THz-pump and X-ray-probe sources based on an electron linac.

PubMed

Setiniyaz, Sadiq; Park, Seong Hee; Kim, Hyun Woo; Vinokurov, Nikolay A; Jang, Kyu-Ha; Lee, Kitae; Baek, In Hyung; Jeong, Young Uk

2017-11-01

We describe a compact THz-pump and X-ray-probe beamline, based on an electron linac, for ultrafast time-resolved diffraction applications. Two high-energy electron (γ > 50) bunches, 5 ns apart, impinge upon a single-foil or multifoil radiator and generate THz radiation and X-rays simultaneously. The THz pulse from the first bunch is synchronized to the X-ray beam of the second bunch by using an adjustable optical delay of a THz pulse. The peak power of THz radiation from the multifoil radiator is estimated to be 0.14 GW for a 200 pC well-optimized electron bunch. GEANT4 simulations show that a carbon foil with a thickness of 0.5-1.0 mm has the highest yield of 10-20 keV hard X-rays for a 25 MeV beam, which is approximately 10 3 photons/(keV pC-electrons) within a few degrees of the polar angle. A carbon multifoil radiator with 35 foils (25 μm thick each) can generate close to 10 3 hard X-rays/(keV pC-electrons) within a 2° acceptance angle. With 200 pC charge and a 100 Hz repetition rate, we can generate 10 7 X-rays per 1 keV energy bin per second or 10 5 X-rays per 1 keV energy bin per pulse. The longitudinal time profile of an X-ray pulse ranges from 400 to 600 fs depending on the acceptance angle. The broadening of the time duration of an X-ray pulse is observed owing to its diverging effect. A double-crystal monochromator will be used to select and transport the desired X-rays to the sample. The heating of the radiators by an electron beam is negligible because of the low beam current.

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

Investigating a multi-purpose target for electron linac based photoneutron sources for BNCT of deep-seated tumors

NASA Astrophysics Data System (ADS)

Masoudi, S. Farhad; Rasouli, Fatemeh S.

2015-08-01

Recent studies in BNCT have focused on investigating appropriate neutron sources as alternatives for nuclear reactors. As the most prominent facilities, the electron linac based photoneutron sources benefit from two consecutive reactions, (e, γ) and (γ, n). The photoneutron sources designed so far are composed of bipartite targets which involve practical problems and are far from the objective of achieving an optimized neutron source. This simulation study deals with designing a compact, optimized, and geometrically simple target for a photoneutron source based on an electron linac. Based on a set of MCNPX simulations, tungsten is found to have the potential of utilizing as both photon converter and photoneutron target. Besides, it is shown that an optimized dimension for such a target slows-down the produced neutrons toward the desired energy range while keeping them economy, which makes achieving the recommended criteria for BNCT of deep-tumors more available. This multi-purpose target does not involve complicated designing, and can be considered as a significant step toward finding application of photoneutron sources for in-hospital treatments. In order to shape the neutron beam emitted from such a target, the beam is planned to pass through an optimized arrangement of materials composed of moderators, filters, reflector, and collimator. By assessment with the recommended in-air parameters, it is shown that the designed beam provides high intensity of desired neutrons, as well as low background contamination. The last section of this study is devoted to investigate the performance of the resultant beam in deep tissue. A typical simulated liver tumor, located within a phantom of human body, was subjected to the irradiation of the designed spectrum. The dosimetric results, including evaluated depth-dose curves and carried out in-phantom parameters show that the proposed configuration establishes acceptable agreement between the appropriate neutron intensity, and

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

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

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.

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

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

Commercial Superconducting Electron Linac for Radioisotope Production

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

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

2015-08-13

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

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

SU-F-T-300: Impact of Electron Density Modeling of ArcCHECK Cylindricaldiode Array On 3DVH Patient Specific QA Software Tool Analysis

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

Patwe, P; Mhatre, V; Dandekar, P

Purpose: 3DVH software is a patient specific quality assurance tool which estimates the 3D dose to the patient specific geometry with the help of Planned Dose Perturbation algorithm. The purpose of this study is to evaluate the impact of HU value of ArcCHECK phantom entered in Eclipse TPS on 3D dose & DVH QA analysis. Methods: Manufacturer of ArcCHECK phantom provides CT data set of phantom & recommends considering it as a homogeneous phantom with electron density (1.19 gm/cc or 282 HU) close to PMMA. We performed this study on Eclipse TPS (V13, VMS) & trueBEAM STx VMS Linac &more » ArcCHECK phantom (SNC). Plans were generated for 6MV photon beam, 20cm×20cm field size at isocentre & SPD (Source to phantom distance) of 86.7 cm to deliver 100cGy at isocentre. 3DVH software requires patients DICOM data generated by TPS & plan delivered on ArcCHECK phantom. Plans were generated in TPS by assigning different HU values to phantom. We analyzed gamma index & the dose profile for all plans along vertical down direction of beam’s central axis for Entry, Exit & Isocentre dose. Results: The global gamma passing rate (2% & 2mm) for manufacturer recommended HU value 282 was 96.3%. Detector entry, Isocentre & detector exit Doses were 1.9048 (1.9270), 1.00(1.0199) & 0.5078(0.527) Gy for TPS (Measured) respectively.The global gamma passing rate for electron density 1.1302 gm/cc was 98.6%. Detector entry, Isocentre & detector exit Doses were 1.8714 (1.8873), 1.00(0.9988) & 0.5211(0.516) Gy for TPS (Measured) respectively. Conclusion: Electron density value assigned by manufacturer does not hold true for every user. Proper modeling of electron density of ArcCHECK in TPS is essential to avoid systematic error in dose calculation of patient specific QA.« less

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

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

Hickling, S; El Naqa, I

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

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.

Energy-Recovery Linacs for Commercial Radioisotope Production

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

Johnson, Rolland Paul

Most radioisotopes are produced by nuclear reactors or positive ion accelerators, which are expensive to construct and to operate. Photonuclear reactions using bremsstrahlung photon beams from less-expensive electron linacs can generate isotopes of critical interest, but much of the beam energy in a conventional electron linac is dumped at high energy, making unwanted radioactivation. The largest part of this radioactivation may be completely eliminated by applying energy recovery linac technology to the problem with an additional benefit that the energy cost to produce a given amount of isotope is reduced. Consequently, a Superconducting Radio Frequency (SRF) Energy Recovery Linac (ERL)more » is a path to a more diverse and reliable domestic supply of short-lived, high-value, high-demand isotopes at a cost lower than that of isotopes produced by reactors or positive-ion accelerators. A Jefferson Lab approach to this problem involves a thin photon production radiator, which allows the electron beam to recirculate through rf cavities so the beam energy can be recovered while the spent electrons are extracted and absorbed at a low enough energy to minimize unwanted radioactivation. The thicker isotope photoproduction target is not in the beam. MuPlus, with Jefferson Lab and Niowave, proposed to extend this ERL technology to the commercial world of radioisotope production. In Phase I we demonstrated that 1) the ERL advantage for producing radioisotopes is at high energies (~100 MeV), 2) the range of acceptable radiator thickness is narrow (too thin and there is no advantage relative to other methods and too thick means energy recovery is too difficult), 3) using optics techniques developed under an earlier STTR for collider low beta designs greatly improves the fraction of beam energy that can be recovered (patent pending), 4) many potentially useful radioisotopes can be made with this ERL technique that have never before been available in significant commercial

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

Response of TLD-100 in mixed fields of photons and electrons.

PubMed

Lawless, Michael J; Junell, Stephanie; Hammer, Cliff; DeWerd, Larry A

2013-01-01

Thermoluminescent dosimeters (TLDs) are routinely used for dosimetric measurements of high energy photon and electron fields. However, TLD response in combined fields of photon and electron beam qualities has not been characterized. This work investigates the response of TLD-100 (LiF:Mg,Ti) to sequential irradiation by high-energy photon and electron beam qualities. TLDs were irradiated to a known dose by a linear accelerator with a 6 MV photon beam, a 6 MeV electron beam, and a NIST-traceable (60)Co beam. TLDs were also irradiated in a mixed field of the 6 MeV electron beam and the 6 MV photon beam. The average TLD response per unit dose of the TLDs for each linac beam quality was normalized to the average response per unit dose of the TLDs irradiated by the (60)Co beam. Irradiations were performed in water and in a Virtual Water™ phantom. The 6 MV photon beam and 6 MeV electron beam were used to create dose calibration curves relating TLD response to absorbed dose to water, which were applied to the TLDs irradiated in the mixed field. TLD relative response per unit dose in the mixed field was less sensitive than the relative response in the photon field and more sensitive than the relative response in the electron field. Application of the photon dose calibration curve to the TLDs irradiated in a mixed field resulted in an underestimation of the delivered dose, while application of the electron dose calibration curve resulted in an overestimation of the dose. The relative response of TLD-100 in mixed fields fell between the relative response in the photon-only and electron-only fields. TLD-100 dosimetry of mixed fields must account for this intermediate response to minimize the estimation errors associated with calibration factors obtained from a single beam quality.

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

IRIDE: Interdisciplinary research infrastructure based on dual electron linacs and lasers

NASA Astrophysics Data System (ADS)

Ferrario, M.; Alesini, D.; Alessandroni, M.; Anania, M. P.; Andreas, S.; Angelone, M.; Arcovito, A.; Arnesano, F.; Artioli, M.; Avaldi, L.; Babusci, D.; Bacci, A.; Balerna, A.; Bartalucci, S.; Bedogni, R.; Bellaveglia, M.; Bencivenga, F.; Benfatto, M.; Biedron, S.; Bocci, V.; Bolognesi, M.; Bolognesi, P.; Boni, R.; Bonifacio, R.; Boscherini, F.; Boscolo, M.; Bossi, F.; Broggi, F.; Buonomo, B.; Calo, V.; Catone, D.; Capogni, M.; Capone, M.; Cassou, K.; Castellano, M.; Castoldi, A.; Catani, L.; Cavoto, G.; Cherubini, N.; Chirico, G.; Cestelli-Guidi, M.; Chiadroni, E.; Chiarella, V.; Cianchi, A.; Cianci, M.; Cimino, R.; Ciocci, F.; Clozza, A.; Collini, M.; Colo, G.; Compagno, A.; Contini, G.; Coreno, M.; Cucini, R.; Curceanu, C.; Curciarello, F.; Dabagov, S.; Dainese, E.; Davoli, I.; Dattoli, G.; De Caro, L.; De Felice, P.; De Leo, V.; Dell Agnello, S.; Della Longa, S.; Delle Monache, G.; De Spirito, M.; Di Cicco, A.; Di Donato, C.; Di Gioacchino, D.; Di Giovenale, D.; Di Palma, E.; Di Pirro, G.; Dodaro, A.; Doria, A.; Dosselli, U.; Drago, A.; Dupraz, K.; Escribano, R.; Esposito, A.; Faccini, R.; Ferrari, A.; Filabozzi, A.; Filippetto, D.; Fiori, F.; Frasciello, O.; Fulgentini, L.; Gallerano, G. P.; Gallo, A.; Gambaccini, M.; Gatti, C.; Gatti, G.; Gauzzi, P.; Ghigo, A.; Ghiringhelli, G.; Giannessi, L.; Giardina, G.; Giannini, C.; Giorgianni, F.; Giovenale, E.; Giulietti, D.; Gizzi, L.; Guaraldo, C.; Guazzoni, C.; Gunnella, R.; Hatada, K.; Iannone, M.; Ivashyn, S.; Jegerlehner, F.; Keeffe, P. O.; Kluge, W.; Kupsc, A.; Labate, L.; Levi Sandri, P.; Lombardi, V.; Londrillo, P.; Loreti, S.; Lorusso, A.; Losacco, M.; Lukin, A.; Lupi, S.; Macchi, A.; Magazù, S.; Mandaglio, G.; Marcelli, A.; Margutti, G.; Mariani, C.; Mariani, P.; Marzo, G.; Masciovecchio, C.; Masjuan, P.; Mattioli, M.; Mazzitelli, G.; Merenkov, N. P.; Michelato, P.; Migliardo, F.; Migliorati, M.; Milardi, C.; Milotti, E.; Milton, S.; Minicozzi, V.; Mobilio, S.; Morante, S.; Moricciani, D.; Mostacci, A.; Muccifora, V.; Murtas, F.; Musumeci, P.; Nguyen, F.; Orecchini, A.; Organtini, G.; Ottaviani, P. L.; Pace, C.; Pace, E.; Paci, M.; Pagani, C.; Pagnutti, S.; Palmieri, V.; Palumbo, L.; Panaccione, G. C.; Papadopoulos, C. F.; Papi, M.; Passera, M.; Pasquini, L.; Pedio, M.; Perrone, A.; Petralia, A.; Petrarca, M.; Petrillo, C.; Petrillo, V.; Pierini, P.; Pietropaolo, A.; Pillon, M.; Polosa, A. D.; Pompili, R.; Portoles, J.; Prosperi, T.; Quaresima, C.; Quintieri, L.; Rau, J. V.; Reconditi, M.; Ricci, A.; Ricci, R.; Ricciardi, G.; Ricco, G.; Ripani, M.; Ripiccini, E.; Romeo, S.; Ronsivalle, C.; Rosato, N.; Rosenzweig, J. B.; Rossi, A. A.; Rossi, A. R.; Rossi, F.; Rossi, G.; Russo, D.; Sabatucci, A.; Sabia, E.; Sacchetti, F.; Salducco, S.; Sannibale, F.; Sarri, G.; Scopigno, T.; Sekutowicz, J.; Serafini, L.; Sertore, D.; Shekhovtsova, O.; Spassovsky, I.; Spadaro, T.; Spataro, B.; Spinozzi, F.; Stecchi, A.; Stellato, F.; Surrenti, V.; Tenore, A.; Torre, A.; Trentadue, L.; Turchini, S.; Vaccarezza, C.; Vacchi, A.; Valente, P.; Venanzoni, G.; Vescovi, S.; Villa, F.; Zanotti, G.; Zema, N.; Zobov, M.; Zomer, F.

2014-03-01

This paper describes the scientific aims and potentials as well as the preliminary technical design of IRIDE, an innovative tool for multi-disciplinary investigations in a wide field of scientific, technological and industrial applications. IRIDE will be a high intensity "particles factory", based on a combination of high duty cycle radio-frequency superconducting electron linacs and of high energy lasers. Conceived to provide unique research possibilities for particle physics, for condensed matter physics, chemistry and material science, for structural biology and industrial applications, IRIDE will open completely new research possibilities and advance our knowledge in many branches of science and technology. IRIDE is also supposed to be realized in subsequent stages of development depending on the assigned priorities.

SU-F-T-656: Monte Carlo Study On Air Activation Around a Medical Electron Linac

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

Horst, F; GSI Helmholtz Centre for Heavy Ion Research, Darmstadt; Fehrenbacher, G

Purpose: In high energy photon therapy, several radiation protection issues result from photonuclear reactions. The activation of air - directly by photonuclear reactions as well as indirectly by capture of photoneutrons generated inside the linac head - is a major point of concern for the medical staff. The purpose of this study was to estimate the annual effective dose to medical workers due to activated air around a medical high energy electron linac by means of Monte Carlo simulations. Methods: The treatment head of a Varian Clinac in 18 MV-X mode as well as the surrounding concrete bunker were modeledmore » and the radiation transport was simulated using the Monte Carlo code FLUKA, starting from the primary electron striking the bremsstrahlung target. The activation yields in air from photo-disintegration of O-16 and N-14 nuclei as well as from neutron capture on Ar-40 nuclei were obtained from the simulations. The activation build-up, radioactive decay and air ventilation were studied using a mathematical model. The annual effective dose to workers was estimated by using published isotope specific conversion factors. Results: The oxygen and nitrogen activation yields were in contrast to the argon activation yield found to be field size dependent. The impact of the treatment room ventilation on the different air activation products was investigated and quantified. An estimate with very conservative assumptions gave an annual effective dose to workers of < 1 mSv/a. Conclusion: From the results of this study it can be concluded that the contribution of air activation to the radiation exposure to medical workers should be negligible in modern photon therapy, especially when it is compared to the dose due to prompt neutrons and the activation of heavy solid materials such as the jaws and the collimators inside the linac head.« less

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

DOEpatents

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

2015-09-08

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

Linac head scatter factor for asymmetric radiation field

NASA Astrophysics Data System (ADS)

Soubra, Mazen Ahmed

1997-11-01

The head scatter factor, Sh is an important dosimetric quantity used in radiation therapy dose calculation. It is empirically determined and its field size dependence reflects changes in photon scatter from components in the linac treatment head. In this work a detailed study of the physical factors influencing the determination of Sh was performed with particular attention given to asymmetric field geometries. Ionization measurements for 6 and 18 MV photon beams were made to examine the factors which determine Sh. These include: phantom size and material, collimator backscatter, non-lateral electronic equilibrium (LEE) conditions, electron contamination, collimator-exchange, photon energy, flattening filter and off-axis distance (OAD). Results indicated that LEE is not required for Sh measurements if electron contamination is minimized. Brass caps or polystyrene miniphantoms can both be used in Sh measurements provided the phantom thickness is large enough to stop contaminant electrons. Backscatter radiation effects into the monitor chamber were found to be negligible for the Siemens linac. It was found that the presence and shape of the flattening filter had a significant effect on the empirically determined value of Sh was also shown to be a function of OAD, particularly for small fields. For fields larger than 12×12 cm2/ Sh was independent of OAD. A flattening filter mass model was introduced to explain qualitatively the above results. A detailed Monte Carlo simulation of the Siemens KD2 linac head in 6 MV mode was performed to investigate the sources of head scatter which contribute to the measured Sh. The simulated head components include the flattening filter, the electron beam stopper, the primary collimator, the photon monitor chamber and the secondary collimators. The simulations showed that the scatter from the head of the Siemens linac is a complex function of the head components. On the central axis the flattening filter played the dominant role in

Response of TLD-100 in mixed fields of photons and electrons

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

Lawless, Michael J.; Junell, Stephanie; Hammer, Cliff

Purpose: Thermoluminescent dosimeters (TLDs) are routinely used for dosimetric measurements of high energy photon and electron fields. However, TLD response in combined fields of photon and electron beam qualities has not been characterized. This work investigates the response of TLD-100 (LiF:Mg,Ti) to sequential irradiation by high-energy photon and electron beam qualities. Methods: TLDs were irradiated to a known dose by a linear accelerator with a 6 MV photon beam, a 6 MeV electron beam, and a NIST-traceable {sup 60}Co beam. TLDs were also irradiated in a mixed field of the 6 MeV electron beam and the 6 MV photon beam.more » The average TLD response per unit dose of the TLDs for each linac beam quality was normalized to the average response per unit dose of the TLDs irradiated by the {sup 60}Co beam. Irradiations were performed in water and in a Virtual Water Trade-Mark-Sign phantom. The 6 MV photon beam and 6 MeV electron beam were used to create dose calibration curves relating TLD response to absorbed dose to water, which were applied to the TLDs irradiated in the mixed field. Results: TLD relative response per unit dose in the mixed field was less sensitive than the relative response in the photon field and more sensitive than the relative response in the electron field. Application of the photon dose calibration curve to the TLDs irradiated in a mixed field resulted in an underestimation of the delivered dose, while application of the electron dose calibration curve resulted in an overestimation of the dose. Conclusions: The relative response of TLD-100 in mixed fields fell between the relative response in the photon-only and electron-only fields. TLD-100 dosimetry of mixed fields must account for this intermediate response to minimize the estimation errors associated with calibration factors obtained from a single beam quality.« less

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.

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

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

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

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

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.

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

DOE PAGES

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

2018-03-23

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

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

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

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

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

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

SU-E-T-554: Comparison of Electron Disequilibrium Factor in External Photon Beams for Different Models of Linear Accelerators

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

LIU, B; Zhu, T

Purpose: The dose in the buildup region of a photon beam is usually determined by the transport of the primary secondary electrons and the contaminating electrons from accelerator head. This can be quantified by the electron disequilibrium factor, E, defined as the ratio between total dose and equilibrium dose (proportional to total kerma), E = 1 in regions beyond buildup region. Ecan be different among accelerators of different models and/or manufactures of the same machine. This study compares E in photon beams from different machine models/ Methods: Photon beam data such as fractional depth dose curve (FDD) and phantom scattermore » factors as a function of field size and phantom depth were measured for different Linac machines. E was extrapolated from these fractional depth dose data while taking into account inverse-square law. The ranges of secondary electron were chosen as 3 and 6 cm for 6 and 15 MV photon beams, respectively. The field sizes range from 2x2 to 40x40 cm{sup 2}. Results: The comparison indicates the standard deviations of electron contamination among different machines are about 2.4 - 3.3% at 5 mm depth for 6 MV and 1.2 - 3.9% at 1 cm depth for 15 MV for the same field size. The corresponding maximum deviations are 3.0 - 4.6% and 2 - 4% for 6 and 15 MV, respectively. Both standard and maximum deviations are independent of field sizes in the buildup region for 6 MV photons, and slightly decreasing with increasing field size at depths up to 1 cm for 15 MV photons. Conclusion: The deviations of electron disequilibrium factor for all studied Linacs are less than 3% beyond the depth of 0.5 cm for the photon beams for the full range of field sizes (2-40 cm) so long as they are from the same manufacturer.« less

Means and method for calibrating a photon detector utilizing electron-photon coincidence

NASA Technical Reports Server (NTRS)

Srivastava, S. K. (Inventor)

1984-01-01

An arrangement for calibrating a photon detector particularly applicable for the ultraviolet and vacuum ultraviolet regions is based on electron photon coincidence utilizing crossed electron beam atom beam collisions. Atoms are excited by electrons which lose a known amount of energy and scatter with a known remaining energy, while the excited atoms emit photons of known radiation. Electrons of the known remaining energy are separated from other electrons and are counted. Photons emitted in a direction related to the particular direction of scattered electrons are detected to serve as a standard. Each of the electrons is used to initiate the measurements of a time interval which terminates with the arrival of a photon exciting the photon detector. Only the number of time intervals related to the coincidence correlation and of electrons scattered in the particular direction with the known remaining energy and photons of a particular radiation level emitted due to the collisions of such scattered electrons are counted. The detector calibration is related to the number of counted electrons and photons.

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.

Monte Carlo simulations and benchmark measurements on the response of TE(TE) and Mg(Ar) ionization chambers in photon, electron and neutron beams

NASA Astrophysics Data System (ADS)

Lin, Yi-Chun; Huang, Tseng-Te; Liu, Yuan-Hao; Chen, Wei-Lin; Chen, Yen-Fu; Wu, Shu-Wei; Nievaart, Sander; Jiang, Shiang-Huei

2015-06-01

The paired ionization chambers (ICs) technique is commonly employed to determine neutron and photon doses in radiology or radiotherapy neutron beams, where neutron dose shows very strong dependence on the accuracy of accompanying high energy photon dose. During the dose derivation, it is an important issue to evaluate the photon and electron response functions of two commercially available ionization chambers, denoted as TE(TE) and Mg(Ar), used in our reactor based epithermal neutron beam. Nowadays, most perturbation corrections for accurate dose determination and many treatment planning systems are based on the Monte Carlo technique. We used general purposed Monte Carlo codes, MCNP5, EGSnrc, FLUKA or GEANT4 for benchmark verifications among them and carefully measured values for a precise estimation of chamber current from absorbed dose rate of cavity gas. Also, energy dependent response functions of two chambers were calculated in a parallel beam with mono-energies from 20 keV to 20 MeV photons and electrons by using the optimal simple spherical and detailed IC models. The measurements were performed in the well-defined (a) four primary M-80, M-100, M120 and M150 X-ray calibration fields, (b) primary 60Co calibration beam, (c) 6 MV and 10 MV photon, (d) 6 MeV and 18 MeV electron LINACs in hospital and (e) BNCT clinical trials neutron beam. For the TE(TE) chamber, all codes were almost identical over the whole photon energy range. In the Mg(Ar) chamber, MCNP5 showed lower response than other codes for photon energy region below 0.1 MeV and presented similar response above 0.2 MeV (agreed within 5% in the simple spherical model). With the increase of electron energy, the response difference between MCNP5 and other codes became larger in both chambers. Compared with the measured currents, MCNP5 had the difference from the measurement data within 5% for the 60Co, 6 MV, 10 MV, 6 MeV and 18 MeV LINACs beams. But for the Mg(Ar) chamber, the derivations reached 7

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

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

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

NASA Astrophysics Data System (ADS)

Buakor, K.; Rimjaem, S.

2017-09-01

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

SU-E-T-137: The Response of TLD-100 in Mixed Fields of Photons and Electrons.

PubMed

Lawless, M; Junell, S; Hammer, C; DeWerd, L

2012-06-01

Thermoluminescent dosimeters are used routinely for dosimetric measurements of photon and electron fields. However, no work has been published characterizing TLDs for use in combined photon and electron fields. This work investigates the response of TLD-100 (LiF:Mg,Ti) in mixed fields of photon and electron beam qualities. TLDs were irradiated in a 6 MV photon beam, 6 MeV electron beam, and a NIST traceable cobalt-60 beam. TLDs were also irradiated in a mixed field of the electron and photon beams. All irradiations were normalized to absorbed dose to water as defined in the AAPM TG-51 report. The average response per dose (nC/Gy) for each linac beam quality was normalized to the average response per dose of the TLDs irradiated by the cobalt-60 standard.Irradiations were performed in a water tank and a Virtual Water™ phantom. Two TLD dose calibration curves for determining absorbed dose to water were generated using photon and electron field TLD response data. These individual beam quality dose calibration curves were applied to the TLDs irradiated in the mixed field. The TLD response in the mixed field was less sensitive than the response in the photon field and more sensitive than the response in the electron field. TLD determination of dose in the mixed field using the dose calibration curve generated by TLDs irradiated by photons resulted in an underestimation of the delivered dose, while the use of a dose calibration curve generated using electrons resulted in an overestimation of the delivered dose. The relative response of TLD-100 in mixed fields fell consistently between the photon nd electron relative responses. When using TLD-100 in mixed fields, the user must account for this intermediate response to avoid an over- or underestimation of the dose due to calibration in a single photon or electron field. © 2012 American Association of Physicists in Medicine.

A high-brightness, electron-based source of polarized photons and neutrons

NASA Astrophysics Data System (ADS)

Spencer, J. E.

