data System (ADS)

Pathak, Manish; Senecha, V. K.; Kumar, Rajnish; Ghodke, Dharmraj. V.

2016-12-01

A computer simulation study for multi-cusp RF based H- ion source has been carried out using energy and particle balance equation for inductively coupled uniformly dense plasma considering sheath formation near the boundary wall of the plasma chamber for RF ion source used as high current injector for 1 Gev H- Linac project for SNS applications. The average reaction rates for different reactions responsible for H- ion production and destruction have been considered in the simulation model. The RF power requirement for the caesium free H- ion source for a maximum possible H- ion beam current has been derived by evaluating the required current and RF voltage fed to the coil antenna using transformer model for Inductively Coupled Plasma (ICP). Different parameters of RF based H- ion source like excited hydrogen molecular density, H- ion density, RF voltage and current of RF antenna have been calculated through simulations in the presence and absence of multicusp magnetic field to distinctly observe the effect of multicusp field. The RF power evaluated for different H- ion current values have been compared with the experimental reported results showing reasonably good agreement considering the fact that some RF power will be reflected from the plasma medium. The results obtained have helped in understanding the optimum field strength and field free regions suitable for volume emission based H- ion sources. The compact RF ion source exhibits nearly 6 times better efficiency compare to large diameter ion source.

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.

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.

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.

Dynamic reflexivity in action: an armchair walkthrough of a qualitatively driven mixed-method and multiple methods study of mindfulness training in schoolchildren.

PubMed

Cheek, Julianne; Lipschitz, David L; Abrams, Elizabeth M; Vago, David R; Nakamura, Yoshio

2015-06-01

Dynamic reflexivity is central to enabling flexible and emergent qualitatively driven inductive mixed-method and multiple methods research designs. Yet too often, such reflexivity, and how it is used at various points of a study, is absent when we write our research reports. Instead, reports of mixed-method and multiple methods research focus on what was done rather than how it came to be done. This article seeks to redress this absence of emphasis on the reflexive thinking underpinning the way that mixed- and multiple methods, qualitatively driven research approaches are thought about and subsequently used throughout a project. Using Morse's notion of an armchair walkthrough, we excavate and explore the layers of decisions we made about how, and why, to use qualitatively driven mixed-method and multiple methods research in a study of mindfulness training (MT) in schoolchildren. © The Author(s) 2015.

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.

Miniature Gas-Circulating Machine

NASA Technical Reports Server (NTRS)

Swift, Walter L.; Valenzuela, Javier A.; Sixsmith, Herbert; Nutt, William E.

1993-01-01

Proposed gas-circulating machine consists essentially of centrifugal pump driven by induction motor. Noncontact bearings suppress wear and contamination. Used to circulate helium (or possibly hydrogen or another gas) in regeneration sorption-compressor refrigeration system aboard spacecraft. Also proves useful in terrestrial applications in which long life, reliability, and low contamination essential.

Driving lamps by induction

NASA Technical Reports Server (NTRS)

Laue, H. H.; Clough, L. G. (Inventor)

1973-01-01

An electrodeless lamp circuit with a coil surrounding a krypton lamp is driven by an RF input source. A coil surrounding a mercury lamp is tapped across the connection of the input central to the krypton-lamp coil. Each coil is connected in parallel with separate capacitors which form resonant circuits at the input frequency.

TAL effector driven induction of a SWEET gene confers susceptibility to bacterial blight of cotton

USDA-ARS?s Scientific Manuscript database

Bacterial blight of cotton (BBC), caused by Xanthomonas citri subsp. malvacearum (Xcm), is among the most destructive diseases in cotton (Gossypium spp.). Transcription activator-like (TAL) effectors from Xcm are essential for BBC disease progression. Here, we carried out whole-genome PacBio-seque...

On controlling the flow behavior driven by induction electrohydrodynamics in microfluidic channels.

PubMed

Li, Yanbo; Ren, Yukun; Liu, Weiyu; Chen, Xiaoming; Tao, Ye; Jiang, Hongyuan

2017-04-01

In this study, we develop a nondimensional physical model to demonstrate fluid flow at the micrometer dimension driven by traveling-wave induction electrohydrodynamics (EHD) through direct numerical simulation. In order to realize an enhancement in the pump flow rate as well as a flexible adjustment of anisotropy of flow behavior generated by induction EHD in microchannels, while not adding the risk of causing dielectric breakdown of working solution and material for insulation, a pair of synchronized traveling-wave voltage signals are imposed on double-sided electrode arrays that are mounted on the top and bottom insulating substrate, respectively. Accordingly, we present a model evidence, that not only the pump performance is improved evidently, but a variety of flow profiles, including the symmetrical and parabolic curve, plug-like shape and even biased flow behavior of quite high anisotropy are produced by the device design of "mix-type", "superimposition-type" and "adjustable-type" proposed herein as well, with the resulting controllable fluid motion being able to greatly facilitate an on-demand transportation mode of on-chip bio-microfluidic samples. Besides, automatic conversion in the direction of pump flow is achievable by switching on and off a second voltage wave. Our results provide utilitarian guidelines for constructing flexible electrokinetic framework useful in controllable transportation of particle and fluid samples in modern microfluidic systems. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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

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

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

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.

Empathy promotes altruistic behavior in economic interactions

PubMed Central

Klimecki, Olga M.; Mayer, Sarah V.; Jusyte, Aiste; Scheeff , Jonathan; Schönenberg, Michael

2016-01-01

What are the determinants of altruism? While economists assume that altruism is mainly driven by fairness norms, social psychologists consider empathy to be a key motivator for altruistic behavior. To unite these two theories, we conducted an experiment in which we compared behavior in a standard economic game that assesses altruism (the so-called Dictator Game) with a Dictator Game in which participants’ behavioral choices were preceded either by an empathy induction or by a control condition without empathy induction. The results of this within-subject manipulation show that the empathy induction substantially increased altruistic behavior. Moreover, the increase in experienced empathy predicted over 40% of the increase in sharing behavior. These data extend standard economic theories that altruism is based on fairness considerations, by showing that empathic feelings can be a key motivator for altruistic behavior in economic interactions. PMID:27578563

Radiosurgery performed with the aid of a 3-mm collimator in the subthalamic nucleus and substantia nigra of the vervet monkey.