1999-06-01

A compact and comparatively inexpensive system that is practical for universities is described based on a low-energy, electron storage ring with at least one undulator based oscillator to store photons. If the oscillator cavity length is relativistically corrected to be an harmonic of the ring circumference (LC=βLRn/nB with nB the number of bunches), higher-energy, secondary photons from Compton backscattering may become significant. Then, besides synchrotron radiation from the ring dipoles and damping wigglers as well as undulator photons, there are frequency upshifted Compton photons and photoneutrons from low Q-value targets such as Beryllium (Qn=-1.66) or Deuterium (Qn=-2.22 MeV). For 100 MeV electron bunches, an adjustable-phase, planar, helical undulator can be made to produce circularly polarized UV photons having a fundamental ɛγ1=11.1 eV. If these photons are stored in a multimode, hole-coupled resonator they produce a Compton endpoint energy up to ɛγ2=1.7 MeV. When incident on a Be conversion target these secondary photons make unmoderated, epithermal neutrons having mean energy ɛn=24.8±6.8 keV from the two-body reaction Be9+γ→n+Be8(→2α)with negligible, residual radioactivity. The system is shown in Fig. 1. When the target is unpolarized, one expects neutron rates of 1011 epithermal n/s for 1015 Comptons/s and a circulating current of 1 A with polarizations PRHC(n⃗)=-0.5, PLHC(n⃗)=0.5, both with reduced flux, and PLin(n⃗)=0. With a 1 cm thick cylindrical tungsten sheath surrounding the Be to attenuate scattered photons exiting at 90° to the incident photons, there is a peak neutron flux of ≈109 epithermal n/s/cm2 cylindrically symmetric around the surface. No attempt was made to optimize this because there is still no accepted treatment protocol (dose rates or preferred neutron energy distribution). Although these factors depend on the individual case, several thousand BNCT treatments per year appear feasible. A potential clinical

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

WE-G-BRD-09: Novel MRI Compatible Electron Accelerator for MRI-Linac Radiotherapy

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

Whelan, B; Keall, P; Gierman, S

Purpose: MRI guided radiotherapy is a rapidly growing field; however current linacs are not designed to operate in MRI fringe fields. As such, current MRI- Linac systems require magnetic shielding, impairing MR image quality and system flexibility. Here, we present a bespoke electron accelerator concept with robust operation in in-line magnetic fields. Methods: For in-line MRI-Linac systems, electron gun performance is the major constraint on accelerator performance. To overcome this, we propose placing a cathode directly within the first accelerating cavity. Such a configuration is used extensively in high energy particle physics, but not previously for radiotherapy. Benchmarked computational modellingmore » (CST, Darmstadt, Germany) was employed to design and assess a 5.5 cell side coupled accelerator with a temperature limited thermionic cathode in the first accelerating cell. This simulation was coupled to magnetic fields from a 1T MRI model to assess robustness in magnetic fields for Source to Isocenter Distance between 1 and 2 meters. Performance was compared to a conventional electron gun based system in the same magnetic field. Results: A temperature limited cathode (work function 1.8eV, temperature 1245K, emission constant 60A/K/cm{sup 2}) will emit a mean current density of 24mA/mm{sup 2} (Richardson’s Law). We modeled a circular cathode with radius 2mm and mean current 300mA. Capture efficiency of the device was 43%, resulting in target current of 130 mA. The electron beam had a FWHM of 0.2mm, and mean energy of 5.9MeV (interquartile spread of 0.1MeV). Such an electron beam is suitable for radiotherapy, comparing favourably to conventional systems. This model was robust to operation the MRI fringe field, with a maximum current loss of 6% compared to 85% for the conventional system. Conclusion: The bespoke electron accelerator is robust to operation in in-line magnetic fields. This will enable MRI-Linacs with no accelerator magnetic shielding, and

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.

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

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.

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

Feasibility study on the use of uranium in photoneutron target and BSA optimization for Linac based BNCT

NASA Astrophysics Data System (ADS)

Rahmani, Faezeh; Shahriari, Majid; Minoochehr, Abdolhamid; Nedaie, Hasan

2011-06-01

A hybrid photoneutron target including natural uranium has been studied for a 20 MeV linear electron accelerator (Linac) based Boron Neutron Capture Therapy (BNCT) facility. In this study the possibility of using uranium to increase the neutron intensity has been investigated by focusing on the time dependence behavior of the build-up and decay of the delayed gamma rays from fission fragments and activation products through photo-fission reactions in the BSA (Beam Shaping Assembly) configuration design. Delayed components of neutrons and photons were calculated. The obtained BSA parameters are in agreement with the IAEA recommendation and compared to the hybrid photoneutron target without U. The epithermal flux in the suggested design is 2.67E9 (n/cm 2s/mA).

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

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 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.

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

Optimization of combined electron and photon beams for breast cancer

NASA Astrophysics Data System (ADS)

Xiong, W.; Li, J.; Chen, L.; Price, R. A.; Freedman, G.; Ding, M.; Qin, L.; Yang, J.; Ma, C.-M.

2004-05-01

Recently, intensity-modulated radiation therapy and modulated electron radiotherapy have gathered a growing interest for the treatment of breast and head and neck tumours. In this work, we carried out a study to combine electron and photon beams to achieve differential dose distributions for multiple target volumes simultaneously. A Monte Carlo based treatment planning system was investigated, which consists of a set of software tools to perform accurate dose calculation, treatment optimization, leaf sequencing and plan analysis. We compared breast treatment plans generated using this home-grown optimization and dose calculation software for different treatment techniques. Five different planning techniques have been developed for this study based on a standard photon beam whole breast treatment and an electron beam tumour bed cone down. Technique 1 includes two 6 MV tangential wedged photon beams followed by an anterior boost electron field. Technique 2 includes two 6 MV tangential intensity-modulated photon beams and the same boost electron field. Technique 3 optimizes two intensity-modulated photon beams based on a boost electron field. Technique 4 optimizes two intensity-modulated photon beams and the weight of the boost electron field. Technique 5 combines two intensity-modulated photon beams with an intensity-modulated electron field. Our results show that technique 2 can reduce hot spots both in the breast and the tumour bed compared to technique 1 (dose inhomogeneity is reduced from 34% to 28% for the target). Techniques 3, 4 and 5 can deliver a more homogeneous dose distribution to the target (with dose inhomogeneities for the target of 22%, 20% and 9%, respectively). In many cases techniques 3, 4 and 5 can reduce the dose to the lung and heart. It is concluded that combined photon and electron beam therapy may be advantageous for treating breast cancer compared to conventional treatment techniques using tangential wedged photon beams followed by a boost

THz Hot-Electron Photon Counter

NASA Technical Reports Server (NTRS)

Karasik, Boris S.; Sergeev, Andrei V.

2004-01-01

We present a concept for the hot-electron transition-edge sensor capable of counting THz photons. The main need for such a sensor is a spectroscopy on future space telescopes where a background limited NEP approx. 10(exp -20) W/H(exp 1/2) is expected at around 1 THz. Under these conditions, the rate of photon arrival is very low and any currently imaginable detector with sufficient sensitivity will operate in the photon counting mode. The Hot-Electron Photon Counter based on a submicron-size Ti bridge has a very low heat capacity which provides a high enough energy resolution (approx.140 GHz) at 0.3 K. With the sensor time constant of a few microseconds, the dynamic range would be approx. 30 dB. The sensor couples to radiation via a planar antenna and is read by a SQUID amplifier or by a 1-bit RSFQ ADC. A compact array of the antenna-coupled counters can be fabricated on a silicon wafer without membranes.

Electron beam energy chirp control with a rectangular corrugated structure at the Linac Coherent Light Source

DOE PAGES

Zhang, Zhen; Bane, Karl; Ding, Yuantao; ...

2015-01-30

In this study, electron beam energy chirp is an important parameter that affects the bandwidth and performance of a linac-based, free-electron laser. In this paper we study the wakefields generated by a beam passing between at metallic plates with small corrugations, and then apply such a device as a passive dechirper for the Linac Coherent Light Source (LCLS) energy chirp control with a multi-GeV and femtosecond electron beam. Similar devices have been tested in several places at relatively low energies (~100 MeV) and with relatively long bunches (> 1ps). In the parameter regime of the LCLS dechirper, with the corrugationmore » size similar to the gap between the plates, the analytical solutions of the wakefields are no longer applicable, and we resort to a field matching program to obtain the wakes. Based on the numerical calculations, we fit the short-range, longitudinal wakes to simple formulas, valid over a large, useful parameter range. Finally, since the transverse wakefields - both dipole and quadrupole-are strong, we compute and include them in beam dynamics simulations to investigate the error tolerances when this device is introduced in the LCLS.« less

The design and dosimetric evaluation of tannin-based Rhizophora spp. particleboards as phantoms for high energy photons and electrons

NASA Astrophysics Data System (ADS)

Yusof, M. F. Mohd; Abdullah, R.; Tajuddin, A. A.; Hashim, R.; Bauk, S.; Hamid, P. N. K. Abd

2018-01-01

A set of phantom with an external dimension of 30 cm x 30 cm was constructed from tannin-based Rhizophora spp. particleboards similar to the solid water phantoms. The dosimetric characteristics of the particleboard phantoms were evaluated at high energy photons and electrons by measuring the beam output at 6 MV photons and 6 MeV electrons based on the IAEA TRS 398:2000 protocol. The tissue-phantom ratio (TPR20,10) was measured at 6 and 10 MV photons. The beam output calibration of the particleboards was in good agreement to water and solid water phantoms at 6 MV photons with percentage difference of 1.7 and 6.2% respectively. The beam output calibration of the tannin-based Rhizophora spp. particleboards at 6 MeV electrons on the other hand were in excellent agreement to water with percentage difference of 0.3. The percentage depth dose of tannin-based Rhizophora spp. particleboards were in agreement to water and solid water within 4.5% when measured using ionization chamber and EBT2 film. The electron beam parameters of R50, R80 and R90 at 6 MeV electrons also were in good agreement to water and solid water phantoms. The overall results had indicated the suitability of tannin-based Rhizophora spp. particleboards as water substitute phantom materials for high energy photons and electrons.

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.

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

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.

Breakdown of Bragg-Gray behaviour for low-density detectors under electronic disequilibrium conditions in small megavoltage photon fields.

PubMed

Kumar, Sudhir; Fenwick, John D; Underwood, Tracy S A; Deshpande, Deepak D; Scott, Alison J D; Nahum, Alan E

2015-10-21

In small photon fields ionisation chambers can exhibit large deviations from Bragg-Gray behaviour; the EGSnrc Monte Carlo (MC) code system has been employed to investigate this 'Bragg-Gray breakdown'. The total electron (+positron) fluence in small water and air cavities in a water phantom has been computed for a full linac beam model as well as for a point source spectrum for 6 MV and 15 MV qualities for field sizes from 0.25  ×  0.25 cm(2) to 10  ×  10 cm(2). A water-to-air perturbation factor has been derived as the ratio of total electron (+positron) fluence, integrated over all energies, in a tiny water volume to that in a 'PinPoint 3D-chamber-like' air cavity; for the 0.25  ×  0.25 cm(2) field size the perturbation factors are 1.323 and 2.139 for 6 MV and 15 MV full linac geometries respectively. For the 15 MV full linac geometry for field sizes of 1  ×  1 cm(2) and smaller not only the absolute magnitude but also the 'shape' of the total electron fluence spectrum in the air cavity is significantly different to that in the water 'cavity'. The physics of this 'Bragg-Gray breakdown' is fully explained, making reference to the Fano theorem. For the 15 MV full linac geometry in the 0.25  ×  0.25 cm(2) field the directly computed MC dose ratio, water-to-air, differs by 5% from the product of the Spencer-Attix stopping-power ratio (SPR) and the perturbation factor; this 'difference' is explained by the difference in the shapes of the fluence spectra and is also formulated theoretically. We show that the dimensions of an air-cavity with a perturbation factor within 5% of unity would have to be impractically small in these highly non-equilibrium photon fields. In contrast the dose to water in a 0.25  ×  0.25 cm(2) field derived by multiplying the dose in the single-crystal diamond dosimeter (SCDDo) by the Spencer-Attix ratio is within 2.9% of the dose computed directly in the water voxel for full linac

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

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

NASA Astrophysics Data System (ADS)

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

2004-12-01

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

Design and testing of focusing magnets for a compact electron linac

NASA Astrophysics Data System (ADS)

Chen, Qushan; Qin, Bin; Liu, Kaifeng; Liu, Xu; Fu, Qiang; Tan, Ping; Hu, Tongning; Pei, Yuanji

2015-10-01

Solenoid field errors have great influence on electron beam qualities. In this paper, design and testing of high precision solenoids for a compact electron linac is presented. We proposed an efficient and practical method to solve the peak field of the solenoid for relativistic electron beams based on the reduced envelope equation. Beam dynamics involving space charge force were performed to predict the focusing effects. Detailed optimization methods were introduced to achieve an ultra-compact configuration as well as high accuracy, with the help of the POISSON and OPERA packages. Efforts were attempted to restrain system errors in the off-line testing, which showed the short lens and the main solenoid produced a peak field of 0.13 T and 0.21 T respectively. Data analysis involving central and off axes was carried out and demonstrated that the testing results fitted well with the design.

[Technique of complex mammary irradiation: Mono-isocentric 3D conformational radiotherapy and helical tomotherapy].

PubMed

Vandendorpe, B; Guilbert, P; Champagne, C; Antoni, T; Nguyen, T D; Gaillot-Petit, N; Servagi Vernat, S

2017-12-01

To evaluate the dosimetric contribution of helical tomotherapy for breast cancers compared with conformal radiotherapy in mono-isocentric technique. For 23 patients, the dosimetric results in mono-isocentric 3D conformational radiotherapy did not satisfy the constraints either of target volumes nor organs at risk. A prospective dosimetric comparison between mono-isocentric 3D conformational radiotherapy and helical tomotherapy was therefore carried out. The use of helical tomotherapy showed a benefit in these 23 patients, with either an improvement in the conformity index or homogeneity, but with an increase in low doses. Of the 23 patients, two had pectus excavatum, five had past thoracic irradiation and two required bilateral irradiation. The other 14 patients had a combination of morphology and/or indication of lymph node irradiation. For these patients, helical tomotherapy was therefore preferred to mono-isocentric 3D conformational radiotherapy. Tomotherapy appears to provide better homogeneity and tumour coverage. This technique of irradiation may be justified in the case of morphological situations such as pectus exavatum and in complex clinical situations. In other cases, conformal radiotherapy in mono-isocentric technique remains to be favoured. Copyright © 2017 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.

Compact quasi-monoenergetic photon sources from laser-plasma accelerators for nuclear detection and characterization

NASA Astrophysics Data System (ADS)

Geddes, Cameron G. R.; Rykovanov, Sergey; Matlis, Nicholas H.; Steinke, Sven; Vay, Jean-Luc; Esarey, Eric H.; Ludewigt, Bernhard; Nakamura, Kei; Quiter, Brian J.; Schroeder, Carl B.; Toth, Csaba; Leemans, Wim P.

2015-05-01

Near-monoenergetic photon sources at MeV energies offer improved sensitivity at greatly reduced dose for active interrogation, and new capabilities in treaty verification, nondestructive assay of spent nuclear fuel and emergency response. Thomson (also referred to as Compton) scattering sources are an established method to produce appropriate photon beams. Applications are however restricted by the size of the required high-energy electron linac, scattering (photon production) system, and shielding for disposal of the high energy electron beam. Laser-plasma accelerators (LPAs) produce GeV electron beams in centimeters, using the plasma wave driven by the radiation pressure of an intense laser. Recent LPA experiments are presented which have greatly improved beam quality and efficiency, rendering them appropriate for compact high-quality photon sources based on Thomson scattering. Designs for MeV photon sources utilizing the unique properties of LPAs are presented. It is shown that control of the scattering laser, including plasma guiding, can increase photon production efficiency. This reduces scattering laser size and/or electron beam current requirements to scale compatible with the LPA. Lastly, the plasma structure can decelerate the electron beam after photon production, reducing the size of shielding required for beam disposal. Together, these techniques provide a path to a compact photon source system.

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.

Evaluation of beam delivery and ripple filter design for non-isocentric proton and carbon ion therapy.

PubMed

Grevillot, L; Stock, M; Vatnitsky, S

2015-10-21

This study aims at selecting and evaluating a ripple filter design compatible with non-isocentric proton and carbon ion scanning beam treatment delivery for a compact nozzle. The use of non-isocentric treatments when the patient is shifted as close as possible towards the nozzle exit allows for a reduction in the air gap and thus an improvement in the quality of scanning proton beam treatment delivery. Reducing the air gap is less important for scanning carbon ions, but ripple filters are still necessary for scanning carbon ion beams to reduce the number of energy steps required to deliver homogeneous SOBP. The proper selection of ripple filters also allows a reduction in the possible transverse and depth-dose inhomogeneities that could appear in non-isocentric conditions in particular. A thorough review of existing ripple filter designs over the past 16 years is performed and a design for non-isocentric treatment delivery is presented. A unique ripple filter quality index (QIRiFi) independent of the particle type and energy and representative of the ratio between energy modulation and induced scattering is proposed. The Bragg peak width evaluated at the 80% dose level (BPW80) is proposed to relate the energy modulation of the delivered Bragg peaks and the energy layer step size allowing the production of homogeneous SOBP. Gate/Geant4 Monte Carlo simulations have been validated for carbon ion and ripple filter simulations based on measurements performed at CNAO and subsequently used for a detailed analysis of the proposed ripple filter design. A combination of two ripple filters in a series has been validated for non-isocentric delivery and did not show significant transverse and depth-dose inhomogeneities. Non-isocentric conditions allow a significant reduction in the spot size at the patient entrance (up to 350% and 200% for protons and carbon ions with range shifter, respectively), and therefore in the lateral penumbra in the patients.

The X-ray correlation spectroscopy instrument at the Linac Coherent Light Source

DOE PAGES

Alonso-Mori, Roberto; Caronna, Chiara; Chollet, Matthieu; ...

2015-03-03

The X-ray Correlation Spectroscopy instrument is dedicated to the study of dynamics in condensed matter systems using the unique coherence properties of free-electron lasers. It covers a photon energy range of 4–25 keV. The intrinsic temporal characteristics of the Linac Coherent Light Source, in particular the 120 Hz repetition rate, allow for the investigation of slow dynamics (milliseconds) by means of X-ray photon correlation spectroscopy. Double-pulse schemes could probe dynamics on the picosecond timescale. In addition, a description of the instrument capabilities and recent achievements is presented.

Energy Recovery Linacs for Light Source Applications

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

George Neil

2011-04-01

Energy Recovery Linacs are being considered for applications in present and future light sources. ERLs take advantage of the continuous operation of superconducting rf cavities to accelerate high average current beams with low losses. The electrons can be directed through bends, undulators, and wigglers for high brightness x ray production. They are then decelerated to low energy, recovering power so as to minimize the required rf drive and electrical draw. When this approach is coupled with advanced continuous wave injectors, very high power, ultra-short electron pulse trains of very high brightness can be achieved. This paper will review the statusmore » of worldwide programs and discuss the technology challenges to provide such beams for photon production.« less

Bowel sparing in pediatric cranio-spinal radiotherapy: a comparison of combined electron and photon and helical TomoTherapy techniques to a standard photon method

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

Harron, Elizabeth, E-mail: elizabeth.harron@nuh.nhs.uk; Lewis, Joanne

2012-07-01

The aim of this study was to compare the dose to organs at risk (OARs) from different craniospinal radiotherapy treatment approaches available at the Northern Centre for Cancer Care (NCCC), with a particular emphasis on sparing the bowel. Method: Treatment plans were produced for a pediatric medulloblastoma patient with inflammatory bowel disease using 3D conformal 6-MV photons (3DCP), combined 3D 6-MV photons and 18-MeV electrons (3DPE), and helical photon TomoTherapy (HT). The 3DPE plan was a modification of the standard 3DCP technique, using electrons to treat the spine inferior to the level of the diaphragm. The plans were compared inmore » terms of the dose-volume data to OARs and the nontumor integral dose. Results: The 3DPE plan was found to give the lowest dose to the bowel and the lowest nontumor integral dose of the 3 techniques. However, the coverage of the spine planning target volume (PTV) was least homogeneous using this technique, with only 74.6% of the PTV covered by 95% of the prescribed dose. HT was able to achieve the best coverage of the PTVs (99.0% of the whole-brain PTV and 93.1% of the spine PTV received 95% of the prescribed dose), but delivered a significantly higher integral dose. HT was able to spare the heart, thyroid, and eyes better than the linac-based techniques, but other OARs received a higher dose. Conclusions: Use of electrons was the best method for reducing the dose to the bowel and the integral dose, at the expense of compromised spine PTV coverage. For some patients, HT may be a viable method of improving dose homogeneity and reducing selected OAR doses.« less

Longitudinal dynamics of twin electron bunches in the Linac Coherent Light Source

DOE PAGES

Zhang, Zhen; Ding, Yuantao; Marinelli, Agostino; ...

2015-03-02

The recent development of two-color x-ray free-electron lasers, as well as the successful demonstration of high-gradient witness bunch acceleration in a plasma, have generated strong interest in electron bunch trains, where two or more electron bunches are generated, accelerated and compressed in the same accelerating bucket. In this paper we give a detailed analysis of a twin-bunch technique in a high-energy linac. This method allows the generation of two electron bunches with high peak current and independent control of time delay and energy separation. We find that the wakefields in the accelerator structures play an important role in the twin-bunchmore » compression, and through analysis show that they can be used to extend the available time delay range. As a result, based on the theoretical model and simulations we propose several methods to achieve larger time delay.« less

Accelerator structure and beam transport system for the KEK photon factory injector

NASA Astrophysics Data System (ADS)

Sato, Isamu

1980-11-01

The injector is a 2.5 GeV electron linac which serves multiple purposes, being not only the injector for the various storage rings of the Photon Factory but also for the next planned project, the TRISTAN RING, and also as an intense electron or γ-ray source for research on phenomena in widely diverse scientific fields. The accelerator structure and beam transport system for the linac were designed with the greatest care in order to avoid beam blow-up difficulties, and also to be as suitable as possible to enable the economical mass production of the accelerator guides and focusing magnets.

The X-ray Correlation Spectroscopy instrument at the Linac Coherent Light Source

PubMed Central

Alonso-Mori, Roberto; Caronna, Chiara; Chollet, Matthieu; Curtis, Robin; Damiani, Daniel S.; Defever, Jim; Feng, Yiping; Flath, Daniel L.; Glownia, James M.; Lee, Sooheyong; Lemke, Henrik T.; Nelson, Silke; Bong, Eric; Sikorski, Marcin; Song, Sanghoon; Srinivasan, Venkat; Stefanescu, Daniel; Zhu, Diling; Robert, Aymeric

2015-01-01

The X-ray Correlation Spectroscopy instrument is dedicated to the study of dynamics in condensed matter systems using the unique coherence properties of free-electron lasers. It covers a photon energy range of 4–25 keV. The intrinsic temporal characteristics of the Linac Coherent Light Source, in particular the 120 Hz repetition rate, allow for the investigation of slow dynamics (milli­seconds) by means of X-ray photon correlation spectroscopy. Double-pulse schemes could probe dynamics on the picosecond timescale. A description of the instrument capabilities and recent achievements is presented. PMID:25931061

A photon source model based on particle transport in a parameterized accelerator structure for Monte Carlo dose calculations.

PubMed

Ishizawa, Yoshiki; Dobashi, Suguru; Kadoya, Noriyuki; Ito, Kengo; Chiba, Takahito; Takayama, Yoshiki; Sato, Kiyokazu; Takeda, Ken

2018-05-17

An accurate source model of a medical linear accelerator is essential for Monte Carlo (MC) dose calculations. This study aims to propose an analytical photon source model based on particle transport in parameterized accelerator structures, focusing on a more realistic determination of linac photon spectra compared to existing approaches. We designed the primary and secondary photon sources based on the photons attenuated and scattered by a parameterized flattening filter. The primary photons were derived by attenuating bremsstrahlung photons based on the path length in the filter. Conversely, the secondary photons were derived from the decrement of the primary photons in the attenuation process. This design facilitates these sources to share the free parameters of the filter shape and be related to each other through the photon interaction in the filter. We introduced two other parameters of the primary photon source to describe the particle fluence in penumbral regions. All the parameters are optimized based on calculated dose curves in water using the pencil-beam-based algorithm. To verify the modeling accuracy, we compared the proposed model with the phase space data (PSD) of the Varian TrueBeam 6 and 15 MV accelerators in terms of the beam characteristics and the dose distributions. The EGS5 Monte Carlo code was used to calculate the dose distributions associated with the optimized model and reference PSD in a homogeneous water phantom and a heterogeneous lung phantom. We calculated the percentage of points passing 1D and 2D gamma analysis with 1%/1 mm criteria for the dose curves and lateral dose distributions, respectively. The optimized model accurately reproduced the spectral curves of the reference PSD both on- and off-axis. The depth dose and lateral dose profiles of the optimized model also showed good agreement with those of the reference PSD. The passing rates of the 1D gamma analysis with 1%/1 mm criteria between the model and PSD were 100% for 4�

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

Trajectory modulated prone breast irradiation: a LINAC-based technique combining intensity modulated delivery and motion of the couch.

PubMed

Fahimian, Benjamin; Yu, Victoria; Horst, Kathleen; Xing, Lei; Hristov, Dimitre

2013-12-01

External beam radiation therapy (EBRT) provides a non-invasive treatment alternative for accelerated partial breast irradiation (APBI), however, limitations in achievable dose conformity of current EBRT techniques have been correlated to reported toxicity. To enhance the conformity of EBRT APBI, a technique for conventional LINACs is developed, which through combined motion of the couch, intensity modulated delivery, and a prone breast setup, enables wide-angular coronal arc irradiation of the ipsilateral breast without irradiating through the thorax and contralateral breast. A couch trajectory optimization technique was developed to determine the trajectories that concurrently avoid collision with the LINAC and maintain the target within the MLC apertures. Inverse treatment planning was performed along the derived trajectory. The technique was experimentally implemented by programming the Varian TrueBeam™ STx in Developer Mode. The dosimetric accuracy of the delivery was evaluated by ion chamber and film measurements in phantom. The resulting optimized trajectory was shown to be necessarily non-isocentric, and contain both translation and rotations of the couch. Film measurements resulted in 93% of the points in the measured two-dimensional dose maps passing the 3%/3mm Gamma criterion. Preliminary treatment plan comparison to 5-field 3D-conformal, IMRT, and VMAT demonstrated enhancement in conformity, and reduction of the normal tissue V50% and V100% parameters that have been correlated with EBRT toxicity. The feasibility of wide-angular intensity modulated partial breast irradiation using motion of the couch has been demonstrated experimentally on a standard LINAC for the first time. For patients eligible for a prone setup, the technique may enable improvement of dose conformity and associated dose-volume parameters correlated with toxicity. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

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.

Gamma ray pulsars. [electron-photon cascades

NASA Technical Reports Server (NTRS)

Oegelman, H.; Ayasli, S.; Hacinliyan, A.

1977-01-01

Data from the SAS-2 high-energy gamma-ray experiment reveal the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma-ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields (10 to the 12th power gauss) correspond to many radiation lengths which cause electrons to emit photons by magnetic bremsstrahlung and which cause these photons to pair-produce. The cascade develops until the mean photon energy drops below the pair-production threshold which is in the gamma-ray range; at this stage, the photons break out from the source.

Developing field emission electron sources based on ultrananocrystalline diamond for accelerators

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

Baryshev, Sergey V.; Jing, Chunguang; Qiu, Jiaqi

Radiofrequency (RF) electron guns work by establishing an RF electromagnetic field inside a cavity having conducting walls. Electrons from a cathode are generated in the injector and immediately become accelerated by the RF electric field, and exit the gun as a series of electron bunches. Finding simple solutions for electron injection is a long standing problem. While energies of 30-50 MeV are achievable in linear accelerators (linacs), finding an electron source able to survive under MW electric loads and provide an average current of 1-10 mA is important. Meeting these requirements would open various linac applications for industry. The naturalmore » way to simplify and integrate RF injector architectures with the electron source would be to place the source directly into the RF cavity with no need for additional heaters/lasers. Euclid TechLabs in collaboration with Argonne National Lab are prototyping a family of highly effective field emission electron sources based on a nitrogen-incorporated ultrananocrystalline diamond ((N)UNCD) platform. Determined metrics suggest that our emitters are emissive enough to meet requirements for magnetized cooling at electron-ion colliders, linac-based radioisotope production and X-ray sterilization, and others.« less

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.

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.

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

X-ray two-photon absorption with high fluence XFEL pulses

DOE PAGES

Hoszowska, Joanna; Szlachetko, J.; Dousse, J. -Cl.; ...

2015-09-07

Here, we report on nonlinear interaction of solid Fe with intense femtosecond hard x-ray free-electron laser (XFEL) pulses. The experiment was performed at the CXI end-station of the Linac Coherent Light Source (LCLS) by means of high- resolution x-ray emission spectroscopy. The focused x-ray beam provided extreme fluence of ~10 5 photons/Å 2. Two-photon absorption leading to K-shell hollow atom formation and to single K-shell ionization of solid Fe was investigated.

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.

SU-F-I-70: Investigation of Gafchromic EBT3 Film Energy Dependence Using Proton, Photon, and Electron Beams

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

Ferreira, C; Schnell, E; Ahmad, S

Purpose: To investigate the energy dependence of Gafchromic EBT3 film over a range of clinically used proton, photon and electron energies. Methods: Proton beam energies of 117 and 204 MeV, corresponding respectively to ranges in water of 10 cm and 27 cm from a Mevion S250 double scatter system unit were used. Electron energies of 6 and 20 MeV and photon energies of 6 and 18 MV from a Varian Clinac 21EX Linac were used. Two pieces of film (5×5 cm{sup 2}) were irradiated sequentially for doses of 100, 500, and 1000 cGy for all energies and modalities. Films weremore » placed on the central beam axis for a 10×10 cm{sup 2} field size in the middle of spread out Bragg peak (SOBP) for proton and in respective dmax for photon and electron energies. Films were scanned on a flatbed Epson Expression 10000 XL scanner on the central region of the scanning window using 48-bit, 300 dpi, and landscape orientation after 48 hours post-irradiation of film to account for optical density (OD) stabilization. Film analysis of the red channel was performed using ImageJ 1.48v (National Institutes of Health). Results: The energy dependency of EBT3 among all energies and modalities for all doses studied was small within measurement uncertainties (1σ = ± 4.1%). The mean net OD in red channel for films receiving the same dose in the same energy modality had standard deviations within 0.9% for photons, 4.9% for electrons and 1.8% for protons. It was observed that film pieces were activated during proton irradiation, e.g., 7 mR/hr at surface after 30 minutes of irradiation, lasting for 2 hours post irradiation. Conclusion: EBT3 energy dependency was evaluated for clinically used proton, photon, and electron energies. The film self-activation may have contributed to fog and negligible dose.« less

Electron-positron pair production by ultrarelativistic electrons in a soft photon field

NASA Technical Reports Server (NTRS)

Mastichiadis, A.; Marscher, A. P.; Brecher, K.

1986-01-01

The fully differential cross section for photon-electron pair production is integrated numerically over phase space. Results are obtained for the astrophysically interesting case in which the interaction between an ultrarelativistic electron and a soft photon results in electron-positron pair production. The positron spectrum is a function of the energies of both the photon and the electron, as well as the angle of interaction. It is found that the energy at which the positron distribution peaks is inversely proportional to the photon energy and independent of the electron energy. The positron spectrum is integrated once more over initial electron energies for a power-law energy distribution of primary electrons. The same procedure is repeated for the recoil particle; it is shown that the peak of the recoil energy distribution depends linearly on the energy of the primary electron. Finally, semianalytical expressions are obtained for the energy losses of the primary electrons.

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.

Hot-Electron Photon Counters for Detecting Terahertz Photons

NASA Technical Reports Server (NTRS)

Karasik, Boris; Sergeyev, Andrei

2005-01-01

A document proposes the development of hot-electron photon counters (HEPCs) for detecting terahertz photons in spaceborne far-infrared astronomical instruments. These would be superconducting- transition-edge devices: they would contain superconducting bridges that would have such low heat capacities that single terahertz photons would cause transient increases in their electron temperatures through the superconducting- transition range, thereby yielding measurable increases in electrical resistance. Single devices or imaging arrays of the devices would be fabricated as submicron-sized bridges made from films of disordered Ti (which has a superconducting- transition temperature of .0.35 K) between Nb contacts on bulk silicon or sapphire substrates. In operation, these devices would be cooled to a temperature of .0.3 K. The proposed devices would cost less to fabricate and operate, relative to integrating bolometers of equal sensitivity, which must be operated at a temperature of approx. = 0.1 K.

Covariance mapping of two-photon double core hole states in C 2 H 2 and C 2 H 6 produced by an x-ray free electron laser

DOE PAGES

Mucke, M; Zhaunerchyk, V; Frasinski, L J; ...

2015-07-01

Few-photon ionization and relaxation processes in acetylene (C 2H 2) and ethane (C 2H 6) were investigated at the linac coherent light source x-ray free electron laser (FEL) at SLAC, Stanford using a highly efficient multi-particle correlation spectroscopy technique based on a magnetic bottle. The analysis method of covariance mapping has been applied and enhanced, allowing us to identify electron pairs associated with double core hole (DCH) production and competing multiple ionization processes including Auger decay sequences. The experimental technique and the analysis procedure are discussed in the light of earlier investigations of DCH studies carried out at the samemore » FEL and at third generation synchrotron radiation sources. In particular, we demonstrate the capability of the covariance mapping technique to disentangle the formation of molecular DCH states which is barely feasible with conventional electron spectroscopy methods.« less

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

PubMed

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

2012-02-01

In our current linac-magnetic resonance (MR) design, a 6 MV in-line linac is placed along the central axis of the MR's magnet where the MR's fringe magnetic fields are parallel to the overall electron trajectories in the linac waveguide. Our previous study of this configuration comprising a linac-MR SAD of 100 cm and a 0.5 T superconducting (open, split) MR imager. It showed the presence of longitudinal magnetic fields of 0.011 T at the electron gun, which caused a reduction in target current to 84% of nominal. In this study, passive and active magnetic shielding was investigated to recover the linac output losses caused by magnetic deflections of electron trajectories in the linac within a parallel linac-MR configuration. Magnetic materials and complex shield structures were used in a 3D finite element method (FEM) magnetic field model, which emulated the fringe magnetic fields of the MR imagers. The effects of passive magnetic shielding was studied by surrounding the electron gun and its casing with a series of capped steel cylinders of various inner lengths (26.5-306.5 mm) and thicknesses (0.75-15 mm) in the presence of the fringe magnetic fields from a commercial MR imager. In addition, the effects of a shield of fixed length (146.5 mm) with varying thicknesses were studied against a series of larger homogeneous magnetic fields (0-0.2 T). The effects of active magnetic shielding were studied by adding current loops around the electron gun and its casing. The loop currents, separation, and location were optimized to minimize the 0.011 T longitudinal magnetic fields in the electron gun. The magnetic field solutions from the FEM model were added to a validated linac simulation, consisting of a 3D electron gun (using OPERA-3d/scala) and 3D waveguide (using comsol Multiphysics and PARMELA) simulations. PARMELA's target current and output phase-space were analyzed to study the linac's output performance within the magnetic shields. The FEM model above agreed within 1

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

PubMed

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

2014-05-01

A potential side effect of inline MRI-linac systems is electron contamination focusing causing a high skin dose. In this work, the authors reexamine this prediction for an open bore 1 T MRI system being constructed for the Australian MRI-Linac Program. The efficiency of an electron contamination deflector (ECD) in purging electron contamination from the linac head is modeled, as well as the impact of a helium gas region between the deflector and phantom surface for lowering the amount of air-generated contamination. Magnetic modeling of the 1 T MRI was used to generate 3D magnetic field maps both with and without the presence of an ECD located immediately below the MLC's. Forty-seven different ECD designs were modeled and for each the magnetic field map was imported into Geant4 Monte Carlo simulations including the linac head, ECD, and a 30 × 30 × 30 cm(3) water phantom located at isocenter. For the first generation system, the x-ray source to isocenter distance (SID) will be 160 cm, resulting in an 81.2 cm long air gap from the base of the ECD to the phantom surface. The first 71.2 cm was modeled as air or helium gas, with the latter encased between two windows of 50 μm thick high density polyethlyene. 2D skin doses (at 70 μm depth) were calculated across the phantom surface at 1 × 1 mm(2) resolution for 6 MV beams of field size of 5 × 5, 10 × 10, and 20 × 20 cm(2). The skin dose was predicted to be of similar magnitude as the generic systems modeled in previous work, 230% to 1400% of D(max) for 5 × 5 to 20 × 20 cm(2), respectively. Inclusion of the ECD introduced a nonuniformity to the MRI imaging field that ranged from ∼20 to ∼140 ppm while the net force acting on the ECD ranged from ∼151 N to ∼1773 N. Various ECD designs were 100% efficient at purging the electron contamination into the ECD magnet banks; however, a small percentage were scattered back into the beam and continued to the phantom surface. Replacing a large portion of the extended

SU-E-J-200: Operation of An Electron Accelerator On An Integrated MR-Linac System

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

Harasimowicz, J; Roberts, D; Shinton, I

2015-06-15

Purpose: An integrated MRI guided radiotherapy system poses a challenge of operating a linear accelerator in the presence of a magnetic field as the magnetic force acting on the electrons could Result in radiation source displacement and subsequent reduction of dose output. It was the purpose of this work to test the performance of a linac in the presence of a 1.5T MRI system. Methods: The first experimental MRI guided radiotherapy system at UMC-Utrecht consisting of an Elekta linac rotating around a 1.5T Magnex magnet was examined. A passive magnetic shield was simulated, designed and installed to reduce the influencemore » of the MRI magnet stray field on the electron beamline. The B field inside the shield was measured as a function of gantry angle and measurements of dose rate constancy upon gantry rotation were performed. Results: The magnitude of the magnetic field on the electron beam path without the shield was as high as 70G. It varied by up to 15G with gantry rotation due to the presence of metal beams in the bunker floor which resulted in dose output drop of up to 70% at certain gantry angles. With the prototype shield, field magnitude was reduced to well below 0.5G everywhere along the electron beam path. Field variation with gantry rotation was decreased to below 0.2G and enabled dose output of the linac to be recovered at all gantry angles. The homogeneity of the field inside the MRI magnet has not been compromised. Conclusion: It was demonstrated that the influence of the 1.5T magnet and the bunker design on the linac operation has been minimised. The performance will be further improved on the Elekta Atlantic system which incorporates a newly developed and optimised Philips magnet design and bunker construction. J Harasimowicz, D Roberts, I Shinton and S Sund are employed by Elekta Limited Crawley, H Wang and M Zhong are employed by Elekta Beijing Medical Systems Co. Ltd., J Overweg is employed by Philips Technologie GmbH Forschungslaboratorien.« less

Skeletal dosimetry in a voxel-based rat phantom for internal exposures to photons and electrons

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

Xie Tianwu; Han Dao; Liu Yang

2010-05-15

Purpose: The skeleton makes a significant contribution to the whole body absorbed dose evaluation of rats, since the bone marrow and bone surface in the skeleton express high radiosensitivity and are considered to be important dose-limiting tissues. The bone marrow can be categorized as red bone marrow (RBM) and yellow bone marrow (YBM). It is important to investigate the bone marrow in skeletal dosimetry. Methods: Cryosectional color images of the skeleton of a 156 g rat were segmented into mineral bone (including cortical bone and trabecular bone), RBM, and YBM. These three tissue types were identified at 40 different bonemore » sites and integrated into a previously developed voxel-based rat computational phantom. Photon and electron skeletal absorbed fractions were then calculated using the MCNPX Monte Carlo code. Results: Absorbed fraction (AF) and specific absorbed fraction (SAF) for mineral bone, RBM, and YBM at the 40 different bone sites were established for monoenergetic photon and electron sources placed in 18 organs and seven bone sites. Discrete photon energy was varied from 0.01 to 5.0 MeV in 21 discrete steps, while 21 discrete electron energies were studied, from 0.1 to 10.0 MeV. The trends and values found were consistent with the results of other researchers [M. G. Stabin, T. E. Peterson, G. E. Holburn, and M. A. Emmons, ''Voxel-based mouse and rat models for internal dose calculations,'' J. Nucl. Med. 47, 655-659 (2006)]. S-factors for the radionuclides {sup 169}Er, {sup 143}Pr, {sup 89}Sr, {sup 32}P, and {sup 90}Y, located in 18 organs and seven bone sites for the skeleton, were calculated and are provided in detail. Conclusions: For internal dose calculations, the AF data reveal that the mineral bone in the rat skeletal system is responsible for significant attenuation of gamma rays, especially at low energies. The photon SAF curves of RBM show that, for photon energies greater than 0.6 MeV, there is an increase in secondary photons emitted

Electron beam collimation with a photon MLC for standard electron treatments

NASA Astrophysics Data System (ADS)

Mueller, S.; Fix, M. K.; Henzen, D.; Frei, D.; Frauchiger, D.; Loessl, K.; Stampanoni, M. F. M.; Manser, P.

2018-01-01

Standard electron treatments are currently still performed using standard or molded patient-specific cut-outs placed in the electron applicator. Replacing cut-outs and electron applicators with a photon multileaf collimator (pMLC) for electron beam collimation would make standard electron treatments more efficient and would facilitate advanced treatment techniques like modulated electron radiotherapy (MERT) and mixed beam radiotherapy (MBRT). In this work, a multiple source Monte Carlo beam model for pMLC shaped electron beams commissioned at a source-to-surface distance (SSD) of 70 cm is extended for SSDs of up to 100 cm and validated for several Varian treatment units with field sizes typically used for standard electron treatments. Measurements and dose calculations agree generally within 3% of the maximal dose or 2 mm distance to agreement. To evaluate the dosimetric consequences of using pMLC collimated electron beams for standard electron treatments, pMLC-based and cut-out-based treatment plans are created for a left and a right breast boost, a sternum, a testis and a parotid gland case. The treatment plans consist of a single electron field, either alone (1E) or in combination with two 3D conformal tangential photon fields (1E2X). For each case, a pMLC plan with similar treatment plan quality in terms of dose homogeneity to the target and absolute mean dose values to the organs at risk (OARs) compared to a cut-out plan is found. The absolute mean dose to an OAR is slightly increased for pMLC-based compared to cut-out-based 1E plans if the OAR is located laterally close to the target with respect to beam direction, or if a 6 MeV electron beam is used at an extended SSD. In conclusion, treatment plans using cut-out collimation can be replaced by plans of similar treatment plan quality using pMLC collimation with accurately calculated dose distributions.

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.

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

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.

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.

Radiosurgery with photons or protons for benign and malignant tumours of the skull base: a review.

PubMed

Amichetti, Maurizio; Amelio, Dante; Minniti, Giuseppe

2012-12-14

Stereotactic radiosurgery (SRS) is an important treatment option for intracranial lesions. Many studies have shown the effectiveness of photon-SRS for the treatment of skull base (SB) tumours; however, limited data are available for proton-SRS.Several photon-SRS techniques, including Gamma Knife, modified linear accelerators (Linac) and CyberKnife, have been developed and several studies have compared treatment plan characteristics between protons and photons.The principles of classical radiobiology are similar for protons and photons even though they differ in terms of physical properties and interaction with matter resulting in different dose distributions.Protons have special characteristics that allow normal tissues to be spared better than with the use of photons, although their potential clinical superiority remains to be demonstrated.A critical analysis of the fundamental radiobiological principles, dosimetric characteristics, clinical results, and toxicity of proton- and photon-SRS for SB tumours is provided and discussed with an attempt of defining the advantages and limits of each radiosurgical technique.

Radiosurgery with photons or protons for benign and malignant tumours of the skull base: a review

PubMed Central

2012-01-01

Stereotactic radiosurgery (SRS) is an important treatment option for intracranial lesions. Many studies have shown the effectiveness of photon-SRS for the treatment of skull base (SB) tumours; however, limited data are available for proton-SRS. Several photon-SRS techniques, including Gamma Knife, modified linear accelerators (Linac) and CyberKnife, have been developed and several studies have compared treatment plan characteristics between protons and photons. The principles of classical radiobiology are similar for protons and photons even though they differ in terms of physical properties and interaction with matter resulting in different dose distributions. Protons have special characteristics that allow normal tissues to be spared better than with the use of photons, although their potential clinical superiority remains to be demonstrated. A critical analysis of the fundamental radiobiological principles, dosimetric characteristics, clinical results, and toxicity of proton- and photon-SRS for SB tumours is provided and discussed with an attempt of defining the advantages and limits of each radiosurgical technique. PMID:23241206

Continuous wave superconducting radio frequency electron linac for nuclear physics research

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

Reece, Charles E.

CEBAF, the Continuous Electron Beam Accelerator Facility, has been actively serving the nuclear physics research community as a unique forefront international resource since 1995. This cw electron linear accelerator (linac) at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility (Jefferson Lab) has continued to evolve as a precision tool for discerning the structure and dynamics within nuclei. Superconducting rf (SRF) technology has been the essential foundation for CEBAF, first as a 4 GeV machine, then 6 GeV, and currently capable of 12 GeV. Lastly, we review the development, implementation, and performance of SRF systems for CEBAF from itsmore » early beginnings to the commissioning of the 12 GeV era.« less

Continuous wave superconducting radio frequency electron linac for nuclear physics research

DOE PAGES

Reece, Charles E.

2016-12-28

CEBAF, the Continuous Electron Beam Accelerator Facility, has been actively serving the nuclear physics research community as a unique forefront international resource since 1995. This cw electron linear accelerator (linac) at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility (Jefferson Lab) has continued to evolve as a precision tool for discerning the structure and dynamics within nuclei. Superconducting rf (SRF) technology has been the essential foundation for CEBAF, first as a 4 GeV machine, then 6 GeV, and currently capable of 12 GeV. Lastly, we review the development, implementation, and performance of SRF systems for CEBAF from itsmore » early beginnings to the commissioning of the 12 GeV era.« less

SU-E-T-272: Direct Verification of a Treatment Planning System Megavoltage Linac Beam Photon Spectra Models, and Analysis of the Effects On Patient Plans

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

Leheta, D; Shvydka, D; Parsai, E

2015-06-15

Purpose: For the photon dose calculation Philips Pinnacle Treatment Planning System (TPS) uses collapsed cone convolution algorithm, which relies on energy spectrum of the beam in computing the scatter component. The spectrum is modeled based on Linac’s standard commissioning data and typically is not independently verified. We explored a methodology of using transmission measurements in combination with regularization data processing to unfold Linac spectra. The measured spectra were compared to those modeled by the TPS, and the effect on patient plans was evaluated. Methods: Transmission measurements were conducted in narrow-beam geometry using a standard Farmer ionization chamber. Two attenuating materialsmore » and two build -up caps, having different atomic numbers, served to enhance discrimination between absorption of low and high-energy portions of the spectra, thus improving the accuracy of the results. The data was analyzed using a regularization technique implemented through spreadsheet-based calculations. Results: The unfolded spectra were found to deviate from the TPS beam models. The effect of such deviations on treatment planning was evaluated for patient plans through dose distribution calculations with either TPS modeled or measured energy spectra. The differences were reviewed through comparison of isodose distributions, and quantified based on maximum dose values for critical structures. While in most cases no drastic differences in the calculated doses were observed, plans with deviations of 4 to 8% in the maximum dose values for critical structures were discovered. The anatomical sites with large scatter contributions are the most vulnerable to inaccuracies in the modeled spectrum. Conclusion: An independent check of the TPS model spectrum is highly desirable and should be included as part of commissioning of a new Linac. The effect is particularly important for dose calculations in high heterogeneity regions. The developed approach makes

A Monte Carlo method using octree structure in photon and electron transport

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

Ogawa, K.; Maeda, S.

Most of the early Monte Carlo calculations in medical physics were used to calculate absorbed dose distributions, and detector responses and efficiencies. Recently, data acquisition in Single Photon Emission CT (SPECT) has been simulated by a Monte Carlo method to evaluate scatter photons generated in a human body and a collimator. Monte Carlo simulations in SPECT data acquisition are generally based on the transport of photons only because the photons being simulated are low energy, and therefore the bremsstrahlung productions by the electrons generated are negligible. Since the transport calculation of photons without electrons is much simpler than that withmore » electrons, it is possible to accomplish the high-speed simulation in a simple object with one medium. Here, object description is important in performing the photon and/or electron transport using a Monte Carlo method efficiently. The authors propose a new description method using an octree representation of an object. Thus even if the boundaries of each medium are represented accurately, high-speed calculation of photon transport can be accomplished because the number of voxels is much fewer than that of the voxel-based approach which represents an object by a union of the voxels of the same size. This Monte Carlo code using the octree representation of an object first establishes the simulation geometry by reading octree string, which is produced by forming an octree structure from a set of serial sections for the object before the simulation; then it transports photons in the geometry. Using the code, if the user just prepares a set of serial sections for the object in which he or she wants to simulate photon trajectories, he or she can perform the simulation automatically using the suboptimal geometry simplified by the octree representation without forming the optimal geometry by handwriting.« less

Measurements of wake-induced electron beam deflection in a dechirper at the Linac Coherent Light Source

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

Zemella, Johann; Bane, Karl; Fisher, Alan

The RadiaBeam/SLAC dechirper, a structure consisting of pairs of flat, metallic, corrugated plates, has been installed just upstream of the undulators in the Linac Coherent Light Source (LCLS). As a dechirper, with the beam passing between the plates on axis, longitudinal wakefields are induced that can remove unwanted energy chirp in the beam. However, with the beam passing off axis, strong transverse wakes are also induced. This mode of operation has already been used for the production of intense, multicolor photon beams using the fresh-slice technique, and is being used to develop a diagnostic for attosecond bunch length measurements. Heremore » we measure, as a function of offset, the strength of the transverse wakefields that are excited between the two plates, and also for the case of the beam passing near to a single plate. We compare with analytical formulas from the literature, and find good agreement. As a result, this report presents the first systematic measurements of the transverse wake strength in a dechirper, one that has been excited by a bunch with the short pulse duration and high energy found in an x-ray free electron laser.« less

Measurements of wake-induced electron beam deflection in a dechirper at the Linac Coherent Light Source

DOE PAGES

Zemella, Johann; Bane, Karl; Fisher, Alan; ...

2017-10-19

The RadiaBeam/SLAC dechirper, a structure consisting of pairs of flat, metallic, corrugated plates, has been installed just upstream of the undulators in the Linac Coherent Light Source (LCLS). As a dechirper, with the beam passing between the plates on axis, longitudinal wakefields are induced that can remove unwanted energy chirp in the beam. However, with the beam passing off axis, strong transverse wakes are also induced. This mode of operation has already been used for the production of intense, multicolor photon beams using the fresh-slice technique, and is being used to develop a diagnostic for attosecond bunch length measurements. Heremore » we measure, as a function of offset, the strength of the transverse wakefields that are excited between the two plates, and also for the case of the beam passing near to a single plate. We compare with analytical formulas from the literature, and find good agreement. As a result, this report presents the first systematic measurements of the transverse wake strength in a dechirper, one that has been excited by a bunch with the short pulse duration and high energy found in an x-ray free electron laser.« less

Performance of a clinical gridded electron gun in magnetic fields: Implications for MRI-linac therapy.

PubMed

Whelan, Brendan; Holloway, Lois; Constantin, Dragos; Oborn, Brad; Bazalova-Carter, Magdalena; Fahrig, Rebecca; Keall, Paul

2016-11-01

MRI-linac therapy is a rapidly growing field, and requires that conventional linear accelerators are operated with the fringe field of MRI magnets. One of the most sensitive accelerator components is the electron gun, which serves as the source of the beam. The purpose of this work was to develop a validated finite element model (FEM) model of a clinical triode (or gridded) electron gun, based on accurate geometric and electrical measurements, and to characterize the performance of this gun in magnetic fields. The geometry of a Varian electron gun was measured using 3D laser scanning and digital calipers. The electric potentials and emission current of these guns were measured directly from six dose matched true beam linacs for the 6X, 10X, and 15X modes of operation. Based on these measurements, a finite element model (FEM) of the gun was developed using the commercial software opera/scala. The performance of the FEM model in magnetic fields was characterized using parallel fields ranging from 0 to 200 G in the in-line direction, and 0-35 G in the perpendicular direction. The FEM model matched the average measured emission current to within 5% across all three modes of operation. Different high voltage settings are used for the different modes; the 6X, 10X, and 15X modes have an average high voltage setting of 15, 10, and 11 kV. Due to these differences, different operating modes show different sensitivities in magnetic fields. For in line fields, the first current loss occurs at 40, 20, and 30 G for each mode. This is a much greater sensitivity than has previously been observed. For perpendicular fields, first beam loss occurred at 8, 5, and 5 G and total beam loss at 27, 22, and 20 G. A validated FEM model of a clinical triode electron gun has been developed based on accurate geometric and electrical measurements. Three different operating modes were simulated, with a maximum mean error of 5%. This gun shows greater sensitivity to in-line magnetic fields than

Performance of a clinical gridded electron gun in magnetic fields: Implications for MRI-linac therapy

PubMed Central

Whelan, Brendan; Holloway, Lois; Constantin, Dragos; Oborn, Brad; Bazalova-Carter, Magdalena; Fahrig, Rebecca; Keall, Paul

2016-01-01

Purpose: MRI-linac therapy is a rapidly growing field, and requires that conventional linear accelerators are operated with the fringe field of MRI magnets. One of the most sensitive accelerator components is the electron gun, which serves as the source of the beam. The purpose of this work was to develop a validated finite element model (FEM) model of a clinical triode (or gridded) electron gun, based on accurate geometric and electrical measurements, and to characterize the performance of this gun in magnetic fields. Methods: The geometry of a Varian electron gun was measured using 3D laser scanning and digital calipers. The electric potentials and emission current of these guns were measured directly from six dose matched true beam linacs for the 6X, 10X, and 15X modes of operation. Based on these measurements, a finite element model (FEM) of the gun was developed using the commercial software opera/scala. The performance of the FEM model in magnetic fields was characterized using parallel fields ranging from 0 to 200 G in the in-line direction, and 0–35 G in the perpendicular direction. Results: The FEM model matched the average measured emission current to within 5% across all three modes of operation. Different high voltage settings are used for the different modes; the 6X, 10X, and 15X modes have an average high voltage setting of 15, 10, and 11 kV. Due to these differences, different operating modes show different sensitivities in magnetic fields. For in line fields, the first current loss occurs at 40, 20, and 30 G for each mode. This is a much greater sensitivity than has previously been observed. For perpendicular fields, first beam loss occurred at 8, 5, and 5 G and total beam loss at 27, 22, and 20 G. Conclusions: A validated FEM model of a clinical triode electron gun has been developed based on accurate geometric and electrical measurements. Three different operating modes were simulated, with a maximum mean error of 5%. This gun shows greater

Photon Counting Imaging with an Electron-Bombarded Pixel Image Sensor

PubMed Central

Hirvonen, Liisa M.; Suhling, Klaus

2016-01-01

Electron-bombarded pixel image sensors, where a single photoelectron is accelerated directly into a CCD or CMOS sensor, allow wide-field imaging at extremely low light levels as they are sensitive enough to detect single photons. This technology allows the detection of up to hundreds or thousands of photon events per frame, depending on the sensor size, and photon event centroiding can be employed to recover resolution lost in the detection process. Unlike photon events from electron-multiplying sensors, the photon events from electron-bombarded sensors have a narrow, acceleration-voltage-dependent pulse height distribution. Thus a gain voltage sweep during exposure in an electron-bombarded sensor could allow photon arrival time determination from the pulse height with sub-frame exposure time resolution. We give a brief overview of our work with electron-bombarded pixel image sensor technology and recent developments in this field for single photon counting imaging, and examples of some applications. PMID:27136556

Photon gating in four-dimensional ultrafast electron microscopy.