PubMed

De Salles, A A; Melega, W P; Laćan, G; Steele, L J; Solberg, T D

2001-12-01

Radiosurgery for functional neurosurgery performed using a linear accelerator (LINAC) has not been extensively characterized in preclinical studies. In the present study, the properties of a newly designed 3-mm-diameter collimator were evaluated in a dedicated LINAC, which produced lesions in the basal ganglia of vervet monkeys. Lesion formation was determined in vivo in three animals by examining magnetic resonance (MR) images to show the dose-delivery precision of targeting and the geometry and extent of the lesions. Postmortem immunohistochemical studies were conducted to determine the extent of lesion-induced radiobiological effects. In three male vervet monkeys, the subthalamic nucleus (STN; one animal) and the pars compacta of the lateral substantia nigra (SN; two animals) were targeted by a Novalis Shaped Beam Surgery System that included a 3-mm collimator and delivered a maximum dose of 150 Gy. Magnetic resonance images obtained 4, 5, and 9 months posttreatment were reviewed, and the animals were killed so that immunohistological characterizations could be made. The generation of precise radiosurgical lesions by a 3-mm collimator was validated in studies that targeted the basal ganglia of the vervet monkey. The extent of the lesions created in all animals remained restricted in diameter (< 3 mm) throughout the duration of the studies, as assessed by reviewing MR images. Histological studies showed that the lesions were contained within the STN and SN target areas and that there were persistent increases in glial fibrillary acidic protein immunoreactivity. Increases in immunoreactivity for tyrosine hydroxylase, the serotonin transporter, and the GluR1 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate glutamate receptor in penumbral regions of the lesion were suggestive of compensatory neuronal adaptations. This radiosurgical approach may be of particular interest for the induction of lesions of the STN and SN in studies of experimental parkinsonism, as well as for the development of potential radiosurgical treatments for Parkinson disease.

Cost evaluation to optimise radiation therapy implementation in different income settings: A time-driven activity-based analysis.

PubMed

Van Dyk, Jacob; Zubizarreta, Eduardo; Lievens, Yolande

2017-11-01

With increasing recognition of growing cancer incidence globally, efficient means of expanding radiotherapy capacity is imperative, and understanding the factors impacting human and financial needs is valuable. A time-driven activity-based costing analysis was performed, using a base case of 2-machine departments, with defined cost inputs and operating parameters. Four income groups were analysed, ranging from low to high income. Scenario analyses included department size, operating hours, fractionation, treatment complexity, efficiency, and centralised versus decentralised care. The base case cost/course is US$5,368 in HICs, US$2,028 in LICs; the annual operating cost is US$4,595,000 and US$1,736,000, respectively. Economies of scale show cost/course decreasing with increasing department size, mainly related to the equipment cost and most prominent up to 3 linacs. The cost in HICs is two or three times as high as in U-MICs or LICs, respectively. Decreasing operating hours below 8h/day has a dramatic impact on the cost/course. IMRT increases the cost/course by 22%. Centralising preparatory activities has a moderate impact on the costs. The results indicate trends that are useful for optimising local and regional circumstances. This methodology can provide input into a uniform and accepted approach to evaluating the cost of radiotherapy. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.

Operation and development status of the J-PARC ion source

NASA Astrophysics Data System (ADS)

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

2014-02-01

A cesium-free H- ion source driven with a LaB6 filament is being operated at the Japan Proton Accelerator Research Complex (J-PARC) without any serious trouble since the restoration from the March 2011 earthquake. The H- ion current from the ion source is routinely restricted approximately 19 mA for the lifetime of the filament. In order to increase the beam power at the linac beam operation (January to February 2013), the beam current from the ion source was increased to 22 mA. At this operation, the lifetime of the filament was estimated by the reduction in the filament current. According to the steep reduction in the filament current, the break of the filament was predicted. Although the filament has broken after approximately 10 h from the steep current reduction, the beam operation was restarted approximately 8 h later by the preparation for the exchange of new filament. At the study time for the 3 GeV rapid cycling synchrotron (April 2013), the ion source was operated at approximately 30 mA for 8 days. As a part of the beam current upgrade plan for the J-PARC, the front end test stand consisting of the ion source and the radio frequency quadrupole is under preparation. The RF-driven H- ion source developed for the J-PARC 2nd stage requirements will be tested at this test stand.

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

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.

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.

MO-G-201-04: Knowledge-Based Planning for Single-Isocenter Stereotactic Radiosurgery to Multiple Brain Metastases

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

Ziemer, B; Shiraishi, S; Hattangadi-Gluth, J

Purpose: Single-isocenter, linac-based SRS for multiple brain metastases (multi-mets) can deliver highly conformal radiation doses and reduce overall patient treatment time compared to other therapy techniques. This study aims to quantify the dosimetric benefits of knowledge-based planning (KBP) for multi-met treatments. Methods: Using a previously-published KBP methodology (an artificial neural network (ANN) trained on single-target linac-based SRS plans), 3D dose distribution predictions for multi-met patients were obtained by treating each brain lesion as a solitary target and subsequently combining individual predictions into a single distribution using a dose-weighted geometric averaging to obtain the best results in the inter-target space. 17more » previously-treated multi-met plans, with target numbers ranging from N=2–5, were used to validate the ANN predictions and subsequent KBP auto-planning routine. The fully-deliverable KBP plans were developed by converting dose distribution predictions into patient-specific optimization objectives while maintaining identical target normalizations (typically PTV V100%=D98%). Plan quality improvements were quantified by the difference between SRS quality metrics (QMs): δdQM=QM(clinical)-QM(KBP). QMs of interest were: gradient measure (GM), conformity index (CI), brain V10 and V5, brainstem D0.1cc and heterogeneity index (HI). Finally, overall plan quality was judged via blinded plan comparison by SRS-specializing physicians. Results: Two clinical plans were found to be significant outliers wherein plan quality was dramatically worse than KBP. Despite indicating KBP superiority, these were removed from the QM analysis to prevent skewing the results. In the remaining cases, clinical and KBP QMs were nearly identical with modest improvements in the KBP sample: δGM=0.12±0.56mm, δCI=−0.01±0.04, Brain δV10=0.8±2.6cc, brain δV5=6.3 ±10.7cc, brainstem δD0.1cc=0.06±1.19Gy and δHI= −0.04±0.05. Ultimately, 13/17 KBP plans were deemed superior to the manual plans in blinded physician review. Conclusion: The results demonstrate that KBP-driven automated planning in linac-based single-isocenter treatments for multiple brain metastases is indistinguishable from, or even better than, traditional manual planning. J. Hattangadi: Research Grant; Varian Medical Systems; K.L. Moore: Research Grant: Varian Medical Systems.« less