PubMed

Hassan, Mohammed T; Liu, Haihua; Baskin, John Spencer; Zewail, Ahmed H

2015-10-20

Ultrafast electron microscopy (UEM) is a pivotal tool for imaging of nanoscale structural dynamics with subparticle resolution on the time scale of atomic motion. Photon-induced near-field electron microscopy (PINEM), a key UEM technique, involves the detection of electrons that have gained energy from a femtosecond optical pulse via photon-electron coupling on nanostructures. PINEM has been applied in various fields of study, from materials science to biological imaging, exploiting the unique spatial, energy, and temporal characteristics of the PINEM electrons gained by interaction with a "single" light pulse. The further potential of photon-gated PINEM electrons in probing ultrafast dynamics of matter and the optical gating of electrons by invoking a "second" optical pulse has previously been proposed and examined theoretically in our group. Here, we experimentally demonstrate this photon-gating technique, and, through diffraction, visualize the phase transition dynamics in vanadium dioxide nanoparticles. With optical gating of PINEM electrons, imaging temporal resolution was improved by a factor of 3 or better, being limited only by the optical pulse widths. This work enables the combination of the high spatial resolution of electron microscopy and the ultrafast temporal response of the optical pulses, which provides a promising approach to attain the resolution of few femtoseconds and attoseconds in UEM.

Peripheral photon and neutron doses from prostate cancer external beam irradiation.

PubMed

Bezak, Eva; Takam, Rundgham; Marcu, Loredana G

2015-12-01

Peripheral photon and neutron doses from external beam radiotherapy (EBRT) are associated with increased risk of carcinogenesis in the out-of-field organs; thus, dose estimations of secondary radiation are imperative. Peripheral photon and neutron doses from EBRT of prostate carcinoma were measured in Rando phantom. (6)LiF:Mg,Cu,P and (7)LiF:Mg,Cu,P glass-rod thermoluminescence dosemeters (TLDs) were inserted in slices of a Rando phantom followed by exposure to 80 Gy with 18-MV photon four-field 3D-CRT technique. The TLDs were calibrated using 6- and 18-MV X-ray beam. Neutron dose equivalents measured with CR-39 etch-track detectors were used to derive readout-to-neutron dose conversion factor for (6)LiF:Mg,Cu,P TLDs. Average neutron dose equivalents per 1 Gy of isocentre dose were 3.8±0.9 mSv Gy(-1) for thyroid and 7.0±5.4 mSv Gy(-1) for colon. For photons, the average dose equivalents per 1 Gy of isocentre dose were 0.2±0.1 mSv Gy(-1) for thyroid and 8.1±9.7 mSv Gy(-1) for colon. Paired (6)LiF:Mg,Cu,P and (7)LiF:Mg,Cu,P TLDs can be used to measure photon and neutron doses simultaneously. Organs in close proximity to target received larger doses from photons than those from neutrons whereas distally located organs received higher neutron versus photon dose. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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

Directly tailoring photon-electron coupling for sensitive photoconductance

NASA Astrophysics Data System (ADS)

Huang, Zhiming; Zhou, Wei; Huang, Jingguo; Wu, Jing; Gao, Yanqing; Qu, Yue; Chu, Junhao

2016-03-01

The coupling between photons and electrons is at the heart of many fundamental phenomena in nature. Despite tremendous advances in controlling electrons by photons in engineered energy-band systems, control over their coupling is still widely lacking. Here we demonstrate an unprecedented ability to couple photon-electron interactions in real space, in which the incident electromagnetic wave directly tailors energy bands of solid to generate carriers for sensitive photoconductance. By spatially coherent manipulation of metal-wrapped material system through anti-symmetric electric field of the irradiated electromagnetic wave, electrons in the metals are injected and accumulated in the induced potential well (EIW) produced in the solid. Respective positive and negative electric conductances are easily observed in n-type and p-type semiconductors into which electrons flow down from the two metallic sides under light irradiation. The photoconductivity is further confirmed by sweeping the injected electrons out of the semiconductor before recombination applied by sufficiently strong electric fields. Our work opens up new perspectives for tailoring energy bands of solids and is especially relevant to develop high effective photon detection, spin injection, and energy harvesting in optoelectronics and electronics.

Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 03: Energy dependence of a clinical probe-format calorimeter and its pertinence to absolute photon and electron beam dosimetry

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

Renaud, James; Seuntjens, Jan; Sarfehnia, Arman

Purpose: To evaluate the intrinsic and absorbed-dose energy dependence of a small-scale graphite calorimeter probe (GPC) developed for use as a routine clinical dosimeter. The influence of charge deposition on the response of the GPC was also assessed by performing absolute dosimetry in clinical linac-based electron beams. Methods: Intrinsic energy dependence was determined by performing constant-temperature calorimetry dose measurements in a water-equivalent solid phantom, under otherwise reference conditions, in five high-energy photon (63.5 < %dd(10){sub X} < 76.3), and five electron (2.3 cm < R{sub 50} < 8.3 cm) beams. Reference dosimetry was performed for all beams in question usingmore » an Exradin A19 ion chamber with a calibration traceable to national standards. The absorbed-dose component of the overall energy dependence was calculated using the EGSnrc egs-chamber user code. Results: A total of 72 measurements were performed with the GPC, resulting in a standard error on the mean absorbed dose of better than 0.3 % for all ten beams. For both the photon and electron beams, no statistically-significant energy dependence was observed experimentally. Peak-to-peak, variations in the relative response of the GPC across all beam qualities of a given radiation type were on the order of 1 %. No effects, either transient or permanent, were attributable to the charge deposited by the electron beams. Conclusions: The GPC’s apparent energy-independence, combined with its well-established linearity and dose rate independence, make it a potentially useful dosimetry system capable measuring photon and electron doses in absolute terms at the clinical level.« less

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.

Two-photon coincident emission from thick targets for 70-keV incident electrons

NASA Astrophysics Data System (ADS)

Liu, J.; Kahler, D. L.; Quarles, C. A.

1993-04-01

Two-photon coincidence yields have been measured in thick targets of C, Al, Ag, and Ta for 70 keV incident electrons and photons radiated at +/-45° to the incident beam. A theoretical model, which is more rigorous, has been developed to simulate the two-photon processes of coherent thick-target double bremsstrahlung (TTDB) and the incoherent emission of two single-bremsstrahlung (SBSB) photons in a thick-target environment. The model is based on an integration of the thin-target cross sections over the target thickness taking into account electron energy loss, electron backscattering, and photon attenuation. It predicts a yield that is much lower than that of the previous model. The prediction of the model fits the present experimental data well by adjusting the relative weight of the two competing processes, and we find that TTDB dominates at low Z and incoherent SBSB dominates at higher Z.

Beam shaping to improve the free-electron laser performance at the Linac Coherent Light Source

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

Ding, Y.; Bane, K. L. F.; Colocho, W.

2016-10-27

A new operating mode has been developed for the Linac Coherent Light Source (LCLS) in which we shape the longitudinal phase space of the electron beam. This mode of operation is realized using a horizontal collimator located in the middle of the first bunch compressor to truncate the head and tail of the beam. With this method, the electron beam longitudinal phase space and current profile are reshaped, and improvement in lasing performance can be realized. As a result, we present experimental studies at the LCLS of the beam shaping effects on the free-electron laser performance.

Electron and photon identification in the D0 experiment

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

Abazov, V. M.; Abbott, B.; Acharya, B. S.

2014-06-01

The electron and photon reconstruction and identification algorithms used by the D0 Collaboration at the Fermilab Tevatron collider are described. The determination of the electron energy scale and resolution is presented. Studies of the performance of the electron and photon reconstruction and identification are summarized.

PERLE. Powerful energy recovery linac for experiments. Conceptual design report

NASA Astrophysics Data System (ADS)

Angal-Kalinin, D.; Arduini, G.; Auchmann, B.; Bernauer, J.; Bogacz, A.; Bordry, F.; Bousson, S.; Bracco, C.; Brüning, O.; Calaga, R.; Cassou, K.; Chetvertkova, V.; Cormier, E.; Daly, E.; Douglas, D.; Dupraz, K.; Goddard, B.; Henry, J.; Hutton, A.; Jensen, E.; Kaabi, W.; Klein, M.; Kostka, P.; Lasheras, N.; Levichev, E.; Marhauser, F.; Martens, A.; Milanese, A.; Militsyn, B.; Peinaud, Y.; Pellegrini, D.; Pietralla, N.; Pupkov, Y.; Rimmer, R.; Schirm, K.; Schulte, D.; Smith, S.; Stocchi, A.; Valloni, A.; Welsch, C.; Willering, G.; Wollmann, D.; Zimmermann, F.; Zomer, F.

2018-06-01

A conceptual design is presented of a novel energy-recovering linac (ERL) facility for the development and application of the energy recovery technique to linear electron accelerators in the multi-turn, large current and large energy regime. The main characteristics of the powerful energy recovery linac experiment facility (PERLE) are derived from the design of the Large Hadron electron Collider, an electron beam upgrade under study for the LHC, for which it would be the key demonstrator. PERLE is thus projected as a facility to investigate efficient, high current (HC) (>10 mA) ERL operation with three re-circulation passages through newly designed SCRF cavities, at 801.58 MHz frequency, and following deceleration over another three re-circulations. In its fully equipped configuration, PERLE provides an electron beam of approximately 1 GeV energy. A physics programme possibly associated with PERLE is sketched, consisting of high precision elastic electron–proton scattering experiments, as well as photo-nuclear reactions of unprecedented intensities with up to 30 MeV photon beam energy as may be obtained using Fabry–Perot cavities. The facility has further applications as a general technology test bed that can investigate and validate novel superconducting magnets (beam induced quench tests) and superconducting RF structures (structure tests with HC beams, beam loading and transients). Besides a chapter on operation aspects, the report contains detailed considerations on the choices for the SCRF structure, optics and lattice design, solutions for arc magnets, source and injector and on further essential components. A suitable configuration derived from the here presented design concept may next be moved forward to a technical design and possibly be built by an international collaboration which is being established.

Photon-assisted electron energy loss spectroscopy and ultrafast imaging.

PubMed

Howie, Archie

2009-08-01

A variety of ways is described in which photons can be used not only for ultrafast electron microscopy but also to enormously widen the energy range of spatially-resolved electron spectroscopy. Periodic chains of femtosecond laser pulses are a particularly important and accurately timed source for single-shot imaging and diffraction as well as for several forms of pump-probe microscopy at even higher spatial resolution and sub-picosecond timing. Many exciting new fields are opened up for study by these developments. Ultrafast, single shot diffraction with intense pulses of X-rays supplemented by phase retrieval techniques may eventually offer a challenging alternative and purely photon-based route to dynamic imaging at high spatial resolution.

Link between the photonic and electronic topological phases in artificial graphene

NASA Astrophysics Data System (ADS)

Lannebère, Sylvain; Silveirinha, Mário G.

2018-04-01

In recent years the study of topological phases of matter has emerged as a very exciting field of research, both in photonics and in electronics. However, up to now the electronic and photonic properties have been regarded as totally independent. Here we establish a link between the electronic and the photonic topological phases of the same material system and theoretically demonstrate that they are intimately related. We propose a realization of the Haldane model as a patterned two-dimensional electron gas and determine its optical response using the Kubo formula. It is shown that the electronic and photonic phase diagrams of the patterned electron gas are strictly related. In particular, the system has a trivial photonic topology when the inversion symmetry is the prevalent broken symmetry, whereas it has a nontrivial photonic topology for a dominant broken time-reversal symmetry, similar to the electronic case. To confirm these predictions, we numerically demonstrate the emergence of topologically protected unidirectional electromagnetic edge states at the interface with a trivial photonic material.

Evaluation of radiosurgery techniques–Cone-based linac radiosurgery vs tomotherapy-based radiosurgery

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

Yip, Ho Yin, E-mail: hoyinyip@yahoo.com.hk; Mui, Wing Lun A.; Lee, Joseph W.Y.

2013-07-01

Performances of radiosurgery of intracranial lesions between cone-based Linac system and Tomotherapy-based system were compared in terms of dosimetry and time. Twelve patients with single intracranial lesion treated with cone-based Linac radiosurgery system from 2005 to 2009 were replanned for Tomotherapy-based radiosurgery treatment. The conformity index, homogeneity index (HI), and gradient score index (GSI) of each case was calculated. The Wilcoxon matched-pair test was used to compare the 3 indices between both systems. The cases with regular target (n = 6) and those with irregular target (n = 6) were further analyzed separately. The estimated treatment time between both systemsmore » was also compared. Significant differences were found in HI (p = 0.05) and in GSI (p = 0.03) for the whole group. Cone-based radiosurgery was better in GSI whereas Tomotherapy-based radiosurgery was better in HI. Cone-based radiosurgery was better in conformity index (p = 0.03) and GSI (p = 0.03) for regular targets, whereas Tomotherapy-based radiosurgery system performed significantly better in HI (p = 0.03) for irregular targets. The estimated total treatment time for Tomotherapy-based radiosurgery ranged from 24 minutes to 35 minutes, including 15 minutes of pretreatment megavoltage computed tomography (MVCT) and image registration, whereas that for cone-based radiosurgery ranged from 15 minutes for 1 isocenter to 75 minutes for 5 isocenters. As a rule of thumb, Tomotherapy-based radiosurgery system should be the first-line treatment for irregular lesions because of better dose homogeneity and shorter treatment time. Cone-based Linac radiosurgery system should be the treatment of choice for regular targets because of the better dose conformity, rapid dose fall-off, and reasonable treatment time.« less

A TLD-based few-channel spectrometer for mixed photon, electron, and ion fields with high fluence rates.

PubMed

Behrens, R; Ambrosi, P

2002-01-01

A few-channel spectrometer for mixed photon, electron and ion radiation fields has been developed. It consists of a front layer of an etched-track detector foil for detecting protons and ions, a stack of PMMA with thermoluminescent detectors at different depths for gaining spectral information about electrons, and a stack of metallic filters with increasing cut-off photon energies, interspersed with thermoluminescent detectors for gaining spectral information about photons. From the reading of the TL detectors the spectral fluence of the electrons (400 keV to 9 MeV) and photons (20 keV to 2 MeV) can be determined by an unfolding procedure. The spectrometer can be used in pulsed radiation fields with extremely high momentary values of the fluence rate. Design and calibration of the spectrometer are described.

Cloud-based design of high average power traveling wave linacs

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

SU-E-T-409: Evaluation of Tissue Composition Effect On Dose Distribution in Radiotherapy with 6 MV Photon Beam of a Medical Linac

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

Ghorbani, M; Tabatabaei, Z; Noghreiyan, A Vejdani

Purpose: The aim of this study is to evaluate soft tissue composition effect on dose distribution for various soft tissues and various depths in radiotherapy with 6 MV photon beam of a medical linac. Methods: A phantom and Siemens Primus linear accelerator were simulated using MCNPX Monte Carlo code. In a homogeneous cubic phantom, six types of soft tissue and three types of tissue-equivalent materials were defined separately. The soft tissues were muscle (skeletal), adipose tissue, blood (whole), breast tissue, soft tissue (9-component) and soft tissue (4-component). The tissue-equivalent materials included: water, A-150 tissue-equivalent plastic and perspex. Photon dose relativemore » to dose in 9-component soft tissue at various depths on the beam’s central axis was determined for the 6 MV photon beam. The relative dose was also calculated and compared for various MCNPX tallies including,F8, F6 and,F4. Results: The results of the relative photon dose in various materials relative to dose in 9-component soft tissue and using different tallies are reported in the form of tabulated data. Minor differences between dose distributions in various soft tissues and tissue-equivalent materials were observed. The results from F6 and F4 were practically the same but different with,F8 tally. Conclusion: Based on the calculations performed, the differences in dose distributions in various soft tissues and tissue-equivalent materials are minor but they could be corrected in radiotherapy calculations to upgrade the accuracy of the dosimetric calculations.« less

Discrete Chromatic Aberrations Arising from Photoinduced Electron-Photon Interactions in Ultrafast Electron Microscopy.

PubMed

Plemmons, Dayne A; Flannigan, David J

2016-05-26

In femtosecond ultrafast electron microscopy (UEM) experiments, the initial excitation period is composed of spatiotemporal overlap of the temporally commensurate pump photon pulse and probe photoelectron packet. Generation of evanescent near-fields at the nanostructure specimens produces a dispersion relation that enables coupling of the photons (ℏω = 2.4 eV, for example) and freely propagating electrons (200 keV, for example) in the near-field. Typically, this manifests as discrete peaks occurring at integer multiples (n) of the photon energy in the low-loss/gain region of electron-energy spectra (i.e., at 200 keV ± nℏω eV). Here, we examine the UEM imaging resolution implications of the strong inelastic near-field interactions between the photons employed in optical excitation and the probe photoelectrons. We find that the additional photoinduced energy dispersion occurring when swift electrons pass through intense evanescent near-fields results in a discrete chromatic aberration that limits the spatial resolving power to several angstroms during the excitation period.

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.

Construction and commissioning of the compact energy-recovery linac at KEK

NASA Astrophysics Data System (ADS)

Akemoto, Mitsuo; Arakawa, Dai; Asaoka, Seiji; Cenni, Enrico; Egi, Masato; Enami, Kazuhiro; Endo, Kuninori; Fukuda, Shigeki; Furuya, Takaaki; Haga, Kaiichi; Hajima, Ryoichi; Hara, Kazufumi; Harada, Kentaro; Honda, Tohru; Honda, Yosuke; Honma, Teruya; Hosoyama, Kenji; Kako, Eiji; Katagiri, Hiroaki; Kawata, Hiroshi; Kobayashi, Yukinori; Kojima, Yuuji; Kondou, Yoshinari; Tanaka, Olga; Kume, Tatsuya; Kuriki, Masao; Matsumura, Hiroshi; Matsushita, Hideki; Michizono, Shinichiro; Miura, Takako; Miyajima, Tsukasa; Nagahashi, Shinya; Nagai, Ryoji; Nakai, Hirotaka; Nakajima, Hiromitsu; Nakamura, Norio; Nakanishi, Kota; Nigorikawa, Kazuyuki; Nishimori, Nobuyuki; Nogami, Takashi; Noguchi, Shuichi; Obina, Takashi; Qiu, Feng; Sagehashi, Hidenori; Sakai, Hiroshi; Sakanaka, Shogo; Sasaki, Shinichi; Satoh, Kotaro; Sawamura, Masaru; Shimada, Miho; Shinoe, Kenji; Shishido, Toshio; Tadano, Mikito; Takahashi, Takeshi; Takai, Ryota; Takenaka, Tateru; Tanimoto, Yasunori; Uchiyama, Takashi; Ueda, Akira; Umemori, Kensei; Watanabe, Ken; Yamamoto, Masahiro

2018-01-01

Energy-recovery linacs (ERLs) are promising for advanced synchrotron light sources, high-power free electron lasers (FELs), high-brightness gamma-ray sources, and electron-ion colliders. To demonstrate the critical technology of ERL-based light sources, we have designed and constructed a test accelerator, the compact ERL (cERL). Using advanced technology that includes a photocathode direct current (DC) electron gun and two types of 1.3-GHz-frequency superconducting cavities, the cERL was designed to be capable of recirculating low emittance (≤1 mm ṡ mrad) and high average-current (≥10 mA) electron beams while recovering the beam energy. During initial commissioning, the cERL demonstrated successful recirculation of high-quality beams with normalized transverse emittance of ∼0.14 mm ṡ mrad and momentum spread of ∼1.2 × 10-4 (rms) at a beam energy of 20 MeV and bunch charge below 100 fC. Energy recovery in the superconducting main linac was also demonstrated for high-average-current continuous-wave beams. These results constitute an important milestone toward realizing ERL-based light sources.

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

SU-F-T-89: Investigation of Simultaneous Optimization of Photon and Electron Apertures for Mixed Beam Radiotherapy Based On An Academic Case

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

Mueller, S; Joosten, A; Fix, MK

Purpose: To estimate the dosimetric potential of mixed beam radiotherapy (MBRT) by using a single process optimizing the shape and weight of photon and electron apertures simultaneously based on Monte Carlo beamlet dose distributions. Methods: A simulated annealing based direct aperture optimization capable to perform simultaneous optimization was developed to generate treatment plans for MERT, photon-IMRT and MBRT. Both photon and electron apertures are collimated with the photon-MLC and are delivered in a segmented manner. For dosimetric comparison and for investigating the dependency on the number of apertures, photon-IMRT, MERT and MBRT plans were generated for an academic case consistingmore » of a water phantom containing two shallow PTVs differing in the maximal depth of 5 and 7 cm, respectively and two OARs in distal and lateral direction to the PTVs. Results: For the superficial PTV, the dose homogeneity (V95%–V107%) and the mean dose (in percent of the prescribed dose) to the distal and the lateral OARs of the MBRT plan (94.9%, 16.9%, 17.8%) are superior or comparable to those for the MERT (74%, 18.4%, 15.4%) and the photon-IMRT plan (89.4%, 20.8%, 24.7%). For the enlarged PTV, the dosimetric superiority of MBRT compared to MERT and photon-IMRT is even more pronounced. Furthermore, an MBRT plan with 12 electron and 10 photon apertures lead to an objective function value 38% lower than that of a photon-IMRT plan with 40 apertures. Conclusion: The results of simultaneous optimization for MBRT are promising with regards to further OAR sparing and improved dose coverage to the PTV compared to photon-IMRT and MERT. Especially superficial targets with deeper subparts (>5 cm) could substantially benefit. Moreover, MBRT seems to be a possible solution of two downsides of photon-IMRT, namely the extended low dose bath and the requirement of numerous apertures. This work was supported by Varian Medical Systems. This work was supported by Varian Medical Systems.« less

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.

Anisotropic Electron-Photon and Electron-Phonon Interactions in Black Phosphorus

DOE PAGES

Ling, Xi; Huang, Shengxi; Hasdeo, Eddwi; ...

2016-03-10

Orthorhombic black phosphorus (BP) and other layered materials, such as gallium telluride (GaTe) and tin selenide (SnSe), stand out among two-dimensional (2D) materials owing to their anisotropic in-plane structure. This anisotropy adds a new dimension to the properties of 2D materials and stimulates the development of angle-resolved photonics and electronics. However, understanding the effect of anisotropy has remained unsatisfactory to-date, as shown by a number of inconsistencies in the recent literatures. We use angle-resolved absorption and Raman spectroscopies to investigate the role of anisotropy on the electron-photon and electron-phonon interactions in BP. We highlight a non-trivial dependence between anisotropies andmore » flake thickness, photon and phonon energies. We show that once understood, the anisotropic optical absorption appears to be a reliable and simple way to identify the crystalline orientation of BP, which cannot be determined from Raman spectroscopy without the explicit consideration of excitation wavelength and flake thickness, as commonly used previously.« less

Present status of the low energy linac-based slow positron beam and positronium spectrometer in Saclay

NASA Astrophysics Data System (ADS)

Liszkay, L.; Comini, P.; Corbel, C.; Debu, P.; Grandemange, P.; Pérez, P.; Rey, J.-M.; Reymond, J.-M.; Ruiz, N.; Sacquin, Y.; Vallage, B.

2014-04-01

A new slow positron beamline featuring a large acceptance positronium lifetime spectrometer has been constructed and tested at the linac-based slow positron source at IRFU CEA Saclay, France. The new instrument will be used in the development of a dense positronium target cloud for the GBAR experiment. The GBAR project aims at precise measurement of the gravitational acceleration of antihydrogen in the gravitational field of the Earth. Beyond application in fundamental science, the positron spectrometer will be used in materials research, for testing thin porous films and layers by means of positronium annihilation. The slow positron beamline is being used as a test bench to develop further instrumentation for positron annihilation spectroscopy (Ps time-of-flight, pulsed positron beam). The positron source is built on a low energy linear electron accelerator (linac). The 4.3 MeV electron energy used is well below the photoneutron threshold, making the source a genuine on-off device, without remaining radioactivity. The spectrometer features large BGO (Bismuth Germanate) scintillator detectors, with sufficiently large acceptance to detect all ortho-positronium annihilation lifetime components (annihilation in vacuum and in nanopores).

Cavity Born-Oppenheimer Approximation for Correlated Electron-Nuclear-Photon Systems.

PubMed

Flick, Johannes; Appel, Heiko; Ruggenthaler, Michael; Rubio, Angel

2017-04-11

In this work, we illustrate the recently introduced concept of the cavity Born-Oppenheimer approximation [ Flick et al. PNAS 2017 , 10.1073/pnas.1615509114 ] for correlated electron-nuclear-photon problems in detail. We demonstrate how an expansion in terms of conditional electronic and photon-nuclear wave functions accurately describes eigenstates of strongly correlated light-matter systems. For a GaAs quantum ring model in resonance with a photon mode we highlight how the ground-state electronic potential-energy surface changes the usual harmonic potential of the free photon mode to a dressed mode with a double-well structure. This change is accompanied by a splitting of the electronic ground-state density. For a model where the photon mode is in resonance with a vibrational transition, we observe in the excited-state electronic potential-energy surface a splitting from a single minimum to a double minimum. Furthermore, for a time-dependent setup, we show how the dynamics in correlated light-matter systems can be understood in terms of population transfer between potential energy surfaces. This work at the interface of quantum chemistry and quantum optics paves the way for the full ab initio description of matter-photon systems.