Improvements to the internal and external antenna H(-) ion sources at the Spallation Neutron Source.

PubMed

Welton, R F; Dudnikov, V G; Han, B X; Murray, S N; Pennisi, T R; Pillar, C; Santana, M; Stockli, M P; Turvey, M W

2014-02-01

The Spallation Neutron Source (SNS), a large scale neutron production facility, routinely operates with 30-40 mA peak current in the linac. Recent measurements have shown that our RF-driven internal antenna, Cs-enhanced, multi-cusp ion sources injects ∼55 mA of H(-) beam current (∼1 ms, 60 Hz) at 65-kV into a Radio Frequency Quadrupole (RFQ) accelerator through a closely coupled electrostatic Low-Energy Beam Transport system. Over the last several years a decrease in RFQ transmission and issues with internal antennas has stimulated source development at the SNS both for the internal and external antenna ion sources. This report discusses progress in improving internal antenna reliability, H(-) yield improvements which resulted from modifications to the outlet aperture assembly (applicable to both internal and external antenna sources) and studies made of the long standing problem of beam persistence with the external antenna source. The current status of the external antenna ion source will also be presented.

High-intensity double-pulse X-ray free-electron laser

DOE PAGES

Marinelli, A.; Ratner, D.; Lutman, A. A.; ...

2015-03-06

The X-ray free-electron laser has opened a new era for photon science, improving the X-ray brightness by ten orders of magnitude over previously available sources. Similar to an optical laser, the spectral and temporal structure of the radiation pulses can be tailored to the specific needs of many experiments by accurately manipulating the lasing medium, that is, the electron beam. Here we report the generation of mJ-level two-colour hard X-ray pulses of few femtoseconds duration with an XFEL driven by twin electron bunches at the Linac Coherent Light Source. This performance represents an improvement of over an order of magnitudemore » in peak power over state-of-the-art two-colour XFELs. The unprecedented intensity and temporal coherence of this new two-colour X-ray free-electron laser enable an entirely new set of scientific applications, ranging from X-ray pump/X-ray probe experiments to the imaging of complex biological samples with multiple wavelength anomalous dispersion.« less

Ultrafast Absorption Spectroscopy of Aluminum Plasmas Created by LCLS using Betatron X-Ray Radiation

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

Albert, Felicie

2016-10-12

This document summarizes the goals and accomplishments of a six month-long LDRD project, awarded through the LLNL director Early and Mid Career Recognition (EMCR) program. This project allowed us to support beamtime awarded at the Matter under Extreme Conditions (MEC) end station of the Linac Coherent Light Source (LCLS). The goal of the experiment was to heat metallic samples with the bright x-rays from the LCLS free electron laser. Then, we studied how they relaxed back to equilibrium by probing them with ultrafast x-ray absorption spectroscopy using laser-based betatron radiation. Our work enabled large collaborations between LLNL, SLAC, LBNL, andmore » institutions in France and in the UK, while providing training to undergraduate and graduate students during the experiment. Following this LDRD project, the PI was awarded a 5-year DOE early career research grant to further develop applications of laser-driven x-ray sources for high energy density science experiments and warm dense matter states.« less

Development of 3He LPSDs and read-out system for the SANS spectrometer at CPHS

NASA Astrophysics Data System (ADS)

Huang, T. C.; Gong, H.; Shao, B. B.; Wang, X. W.; Zhang, Y.; Pang, B. B.

2014-01-01

The Compact Pulsed Hadron Source (CPHS) is a 13-MeV proton-linac-driven neutron source under construction in Tsinghua University. Time-of-flight (TOF) small-angle neutron scattering (SANS) spectrometer is one of the first instruments to be built. It is designed to use linear position-sensitive detectors (LPSDs) of 3He gas proportional counters to cover a 1 m×1 m area. Prototypical LPSDs (Φ = 12 mm, L=1 m) have been made and read-out system is developed based on charge division. This work describes the in-house fabrication of the prototypical LPSDs and design of the read-out system including front-end electronics and data acquisition (DAQ) system. Key factors of the front-end electronics are studied and optimized with PSPICE simulation. DAQ system is designed based on VME bus architecture and FPGA Mezzanine Card (FMC) standard with high flexibility and extendibility. Preliminary experiments are carried out and the results are present and discussed.

Dietary gluten triggers concomitant activation of CD4+ and CD8+ αβ T cells and γδ T cells in celiac disease

PubMed Central

Han, Arnold; Newell, Evan W.; Glanville, Jacob; Fernandez-Becker, Nielsen; Khosla, Chaitan; Chien, Yueh-hsiu; Davis, Mark M.

2013-01-01

Celiac disease is an intestinal autoimmune disease driven by dietary gluten and gluten-specific CD4+ T-cell responses. In celiac patients on a gluten-free diet, exposure to gluten induces the appearance of gluten-specific CD4+ T cells with gut-homing potential in the peripheral blood. Here we show that gluten exposure also induces the appearance of activated, gut-homing CD8+ αβ and γδ T cells in the peripheral blood. Single-cell T-cell receptor sequence analysis indicates that both of these cell populations have highly focused T-cell receptor repertoires, indicating that their induction is antigen-driven. These results reveal a previously unappreciated role of antigen in the induction of CD8+ αβ and γδ T cells in celiac disease and demonstrate a coordinated response by all three of the major types of T cells. More broadly, these responses may parallel adaptive immune responses to viral pathogens and other systemic autoimmune diseases. PMID:23878218

Non-inductively driven tokamak plasmas at near-unity β t in the Pegasus toroidal experiment

DOE PAGES

Reusch, Joshua A.; Bodner, Grant M.; Bongard, Michael W.; ...

2018-03-14

Amore » major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance ℓ i , high elongation κ , and high toroidal and normalized beta ( β t and β N ) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low ℓ i . The low aspect ratio ( R 0 / a ~ 1.2 ) of Pegasus allows access to high κ and high normalized plasma currents I N = I p / a B T > 14 ). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high β t plasmas. Equilibrium analyses indicate that β t up to ~100% is achieved. Finally, these high β t discharges disrupt at the ideal no-wall β limit at β N ~ 7. « less

Non-inductively driven tokamak plasmas at near-unity β t in the Pegasus toroidal experiment

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

Reusch, Joshua A.; Bodner, Grant M.; Bongard, Michael W.

Amore » major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance ℓ i , high elongation κ , and high toroidal and normalized beta ( β t and β N ) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low ℓ i . The low aspect ratio ( R 0 / a ~ 1.2 ) of Pegasus allows access to high κ and high normalized plasma currents I N = I p / a B T > 14 ). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high β t plasmas. Equilibrium analyses indicate that β t up to ~100% is achieved. Finally, these high β t discharges disrupt at the ideal no-wall β limit at β N ~ 7. « less

Data-Intensive Science meets Inquiry-Driven Pedagogy: Interactive Big Data Exploration, Threshold Concepts, and Liminality

NASA Technical Reports Server (NTRS)

Ramachandran, Rahul; Word, Andrea; Nair, Udasysankar

2014-01-01

Threshold concepts in any discipline are the core concepts an individual must understand in order to master a discipline. By their very nature, these concepts are troublesome, irreversible, integrative, bounded, discursive, and reconstitutive. Although grasping threshold concepts can be extremely challenging for each learner as s/he moves through stages of cognitive development relative to a given discipline, the learner's grasp of these concepts determines the extent to which s/he is prepared to work competently and creatively within the field itself. The movement of individuals from a state of ignorance of these core concepts to one of mastery occurs not along a linear path but in iterative cycles of knowledge creation and adjustment in liminal spaces - conceptual spaces through which learners move from the vaguest awareness of concepts to mastery, accompanied by understanding of their relevance, connectivity, and usefulness relative to questions and constructs in a given discipline. For example, challenges in the teaching and learning of atmospheric science can be traced to threshold concepts in fluid dynamics. In particular, Dynamic Meteorology is one of the most challenging courses for graduate students and undergraduates majoring in Atmospheric Science. Dynamic Meteorology introduces threshold concepts - those that prove troublesome for the majority of students but that are essential, associated with fundamental relationships between forces and motion in the atmosphere and requiring the application of basic classical statics, dynamics, and thermodynamic principles to the three dimensionally varying atmospheric structure. With the explosive growth of data available in atmospheric science, driven largely by satellite Earth observations and high-resolution numerical simulations, paradigms such as that of dataintensive science have emerged. These paradigm shifts are based on the growing realization that current infrastructure, tools and processes will not allow us to analyze and fully utilize the complex and voluminous data that is being gathered. In this emerging paradigm, the scientific discovery process is driven by knowledge extracted from large volumes of data. In this presentation, we contend that this paradigm naturally lends to inquiry-driven pedagogy where knowledge is discovered through inductive engagement with large volumes of data rather than reached through traditional, deductive, hypothesis-driven analyses. In particular, data-intensive techniques married with an inductive methodology allow for exploration on a scale that is not possible in the traditional classroom with its typical problem sets and static, limited data samples. In addition, we identify existing gaps and possible solutions for addressing the infrastructure and tools as well as a pedagogical framework through which to implement this inductive approach.

Metal Solidification Imaging Process by Magnetic Induction Tomography.

PubMed

Ma, Lu; Spagnul, Stefano; Soleimani, Manuchehr

2017-11-06

There are growing number of important applications that require a contactless method for monitoring an object surrounded inside a metallic enclosure. Imaging metal solidification is a great example for which there is no real time monitoring technique at present. This paper introduces a technique - magnetic induction tomography - for the real time in-situ imaging of the metal solidification process. Rigorous experimental verifications are presented. Firstly, a single inductive coil is placed on the top of a melting wood alloy to examine the changes of its inductance during solidification process. Secondly, an array of magnetic induction coils are designed to investigate the feasibility of a tomographic approach, i.e., when one coil is driven by an alternating current as a transmitter and a vector of phase changes are measured from the remaining of the coils as receivers. Phase changes are observed when the wood alloy state changes from liquid to solid. Thirdly, a series of static cold phantoms are created to represent various liquid/solid interfaces to verify the system performance. Finally, a powerful temporal reconstruction method is applied to realise real time in-situ visualisation of the solidification and the measurement of solidified shell thickness, a first report of its kind.

The NDCX-II engineering design

NASA Astrophysics Data System (ADS)

Waldron, W. L.; Abraham, W. J.; Arbelaez, D.; Friedman, A.; Galvin, J. E.; Gilson, E. P.; Greenway, W. G.; Grote, D. P.; Jung, J.-Y.; Kwan, J. W.; Leitner, M.; Lidia, S. M.; Lipton, T. M.; Reginato, L. L.; Regis, M. J.; Roy, P. K.; Sharp, W. M.; Stettler, M. W.; Takakuwa, J. H.; Volmering, J.; Vytla, V. K.