Graphene-Based Josephson-Junction Single-Photon Detector

NASA Astrophysics Data System (ADS)

Walsh, Evan D.; Efetov, Dmitri K.; Lee, Gil-Ho; Heuck, Mikkel; Crossno, Jesse; Ohki, Thomas A.; Kim, Philip; Englund, Dirk; Fong, Kin Chung

2017-08-01

We propose to use graphene-based Josephson junctions (GJJs) to detect single photons in a wide electromagnetic spectrum from visible to radio frequencies. Our approach takes advantage of the exceptionally low electronic heat capacity of monolayer graphene and its constricted thermal conductance to its phonon degrees of freedom. Such a system could provide high-sensitivity photon detection required for research areas including quantum information processing and radio astronomy. As an example, we present our device concepts for GJJ single-photon detectors in both the microwave and infrared regimes. The dark count rate and intrinsic quantum efficiency are computed based on parameters from a measured GJJ, demonstrating feasibility within existing technologies.

Simultaneous optimization of photons and electrons for mixed beam radiotherapy

NASA Astrophysics Data System (ADS)

Mueller, S.; Fix, M. K.; Joosten, A.; Henzen, D.; Frei, D.; Volken, W.; Kueng, R.; Aebersold, D. M.; Stampanoni, M. F. M.; Manser, P.

2017-07-01

The aim of this work is to develop and investigate an inverse treatment planning process (TPP) for mixed beam radiotherapy (MBRT) capable of performing simultaneous optimization of photon and electron apertures. A simulated annealing based direct aperture optimization (DAO) is implemented to perform simultaneous optimization of photon and electron apertures, both shaped with the photon multileaf collimator (pMLC). Validated beam models are used as input for Monte Carlo dose calculations. Consideration of photon pMLC transmission during DAO and a weight re-optimization of the apertures after deliverable dose calculation are utilized to efficiently reduce the differences between optimized and deliverable dose distributions. The TPP for MBRT is evaluated for an academic situation with a superficial and an enlarged PTV in the depth, a left chest wall case including the internal mammary chain and a squamous cell carcinoma case. Deliverable dose distributions of MBRT plans are compared to those of modulated electron radiotherapy (MERT), photon IMRT and if available to those of clinical VMAT plans. The generated MBRT plans dosimetrically outperform the MERT, photon IMRT and VMAT plans for all investigated situations. For the clinical cases of the left chest wall and the squamous cell carcinoma, the MBRT plans cover the PTV similarly or more homogeneously than the VMAT plans, while OARs are spared considerably better with average reductions of the mean dose to parallel OARs and D 2% to serial OARs by 54% and 26%, respectively. Moreover, the low dose bath expressed as V 10% to normal tissue is substantially reduced by up to 45% compared to the VMAT plans. A TPP for MBRT including simultaneous optimization is successfully implemented and the dosimetric superiority of MBRT plans over MERT, photon IMRT and VMAT plans is demonstrated for academic and clinical situations including superficial targets with and without deep-seated part.

Simultaneous optimization of photons and electrons for mixed beam radiotherapy.

PubMed

Mueller, S; Fix, M K; Joosten, A; Henzen, D; Frei, D; Volken, W; Kueng, R; Aebersold, D M; Stampanoni, M F M; Manser, P

2017-06-26

The aim of this work is to develop and investigate an inverse treatment planning process (TPP) for mixed beam radiotherapy (MBRT) capable of performing simultaneous optimization of photon and electron apertures. A simulated annealing based direct aperture optimization (DAO) is implemented to perform simultaneous optimization of photon and electron apertures, both shaped with the photon multileaf collimator (pMLC). Validated beam models are used as input for Monte Carlo dose calculations. Consideration of photon pMLC transmission during DAO and a weight re-optimization of the apertures after deliverable dose calculation are utilized to efficiently reduce the differences between optimized and deliverable dose distributions. The TPP for MBRT is evaluated for an academic situation with a superficial and an enlarged PTV in the depth, a left chest wall case including the internal mammary chain and a squamous cell carcinoma case. Deliverable dose distributions of MBRT plans are compared to those of modulated electron radiotherapy (MERT), photon IMRT and if available to those of clinical VMAT plans. The generated MBRT plans dosimetrically outperform the MERT, photon IMRT and VMAT plans for all investigated situations. For the clinical cases of the left chest wall and the squamous cell carcinoma, the MBRT plans cover the PTV similarly or more homogeneously than the VMAT plans, while OARs are spared considerably better with average reductions of the mean dose to parallel OARs and D 2% to serial OARs by 54% and 26%, respectively. Moreover, the low dose bath expressed as V 10% to normal tissue is substantially reduced by up to 45% compared to the VMAT plans. A TPP for MBRT including simultaneous optimization is successfully implemented and the dosimetric superiority of MBRT plans over MERT, photon IMRT and VMAT plans is demonstrated for academic and clinical situations including superficial targets with and without deep-seated part.

Development and reproducibility evaluation of a Monte Carlo-based standard LINAC model for quality assurance of multi-institutional clinical trials.

PubMed

Usmani, Muhammad Nauman; Takegawa, Hideki; Takashina, Masaaki; Numasaki, Hodaka; Suga, Masaki; Anetai, Yusuke; Kurosu, Keita; Koizumi, Masahiko; Teshima, Teruki

2014-11-01

Technical developments in radiotherapy (RT) have created a need for systematic quality assurance (QA) to ensure that clinical institutions deliver prescribed radiation doses consistent with the requirements of clinical protocols. For QA, an ideal dose verification system should be independent of the treatment-planning system (TPS). This paper describes the development and reproducibility evaluation of a Monte Carlo (MC)-based standard LINAC model as a preliminary requirement for independent verification of dose distributions. The BEAMnrc MC code is used for characterization of the 6-, 10- and 15-MV photon beams for a wide range of field sizes. The modeling of the LINAC head components is based on the specifications provided by the manufacturer. MC dose distributions are tuned to match Varian Golden Beam Data (GBD). For reproducibility evaluation, calculated beam data is compared with beam data measured at individual institutions. For all energies and field sizes, the MC and GBD agreed to within 1.0% for percentage depth doses (PDDs), 1.5% for beam profiles and 1.2% for total scatter factors (Scps.). Reproducibility evaluation showed that the maximum average local differences were 1.3% and 2.5% for PDDs and beam profiles, respectively. MC and institutions' mean Scps agreed to within 2.0%. An MC-based standard LINAC model developed to independently verify dose distributions for QA of multi-institutional clinical trials and routine clinical practice has proven to be highly accurate and reproducible and can thus help ensure that prescribed doses delivered are consistent with the requirements of clinical protocols. © The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Coherent manipulation of photons and electrons

NASA Astrophysics Data System (ADS)

Zhao, Lu

coherence length and electrically tunable Fermi levels, electrons in graphene systems have some photon-like behaviors, and could be coherently manipulated. Therefore, in the fourth chapter, we theorize that at a sharp electrostatic step potential in graphene massless Dirac fermions can obtain Goos-Hanchen-like shifts under total internal reflection. Also, we study coherent propagation of the quasiparticles along a sharp graphene p-n-p waveguide, and derive novel dispersion relations for the guided modes. Consequently, coherent graphene-based devices, e.g., movable mirrors, buffers and memories, induced only by the electric field effects may be proposed. Finally, we theoretically investigate the coherent propagation of massive chiral fermions along a sharp bilayer graphene p-n-p waveguide, and indicate that the guided quasiparticles can be coherently slowed, stored and retrieved based on tunable electric field effects. Controlling group velocity in the bilayer graphene p-n-p waveguide is accomplished via interband tunneling through the p-n interfaces, and does not depend on the bandgap opening.

Photon gating in four-dimensional ultrafast electron microscopy

PubMed Central

Hassan, Mohammed T.; Liu, Haihua; Baskin, John Spencer; Zewail, Ahmed H.

2015-01-01

Ultrafast electron microscopy (UEM) is a pivotal tool for imaging of nanoscale structural dynamics with subparticle resolution on the time scale of atomic motion. Photon-induced near-field electron microscopy (PINEM), a key UEM technique, involves the detection of electrons that have gained energy from a femtosecond optical pulse via photon–electron coupling on nanostructures. PINEM has been applied in various fields of study, from materials science to biological imaging, exploiting the unique spatial, energy, and temporal characteristics of the PINEM electrons gained by interaction with a “single” light pulse. The further potential of photon-gated PINEM electrons in probing ultrafast dynamics of matter and the optical gating of electrons by invoking a “second” optical pulse has previously been proposed and examined theoretically in our group. Here, we experimentally demonstrate this photon-gating technique, and, through diffraction, visualize the phase transition dynamics in vanadium dioxide nanoparticles. With optical gating of PINEM electrons, imaging temporal resolution was improved by a factor of 3 or better, being limited only by the optical pulse widths. This work enables the combination of the high spatial resolution of electron microscopy and the ultrafast temporal response of the optical pulses, which provides a promising approach to attain the resolution of few femtoseconds and attoseconds in UEM. PMID:26438835

Ultrafast harmonic rf kicker design and beam dynamics analysis for an energy recovery linac based electron circulator cooler ring

DOE PAGES

Huang, Yulu; Wang, Haipeng; Rimmer, Robert A.; ...

2016-08-01

An ultrafast kicker system is being developed for the energy recovery linac (ERL) based electron circulator cooler ring (CCR) in the proposed Jefferson Lab Electron Ion Collider (JLEIC, previously named MEIC). In the CCR, the injected electron bunches can be recirculated while performing ion cooling for 10–30 turns before the extraction, thus reducing the recirculation beam current in the ERL to 1/10–1/30 (150mA–50 mA) of the cooling beam current (up to 1.5 A). Assuming a bunch repetition rate of 476.3 MHz and a recirculating factor of 10 in the CCR, the kicker is required to operate at a pulse repetitionmore » rate of 47.63 MHz with pulse width of around 2 ns, so that only every 10th bunch in the CCR will experience a transverse kick while the rest of the bunches will not be disturbed. Such a kicker pulse can be synthesized by ten harmonic modes of the 47.63 MHz kicker pulse repetition frequency, using up to four quarter wavelength resonator (QWR) based deflecting cavities. In this paper, several methods to synthesize such a kicker waveform will be discussed and a comparison of their beam dynamics performance is made using ELEGANT. Four QWR cavities are envisaged with high transverse shunt impedance requiring less than 100 W of total rf power for a Flat-Top kick pulse. Multipole fields due to the asymmetry of this type of cavity are analyzed. The transverse emittance growth due to the sextupole component is simulated in ELEGANT. In conclusion, off-axis injection and extraction issues and beam optics using a multicavity kick-drift scheme will also be discussed.« less

Ultrafast harmonic rf kicker design and beam dynamics analysis for an energy recovery linac based electron circulator cooler ring

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

Huang, Yulu; Wang, Haipeng; Rimmer, Robert A.

An ultrafast kicker system is being developed for the energy recovery linac (ERL) based electron circulator cooler ring (CCR) in the proposed Jefferson Lab Electron Ion Collider (JLEIC, previously named MEIC). In the CCR, the injected electron bunches can be recirculated while performing ion cooling for 10–30 turns before the extraction, thus reducing the recirculation beam current in the ERL to 1/10–1/30 (150mA–50 mA) of the cooling beam current (up to 1.5 A). Assuming a bunch repetition rate of 476.3 MHz and a recirculating factor of 10 in the CCR, the kicker is required to operate at a pulse repetitionmore » rate of 47.63 MHz with pulse width of around 2 ns, so that only every 10th bunch in the CCR will experience a transverse kick while the rest of the bunches will not be disturbed. Such a kicker pulse can be synthesized by ten harmonic modes of the 47.63 MHz kicker pulse repetition frequency, using up to four quarter wavelength resonator (QWR) based deflecting cavities. In this paper, several methods to synthesize such a kicker waveform will be discussed and a comparison of their beam dynamics performance is made using ELEGANT. Four QWR cavities are envisaged with high transverse shunt impedance requiring less than 100 W of total rf power for a Flat-Top kick pulse. Multipole fields due to the asymmetry of this type of cavity are analyzed. The transverse emittance growth due to the sextupole component is simulated in ELEGANT. In conclusion, off-axis injection and extraction issues and beam optics using a multicavity kick-drift scheme will also be discussed.« less

Relation between electron- and photon-caused oxidation in EUVL optics

NASA Astrophysics Data System (ADS)

Malinowski, Michael E.; Steinhaus, Charles A.; Meeker, Donald E.; Clift, W. Miles; Klebanoff, Leonard E.; Bajt, Sasa

2003-06-01

Extreme ultraviolet (EUV)-induced oxidation of silicon-capped, [Mo/Si] multilayer mirrors in the presence of background levels of water vapor is recognized as one of the most serious threats to multilayer lifetime since oxidation of the top silicon layer is an irreversible process. The current work directly compares the oxidation on a silicon-capped, [Mo/Si] multilayers caused by EUV photons with the oxidation caused by 1 keV electrons in the presence of the same water vapor environment (2 x 10-6 Torr). Similar, 4 nm, silicon-capped, [Mo/Si] multilayer mirror samples were exposed to photons (95.3 eV) + water vapor at the ALS, LBNL, and also to a 1 keV electron beam + water vapor in separate experimental systems. The results of this work showed that the oxidation produced by ~1 µA of e-beam current was found to be equivalent to that produced by ~1 mW of EUV exposure. These results will help allow the use of 1 keV electrons beams, instead of EUV photons, to perform environmental testing of multilayers in a low-pressure water environment and to more accurately determine projected mirror lifetimes based on the electron beam exposures.

Relation between electron- and photon-caused oxidation in EUVL optics

NASA Astrophysics Data System (ADS)

Malinowski, Michael E.; Steinhaus, Charles A.; Meeker, Donald E.; Clift, W. Miles; Klebanoff, Leonard E.; Bajt, Sasa

2003-06-01

Extreme ultraviolet (EUV)-induced oxidation of silicon-capped, [Mo/Si] multilayer mirrors in the presence of background levels of water vapor is recognized as one of the most serious threats to multilayer lifetime since oxidation of the top silicon layer is an irreversible process. The current work directly compares the oxidation on a silicon-capped, [Mo/Si] multilayers caused by EUV photons with the oxidation caused by 1 keV electrons in the presence of the same water vapor environment (2 x 10-6 Torr). Similar, 4 nm, silicon-capped, [Mo/Si] multilayer mirror samples were exposed to photons (95.3 eV) + water vapor at the ALS, LBNL, and also to a 1 keV electron beam + water vapor in separate experimental systems. The results of this work showed that the oxidation produced by ~1 ´A of e-beam current was found to be equivalent to that produced by ~1 mW of EUV exposure. These results will help allow the use of 1 keV electrons beams, instead of EUV photons, to perform environmental testing of multilayers in a low-pressure water environment and to more accurately determine projected mirror lifetimes based on the electron beam exposures.

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.

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

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.

TH-EF-207A-03: Photon Counting Implementation Challenges Using An Electron Multiplying Charged-Coupled Device Based Micro-CT System

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

Podgorsak, A; Bednarek, D; Rudin, S

2016-06-15

Purpose: To successfully implement and operate a photon counting scheme on an electron multiplying charged-coupled device (EMCCD) based micro-CT system. Methods: We built an EMCCD based micro-CT system and implemented a photon counting scheme. EMCCD detectors use avalanche transfer registries to multiply the input signal far above the readout noise floor. Due to intrinsic differences in the pixel array, using a global threshold for photon counting is not optimal. To address this shortcoming, we generated a threshold array based on sixty dark fields (no x-ray exposure). We calculated an average matrix and a variance matrix of the dark field sequence.more » The average matrix was used for the offset correction while the variance matrix was used to set individual pixel thresholds for the photon counting scheme. Three hundred photon counting frames were added for each projection and 360 projections were acquired for each object. The system was used to scan various objects followed by reconstruction using an FDK algorithm. Results: Examination of the projection images and reconstructed slices of the objects indicated clear interior detail free of beam hardening artifacts. This suggests successful implementation of the photon counting scheme on our EMCCD based micro-CT system. Conclusion: This work indicates that it is possible to implement and operate a photon counting scheme on an EMCCD based micro-CT system, suggesting that these devices might be able to operate at very low x-ray exposures in a photon counting mode. Such devices could have future implications in clinical CT protocols. NIH Grant R01EB002873; Toshiba Medical Systems Corp.« less

Poster - 42: TB - ARC: A Total Body photon ARC technique using a commercially available linac

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

Evans, Michael D. C.; Ruo, Russell; Patrocinio, Ho

We have developed a total body photon irradiation technique using multiple overlapping open field arcs (TB-ARC). This simple technique uses predetermined arc-weights, with MUs calculated as a function of prescription depth only. Patients lie on a stretcher, in the prone/supine treatment position with AP/PA arcs. This treatment position has many advantages including ease of delivery (especially for tall, pediatric or compromised patients), dose uniformity, simplicity for organ shielding, and imaging capabilities. Using a Varian TrueBeam linac, 14 arcs using 40×40 cm{sup 2} 6 MV open photon beams, sweeping across 10 degrees each, complete a 140 degree arc. The nominal SSDmore » at zero degrees is 200 cm. Arcs at the sweep limits (+/− 70 degrees) are differentially weighted and deliver a dose within 10% of the prescription on central axis, at a depth of 10 cm over a superior-inferior length of 275 cm. CT planning using Varian Eclipse enables dose evaluation. A custom made beam spoiler, consisting of a 2.5 m sheet of polycarbonate (6 mm thick) increases the surface dose from 45% to 90%. This beam spoiler also serves as a support in the event that differential attenuation is required for organs such as lung, heart, liver, kidneys. The geometry of the sweeping beam technique limits organ dose (using varying thicknesses of melting alloy) to about 20% and 40% of prescription at dmax and midplane respectively. Digital imaging with a portable DR cassette enables proper attenuator location prior to treatment.« less

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.

SU-F-T-81: Treating Nose Skin Using Energy and Intensity Modulated Electron Beams with Monte Carlo Based Dose Calculation

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

Jin, L; Fan, J; Eldib, A

Purpose: Treating nose skin with an electron beam is of a substantial challenge due to uneven nose surfaces and tissue heterogeneity, and consequently could have a great uncertainty of dose accuracy on the target. This work explored the method using Monte Carlo (MC)-based energy and intensity modulated electron radiotherapy (MERT), which would be delivered with a photon MLC in a standard medical linac (Artiste). Methods: The traditional treatment on the nose skin involves the usage of a bolus, often with a single energy electron beam. This work avoided using the bolus, and utilized mixed energies of electron beams. An in-housemore » developed Monte Carlo (MC)-based dose calculation/optimization planning system was employed for treatment planning. Phase space data (6, 9, 12 and 15 MeV) were used as an input source for MC dose calculations for the linac. To reduce the scatter-caused penumbra, a short SSD (61 cm) was used. A clinical case of the nose skin, which was previously treated with a single 9 MeV electron beam, was replanned with the MERT method. The resultant dose distributions were compared with the plan previously clinically used. The dose volume histogram of the MERT plan is calculated to examine the coverage of the planning target volume (PTV) and critical structure doses. Results: The target coverage and conformality in the MERT plan are improved as compared to the conventional plan. The MERT can provide more sufficient target coverage and less normal tissue dose underneath the nose skin. Conclusion: Compared to the conventional treatment technique, using MERT for the nose skin treatment has shown the dosimetric advantages in the PTV coverage and conformality. In addition, this technique eliminates the necessity of the cutout and bolus, which makes the treatment more efficient and accurate.« less

Fluctuations in the electron system of a superconductor exposed to a photon flux

PubMed Central

de Visser, P. J.; Baselmans, J. J. A.; Bueno, J.; Llombart, N.; Klapwijk, T. M.

2014-01-01

In a superconductor, in which electrons are paired, the density of unpaired electrons should become zero when approaching zero temperature. Therefore, radiation detectors based on breaking of pairs promise supreme sensitivity, which we demonstrate using an aluminium superconducting microwave resonator. Here we show that the resonator also enables the study of the response of the electron system of the superconductor to pair-breaking photons, microwave photons and varying temperatures. A large range in radiation power (at 1.54 THz) can be chosen by carefully filtering the radiation from a blackbody source. We identify two regimes. At high radiation power, fluctuations in the electron system caused by the random arrival rate of the photons are resolved, giving a straightforward measure of the optical efficiency (48±8%) and showing an unprecedented detector sensitivity. At low radiation power, fluctuations are dominated by excess quasiparticles, the number of which is measured through their recombination lifetime. PMID:24496036

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

NASA Astrophysics Data System (ADS)

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

2014-01-01

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

Matching of electron beams for conformal therapy of target volumes at moderate depths.

PubMed

Zackrisson, B; Karlsson, M

1996-06-01

The basic requirements for conformal electron therapy are an accelerator with a wide range of energies and field shapes. The beams should be well characterised in a full 3-D dose planning system which has been verified for the geometries of the current application. Differences in the basic design of treatment units have been shown to have a large influence on beam quality and dosimetry. Modern equipment can deliver electron beams of good quality with a high degree of accuracy. A race-track microtron with minimised electron scattering and a multi-leaf collimator (MLC) for electron collimating will facilitate the isocentric technique as a general treatment technique for electrons. This will improve the possibility of performing combined electron field techniques in order to conform the dose distribution with no or minimal use of a bolus. Furthermore, the isocentric technique will facilitate multiple field arrangements that decrease the problems with distortion of the dose distribution due to inhomogeneities, etc. These situations are demonstrated by clinical examples where isocentric, matched electron fields for treatment of the nose, thyroid and thoracic wall have been used.

Fiber-Coupled, Time-Gated { {Al}}_{2}{ {O}}_{3} : { {C}} Radioluminescence Dosimetry Technique and Algorithm for Radiation Therapy With LINACs

NASA Astrophysics Data System (ADS)

Magne, Sylvain; Deloule, Sybelle; Ostrowsky, Aimé; Ferdinand, Pierre

2013-08-01

An original algorithm for real-time In Vivo Dosimetry (IVD) based on Radioluminescence (RL) of dosimetric-grade Al2O3:C crystals is described and demonstrated in reference conditions with 12-MV photon beams from a Saturne 43 linear accelerator (LINAC), simulating External Beam Radiation Therapy (EBRT) treatments. During the course of irradiation, a portion of electrons is trapped within the Al2O3:C crystal while another portion recombines and generates RL, recorded on-line using an optical fiber. The RL sensitivity is dose-dependent and increases in accordance with the concentration of trapped electrons. Once irradiation is completed, the Al2O3:C crystal is reset by laser light (reusable) and the resultant OSL (Optically Stimulated Luminescence) is also collected back by the remote RL-OSL reader and finally integrated to yield the absorbed dose. During irradiation, scintillation and Cerenkov lights generated within the optical fiber (“stem effect”) are removed by a time-discrimination method involving a discriminating unit and a fiber-coupled BGO scintillator placed in the irradiation room, next to the LINAC. The RL signals were then calibrated with respect to reference dose and dose rate data using an ionization chamber (IC). The algorithm relies upon the integral of the RL and provides the accumulated dose (useful to the medical physicist) at any time during irradiation, the dose rate being derived afterwards. It is tested with both step and arbitrary dose rate profiles, manually operated from the LINAC control desk. The doses measured by RL and OSL are both compared to reference doses and deviations are about ±2% and ±1% respectively, thus demonstrating the reliability of the algorithm for arbitrary profiles and wide range of dose rates. Although the calculation was done off-line, it is amenable to real-time processing during irradiation.

Chromaticity of the lattice and beam stability in energy recovery linacs

NASA Astrophysics Data System (ADS)

Litvinenko, Vladimir N.

2012-07-01

Energy recovery linacs (ERLs) are an emerging generation of accelerators that promises to revolutionize the fields of high-energy physics and photon sciences. These accelerators combine the advantages of linear accelerators with that of storage rings, and augur the delivery of electron beams of unprecedented power and quality. The use of superconducting radio-frequency cavities converts ERLs into nearly perfect “perpetuum mobile” accelerators, wherein the beam is accelerated to the desired energy, used, and then yields the energy back to the rf field. However, one potential weakness of these devices is transverse beam breakup instability that could severely limit the available beam current. In this paper, I propose a novel method of suppressing these dangerous effects via a natural phenomenon in the accelerators, viz., the chromaticity of the transverse motion.

Chromaticity of the lattice and beam stability in energy-recovery linacs

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

Litvinenko, V.N.

2011-12-23

Energy recovery linacs (ERLs) are an emerging generation of accelerators promising to revolutionize the fields of high-energy physics and photon sciences. These accelerators combine the advantages of linear accelerators with that of storage rings, and hold the promise of delivering electron beams of unprecedented power and quality. Use of superconducting radio-frequency (SRF) cavities converts ERLs into nearly perfect 'perpetuum mobile' accelerators, wherein the beam is accelerated to a desirable energy, used, and then gives the energy back to the RF field. One potential weakness of these devices is transverse beam break-up instability that could severely limit the available beam current.more » In this paper, I present a method of suppressing these dangerous effects using a natural phenomenon in the accelerators, viz., the chromaticity of the transverse motion.« less

Focus on Electronics, Photonics and Renewable Energy.

PubMed

Goodnick, Stephen M; Nemanich, Robert J; Korkin, Anatoli

2018-06-21

This focus collection is based on the research papers presented at the NGC 2017 conference in Tomsk (Russia), the 7th conference in the Nano and Giga Forum series, dedicated to solving scientific and technological problems in several areas of electronics, photonics and renewable energy. As early as the first forum in Moscow, Russia, in 2002, the organizers realized that publication of the lectures notes and selected research papers would be a valuable legacy of the meeting, and a significant educational resource and knowledge base for students, young researchers, and experts alike. © 2018 IOP Publishing Ltd.

Neutron production from flattening filter free high energy medical linac: A Monte Carlo study

NASA Astrophysics Data System (ADS)

Najem, M. A.; Abolaban, F. A.; Podolyák, Z.; Spyrou, N. M.

2015-11-01

One of the problems arising from using a conventional linac at high energy (>8 MV) is the production of neutrons. One way to reduce neutron production is to remove the flattening filter (FF). The main purpose of this work was to study the effect of FF removal on neutron fluence and neutron dose equivalent inside the treatment room at different photon beam energies. Several simulations based on Monte Carlo techniques were carried out in order to calculate the neutron fluence at different locations in the treatment room from different linac energies with and without a FF. In addition, a step-and-shoot intensity modulated radiotherapy (SnS IMRT) for prostate cancer was modelled using the 15 MV photon beam with and without a FF on a water phantom to calculate the neutron dose received in a full treatment. The results obtained show a significant drop-off in neutrons fluence and dose equivalent when the FF was removed. For example, the neutron fluence was decreased by 54%, 76% and 75% for 10, 15 and 18 MV, respectively. This can decrease the neutron dose to the patient as well as reduce the shielding cost of the treatment room. The neutron dose equivalent of the SnS IMRT for prostate cancer was reduced significantly by 71.3% when the FF was removed. It can be concluded that the flattening filter removal from the head of the linac could reduce the risk of causing secondary cancers and the shielding cost of radiotherapy treatment rooms.