2014-01-01

The Neutralized Drift Compression Experiment (NDCX-II) is a user facility located at Lawrence Berkeley National Laboratory which is uniquely designed for ion-beam-driven high energy density laboratory physics and heavy ion fusion research. Construction was completed in March 2012 and the facility is now in the commissioning phase. A significant amount of engineering was carried out in order to meet the performance parameters required for a wide range of target heating experiments while making the most cost-effective use of high-value hardware available from a decommissioned high current electron induction accelerator. The technical challenges and design of this new ion induction accelerator facility are described.

Emittance Growth in the DARHT-II Linear Induction Accelerator

NASA Astrophysics Data System (ADS)

Ekdahl, Carl; Carlson, Carl A.; Frayer, Daniel K.; McCuistian, B. Trent; Mostrom, Christopher B.; Schulze, Martin E.; Thoma, Carsten H.

2017-11-01

The Dual-Axis Radiographic Hydrotest (DARHT) facility uses bremsstrahlung radiation source spots produced by the focused electron beams from two linear induction accelerators (LIAs) to radiograph large hydrodynamic experiments driven by high explosives. Radiographic resolution is determined by the size of the source spot, and beam emittance is the ultimate limitation to spot size. Some of the possible causes for the emittance growth in the DARHT LIA have been investigated using particle-in-cell (PIC) codes, and are discussed in this article. The results suggest that the most likely source of emittance growth is a mismatch of the beam to the magnetic transport, which can cause beam halo.

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.

Redesign of the End Group in the 3.9 GHz LCLS-II Cavity

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

Lunin, Andrei; Gonin, Ivan; Khabiboulline, Timergali

Development and production of Linac Coherent Light Source II (LCLS-II) is underway. The central part of LCLS-II is a continuous wave superconducting RF (CW SCRF) electron linac. The 3.9 GHz third harmonic cavity similar to the XFEL design will be used in LCLS-II for linearizing the longitudinal beam profile*. The initial design of the 3.9 GHz cavity developed for XFEL project has a large, 40 mm, beam pipe aperture for better higher-order mode (HOM) damping. It is resulted in dipole HOMs with frequencies nearby the operating mode, which causes difficulties with HOM coupler notch filter tuning. The CW linac operationmore » requires an extra caution in the design of the HOM coupler in order to prevent its possible overheating. In this paper we present the modified 3.9 GHz cavity End Group for meeting the LCLS-II requirements« less

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.

Motor torque compensation of an induction electric motor by adjusting a slip command during periods of supposed change in motor temperature

DOEpatents

Kelledes, William L.; St. John, Don K.

1992-01-01

The present invention maintains constant torque in an inverter driven AC induction motor during variations in rotor temperature. It is known that the torque output of a given AC induction motor is dependent upon rotor temperature. At rotor temperatures higher than the nominal operating condition the rotor impedance increases, reducing the rotor current and motor torque. In a similar fashion, the rotor impedance is reduced resulting in increased rotor current and motor torque when the rotor temperature is lower than the nominal operating condition. The present invention monitors the bus current from the DC supply to the inverter and adjusts the slip frequency of the inverter drive to maintain a constant motor torque. This adjustment is based upon whether predetermined conditions implying increased rotor temperature or decreased rotor temperature exist for longer that a predetermined interval of time.

Neural network based control of Doubly Fed Induction Generator in wind power generation

NASA Astrophysics Data System (ADS)

Barbade, Swati A.; Kasliwal, Prabha

2012-07-01

To complement the other types of pollution-free generation wind energy is a viable option. Previously wind turbines were operated at constant speed. The evolution of technology related to wind systems industry leaded to the development of a generation of variable speed wind turbines that present many advantages compared to the fixed speed wind turbines. In this paper the phasor model of DFIG is used. This paper presents a study of a doubly fed induction generator driven by a wind turbine connected to the grid, and controlled by artificial neural network ANN controller. The behaviour of the system is shown with PI control, and then as controlled by ANN. The effectiveness of the artificial neural network controller is compared to that of a PI controller. The SIMULINK/MATLAB simulation for Doubly Fed Induction Generator and corresponding results and waveforms are displayed.

Synergistic COX2 Induction by IFNγ and TNFα Self-Limits Type-1 Immunity in the Human Tumor Microenvironment.

PubMed

Wong, Jeffrey L; Obermajer, Nataša; Odunsi, Kunle; Edwards, Robert P; Kalinski, Pawel

2016-04-01

Maintenance of CTL-, Th1-, and NK cell-mediated type-1 immunity is essential for effective antitumor responses. Unexpectedly, we observed that the critical soluble mediators of type-1 immune effector cells, IFNγ and TNFα, synergize in the induction of cyclooxygenase 2 (COX2), the key enzyme in prostaglandin (PG)E2 synthesis, and the subsequent hyperactivation of myeloid-derived suppressor cells (MDSC) within the tumor microenvironment (TME) of ovarian cancer patients. MDSC hyperactivation by type-1 immunity and the resultant overexpression of indoleamine 2,3-dioxygenase (IDO), inducible nitric oxide synthase (iNOS/NOS2), IL10, and additional COX2 result in strong feedback suppression of type-1 immune responses. This paradoxical immune suppression driven by type-1 immune cell activation was found to depend on the synergistic action of IFNγ and TNFα, and could not be reproduced by either of these factors alone. Importantly, from a therapeutic standpoint, these negative feedback limiting type-1 responses could be eliminated by COX2 blockade, allowing amplification of type-1 immunity in the ovarian cancer TME. Our data demonstrate a new mechanism underlying the self-limiting nature of type-1 immunity in the human TME, driven by the synergistic induction of COX2 by IFNγ and TNFα, and provide a rationale for targeting the COX2-PGE2 axis to enhance the effectiveness of cancer immunotherapies. ©2016 American Association for Cancer Research.

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

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

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).

The role of data and inference in the development and application of ecological site concepts and state-and-transition models

USDA-ARS?s Scientific Manuscript database

Information embodied in ecological site descriptions and their state-and-transition models is crucial to effective land management, and as such is needed now. There is not time (or money) to employ a traditional research-based approach (i.e., inductive/deductive, hypothesis driven inference) to addr...

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.

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.

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.

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.

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.

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

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.

Solar powered actuator with continuously variable auxiliary power control

NASA Technical Reports Server (NTRS)

Nola, F. J. (Inventor)

1984-01-01

A solar powered system is disclosed in which a load such as a compressor is driven by a main induction motor powered by a solar array. An auxiliary motor shares the load with the solar powered motor in proportion to the amount of sunlight available, is provided with a power factor controller for controlling voltage applied to the auxiliary motor in accordance with the loading on that motor. In one embodiment, when sufficient power is available from the solar cell, the auxiliary motor is driven as a generator by excess power from the main motor so as to return electrical energy to the power company utility lines.

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

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

A Variable Frequency, Mis-Match Tolerant, Inductive Plasma Source

NASA Astrophysics Data System (ADS)

Rogers, Anthony; Kirchner, Don; Skiff, Fred

2014-10-01

Presented here is a survey and analysis of an inductively coupled, magnetically confined, singly ionized Argon plasma generated by a square-wave, variable frequency plasma source. The helicon-style antenna is driven directly by the class ``D'' amplifier without matching network for increased efficiency while maintaining independent control of frequency and applied power at the feed point. The survey is compared to similar data taken using a traditional exciter--power amplifier--matching network source. Specifically, the flexibility of this plasma source in terms of the independent control of electron plasma temperature and density is discussed in comparison to traditional source arrangements. Supported by US DOE Grant DE-FG02-99ER54543.

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

High quality proton beams from hybrid integrated laser-driven ion acceleration systems

NASA Astrophysics Data System (ADS)

Sinigardi, Stefano; Turchetti, Giorgio; Rossi, Francesco; Londrillo, Pasquale; Giove, Dario; De Martinis, Carlo; Bolton, Paul R.

2014-03-01

We consider a hybrid acceleration scheme for protons where the laser generated beam is selected in energy and angle and injected into a compact linac, which raises the energy from 30 to 60 MeV. The laser acceleration regime is TNSA and the energy spectrum is determined by the cutoff energy and proton temperature. The dependence of the spectrum on the target properties and the incidence angle is investigated with 2D PIC simulations. We base our work on widely available technologies and on laser with a short pulse, having in mind a facility whose cost is approximately 15 M €. Using a recent experiment as the reference, we choose the laser pulse and target so that the energy spectrum obtained from the 3D PIC simulation is close to the one observed, whose cutoff energy was estimated to be over 50 MeV. Laser accelerated protons in the TNSA regime have wide energy spectrum and broad divergence. In this paper we compare three transport lines, designed to perform energy selection and beam collimation. They are based on a solenoid, a quadruplet of permanent magnetic quadrupoles and a chicane. To increase the maximum available energy, which is actually seen as an upper limit due to laser properties and available targets, we propose to inject protons into a small linac for post-acceleration. The number of selected and injected protons is the highest with the solenoid and lower by one and two orders of magnitude with the quadrupoles and the chicane respectively. Even though only the solenoid enables achieving to reach a final intensity at the threshold required for therapy with the highest beam quality, the other systems will be very likely used in the first experiments. Realistic start-to-end simulations, as the ones reported here, are relevant for the design of such experiments.

The Status of Normal Conducting RF (NCRF) Guns, a Summary of the ERL2005 Workshop

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

Dowell, D.H.; /SLAC; Lewellen, J.W.

The 32nd Advanced ICFA Beam Dynamics Workshop on Energy Recovering Linacs (ERL2005) was held at Jefferson Laboratory, March 20 to 23, 2005. A wide range of ERL-related topics were presented and discussed in several working groups with Working Group 1 concentrated upon the physics and technology issues for DC, superconducting RF (SRF) and normal conducting RF (NCRF) guns. This paper summarizes the NCRF gun talks and reviews the status of NCRF gun technology. It begins with the presentations made on the subject of low-frequency, high-duty factor guns most appropriate for ERLs. One such gun at 433MHz was demonstrated at 25%DFmore » in 1992, while the CW and much improved version is currently being constructed at 700MHz for LANL. In addition, the idea of combining the NCRF gun with a SRF linac booster was presented and is described in this paper. There was also a talk on high-field guns typically used for SASE free electron lasers. In particular, the DESY coaxial RF feed design provides rotationally symmetric RF fields and greater flexibility in the placement of the focusing magnetic field. While in the LCLS approach, the symmetric fields are obtained with a dual RF feed and racetrack cell shape. Although these guns cannot be operated at high-duty factor, they do produce the best quality beams. With these limitations in mind, a section with material not presented at the workshop has been included in the paper. This work describes a re-entrant approach which may allow NCRF guns to operate with simultaneously increased RF fields and duty factors. And finally, a novel proposal describing a high-duty factor, two-frequency RF gun using a field emission source instead of a laser driven photocathode was also presented.« less

The status of normal conducting RF (NCRF) guns; a summary of the ERL2005 Workshop

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

D.H. Dowell; J.W. Lewellen; D. Nguyen

The 32nd Advanced ICFA Beam Dynamics Workshop on Energy Recovering Linacs (ERL2005) was held at Jefferson Laboratory, March 20 to 23, 2005. A wide range of ERL-related topics were presented and discussed in several working groups with Working Group 1 concentrated upon the physics and technology issues for DC, superconducting RF (SRF) and normal conducting RF (NCRF) guns. This paper summarizes the NCRF gun talks and reviews the status of NCRF gun technology. It begins with the presentations made on the subject of low-frequency, high-duty factor guns most appropriate for ERLs. One such gun at 433MHz was demonstrated at 25%DFmore » in 1992, while the CW and much improved version is currently being constructed at 700MHz for LANL. In addition, the idea of combining the NCRF gun with a SRF linac booster was presented and is described in this paper. There was also a talk on high-field guns typically used for SASE free electron lasers. In particular, the DESY coaxial RF feed design provides rotationally symmetric RF fields and greater flexibility in the placement of the focusing magnetic field. While in the LCLS approach, the symmetric fields are obtained with a dual RF feed and racetrack cell shape. Although these guns cannot be operated at high-duty factor, they do produce the best quality beams. With these limitations in mind, a section with material not presented at the workshop has been included in the paper. This work describes a re-entrant approach which may allow NCRF guns to operate with simultaneously increased RF fields and duty factors. And finally, a novel proposal describing a high-duty factor, two-frequency RF gun using a field emission source instead of a laser driven photocathode was also presented.« less