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

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.

Photon structure studied at an electron ion collider

DOE PAGES

Chu, X.; Aschenauer, E. C.; Lee, J. H.; ...

2017-10-30

We report that a future electron ion collider (EIC) will be able to provide collisions of polarized electrons with protons and heavy ions over a wide range of center-of-mass energies (20 GeV to 140 GeV) at an instantaneous luminosity of 10 33 - 10 34cm -2s -1. One of its promising physics programs is the study of the partonic structure of quasireal photons. Measuring dijets in quasireal photoproduction events, one can effectively access the underlying parton dynamics of the photons. In this paper, we discuss the feasibility of tagging resolved photon processes and measuring the dijet cross section as a function of jet transverse momentum in the range of 0.01 < xmore » $$rec\\atop{γ}$$ < 1 at an EIC. Finally, it will be shown that both unpolarized and polarized parton distributions in the photon can be extracted, and that the flavor of the parton can be tagged at an EIC.« less

Virtual photon structure functions and the parton content of the electron

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

Drees, M.; Godbole, R.M.

1994-09-01

We point out that in processes involving the parton content of the photon the usual effective photon approximation should be modified. The reason is that the parton content of virtual photons is logarithmically suppressed compared to real photons. We describe this suppression using several simple, physically motivated [ital Ansa]$[ital uml---tze]. Although the parton content of the electron in general no longer factorizes into an electron flux function and a photon structure function, it can still be expressed as a single integral. Numerical examples are given for the [ital e][sup +][ital e][sup [minus

Dosimetry of high-energy electron linac produced photoneutrons and the bremsstrahlung gamma-rays using TLD-500 and TLD-700 dosimeter pairs

NASA Astrophysics Data System (ADS)

Mukherjee, Bhaskar; Makowski, Dariusz; Simrock, Stefan

2005-06-01

The neutron and gamma doses are crucial to interpreting the radiation effects in microelectronic devices operating in a high-energy accelerator environment. This report highlights a method for an accurate estimation of photoneutron and the accompanying bremsstrahlung (gamma) doses produced by a 450 MeV electron linear accelerator (linac) operating in pulsed mode. The principle is based on the analysis of thermoluminescence glow-curves of TLD-500 (Aluminium Oxide) and TLD-700 (Lithium Fluoride) dosimeter pairs. The gamma and fast neutron response of the TLD-500 and TLD-700 dosimeter pairs were calibrated with a 60Co (gamma) and a 241Am-Be (α, n) neutron standard-source, respectively. The Kinetic Energy Released in Materials (kerma) conversion factor for photoneutrons was evaluated by folding the neutron kerma (dose) distribution in 7LiF (the main component of the TLD-700 dosimeter) with the energy spectra of the 241Am-Be (α, n) neutrons and electron accelerator produced photoneutrons. The neutron kerma conversion factors for 241Am-Be neutrons and photoneutrons were calculated to be 2.52×10 -3 and 1.37×10 -3 μGy/a.u. respectively. The bremsstrahlung (gamma) dose conversion factor was evaluated to be 7.32×10 -4 μGy/a.u. The above method has been successfully utilised to assess the photoneutron and bremsstrahlung doses from a 450 MeV electron linac operating at DESY Research Centre in Hamburg, Germany.

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

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.

Single-chip photonic transceiver based on bulk-silicon, as a chip-level photonic I/O platform for optical interconnects.

PubMed

Kim, Gyungock; Park, Hyundai; Joo, Jiho; Jang, Ki-Seok; Kwack, Myung-Joon; Kim, Sanghoon; Kim, In Gyoo; Oh, Jin Hyuk; Kim, Sun Ae; Park, Jaegyu; Kim, Sanggi

2015-06-10

When silicon photonic integrated circuits (PICs), defined for transmitting and receiving optical data, are successfully monolithic-integrated into major silicon electronic chips as chip-level optical I/Os (inputs/outputs), it will bring innovative changes in data computing and communications. Here, we propose new photonic integration scheme, a single-chip optical transceiver based on a monolithic-integrated vertical photonic I/O device set including light source on bulk-silicon. This scheme can solve the major issues which impede practical implementation of silicon-based chip-level optical interconnects. We demonstrated a prototype of a single-chip photonic transceiver with monolithic-integrated vertical-illumination type Ge-on-Si photodetectors and VCSELs-on-Si on the same bulk-silicon substrate operating up to 50 Gb/s and 20 Gb/s, respectively. The prototype realized 20 Gb/s low-power chip-level optical interconnects for λ ~ 850 nm between fabricated chips. This approach can have a significant impact on practical electronic-photonic integration in high performance computers (HPC), cpu-memory interface, hybrid memory cube, and LAN, SAN, data center and network applications.

Dosimetric distribution of the surroundings of different dental crowns and implants during LINAC photon irradiation

NASA Astrophysics Data System (ADS)

Chang, Kwo-Ping; Lin, Wei-Ting; Shiau, An-Cheng; Chie, Yu-Huang

2014-11-01

In radiotherapy of the head and neck, metal dentures or implants will increase the risk of complications such as mucositis and osteoradionecrosis. The aim of this study is to explore the back scatter effect of commercially available dental metal alloys on the mucosa and bone under 6 MV LINAC irradiation. The Monte Carlo method has been employed to calculate the dose distribution in the heterogeneous media of the designed oral phantom based on the oral cavity geometry. Backscatter dose increases up to a maximum of 53%, and is primarily dependent on the physical density and electron density of the metal crown alloy. Ceramic metal crowns have been quantified to increase backscatter dose up to 10% on mucosa. Ceramic serves as an inherent shield of mucosa. The backscatter dose will be greater for a small field size if the tumor is located at a deeper region. Titanium implants will increase the backscatter dose by 13% to bone but will not affect the mucosa. QC-20 (polystyrene resin) is recommended as a shield material (3 mm) to eliminate the backscatter dose on mucosa due to the high density metals.

EDITORIAL: Moore and more progress in electronics and photonics Moore and more progress in electronics and photonics

NASA Astrophysics Data System (ADS)

Meyyappan, Meyya

2009-10-01

parts. The field of optoelectronics and photonics has been benefiting from the ability to synthesize semiconducting nanowires and quantum dots. Advances in light-emitting diodes, photodetectors, nanolasers, solar cells, and field emission devices have been abundantly reported in the journal. The future of these devices depends on our ability to control the size, orientation and properties of one- and zero-dimensional materials. The forecast for electronics and photonics has vastly underestimated developments, with predictions such as 'future computers will weigh no less than 1.5 tons'. Over the past twenty years, the number of transistors on a chip has risen from just 1 million to 2 billion, and is still increasing. Now the biggest question is: what will take over from Moore's law in about a decade? This question has been driving the research agenda in electronics across the industrial and academic world. The first answer appears to be integrating other functional components with logic and memory such as miniature camera modules, GPS, accelerometers, biometric identification, health monitoring systems, etc. Such integration is actively being pursued by industry. In contrast, a lot of new research is still driven by material innovations, for example, carbon nanotube based electronics. Rudimentary devices and circuits using SWCNTs have been demonstrated to outperform silicon devices of comparable size. However, controlling the chirality and diameter of SWCNTs is still a problem, as is the manufacture of 300-400 mm wafers with over 5-10 billion transistors, and all of this assumes that continuing on the path of CMOS but using a different material is the right approach in the first place. In the meantime, silicon and germanium in the form of nanowires may make their way into electronics. Then there is molecular electronics where conducting organic molecules could now become the heart of electronic components, although the precision and controllability of electrical contact

An Empirical Method for deriving RBE values associated with Electrons, Photons and Radionuclides

DOE PAGES

Bellamy, Michael B; Puskin, J.; Eckerman, Keith F.; ...

2015-01-01

There is substantial evidence to justify using relative biological effectiveness (RBE) values greater than one for low-energy electrons and photons. But, in the field of radiation protection, radiation associated with low linear energy transfer (LET) has been assigned a radiation weighting factor w R of one. This value may be suitable for radiation protection but, for risk considerations, it is important to evaluate the potential elevated biological effectiveness of radiation to improve the quality of risk estimates. RBE values between 2 and 3 for tritium are implied by several experimental measurements. Additionally, elevated RBE values have been found for othermore » similar low-energy radiation sources. In this work, RBE values are derived for electrons based upon the fractional deposition of absorbed dose of energies less than a few keV. Using this empirical method, RBE values were also derived for monoenergetic photons and 1070 radionuclides from ICRP Publication 107 for which photons and electrons are the primary emissions.« less

TH-EF-BRB-10: Dosimetric Validation of a Trajectory Based Cranial SRS Treatment Technique On a Varian TrueBeam Linac

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

Wilson, B; Vancouver Cancer Centre, Vancouver, BC; Gete, E

2016-06-15

Purpose: This work investigates the dosimetric accuracy of a trajectory based delivery technique in which an optimized radiation beam is delivered along a Couch-Gantry trajectory that is formed by simultaneous rotation of the linac gantry and the treatment couch. Methods: Nine trajectory based cranial SRS treatment plans were created using in-house optimization software. The plans were calculated for delivery on the TrueBeam STx linac with 6MV photon beam. Dose optimization was performed along a user-defined trajectory using MLC modulation, dose rate modulation and jaw tracking. The pre-defined trajectory chosen for this study is formed by a couch rotation through itsmore » full range of 180 degrees while the gantry makes four partial arc sweeps which are 170 degrees each. For final dose calculation, the trajectory based plans were exported to the Varian Eclipse Treatment Planning System. The plans were calculated on a homogeneous cube phantom measuring 18.2×18.2×18.2 cm3 with the analytical anisotropic algorithm (AAA) using a 1mm3 calculation voxel. The plans were delivered on the TrueBeam linac via the developer’s mode. Point dose measurements were performed on 9 patients with the IBA CC01 mini-chamber with a sensitive volume of 0.01 cc. Gafchromic film measurements along the sagittal and coronal planes were performed on three of the 9 treatment plans. Point dose values were compared with ion chamber measurements. Gamma analysis comparing film measurement and AAA calculations was performed using FilmQA Pro. Results: The AAA calculations and measurements were in good agreement. The point dose difference between AAA and ion chamber measurements were within 2.2%. Gamma analysis test pass rates (2%, 2mm passing criteria) for the Gafchromic film measurements were >95%. Conclusion: We have successfully tested TrueBeam’s ability to deliver accurate trajectory based treatments involving simultaneous gantry and couch rotation with MLC and dose rate modulation

The Atomic, Molecular and Optical Science instrument at the Linac Coherent Light Source

DOE PAGES

Ferguson, Ken R.; Bucher, Maximilian; Bozek, John D.; ...

2015-05-01

The Atomic, Molecular and Optical Science (AMO) instrument at the Linac Coherent Light Source (LCLS) provides a tight soft X-ray focus into one of three experimental endstations. The flexible instrument design is optimized for studying a wide variety of phenomena requiring peak intensity. There is a suite of spectrometers and two photon area detectors available. An optional mirror-based split-and-delay unit can be used for X-ray pump–probe experiments. Recent scientific highlights illustrate the imaging, time-resolved spectroscopy and high-power density capabilities of the AMO instrument.

Commissioning of a Varian Clinac iX 6 MV photon beam using Monte Carlo simulation

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

Dirgayussa, I Gde Eka, E-mail: ekadirgayussa@gmail.com; Yani, Sitti; Haryanto, Freddy, E-mail: freddy@fi.itb.ac.id

2015-09-30

Monte Carlo modelling of a linear accelerator is the first and most important step in Monte Carlo dose calculations in radiotherapy. Monte Carlo is considered today to be the most accurate and detailed calculation method in different fields of medical physics. In this research, we developed a photon beam model for Varian Clinac iX 6 MV equipped with MilleniumMLC120 for dose calculation purposes using BEAMnrc/DOSXYZnrc Monte Carlo system based on the underlying EGSnrc particle transport code. Monte Carlo simulation for this commissioning head LINAC divided in two stages are design head Linac model using BEAMnrc, characterize this model using BEAMDPmore » and analyze the difference between simulation and measurement data using DOSXYZnrc. In the first step, to reduce simulation time, a virtual treatment head LINAC was built in two parts (patient-dependent component and patient-independent component). The incident electron energy varied 6.1 MeV, 6.2 MeV and 6.3 MeV, 6.4 MeV, and 6.6 MeV and the FWHM (full width at half maximum) of source is 1 mm. Phase-space file from the virtual model characterized using BEAMDP. The results of MC calculations using DOSXYZnrc in water phantom are percent depth doses (PDDs) and beam profiles at depths 10 cm were compared with measurements. This process has been completed if the dose difference of measured and calculated relative depth-dose data along the central-axis and dose profile at depths 10 cm is ≤ 5%. The effect of beam width on percentage depth doses and beam profiles was studied. Results of the virtual model were in close agreement with measurements in incident energy electron 6.4 MeV. Our results showed that photon beam width could be tuned using large field beam profile at the depth of maximum dose. The Monte Carlo model developed in this study accurately represents the Varian Clinac iX with millennium MLC 120 leaf and can be used for reliable patient dose calculations. In this commissioning process, the

Electronics and Algorithms for HOM Based Beam Diagnostics

NASA Astrophysics Data System (ADS)

Frisch, Josef; Baboi, Nicoleta; Eddy, Nathan; Nagaitsev, Sergei; Hensler, Olaf; McCormick, Douglas; May, Justin; Molloy, Stephen; Napoly, Olivier; Paparella, Rita; Petrosyan, Lyudvig; Ross, Marc; Simon, Claire; Smith, Tonee

2006-11-01

The signals from the Higher Order Mode (HOM) ports on superconducting cavities can be used as beam position monitors and to do survey structure alignment. A HOM-based diagnostic system has been installed to instrument both couplers on each of the 40 cryogenic accelerating structures in the DESY TTF2 Linac. The electronics uses a single stage down conversion from the 1.7 GHz HOM spectral line to a 20MHz IF which has been digitized. The electronics is based on low cost surface mount components suitable for large scale production. The analysis of the HOM data is based on Singular Value Decomposition. The response of the OM modes is calibrated using conventional BPMs.

TH-AB-BRA-10: The Physics of Interface Effects for Radiation Treatments in a MRI-Linac: A Monte Carlo Study

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

Ahmad, S; Sarfehnia, A; Kim, A

Purpose: To investigate and explain the interface effects for clinically relevant materials being irradiated in the presence of a 1.5 T transverse magnetic field. Methods: Interface effects were investigated using Geant4.10.1 both with (B-On) and without (B-Off) a magnetic field for an Elekta MRI-Linac. A slab of thickness 8 cm, representing inhomogeneity, was placed at a depth of 4 cm in a 20×20×20 cm water phantom. Backscattered electron fluence was calculated through a 20×20 cm plane aligned with the surface of the inhomogeneity. Inhomogeneities investigated were lung, bone, aluminum, titanium, stainless steel, and dental filling. A photon beam with fieldmore » size of 2×2 cm at the isocenter and SAD of 143.5 cm was generated from a point source with energy distribution sampled from a histogram representing the true Elekta MRI-Linac photon spectrum. Results: In the B-On case, if the heterogeneity is a low Z{sub eff} material, such as lung, the backscattered electron fluence is increased considerably, i.e. by 54 %, and the corresponding dose is expected to be higher near the interface compared to the B-Off case. On the contrary, if the heterogeneity is a high Z{sub eff} material then the backscattered electron fluence is reduced in the B-On electron fluence is reduced in the B-On case. This reduction leads to a lower dose deposition at the interface compared to the B-Off case. Conclusion: The reduction in dose at the interface, in the B-On case, is directly related to the reduction in backscattered electron fluence. The reduction in backscattered electron fluence occurs due to two different reasons. First, the electron energy spectrum hitting the interface is changed for the B-On case which changes the electron scattering probability. Second, some electrons that are looping under the influence of the magnetic field are captured by the higher density side of the interface and no longer contribute to the backscattered electron stream. Funding support for this

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.

Advanced photonic, electronic, and web engineering systems: WILGA Symposium, January 2013

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2013-10-01

The cycle of WILGA Symposia [wilga.ise.pw.edu.pl] on Photonics and Web Engineering, Advanced Electronic Systems, under the auspices of SPIE, IEEE, KEiT PAN and WEiTI PW was initiated in 1998 by a Research Team PERG/ELHEP ISE PW. The WILGA conferences take place two times a year and the participants are young scientists from this country and abroad. This paper debates chosen topical tracks and some papers presented during the 31 WILGA Multi-Conference, which took place on 8-10 February 2013 at the Faculty of WEiTI PW. The January conference was attended by around 100 persons. Here we discuss closer the subjects of biomedical photonics, electronics and informatics, as well as chosen aspects of applications of advanced photonic, electronic circuits and systems. The 32 nd WILGA Symposium took place on 27 May - 02 June 2013 in WUT WILGA resort near Warsaw. These two editions of WILGA Conferences - January and May have generated more than 250 articles, from which around 100 were chosen by the Symposium and Conference Committees to be published in this volume of Proc.SPIE. WILGA Symposium papers are traditionally submitted via the WILGA web page [wilga.ise.pw.edu.pl] to the SPIE Proceedings publishing system [spie.org]. Email for the correspondence is: photonics@ise.pw.edu.pl. All Wilga papers are published in journals Elektronika, IJET-PAN and in Proc.SPIE. Topical tracks of the symposium usually embrace, among others, new technologies for photonics, sensory and nonlinear optical fibers, object oriented design of hardware, photonic metrology, optoelectronics and photonics applications, photonics-electronics co-design, optoelectronic and electronic systems for astronomy and high energy physics experiments, JET and pi-of-the sky experiments development. The symposium In its two editions a year is a summary of the development of numerable Ph.D. theses carried out in this country and this geographical region in the area of advanced electronic and photonic systems. It is also

Linac based photofission inspection system employing novel detection concepts

NASA Astrophysics Data System (ADS)

Stevenson, John; Gozani, Tsahi; Elsalim, Mashal; Condron, Cathie; Brown, Craig

2011-10-01

Rapiscan Systems is developing a LINAC based cargo inspection system for detection of special nuclear material (SNM) in cargo containers. The system, called Photofission Based Alarm Resolution (PBAR) is being developed under a DHD/DNDO Advanced Technology Demonstration (ATD) program. The PBAR system is based on the Rapiscan Eagle P9000 X-ray system, which is a portal system with a commercial 9 MeV LINAC X-ray source. For the purposes of the DNDO ATD program, a conveyor system was installed in the portal to allow scanning and precise positioning of 20 ft ISO cargo containers. The system uses a two step inspection process. In the first step, the basic scan, the container is quickly and completely inspected using two independent radiography arrays: the conventional primary array with high spatial resolution and a lower resolution spectroscopic array employing the novel Z-Spec method. The primary array uses cadmium tungstate (CdWO 4) detectors with conventional current mode readouts using photodiodes. The Z-Spec array uses small plastic scintillators capable of performing very fast (up to 10 8 cps) gamma-ray spectroscopy. The two radiography arrays are used to locate high-Z objects in the image such as lead, tungsten, uranium, which could be potential shielding materials as well as SNM itself. In the current system, the Z-Spec works by measuring the energy spectrum of transmitted X-rays. For high-Z materials the higher end of the energy spectrum is more attenuated than for low-Z materials and thus has a lower mean energy and a narrower width than low- and medium-Z materials. The second step in the inspection process is the direct scan or alarm clearing scan. In this step, areas of the container image, which were identified as high Z, are re-inspected. This is done by precisely repositioning the container to the location of the high-Z object and performing a stationary irradiation of the area with X-ray beam. Since there are a large number of photons in the 9 MV

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.

Single-chip photonic transceiver based on bulk-silicon, as a chip-level photonic I/O platform for optical interconnects

PubMed Central

Kim, Gyungock; Park, Hyundai; Joo, Jiho; Jang, Ki-Seok; Kwack, Myung-Joon; Kim, Sanghoon; Gyoo Kim, In; Hyuk Oh, Jin; Ae Kim, Sun; Park, Jaegyu; Kim, Sanggi

2015-01-01

When silicon photonic integrated circuits (PICs), defined for transmitting and receiving optical data, are successfully monolithic-integrated into major silicon electronic chips as chip-level optical I/Os (inputs/outputs), it will bring innovative changes in data computing and communications. Here, we propose new photonic integration scheme, a single-chip optical transceiver based on a monolithic-integrated vertical photonic I/O device set including light source on bulk-silicon. This scheme can solve the major issues which impede practical implementation of silicon-based chip-level optical interconnects. We demonstrated a prototype of a single-chip photonic transceiver with monolithic-integrated vertical-illumination type Ge-on-Si photodetectors and VCSELs-on-Si on the same bulk-silicon substrate operating up to 50 Gb/s and 20 Gb/s, respectively. The prototype realized 20 Gb/s low-power chip-level optical interconnects for λ ~ 850 nm between fabricated chips. This approach can have a significant impact on practical electronic-photonic integration in high performance computers (HPC), cpu-memory interface, hybrid memory cube, and LAN, SAN, data center and network applications. PMID:26061463

Technical Report: Reference photon dosimetry data for Varian accelerators based on IROC-Houston site visit data.

PubMed

Kerns, James R; Followill, David S; Lowenstein, Jessica; Molineu, Andrea; Alvarez, Paola; Taylor, Paige A; Stingo, Francesco C; Kry, Stephen F

2016-05-01

Accurate data regarding linear accelerator (Linac) radiation characteristics are important for treatment planning system modeling as well as regular quality assurance of the machine. The Imaging and Radiation Oncology Core-Houston (IROC-H) has measured the dosimetric characteristics of numerous machines through their on-site dosimetry review protocols. Photon data are presented and can be used as a secondary check of acquired values, as a means to verify commissioning a new machine, or in preparation for an IROC-H site visit. Photon data from IROC-H on-site reviews from 2000 to 2014 were compiled and analyzed. Specifically, data from approximately 500 Varian machines were analyzed. Each dataset consisted of point measurements of several dosimetric parameters at various locations in a water phantom to assess the percentage depth dose, jaw output factors, multileaf collimator small field output factors, off-axis factors, and wedge factors. The data were analyzed by energy and parameter, with similarly performing machine models being assimilated into classes. Common statistical metrics are presented for each machine class. Measurement data were compared against other reference data where applicable. Distributions of the parameter data were shown to be robust and derive from a student's t distribution. Based on statistical and clinical criteria, all machine models were able to be classified into two or three classes for each energy, except for 6 MV for which there were eight classes. Quantitative analysis of the measurements for 6, 10, 15, and 18 MV photon beams is presented for each parameter; supplementary material has also been made available which contains further statistical information. IROC-H has collected numerous data on Varian Linacs and the results of photon measurements from the past 15 years are presented. The data can be used as a comparison check of a physicist's acquired values. Acquired values that are well outside the expected distribution should be

An empirical method for deriving RBE values associated with electrons, photons and radionuclides.

PubMed

Bellamy, M; Puskin, J; Hertel, N; Eckerman, K

2015-12-01

There is substantial evidence to justify using relative biological effectiveness (RBE) values of >1 for low-energy electrons and photons. But, in the field of radiation protection, radiation associated with low linear energy transfer has been assigned a radiation weighting factor wR of 1. This value may be suitable for radiation protection but, for risk considerations, it is important to evaluate the potential elevated biological effectiveness of radiation to improve the quality of risk estimates. RBE values between 2 and 3 for tritium are implied by several experimental measurements. Additionally, elevated RBE values have been found for other similar low-energy radiation sources. In this work, RBE values are derived for electrons based upon the fractional deposition of absorbed dose of energies less than a few kiloelectron volts. Using this empirical method, RBE values were also derived for monoenergetic photons and 1070 radionuclides from ICRP Publication 107 for which photons and electrons are the primary emissions. Published by Oxford University Press 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Photonic slab heterostructures based on opals

NASA Astrophysics Data System (ADS)

Palacios-Lidon, Elisa; Galisteo-Lopez, Juan F.; Juarez, Beatriz H.; Lopez, Cefe

2004-09-01

In this paper the fabrication of photonic slab heterostructures based on artificial opals is presented. The innovated method combines high-quality thin-films growing of opals and silica infiltration by Chemical Vapor Deposition through a multi-step process. By varying structure parameters, such as lattice constant, sample thickness or refractive index, different heterostructures have been obtained. The optical study of these systems, carried out by reflectance and transmittance measurements, shows that the prepared samples are of high quality further confirmed by Scanning Electron Microscopy micrographs. The proposed novel method for sample preparation allows a high control of the involved structure parameters, giving the possibility of tunning their photonic behavior. Special attention in the optical response of these materials has been addressed to the study of planar defects embedded in opals, due to their importance in different photonic fields and future technological applications. Reflectance and transmission measurements show a sharp resonance due to localized states associated with the presence of planar defects. A detailed study of the defect mode position and its dependance on defect thickness and on the surrounding photonic crystal is presented as well as evidence showing the scalability of the problem. Finally, it is also concluded that the proposed method is cheap and versatile allowing the preparation of opal-based complex structures.

A Monte Carlo simulation framework for electron beam dose calculations using Varian phase space files for TrueBeam Linacs.

PubMed

Rodrigues, Anna; Sawkey, Daren; Yin, Fang-Fang; Wu, Qiuwen

2015-05-01

To develop a framework for accurate electron Monte Carlo dose calculation. In this study, comprehensive validations of vendor provided electron beam phase space files for Varian TrueBeam Linacs against measurement data are presented. In this framework, the Monte Carlo generated phase space files were provided by the vendor and used as input to the downstream plan-specific simulations including jaws, electron applicators, and water phantom computed in the EGSnrc environment. The phase space files were generated based on open field commissioning data. A subset of electron energies of 6, 9, 12, 16, and 20 MeV and open and collimated field sizes 3 × 3, 4 × 4, 5 × 5, 6 × 6, 10 × 10, 15 × 15, 20 × 20, and 25 × 25 cm(2) were evaluated. Measurements acquired with a CC13 cylindrical ionization chamber and electron diode detector and simulations from this framework were compared for a water phantom geometry. The evaluation metrics include percent depth dose, orthogonal and diagonal profiles at depths R100, R50, Rp, and Rp+ for standard and extended source-to-surface distances (SSD), as well as cone and cut-out output factors. Agreement for the percent depth dose and orthogonal profiles between measurement and Monte Carlo was generally within 2% or 1 mm. The largest discrepancies were observed within depths of 5 mm from phantom surface. Differences in field size, penumbra, and flatness for the orthogonal profiles at depths R100, R50, and Rp were within 1 mm, 1 mm, and 2%, respectively. Orthogonal profiles at SSDs of 100 and 120 cm showed the same level of agreement. Cone and cut-out output factors agreed well with maximum differences within 2.5% for 6 MeV and 1% for all other energies. Cone output factors at extended SSDs of 105, 110, 115, and 120 cm exhibited similar levels of agreement. We have presented a Monte Carlo simulation framework for electron beam dose calculations for Varian TrueBeam Linacs. Electron beam energies of 6 to 20 MeV for open and collimated

Electron bunch structure in energy recovery linac with high-voltage dc photoelectron gun

NASA Astrophysics Data System (ADS)

Saveliev, Y. M.; Jackson, F.; Jones, J. K.; McKenzie, J. W.