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

MO-F-CAMPUS-T-03: Data Driven Approaches for Determination of Treatment Table Tolerance Values for Record and Verification Systems

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

Gupta, N; DiCostanzo, D; Fullenkamp, M

2015-06-15

Purpose: To determine appropriate couch tolerance values for modern radiotherapy linac R&V systems with indexed patient setup. Methods: Treatment table tolerance values have been the most difficult to lower, due to many factors including variations in patient positioning and differences in table tops between machines. We recently installed nine linacs with similar tables and started indexing every patient in our clinic. In this study we queried our R&V database and analyzed the deviation of couch position values from the acquired values at verification simulation for all patients treated with indexed positioning. Mean and standard deviations of daily setup deviations weremore » computed in the longitudinal, lateral and vertical direction for 343 patient plans. The mean, median and standard error of the standard deviations across the whole patient population and for some disease sites were computed to determine tolerance values. Results: The plot of our couch deviation values showed a gaussian distribution, with some small deviations, corresponding to setup uncertainties on non-imaging days, and SRS/SRT/SBRT patients, as well as some large deviations which were spot checked and found to be corresponding to indexing errors that were overriden. Setting our tolerance values based on the median + 1 standard error resulted in tolerance values of 1cm lateral and longitudinal, and 0.5 cm vertical for all non- SRS/SRT/SBRT cases. Re-analizing the data, we found that about 92% of the treated fractions would be within these tolerance values (ignoring the mis-indexed patients). We also analyzed data for disease site based subpopulations and found no difference in the tolerance values that needed to be used. Conclusion: With the use of automation, auto-setup and other workflow efficiency tools being introduced into radiotherapy workflow, it is very essential to set table tolerances that allow safe treatments, but flag setup errors that need to be reassessed before treatments.« 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.

Spectroscopic sensitivity of real-time, rapidly induced phytochemical change in response to damage.

PubMed

Couture, John J; Serbin, Shawn P; Townsend, Philip A

2013-04-01

An ecological consequence of plant-herbivore interactions is the phytochemical induction of defenses in response to insect damage. Here, we used reflectance spectroscopy to characterize the foliar induction profile of cardenolides in Asclepias syriaca in response to damage, tracked in vivo changes and examined the influence of multiple plant traits on cardenolide concentrations. Foliar cardenolide concentrations were measured at specific time points following damage to capture their induction profile. Partial least-squares regression (PLSR) modeling was employed to calibrate cardenolide concentrations to reflectance spectroscopy. In addition, subsets of plants were either repeatedly sampled to track in vivo changes or modified to reduce latex flow to damaged areas. Cardenolide concentrations and the induction profile of A. syriaca were well predicted using models derived from reflectance spectroscopy, and this held true for repeatedly sampled plants. Correlations between cardenolides and other foliar-related variables were weak or not significant. Plant modification for latex reduction inhibited an induced cardenolide response. Our findings show that reflectance spectroscopy can characterize rapid phytochemical changes in vivo. We used reflectance spectroscopy to identify the mechanisms behind the production of plant secondary metabolites, simultaneously characterizing multiple foliar constituents. In this case, cardenolide induction appears to be largely driven by enhanced latex delivery to leaves following damage. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Theoretical study of the design and performance of a high-gain, high-extraction-efficiency FEL oscillator

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

Goldstein, J.; Nguyen, D.C.; Sheffield, R.L.

1996-10-01

We present the results of theoretical and simulation studies of the design and performance of a new F type of FEL oscillator. This device, known by the acronym RAFEL for Regenerative Amplifier Free-Electron Laser, will be constructed in the space presently occupied by the AFEL (Advanced FEL) at Los Alamos, and will be driven by an upgraded (to higher average power) version of the present AFEL linac. In order to achieve a long-time-averaged optical output power of {approximately} 1 kW using an electron beam with an average power of {approximately} 20 kW, a rather high extraction efficiency {eta} {approximately} 5%more » is required. We have designed a 2-m-long undulator to attain this goal: the first meter is untapered and provides high gain while the second meter is linearly-tapered in magnetic field amplitude to provide high extraction efficiency in the standard K-M-R manner. Two-plane focusing and linear polarization of the undulator are assumed. Electron-beam properties from PARMEIA simulations of the AFEL accelerator were used in the design. A large saturated gain, {approximately} 500, requires a very small optical feedback to keep the device operating at steady-state. However, the large gain leads to distorted optical modes which require two- and three-dimensional simulations to adequately treat diffraction effects. This FEL will be driven by 17 MeV electrons and will operate in the 16 {mu}m spectral region.« less

Physics and Technology of Resonant-Tunneling Devices

DTIC Science & Technology

1992-07-01

Negative differential resistance, quantum-well inductance, suppressed shot noise, superlattice tunneling, Type-Il heterostructures, lattice...of these deviations is carried out in the accompanying manuscript of Appendix C. 3.1.3. Superlattice Resonant Tunneling In the 1970s, interest in...resonant-tunneling was driven by the desire to observe long-range coherent transport phenomena, such as Bloch oscillations in superlattice structures. In

Socio-Technical Relations in the Creation of an Interest-Driven Open Course

ERIC Educational Resources Information Center

Ponti, Marisa

2011-01-01

The aim of this article is to present the findings from a small exploratory case study of an open course on cyberpunk literature conducted at the Peer 2 Peer University (P2PU), an online grass-roots organisation that runs non-accredited courses. Employing actor network theory to inform an ethnographic-inductive approach, the case study sought to…

Beam Dynamics for ARIA

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

Ekdahl, Carl August Jr.