2016-09-01

The internal structure of electron bunches generated in an injector line with a dc photoelectron gun is investigated. Experiments were conducted on the ALICE (accelerators and lasers in combined experiments) energy recovery linac at Daresbury Laboratory. At a relatively low dc gun voltage of 230 kV, the bunch normally consisted of two beamlets with different electron energies, as well as transverse and longitudinal characteristics. The beamlets are formed at the head and the tail of the bunch. At a higher gun voltage of 325 kV, the beam substructure is much less pronounced and could be observed only at nonoptimal injector settings. Experiments and computer simulations demonstrated that the bunch structure develops during the initial beam acceleration in the superconducting rf booster cavity and can be alleviated either by increasing the gun voltage to the highest possible level or by controlling the beam acceleration from the gun voltage in the first accelerating structure.

Spin-photon interface and spin-controlled photon switching in a nanobeam waveguide

NASA Astrophysics Data System (ADS)

Javadi, Alisa; Ding, Dapeng; Appel, Martin Hayhurst; Mahmoodian, Sahand; Löbl, Matthias Christian; Söllner, Immo; Schott, Rüdiger; Papon, Camille; Pregnolato, Tommaso; Stobbe, Søren; Midolo, Leonardo; Schröder, Tim; Wieck, Andreas Dirk; Ludwig, Arne; Warburton, Richard John; Lodahl, Peter

2018-05-01

The spin of an electron is a promising memory state and qubit. Connecting spin states that are spatially far apart will enable quantum nodes and quantum networks based on the electron spin. Towards this goal, an integrated spin-photon interface would be a major leap forward as it combines the memory capability of a single spin with the efficient transfer of information by photons. Here, we demonstrate such an efficient and optically programmable interface between the spin of an electron in a quantum dot and photons in a nanophotonic waveguide. The spin can be deterministically prepared in the ground state with a fidelity of up to 96%. Subsequently, the system is used to implement a single-spin photonic switch, in which the spin state of the electron directs the flow of photons through the waveguide. The spin-photon interface may enable on-chip photon-photon gates, single-photon transistors and the efficient generation of a photonic cluster state.

Recent Advances in Micro-/Nanostructured Metal-Organic Frameworks towards Photonic and Electronic Applications.

PubMed

Yang, Xiaogang; Lin, Xianqing; Zhao, Yong Sheng; Yan, Dongpeng

2018-05-02

Micro- and nanometer-sized metal-organic frameworks (MOFs) materials have attracted great attention due to their unique properties and various potential applications in photonics, electronics, high-density storage, chemo-, and biosensors. The study of these materials supplies insight into how the crystal structure, molecular components, and micro-/nanoscale effects can influence the performance of inorganic-organic hybrid materials. In this Minireview article, we introduce recent breakthroughs in the controlled synthesis of MOF micro-/nanomaterials with specific structures and compositions, the tunable photonic and electronic properties of which would provide a novel platform for multifunctional applications. Firstly, the design strategies for MOFs based on self-assembly and crystal engineering principles are introduced. Attention is then focused on the methods of fabrication of low-dimensional MOF micro-/nanostructures. Their new applications including two-photon excited fluorescence, multi-photon pumped lasing, optical waveguides, nonlinear optical (NLO), and field-effect transistors are also outlined. Finally, we briefly discuss perspectives on the further development of these hybrid crystalline micro-/nanomaterials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

Plan of production of MeV laser electron photons at SPring-8

NASA Astrophysics Data System (ADS)

Arimoto, Y.; Ohkuma, H.; Suzuki, S.; Tamura, K.; Kumagai, N.; Okajima, S.; Fujiwara, M.

2001-10-01

MeV photons at SPring-8 are produced by backward Compton scattering (BCS) of far infrared (FIR) laser photons from a 8 GeV electron beam. The MeV photons are a powerful probe to study nuclear physics, astro-nuclear physics, nuclear engineering, condensed matter physics, etc. owing to their attractive properties such as small emittance, high intensity, high polarization, etc. The 10 MeV photons which can be produced by the BCS process between the 8 GeV electron of SPring-8 storage ring and FIR laser photons with a wavelength of ~100 μm have a great advantage. Since energy loss of the electron due to the BCS process is smaller than energy acceptance of the storage ring (±160 MeV), the stored electron beam is not lost. A stable CO_2-pumped FIR laser with the wavelength of ~100 μm is practically using as a probe of plasma diagnostics at a nuclear fusion reactor. Furthermore, since the laser has many oscillations in wide wavelength region, the BCS photons in wide range can be obtained. We plan to produce the MeV laser electron photons by the BCS at SPring-8. For these purpose, we are now developing a high power CO_2-pumped FIR laser. Up to now ~1.5 watts CW laser action at a wavelength of 118.8 μm has been achieved. In this meeting, we will present a current status of the FIR laser system, a plan of construction of the test beam-line for the production of MeV photons at SPring-8, and future plan of this project.

Accuracy evaluation of distance inverse square law in determining virtual electron source location in Siemens Primus linac.

PubMed

Douk, Hamid Shafaei; Aghamiri, Mahmoud Reza; Ghorbani, Mahdi; Farhood, Bagher; Bakhshandeh, Mohsen; Hemmati, Hamid Reza

2018-01-01

The aim of this study is to evaluate the accuracy of the inverse square law (ISL) method for determining location of virtual electron source ( S Vir ) in Siemens Primus linac. So far, different experimental methods have presented for determining virtual and effective electron source location such as Full Width at Half Maximum (FWHM), Multiple Coulomb Scattering (MCS), and Multi Pinhole Camera (MPC) and Inverse Square Law (ISL) methods. Among these methods, Inverse Square Law is the most common used method. Firstly, Siemens Primus linac was simulated using MCNPX Monte Carlo code. Then, by using dose profiles obtained from the Monte Carlo simulations, the location of S Vir was calculated for 5, 7, 8, 10, 12 and 14 MeV electron energies and 10 cm × 10 cm, 15 cm × 15 cm, 20 cm × 20 cm and 25 cm × 25 cm field sizes. Additionally, the location of S Vir was obtained by the ISL method for the mentioned electron energies and field sizes. Finally, the values obtained by the ISL method were compared to the values resulted from Monte Carlo simulation. The findings indicate that the calculated S Vir values depend on beam energy and field size. For a specific energy, with increase of field size, the distance of S Vir increases for most cases. Furthermore, for a special applicator, with increase of electron energy, the distance of S Vir increases for most cases. The variation of S Vir values versus change of field size in a certain energy is more than the variation of S Vir values versus change of electron energy in a certain field size. According to the results, it is concluded that the ISL method can be considered as a good method for calculation of S Vir location in higher electron energies (14 MeV).

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.

Inexpensive electronics and software for photon statistics and correlation spectroscopy.

PubMed

Gamari, Benjamin D; Zhang, Dianwen; Buckman, Richard E; Milas, Peker; Denker, John S; Chen, Hui; Li, Hongmin; Goldner, Lori S

2014-07-01

Single-molecule-sensitive microscopy and spectroscopy are transforming biophysics and materials science laboratories. Techniques such as fluorescence correlation spectroscopy (FCS) and single-molecule sensitive fluorescence resonance energy transfer (FRET) are now commonly available in research laboratories but are as yet infrequently available in teaching laboratories. We describe inexpensive electronics and open-source software that bridges this gap, making state-of-the-art research capabilities accessible to undergraduates interested in biophysics. We include a discussion of the intensity correlation function relevant to FCS and how it can be determined from photon arrival times. We demonstrate the system with a measurement of the hydrodynamic radius of a protein using FCS that is suitable for the undergraduate teaching laboratory. The FPGA-based electronics, which are easy to construct, are suitable for more advanced measurements as well, and several applications are described. As implemented, the system has 8 ns timing resolution, can control up to four laser sources, and can collect information from as many as four photon-counting detectors.

A scalable multi-photon coincidence detector based on superconducting nanowires.

PubMed

Zhu, Di; Zhao, Qing-Yuan; Choi, Hyeongrak; Lu, Tsung-Ju; Dane, Andrew E; Englund, Dirk; Berggren, Karl K

2018-06-04

Coincidence detection of single photons is crucial in numerous quantum technologies and usually requires multiple time-resolved single-photon detectors. However, the electronic readout becomes a major challenge when the measurement basis scales to large numbers of spatial modes. Here, we address this problem by introducing a two-terminal coincidence detector that enables scalable readout of an array of detector segments based on superconducting nanowire microstrip transmission line. Exploiting timing logic, we demonstrate a sixteen-element detector that resolves all 136 possible single-photon and two-photon coincidence events. We further explore the pulse shapes of the detector output and resolve up to four-photon events in a four-element device, giving the detector photon-number-resolving capability. This new detector architecture and operating scheme will be particularly useful for multi-photon coincidence detection in large-scale photonic integrated circuits.

Discovery of a diamond-based photonic crystal structure in beetle scales.

PubMed

Galusha, Jeremy W; Richey, Lauren R; Gardner, John S; Cha, Jennifer N; Bartl, Michael H

2008-05-01

We investigated the photonic crystal structure inside iridescent scales of the weevil Lamprocyphus augustus. By combining a high-resolution structure analysis technique based on sequential focused ion beam milling and scanning electron microscopy imaging with theoretical modeling and photonic band-structure calculations, we discovered a natural three-dimensional photonic structure with a diamond-based crystal lattice operating at visible wavelengths. Moreover, we found that within individual scales, the diamond-based structure is assembled in the form of differently oriented single-crystalline micrometer-sized pixels with only selected lattice planes facing the scales' top surface. A comparison of results obtained from optical microreflectance measurements with photonic band-structure calculations reveals that it is this sophisticated microassembly of the diamond-based crystal lattice that lends Lamprocyphus augustus its macroscopically near angle-independent green coloration.

Dispersive approach to two-photon exchange in elastic electron-proton scattering

DOE PAGES

Blunden, P. G.; Melnitchouk, W.

2017-06-14

We examine the two-photon exchange corrections to elastic electron-nucleon scattering within a dispersive approach, including contributions from both nucleon and Δ intermediate states. The dispersive analysis avoids off-shell uncertainties inherent in traditional approaches based on direct evaluation of loop diagrams, and guarantees the correct unitary behavior in the high energy limit. Using empirical information on the electromagnetic nucleon elastic and NΔ transition form factors, we compute the two-photon exchange corrections both algebraically and numerically. Finally, results are compared with recent measurements of e + p to e - p cross section ratios from the CLAS, VEPP-3 and OLYMPUS experiments.

Advances in graphene-based optoelectronics, plasmonics and photonics

NASA Astrophysics Data System (ADS)

Nguyen, Bich Ha; Hieu Nguyen, Van

2016-03-01

Since the early works on graphene it has been remarked that graphene is a marvelous electronic material. Soon after its discovery, graphene was efficiently utilized in the fabrication of optoelectronic, plasmonic and photonic devices, including graphene-based Schottky junction solar cells. The present work is a review of the progress in the experimental research on graphene-based optoelectronics, plasmonics and photonics, with the emphasis on recent advances. The main graphene-based optoelectronic devices presented in this review are photodetectors and modulators. In the area of graphene-based plasmonics, a review of the plasmonic nanostructures enhancing or tuning graphene-light interaction, as well as of graphene plasmons is presented. In the area of graphene-based photonics, we report progress on fabrication of different types of graphene quantum dots as well as functionalized graphene and graphene oxide, the research on the photoluminescence and fluorescence of graphene nanostructures as well as on the energy exchange between graphene and semiconductor quantum dots. In particular, the promising achievements of research on graphene-based Schottky junction solar cells is presented.

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.

A novel supine isocentric approach for craniospinal irradiation and its clinical outcome.

PubMed

Cheng, Yi-Kan; Zeng, Lei; Ye, Shu-Biao; Zheng, Jian; Zhang, Lin; Sun, Peng; Jiang, Xiao-Bo; Sun, Wen-Zhao; Xu, Tao; Chen, Lei

2016-09-01

To report a novel approach for craniospinal irradiation (CSI) using a supine isocentric technique. Patients were treated in the supine position using CT simulation. Half-beam-blocked lateral cranial fields and superior spinal fields have the same isocentre, and their beam divergences match. Tangential irradiation provides a non-divergent junction for the other two full-beam spinal fields. Shielding for cranial fields was generated, and dose distribution was calculated using a three-dimensional planning system. When sacral spinal fields were required, two lateral opposite fields were designed to protect the urogenital organs. All treatment portals were filmed once per week. At a median follow-up of 49.8 months, 5 relapses and no cases of radiation myelitis developed in 26 consecutive patients. In the junctions of the brain-spine or spine-spine field, no failure occurred. Three failures occurred in the primary site alone, two in the spinal axis alone. The results of our study have shown that our novel approach for CSI was not associated with increased failures at the field junction and deaths. In addition, no radiation myelitis, pneumonia, severe damage to the heart and gastrointestinal tract, and second cancers occurred in our study. This new approach is an optimal alternative in cancer centre without tomotherapy because of its convenience for immobilization, repeatability, optimal dose distribution and satisfactory clinical outcome.

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

An Electron/Photon/Relaxation Data Library for MCNP6

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

Hughes, III, H. Grady

The capabilities of the MCNP6 Monte Carlo code in simulation of electron transport, photon transport, and atomic relaxation have recently been significantly expanded. The enhancements include not only the extension of existing data and methods to lower energies, but also the introduction of new categories of data and methods. Support of these new capabilities has required major additions to and redesign of the associated data tables. In this paper we present the first complete documentation of the contents and format of the new electron-photon-relaxation data library now available with the initial production release of MCNP6.

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.

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

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

NASA Astrophysics Data System (ADS)

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

2014-01-01

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

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).

Single Photon Counting Performance and Noise Analysis of CMOS SPAD-Based Image Sensors.

PubMed

Dutton, Neale A W; Gyongy, Istvan; Parmesan, Luca; Henderson, Robert K

2016-07-20

SPAD-based solid state CMOS image sensors utilising analogue integrators have attained deep sub-electron read noise (DSERN) permitting single photon counting (SPC) imaging. A new method is proposed to determine the read noise in DSERN image sensors by evaluating the peak separation and width (PSW) of single photon peaks in a photon counting histogram (PCH). The technique is used to identify and analyse cumulative noise in analogue integrating SPC SPAD-based pixels. The DSERN of our SPAD image sensor is exploited to confirm recent multi-photon threshold quanta image sensor (QIS) theory. Finally, various single and multiple photon spatio-temporal oversampling techniques are reviewed.

Single Photon Counting Performance and Noise Analysis of CMOS SPAD-Based Image Sensors

PubMed Central

Dutton, Neale A. W.; Gyongy, Istvan; Parmesan, Luca; Henderson, Robert K.

2016-01-01

SPAD-based solid state CMOS image sensors utilising analogue integrators have attained deep sub-electron read noise (DSERN) permitting single photon counting (SPC) imaging. A new method is proposed to determine the read noise in DSERN image sensors by evaluating the peak separation and width (PSW) of single photon peaks in a photon counting histogram (PCH). The technique is used to identify and analyse cumulative noise in analogue integrating SPC SPAD-based pixels. The DSERN of our SPAD image sensor is exploited to confirm recent multi-photon threshold quanta image sensor (QIS) theory. Finally, various single and multiple photon spatio-temporal oversampling techniques are reviewed. PMID:27447643

Use of electronic portal imaging devices for electron treatment verification.

PubMed

Kairn, T; Aland, T; Crowe, S B; Trapp, J V

2016-03-01

This study aims to help broaden the use of electronic portal imaging devices (EPIDs) for pre-treatment patient positioning verification, from photon-beam radiotherapy to photon- and electron-beam radiotherapy, by proposing and testing a method for acquiring clinically-useful EPID images of patient anatomy using electron beams, with a view to enabling and encouraging further research in this area. EPID images used in this study were acquired using all available beams from a linac configured to deliver electron beams with nominal energies of 6, 9, 12, 16 and 20 MeV, as well as photon beams with nominal energies of 6 and 10 MV. A widely-available heterogeneous, approximately-humanoid, thorax phantom was used, to provide an indication of the contrast and noise produced when imaging different types of tissue with comparatively realistic thicknesses. The acquired images were automatically calibrated, corrected for the effects of variations in the sensitivity of individual photodiodes, using a flood field image. For electron beam imaging, flood field EPID calibration images were acquired with and without the placement of blocks of water-equivalent plastic (with thicknesses approximately equal to the practical range of electrons in the plastic) placed upstream of the EPID, to filter out the primary electron beam, leaving only the bremsstrahlung photon signal. While the electron beam images acquired using a standard (unfiltered) flood field calibration were observed to be noisy and difficult to interpret, the electron beam images acquired using the filtered flood field calibration showed tissues and bony anatomy with levels of contrast and noise that were similar to the contrast and noise levels seen in the clinically acceptable photon beam EPID images. The best electron beam imaging results (highest contrast, signal-to-noise and contrast-to-noise ratios) were achieved when the images were acquired using the higher energy electron beams (16 and 20 MeV) when the EPID was

Electroluminescence Caused by the Transport of Interacting Electrons through Parallel Quantum Dots in a Photon Cavity

NASA Astrophysics Data System (ADS)

Gudmundsson, Vidar; Abdulla, Nzar Rauf; Sitek, Anna; Goan, Hsi-Sheng; Tang, Chi-Shung; Manolescu, Andrei

2018-02-01

We show that a Rabi-splitting of the states of strongly interacting electrons in parallel quantum dots embedded in a short quantum wire placed in a photon cavity can be produced by either the para- or the dia-magnetic electron-photon interactions when the geometry of the system is properly accounted for and the photon field is tuned close to a resonance with the electron system. We use these two resonances to explore the electroluminescence caused by the transport of electrons through the one- and two-electron ground states of the system and their corresponding conventional and vacuum electroluminescense as the central system is opened up by coupling it to external leads acting as electron reservoirs. Our analysis indicates that high-order electron-photon processes are necessary to adequately construct the cavity-photon dressed electron states needed to describe both types of electroluminescence.

Electromagnetic cascade in high-energy electron, positron, and photon interactions with intense laser pulses

NASA Astrophysics Data System (ADS)

Bulanov, S. S.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

2013-06-01

The interaction of high-energy electrons, positrons, and photons with intense laser pulses is studied in head-on collision geometry. It is shown that electrons and/or positrons undergo a cascade-type process involving multiple emissions of photons. These photons can consequently convert into electron-positron pairs. As a result charged particles quickly lose their energy developing an exponentially decaying energy distribution, which suppresses the emission of high-energy photons, thus reducing the number of electron-positron pairs being generated. Therefore, this type of interaction suppresses the development of the electromagnetic avalanche-type discharge, i.e., the exponential growth of the number of electrons, positrons, and photons does not occur in the course of interaction. The suppression will occur when three-dimensional effects can be neglected in the transverse particle orbits, i.e., for sufficiently broad laser pulses with intensities that are not too extreme. The final distributions of electrons, positrons, and photons are calculated for the case of a high-energy e-beam interacting with a counterstreaming, short intense laser pulse. The energy loss of the e-beam, which requires a self-consistent quantum description, plays an important role in this process, as well as provides a clear experimental observable for the transition from the classical to quantum regime of interaction.

Thermoluminescence Response of Ge-Doped Cylindrical-, Flat- and Photonic Crystal Silica-Fibres to Electron and Photon Radiation

PubMed Central

Entezam, A.; Khandaker, M. U.; Amin, Y. M.; Ung, N. M.; Bradley, D. A.; Maah, J.; Safari, M. J.; Moradi, F.

2016-01-01

Study has been made of the thermoluminescence (TL) response of silica-based Ge-doped cylindrical, flat and photonic crystal fibres (referred to herein as PCF-collapsed) to electron (6, 12 and 20 MeV) and photon (6, 10 MV) irradiation and 1.25 MeV γ-rays, for doses from 0.1 Gy to 100 Gy. The electron and photon irradiations were delivered through use of a Varian Model 2100C linear accelerator located at the University of Malaya Medical Centre and γ-rays delivered from a 60Co irradiator located at the Secondary Standard Dosimetry Laboratory (SSDL), Malaysian Nuclear Agency. Tailor-made to be of various dimensions and dopant concentrations (6–10% Ge), the fibres were observed to provide TL yield linear with radiation dose, reproducibility being within 1–5%, with insensitivity to energy and angular variation. The sensitivity dependency of both detectors with respect to field size follows the dependency of the output factors. For flat fibres exposed to 6 MV X-rays, the 6% Ge-doped fibre provided the greatest TL yield while PCF-collapsed showed a response 2.4 times greater than that of the 6% Ge-doped flat fibres. The response of cylindrical fibres increased with core size. The fibres offer uniform response, high spatial resolution and sensitivity, providing the basis of promising TL systems for radiotherapy applications. PMID:27149115

Relativistic spin-orbit interactions of photons and electrons

NASA Astrophysics Data System (ADS)

Smirnova, D. A.; Travin, V. M.; Bliokh, K. Y.; Nori, F.

2018-04-01

Laboratory optics, typically dealing with monochromatic light beams in a single reference frame, exhibits numerous spin-orbit interaction phenomena due to the coupling between the spin and orbital degrees of freedom of light. Similar phenomena appear for electrons and other spinning particles. Here we examine transformations of paraxial photon and relativistic-electron states carrying the spin and orbital angular momenta (AM) under the Lorentz boosts between different reference frames. We show that transverse boosts inevitably produce a rather nontrivial conversion from spin to orbital AM. The converted part is then separated between the intrinsic (vortex) and extrinsic (transverse shift or Hall effect) contributions. Although the spin, intrinsic-orbital, and extrinsic-orbital parts all point in different directions, such complex behavior is necessary for the proper Lorentz transformation of the total AM of the particle. Relativistic spin-orbit interactions can be important in scattering processes involving photons, electrons, and other relativistic spinning particles, as well as when studying light emitted by fast-moving bodies.

Internal photon and electron dosimetry of the newborn patient—a hybrid computational phantom study

NASA Astrophysics Data System (ADS)

Wayson, Michael; Lee, Choonsik; Sgouros, George; Treves, S. Ted; Frey, Eric; Bolch, Wesley E.

2012-03-01

Estimates of radiation absorbed dose to organs of the nuclear medicine patient are a requirement for administered activity optimization and for stochastic risk assessment. Pediatric patients, and in particular the newborn child, represent that portion of the patient population where such optimization studies are most crucial owing to the enhanced tissue radiosensitivities and longer life expectancies of this patient subpopulation. In cases where whole-body CT imaging is not available, phantom-based calculations of radionuclide S values—absorbed dose to a target tissue per nuclear transformation in a source tissue—are required for dose and risk evaluation. In this study, a comprehensive model of electron and photon dosimetry of the reference newborn child is presented based on a high-resolution hybrid-voxel phantom from the University of Florida (UF) patient model series. Values of photon specific absorbed fraction (SAF) were assembled for both the reference male and female newborn using the radiation transport code MCNPX v2.6. Values of electron SAF were assembled in a unique and time-efficient manner whereby the collisional and radiative components of organ dose--for both self- and cross-dose terms—were computed separately. Dose to the newborn skeletal tissues were assessed via fluence-to-dose response functions reported for the first time in this study. Values of photon and electron SAFs were used to assemble a complete set of S values for some 16 radionuclides commonly associated with molecular imaging of the newborn. These values were then compared to those available in the OLINDA/EXM software. S value ratios for organ self-dose ranged from 0.46 to 1.42, while similar ratios for organ cross-dose varied from a low of 0.04 to a high of 3.49. These large discrepancies are due in large part to the simplistic organ modeling in the stylized newborn model used in the OLINDA/EXM software. A comprehensive model of internal dosimetry is presented in this study for

Inexpensive electronics and software for photon statistics and correlation spectroscopy

PubMed Central

Gamari, Benjamin D.; Zhang, Dianwen; Buckman, Richard E.; Milas, Peker; Denker, John S.; Chen, Hui; Li, Hongmin; Goldner, Lori S.

2016-01-01

Single-molecule-sensitive microscopy and spectroscopy are transforming biophysics and materials science laboratories. Techniques such as fluorescence correlation spectroscopy (FCS) and single-molecule sensitive fluorescence resonance energy transfer (FRET) are now commonly available in research laboratories but are as yet infrequently available in teaching laboratories. We describe inexpensive electronics and open-source software that bridges this gap, making state-of-the-art research capabilities accessible to undergraduates interested in biophysics. We include a discussion of the intensity correlation function relevant to FCS and how it can be determined from photon arrival times. We demonstrate the system with a measurement of the hydrodynamic radius of a protein using FCS that is suitable for the undergraduate teaching laboratory. The FPGA-based electronics, which are easy to construct, are suitable for more advanced measurements as well, and several applications are described. As implemented, the system has 8 ns timing resolution, can control up to four laser sources, and can collect information from as many as four photon-counting detectors. PMID:26924846

A Monte Carlo simulation framework for electron beam dose calculations using Varian phase space files for TrueBeam Linacs

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

Rodrigues, Anna; Yin, Fang-Fang; Wu, Qiuwen, E-mail: Qiuwen.Wu@Duke.edu

2015-05-15

Purpose: To develop a framework for accurate electron Monte Carlo dose calculation. In this study, comprehensive validations of vendor provided electron beam phase space files for Varian TrueBeam Linacs against measurement data are presented. Methods: In this framework, the Monte Carlo generated phase space files were provided by the vendor and used as input to the downstream plan-specific simulations including jaws, electron applicators, and water phantom computed in the EGSnrc environment. The phase space files were generated based on open field commissioning data. A subset of electron energies of 6, 9, 12, 16, and 20 MeV and open and collimatedmore » field sizes 3 × 3, 4 × 4, 5 × 5, 6 × 6, 10 × 10, 15 × 15, 20 × 20, and 25 × 25 cm{sup 2} were evaluated. Measurements acquired with a CC13 cylindrical ionization chamber and electron diode detector and simulations from this framework were compared for a water phantom geometry. The evaluation metrics include percent depth dose, orthogonal and diagonal profiles at depths R{sub 100}, R{sub 50}, R{sub p}, and R{sub p+} for standard and extended source-to-surface distances (SSD), as well as cone and cut-out output factors. Results: Agreement for the percent depth dose and orthogonal profiles between measurement and Monte Carlo was generally within 2% or 1 mm. The largest discrepancies were observed within depths of 5 mm from phantom surface. Differences in field size, penumbra, and flatness for the orthogonal profiles at depths R{sub 100}, R{sub 50}, and R{sub p} were within 1 mm, 1 mm, and 2%, respectively. Orthogonal profiles at SSDs of 100 and 120 cm showed the same level of agreement. Cone and cut-out output factors agreed well with maximum differences within 2.5% for 6 MeV and 1% for all other energies. Cone output factors at extended SSDs of 105, 110, 115, and 120 cm exhibited similar levels of agreement. Conclusions: We have presented a Monte Carlo simulation framework for electron beam dose calculations

Polarization of photons scattered by electrons in any spectral distribution

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

Chang, Zhe; Lin, Hai-Nan; Jiang, Yunguo, E-mail: jiangyg@ihep.ac.cn

On the basis of the quantum electrodynamics, we present a generic formalism of the polarization for beamed monochromatic photons scattered by electrons in any spectral distribution. The formulae reduce to the components of the Fano matrix when electrons are at rest. We mainly investigate the polarization in three scenarios, i.e., electrons at rest, isotropic electrons with a power-law spectrum, and thermal electrons. If the incident beam is polarized, the polarization is reduced significantly by isotropic electrons at large viewing angles; the degree of polarization caused by thermal electrons is about half of that caused by power-law electrons. If the incidentmore » bean is unpolarized, soft γ-rays can lead to about 15% polarization at viewing angles around π/4. For isotropic electrons, one remarkable feature is that the polarization as a function of the incident photon energy always peaks roughly at 1 MeV; this is valid for both the thermal and power-law cases. This feature can be used to distinguish the model of the inverse Compton scattering from that of the synchrotron radiation.« less

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.