2014-10-14

Beam dynamics issues are assessed for a new linear induction electron accelerator being designed for flash radiography of large explosively driven hydrodynamic experiments. Special attention is paid to equilibrium beam transport, possible emittance growth, and beam stability. It is concluded that a radiographic quality beam will be produced possible if engineering standards and construction details are equivalent to those on the present radiography accelerators at Los Alamos.

Point-source helicity injection for ST plasma startup in Pegasus

NASA Astrophysics Data System (ADS)

Redd, A. J.; Battaglia, D. J.; Bongard, M. W.; Fonck, R. J.; Schlossberg, D. J.

2009-11-01

Plasma current guns are used as point-source DC helicity injectors for forming non-solenoidal tokamak plasmas in the Pegasus Toroidal Experiment. Discharges driven by this injection scheme have achieved Ip>= 100 kA using Iinj<= 4 kA. They form at the outboard midplane, transition to a tokamak-like equilibrium, and continue to grow inward as Ip increases due to helicity injection and outer- PF induction. The maximum Ip is determined by helicity balance (injection rate vs resistive dissipation) and a Taylor relaxation limit, in which Ip√ITF Iinj/w, where w is the radial thickness of the gun-driven edge. Preliminary experiments tentatively confirm these scalings with ITF, Iinj, and w, increasing confidence in this simple relaxation model. Adding solenoidal inductive drive during helicity injection can push Ip up to, but not beyond, the predicted relaxation limit, demonstrating that this is a hard performance limit. Present experiments are focused on increasing the injection voltage (i.e., helicity injection rate) and reducing w. Near-term goals are to further test scalings predicted by the simple relaxation model and to study in detail the observed bursty n=1 activity correlated with rapid increases in Ip.

High speed displacement measurement based on electro-magnetic induction applied to electromagnetically driven ring expansion

NASA Astrophysics Data System (ADS)

Han, Xiaotao; Wu, Jiawei; Huang, Lantao; Qiu, Lei; Chen, Qi; Cao, Quanliang; Herlach, Fritz; Li, Liang

2017-11-01

Investigating the mechanism of electromagnetic forming (EMF) becomes a hot topic in the field of metal forming. The high speed up to 200 m/s in EMF makes it a real challenge to capture the forming process. To this end, a new method for measuring displacement at high speed based on electromagnetic induction has been developed. Specifically this is used to measure the displacement of an expanding metal ring driven by a pulsed magnetic field; this is one of the basic EMF processes. The new method is simple and practical, and it combines high-speed response with adequate precision. The new measurement system consists of a printed circuit board (PCB) and a Rogowski probe. Eleven coaxial annular detecting probes are arranged in the PCB plate to acquire induced voltage at different positions, and a Rogowski probe is used to measure the current in the driving coil. The displacement of the ring is deduced by analyzing the output voltages of the detecting probes and the Rogowski probe. The feasibility of the method is verified by comparing the results with pictures from a high speed camera taken simultaneously.

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.

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.

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.

Hypoxia-driven angiogenesis: role of tip cells and extracellular matrix scaffolding.

PubMed

Germain, Stéphane; Monnot, Catherine; Muller, Laurent; Eichmann, Anne

2010-05-01

Angiogenesis is a highly coordinated tissue remodeling process leading to blood vessel formation. Hypoxia triggers angiogenesis via induction of expression of growth factors such as vascular endothelial growth factor (VEGF). VEGF instructs endothelial cells to form tip cells, which lead outgrowing capillary sprouts, whereas Notch signaling inhibits sprout formation. Basement membrane deposition and mechanical cues from the extracellular matrix (ECM) induced by hypoxia may participate to coordinated vessel sprouting in conjunction with the VEGF and Notch signaling pathways. Hypoxia regulates ECM composition, deposition, posttranslational modifications and rearrangement. In particular, hypoxia-driven vascular remodeling is dynamically regulated through modulation of ECM-modifying enzyme activities that eventually affect both matricellular proteins and growth factor availability. Better understanding of the complex interplay between endothelial cells and soluble growth factors and mechanical factors from the ECM will certainly have significant implications for understanding the regulation of developmental and pathological angiogenesis driven by hypoxia.

Early cytokine modulation after the rapid induction phase of sublingual immunotherapy with mite monomeric allergoids.

PubMed

Di Gioacchino, M; Perrone, A; Petrarca, C; Di Claudio, F; Mistrello, G; Falagiani, P; Dadorante, V; Verna, N; Braga, M; Ballone, E; Cavallucci, E

2008-01-01

The influence of different treatment schedules of sublingual immunotherapy (SLIT) in activating IL-10-producing T-cells, crucial in inducing allergen-specific tolerance, is not completely understood. The present work was designed to evaluate allergen driven interleukin release by mononuclear cells in the early phase of SLIT, after application of different induction schemes. Twenty mite-allergic patients were enrolled, 10 (group A) treated with a traditional 98 day induction scheme and 10 (group B) with a 16 day scheme with monomeric allergoid vaccine. At the end of the induction phase, the cumulative doses taken by group A and group B patients were equivalent to 50.5 and 50.3 microg of mite group 1 allergens, respectively. The release of Th1-, Th2- and Treg-related interleukins was assessed in culture supernatants of 5 microg/ml Der-p1-stimulated mononuclear cells, isolated before and after the induction phases. No relevant treatment-related side effects were observed. Interleukin release was similar in the two groups at the enrolment. Non-stimulated and Der p 1 stimulated release of studied cytokines was similar in the two groups at enrolment. Der p 1 stimulation significantly increased IL-10 release (p<0.0002) after treatment in group B patients, and this effect was higher (p=0.05) compared to group A patients. Furthermore, at the end of SLIT induction TNF-alpha, IL-4 and IFN-gamma production were reduced in group B patients (p<0.05, p=0.062 and p=0.060, respectively). The rapid induction scheme of sublingual immunotherapy induces an early immune suppression more effectively than the slower one. The rapid induction scheme should be the preferential way to start sublingual immunotherapy, particularly when monomeric allergoids are utilized.

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.

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.

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

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.