An ultrafast electron microscope gun driven by two-photon photoemission from a nanotip cathode

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

Bormann, Reiner; Strauch, Stefanie; Schäfer, Sascha, E-mail: schaefer@ph4.physik.uni-goettingen.de

We experimentally and numerically investigate the performance of an advanced ultrafast electron source, based on two-photon photoemission from a tungsten needle cathode incorporated in an electron microscope gun geometry. Emission properties are characterized as a function of the electrostatic gun settings, and operating conditions leading to laser-triggered electron beams of very low emittance (below 20 nm mrad) are identified. The results highlight the excellent suitability of optically driven nano-cathodes for the further development of ultrafast transmission electron microscopy.

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

An analytical method for computing voxel S values for electrons and photons.

PubMed

Amato, Ernesto; Minutoli, Fabio; Pacilio, Massimiliano; Campenni, Alfredo; Baldari, Sergio

2012-11-01

The use of voxel S values (VSVs) is perhaps the most common approach to radiation dosimetry for nonuniform distributions of activity within organs or tumors. However, VSVs are currently available only for a limited number of voxel sizes and radionuclides. The objective of this study was to develop a general method to evaluate them for any spectrum of electrons and photons in any cubic voxel dimension of practical interest for clinical dosimetry in targeted radionuclide therapy. The authors developed a Monte Carlo simulation in Geant4 in order to evaluate the energy deposited per disintegration (E(dep)) in a voxelized region of soft tissue from monoenergetic electrons (10-2000 keV) or photons (10-1000 keV) homogeneously distributed in the central voxel, considering voxel dimensions ranging from 3 mm to 10 mm. E(dep) was represented as a function of a dimensionless quantity termed the "normalized radius," R(n) = R∕l, where l is the voxel size and R is the distance from the origin. The authors introduced two parametric functions in order to fit the electron and photon results, and they interpolated the parameters to derive VSVs for any energy and voxel side within the ranges mentioned above. In order to validate the results, the authors determined VSV for two radionuclides ((131)I and (89)Sr) and two voxel dimensions and they compared them with reference data. A validation study in a simple sphere model, accounting for tissue inhomogeneities, is presented. The E(dep)(R(n)) for both monoenergetic electrons and photons exhibit a smooth variation with energy and voxel size, implying that VSVs for monoenergetic electrons or photons may be derived by interpolation over the range of energies and dimensions considered. By integration, S values for continuous emission spectra from β(-) decay may be derived as well. The approach allows the determination of VSVs for monoenergetic (Auger or conversion) electrons and (x-ray or gamma-ray) photons by means of two functions whose

Cavity-photon contribution to the effective interaction of electrons in parallel quantum dots

NASA Astrophysics Data System (ADS)

Gudmundsson, Vidar; Sitek, Anna; Abdullah, Nzar Rauf; Tang, Chi-Shung; Manolescu, Andrei

2016-05-01

A single cavity photon mode is expected to modify the Coulomb interaction of an electron system in the cavity. Here we investigate this phenomena in a parallel double quantum dot system. We explore properties of the closed system and the system after it has been opened up for electron transport. We show how results for both cases support the idea that the effective electron-electron interaction becomes more repulsive in the presence of a cavity photon field. This can be understood in terms of the cavity photons dressing the polarization terms in the effective mutual electron interaction leading to nontrivial delocalization or polarization of the charge in the double parallel dot potential. In addition, we find that the effective repulsion of the electrons can be reduced by quadrupolar collective oscillations excited by an external classical dipole electric field.

Passive and electro-optic polymer photonics and InP electronics integration

NASA Astrophysics Data System (ADS)

Zhang, Z.; Katopodis, V.; Groumas, P.; Konczykowska, A.; Dupuy, J.-.; Beretta, A.; Dede, A.; Miller, E.; Choi, J. H.; Harati, P.; Jorge, F.; Nodjiadjim, V.; Dinu, R.; Cangini, G.; Vannucci, A.; Felipe, D.; Maese-Novo, A.; Keil, N.; Bach, H.-.; Schell, Martin; Avramopoulos, H.; Kouloumentas, Ch.

2015-05-01

Hybrid photonic integration allows individual components to be developed at their best-suited material platforms without sacrificing the overall performance. In the past few years a polymer-enabled hybrid integration platform has been established, comprising 1) EO polymers for constructing low-complexity and low-cost Mach-Zehnder modulators (MZMs) with extremely high modulation bandwidth; 2) InP components for light sources, detectors, and high-speed electronics including MUX drivers and DEMUX circuits; 3) Ceramic (AIN) RF board that links the electronic signals within the package. On this platform, advanced optoelectronic modules have been demonstrated, including serial 100 Gb/s [1] and 2x100 Gb/s [2] optical transmitters, but also 400 Gb/s optoelectronic interfaces for intra-data center networks [3]. To expand the device functionalities to an unprecedented level and at the same time improve the integration compatibility with diversified active / passive photonic components, we have added a passive polymer-based photonic board (polyboard) as the 4th material system. This passive polyboard allows for low-cost fabrication of single-mode waveguide networks, enables fast and convenient integration of various thin-film elements (TFEs) to control the light polarization, and provides efficient thermo-optic elements (TOEs) for wavelength tuning, light amplitude regulation and light-path switching.

The ERL-based Design of Electron-Hadron Collider eRHIC

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

Ptitsyn, Vadim

2016-06-01

Recent developments of the ERL-based design of future high-luminosity electron-hadron collider eRHIC focused on balancing technological risks present in the design versus the design cost. As a result a lower risk design has been adopted at moderate cost increase. The modifications include a change of the main linac RF frequency, reduced number of SRF cavity types and modified electron spin transport using a spin rotator. A luminosity-staged approach is being explored with a Nominal design (more » $$L \\sim 10^{33} {\\rm cm}^2 {\\rm s}^{-1}$$) that employs reduced electron current and could possibly be based on classical electron cooling, and then with the Ultimate design ($$L \\gt 10^{34} {\\rm cm}^{-2} {\\rm s}^{-1}$$) that uses higher electron current and an innovative cooling technique (CeC). The paper describes the recent design modifications, and presents the full status of the eRHIC ERL-based design.« less

LCLS in—photon out: fluorescence measurement of neon using soft x-rays

DOE PAGES

Obaid, Razib; Buth, Christian; Dakovski, Georgi L.; ...

2018-01-09

Here, we measured the fluorescence photon yield of neon upon soft x-ray ionization (~1200 eV) from the x-ray free-electron laser at Linac Coherent Light Source, and demonstrated the usage of a grazing incidence spectrometer with a variable line spacing grating to perform x-ray fluorescence spectroscopy on a gas phase system. Our measurements also allowed us to estimate the focal size of the beam from the theoretical description developed, in terms of the rate equation approximation accounting for photoionization shake off of neutral neon and double auger decay of single core holes.

LCLS in—photon out: fluorescence measurement of neon using soft x-rays

NASA Astrophysics Data System (ADS)

Obaid, Razib; Buth, Christian; Dakovski, Georgi L.; Beerwerth, Randolf; Holmes, Michael; Aldrich, Jeff; Lin, Ming-Fu; Minitti, Michael; Osipov, Timur; Schlotter, William; Cederbaum, Lorenz S.; Fritzsche, Stephan; Berrah, Nora

2018-02-01

We measured the fluorescence photon yield of neon upon soft x-ray ionization (∼1200 eV) from the x-ray free-electron laser at Linac Coherent Light Source, and demonstrated the usage of a grazing incidence spectrometer with a variable line spacing grating to perform x-ray fluorescence spectroscopy on a gas phase system. Our measurements also allowed us to estimate the focal size of the beam from the theoretical description developed, in terms of the rate equation approximation accounting for photoionization shake off of neutral neon and double auger decay of single core holes.

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.

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

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

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

Computational imaging of defects in commercial substrates for electronic and photonic devices

NASA Astrophysics Data System (ADS)

Fukuzawa, Masayuki; Kashiwagi, Ryo; Yamada, Masayoshi

2012-03-01

Computational defect imaging has been performed in commercial substrates for electronic and photonic devices by combining the transmission profile acquired with an imaging type of linear polariscope and the computational algorithm to extract a small amount of birefringence. The computational images of phase retardation δ exhibited spatial inhomogeneity of defect-induced birefringence in GaP, LiNbO3, and SiC substrates, which were not detected by conventional 'visual inspection' based on simple optical refraction or transmission because of poor sensitivity. The typical imaging time was less than 30 seconds for 3-inch diameter substrate with the spatial resolution of 200 μm, while that by scanning polariscope was 2 hours to get the same spatial resolution. Since our proposed technique have been achieved high sensitivity, short imaging time, and wide coverage of substrate materials, which are practical advantages over the laboratory-scale apparatus such as X-ray topography and electron microscope, it is useful for nondestructive inspection of various commercial substrates in production of electronic and photonic devices.

Static beam-based alignment for the Ring-To-Main-Linac of the Compact Linear Collider

NASA Astrophysics Data System (ADS)

Han, Y.; Latina, A.; Ma, L.; Schulte, D.

2017-06-01

The Compact Linear Collider (CLIC) is a future multi-TeV collider for the post-Large Hadron Collider era. It features high-gradient acceleration and ultra-low emittance to achieve its ambitious goals of high collision energy and peak luminosity. Beam-based alignment (BBA) techniques are mandatory for CLIC to preserve the ultra-low emittances from the damping rings to the interaction point. In this paper, a detailed study of BBA techniques has been carried out for the entire 27 km long ``Ring-To-Main-Linac'' (RTML) section of the CLIC, to correct realistic static errors such as element position offsets, angle, magnetic strength and dynamic magnetic centre shifts. The correction strategy is proved to be very effective and leads to a relaxation of the pre-alignment tolerances for the component installation in the tunnel. This is the first time such a large scale and complex lattice has been corrected to match the design budgets. The techniques proposed could be applied to similarly sized facilities, such as the International Linear Collider, where a similar RTML section is used, or free-electron lasers, which, being equipped with linacs and bunch compressors, present challenges similar to those of the CLIC RTML. Moreover, a new technique is investigated for the emittance tuning procedure: the direct measurement of the interactions between the beams and a set of a few consecutive laser wires. The speed of this technique can be faster comparing to the traditional techniques based on emittance reconstructed from beam size measurements at several positions.

Low-power chip-level optical interconnects based on bulk-silicon single-chip photonic transceivers

NASA Astrophysics Data System (ADS)

Kim, Gyungock; Park, Hyundai; Joo, Jiho; Jang, Ki-Seok; Kwack, Myung-Joon; Kim, Sanghoon; Kim, In Gyoo; Kim, Sun Ae; Oh, Jin Hyuk; Park, Jaegyu; Kim, Sanggi

2016-03-01

We present new scheme for chip-level photonic I/Os, based on monolithically integrated vertical photonic devices on bulk silicon, which increases the integration level of PICs to a complete photonic transceiver (TRx) including chip-level light source. A prototype of the single-chip photonic TRx based on a bulk silicon substrate demonstrated 20 Gb/s low power chip-level optical interconnects between fabricated chips, proving that this scheme can offer compact low-cost chip-level I/O solutions and have a significant impact on practical electronic-photonic integration in high performance computers (HPC), cpu-memory interface, 3D-IC, and LAN/SAN/data-center and network applications.

Measurement of cone beam CT coincidence with megavoltage isocentre and image sharpness using the QUASAR Penta-Guide phantom.

PubMed

Sykes, J R; Lindsay, R; Dean, C J; Brettle, D S; Magee, D R; Thwaites, D I

2008-10-07

For image-guided radiotherapy (IGRT) systems based on cone beam CT (CBCT) integrated into a linear accelerator, the reproducible alignment of imager to x-ray source is critical to the registration of both the x-ray-volumetric image with the megavoltage (MV) beam isocentre and image sharpness. An enhanced method of determining the CBCT to MV isocentre alignment using the QUASAR Penta-Guide phantom was developed which improved both precision and accuracy. This was benchmarked against our existing method which used software and a ball-bearing (BB) phantom provided by Elekta. Additionally, a method of measuring an image sharpness metric (MTF(50)) from the edge response function of a spherical air cavity within the Penta-Guide phantom was developed and its sensitivity was tested by simulating misalignments of the kV imager. Reproducibility testing of the enhanced Penta-Guide method demonstrated a systematic error of <0.2 mm when compared to the BB method with near equivalent random error (s=0.15 mm). The mean MTF(50) for five measurements was 0.278+/-0.004 lp mm(-1) with no applied misalignment. Simulated misalignments exhibited a clear peak in the MTF(50) enabling misalignments greater than 0.4 mm to be detected. The Penta-Guide phantom can be used to precisely measure CBCT-MV coincidence and image sharpness on CBCT-IGRT systems.

Scintillating fiber-based photon beam profiler for the Jefferson Lab tagged photon beam line

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

Zorn, C.; Barbosa, F.J.; Freyberger, A.

2000-10-01

A scintillating fiber hodoscope has been built for use as a photon beam profiler in the bremsstrahlung tagged photon beam in Hall B of the Thomas Jefferson National Accelerator Facility (Jefferson Lab). The device consists of a linear array of 64 2-2 mm2 scintillating fibers glued to a corresponding set of light guide fibers. Both fiber types use double-clad technology for maximum intensity. The light guide fibers are gently bent into a square array of holes and air-gap coupled to four compact position-sensitive photomultipliers (16 channel Hamamatsu R5900-M16). Custom electronics amplifies and converts the analog outputs to ECL pulses whichmore » are counted by VME-based scalars. The device consisting of the fibers, photomultipliers, and electronics is sealed within a light-tight aluminum box. Two modules make up a beam imaging 2-D system. The system has been tested successfully during an experimental run« less

Photonic ADC: overcoming the bottleneck of electronic jitter.

PubMed

Khilo, Anatol; Spector, Steven J; Grein, Matthew E; Nejadmalayeri, Amir H; Holzwarth, Charles W; Sander, Michelle Y; Dahlem, Marcus S; Peng, Michael Y; Geis, Michael W; DiLello, Nicole A; Yoon, Jung U; Motamedi, Ali; Orcutt, Jason S; Wang, Jade P; Sorace-Agaskar, Cheryl M; Popović, Miloš A; Sun, Jie; Zhou, Gui-Rong; Byun, Hyunil; Chen, Jian; Hoyt, Judy L; Smith, Henry I; Ram, Rajeev J; Perrott, Michael; Lyszczarz, Theodore M; Ippen, Erich P; Kärtner, Franz X

2012-02-13

Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a target of analog-to-digital converter (ADC) developers, driven by applications in radar systems, software radio, medical imaging, and communication systems. Aperture jitter has been a major bottleneck on the way towards higher speeds and better accuracy. Photonic ADCs, which perform sampling using ultra-stable optical pulse trains generated by mode-locked lasers, have been investigated for many years as a promising approach to overcome the jitter problem and bring ADC performance to new levels. This work demonstrates that the photonic approach can deliver on its promise by digitizing a 41 GHz signal with 7.0 effective bits using a photonic ADC built from discrete components. This accuracy corresponds to a timing jitter of 15 fs - a 4-5 times improvement over the performance of the best electronic ADCs which exist today. On the way towards an integrated photonic ADC, a silicon photonic chip with core photonic components was fabricated and used to digitize a 10 GHz signal with 3.5 effective bits. In these experiments, two wavelength channels were implemented, providing the overall sampling rate of 2.1 GSa/s. To show that photonic ADCs with larger channel counts are possible, a dual 20-channel silicon filter bank has been demonstrated.

Searching for a dark photon with DarkLight

DOE PAGES

Corliss, R.

2016-07-30

Here, we describe the current status of the DarkLight experiment at Jefferson Laboratory. DarkLight is motivated by the possibility that a dark photon in the mass range 10 to 100 MeV/c 2 could couple the dark sector to the Standard Model. DarkLight will precisely measure electron proton scattering using the 100 MeV electron beam of intensity 5 mA at the Jefferson Laboratory energy recovering linac incident on a windowless gas target of molecular hydrogen. We will detect the complete final state including scattered electron, recoil proton, and e +e - pair. A phase-I experiment has been funded and is expectedmore » to take data in the next eighteen months. The complete phase-II experiment is under final design and could run within two years after phase-I is completed. The DarkLight experiment drives development of new technology for beam, target, and detector and provides a new means to carry out electron scattering experiments at low momentum transfers.« less

Self-Assembly of Electron Donor-Acceptor-Based Carbazole Derivatives: Novel Fluorescent Organic Nanoprobes for Both One- and Two-Photon Cellular Imaging.

PubMed

Zhang, Jinfeng; Chen, Wencheng; Kalytchuk, Sergii; Li, King Fai; Chen, Rui; Adachi, Chihaya; Chen, Zhan; Rogach, Andrey L; Zhu, Guangyu; Yu, Peter K N; Zhang, Wenjun; Cheah, Kok Wai; Zhang, Xiaohong; Lee, Chun-Sing

2016-05-11

In this study, we report fluorescent organic nanoprobes with intense blue, green, and orange-red emissions prepared by self-assembling three carbazole derivatives into nanorods/nanoparticles. The three compounds consist of two or four electron-donating carbazole groups linked to a central dicyanobenzene electron acceptor. Steric hindrance from the carbazole groups leads to noncoplanar 3D molecular structures favorable to fluorescence in the solid state, while the donor-acceptor structures endow the molecules with good two-photon excited emission properties. The fluorescent organic nanoprobes exhibit good water dispersibility, low cytotoxicity, superior resistance against photodegradation and photobleaching. Both one- and two-photon fluorescent imaging were shown in the A549 cell line. Two-photon fluorescence imaging with the fluorescent probes was demonstrated to be more effective in visualizing and distinguishing cellular details compared to conventional one-photon fluorescence imaging.

Silicon-based silicon–germanium–tin heterostructure photonics

PubMed Central

Soref, Richard

2014-01-01

The wavelength range that extends from 1550 to 5000 nm is a new regime of operation for Si-based photonic and opto-electronic integrated circuits. To actualize the new chips, heterostructure active devices employing the ternary SiGeSn alloy are proposed in this paper. Foundry-based monolithic integration is described. Opportunities and challenges abound in creating laser diodes, optical amplifiers, light-emitting diodes, photodetectors, modulators, switches and a host of high-performance passive infrared waveguided components. PMID:24567479

SU-E-T-11: A Cloud Based CT and LINAC QA Data Management System

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

Wiersma, R; Grelewicz, Z; Belcher, A

Purpose: The current status quo of QA data management consists of a mixture of paper-based forms and spreadsheets for recording the results of daily, monthly, and yearly QA tests for both CT scanners and LINACs. Unfortunately, such systems suffer from a host of problems as, (1) records can be easily lost or destroyed, (2) data is difficult to access — one must physically hunt down records, (3) poor or no means of historical data analysis, and (4) no remote monitoring of machine performance off-site. To address these issues, a cloud based QA data management system was developed and implemented. Methods:more » A responsive tablet interface that optimizes clinic workflow with an easy-to-navigate interface accessible from any web browser was implemented in HTML/javascript/CSS to allow user mobility when entering QA data. Automated image QA was performed using a phantom QA kit developed in Python that is applicable to any phantom and is currently being used with the Gammex ACR, Las Vegas, Leeds, and Catphan phantoms for performing automated CT, MV, kV, and CBCT QAs, respectively. A Python based resource management system was used to distribute and manage intensive CPU tasks such as QA phantom image analysis or LaTeX-to-PDF QA report generation to independent process threads or different servers such that website performance is not affected. Results: To date the cloud QA system has performed approximately 185 QA procedures. Approximately 200 QA parameters are being actively tracked by the system on a monthly basis. Electronic access to historical QA parameter information was successful in proactively identifying a Linac CBCT scanner’s performance degradation. Conclusion: A fully comprehensive cloud based QA data management system was successfully implemented for the first time. Potential machine performance issues were proactively identified that would have been otherwise missed by a paper or spreadsheet based QA system.« less

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.

Electron beam energy stabilization using a neural network hybrid controller at the Australian Synchrotron Linac.

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

Meier, E.; Morgan, M. J.; Biedron, S. G.

2009-01-01

This paper describes the implementation of a neural network hybrid controller for energy stabilization at the Australian Synchrotron Linac. The structure of the controller consists of a neural network (NNET) feed forward control, augmented by a conventional Proportional-Integral (PI) feedback controller to ensure stability of the system. The system is provided with past states of the machine in order to predict its future state, and therefore apply appropriate feed forward control. The NNET is able to cancel multiple frequency jitter in real-time. When it is not performing optimally due to jitter changes, the system can successfully be augmented by themore » PI controller to attenuate the remaining perturbations. With a view to control the energy and bunch length at the FERMI{at}Elettra Free Electron Laser (FEL), the present study considers a neural network hybrid feed forward-feedback type of control to rectify limitations related to feedback systems, such as poor response for high jitter frequencies or limited bandwidth, while ensuring robustness of control. The Australian Synchrotron Linac is equipped with a beam position monitor (BPM), that was provided by Sincrotrone Trieste from a former transport line thus allowing energy measurements and energy control experiments. The present study will consequently focus on correcting energy jitter induced by variations in klystron phase and voltage.« less

Dosimetry of Al2O3 optically stimulated luminescent dosimeter at high energy photons and electrons

NASA Astrophysics Data System (ADS)

Yusof, M. F. Mohd; Joohari, N. A.; Abdullah, R.; Shukor, N. S. Abd; Kadir, A. B. Abd; Isa, N. Mohd

2018-01-01

The linearity of Al2O3 OSL dosimeters (OSLD) were evaluated for dosimetry works in clinical photons and electrons. The measurements were made at a reference depth of Zref according to IAEA TRS 398:2000 codes of practice at 6 and 10 MV photons and 6 and 9 MeV electrons. The measured dose was compared to the thermoluminescence dosimeters (TLD) and ionization chamber commonly used for dosimetry works for higher energy photons and electrons. The results showed that the measured dose in OSL dosimeters were in good agreement with the reported by the ionization chamber in both high energy photons and electrons. A reproducibility test also reported excellent consistency of readings with the OSL at similar energy levels. The overall results confirmed the suitability of OSL dosimeters for dosimetry works involving high energy photons and electrons in radiotherapy.

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

Development of mini linac-based positron source and an efficient positronium convertor for positively charged antihydrogen production

NASA Astrophysics Data System (ADS)

Muranaka, T.; Debu, P.; Dupré, P.; Liszkay, L.; Mansoulie, B.; Pérez, P.; Rey, J. M.; Ruiz, N.; Sacquin, Y.; Crivelli, P.; Gendotti, U.; Rubbia, A.

2010-04-01

We have installed in Saclay a facility for an intense positron source in November 2008. It is based on a compact 5.5 MeV electron linac connected to a reaction chamber with a tungsten target inside to produce positrons via pair production. The expected production rate for fast positrons is 5·1011 per second. The study of moderation of fast positrons and the construction of a slow positron trap are underway. In parallel, we have investigated an efficient positron-positronium convertor using porous silica materials. These studies are parts of a project to produce positively charged antihydrogen ions aiming to demonstrate the feasibility of a free fall antigravity measurement of neutral antihydrogen.

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.

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.

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

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

Inverse Compton scattering X-ray source yield optimization with a laser path folding system inserted in a pre-existent RF linac

NASA Astrophysics Data System (ADS)

Chaleil, A.; Le Flanchec, V.; Binet, A.; Nègre, J. P.; Devaux, J. F.; Jacob, V.; Millerioux, M.; Bayle, A.; Balleyguier, P.; Prazeres, R.

2016-12-01

An inverse Compton scattering source is under development at the ELSA linac of CEA, Bruyères-le-Châtel. Ultra-short X-ray pulses are produced by inverse Compton scattering of 30 ps-laser pulses by relativistic electron bunches. The source will be able to operate in single shot mode as well as in recurrent mode with 72.2 MHz pulse trains. Within this framework, an optical multipass system that multiplies the number of emitted X-ray photons in both regimes has been designed in 2014, then implemented and tested on ELSA facility in the course of 2015. The device is described from both geometrical and timing viewpoints. It is based on the idea of folding the laser optical path to pile-up laser pulses at the interaction point, thus increasing the interaction probability. The X-ray output gain measurements obtained using this system are presented and compared with calculated expectations.

Experimental Study of Electronic Quantum Interference, Photonic Crystal Cavity, Photonic Band Edge Effects for Optical Amplification

DTIC Science & Technology

2016-01-26

MONITOR’S REPORT Kirtland AFB, NM 87117-5776 NUMBER(S) AFRL -RV-PS-TR-2016-0003 12. DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release...22060-6218 1 cy AFRL /RVIL Kirtland AFB, NM 87117-5776 2 cys Official Record Copy AFRL /RVSS/David Cardimona 1 cy 12 Approved for... AFRL -RV-PS- AFRL -RV-PS- TR-2016-0003 TR-2016-0003 EXPERIMENTAL STUDY OF ELECTRONIC QUANTUM INTERFERENCE, PHOTONIC CRYSTAL CAVITY, PHOTONIC BAND

Generation of High-Power High-Intensity Short X-Ray Free-Electron-Laser Pulses

DOE PAGES

Guetg, Marc W.; Lutman, Alberto A.; Ding, Yuantao; ...

2018-01-03

X-ray free-electron lasers combine a high pulse power, short pulse length, narrow bandwidth, and high degree of transverse coherence. Any increase in the photon pulse power, while shortening the pulse length, will further push the frontier on several key x-ray free-electron laser applications including single-molecule imaging and novel nonlinear x-ray methods. This Letter shows experimental results at the Linac Coherent Light Source raising its maximum power to more than 300% of the current limit while reducing the photon pulse length to 10 fs. As a result, this was achieved by minimizing residual transverse-longitudinal centroid beam offsets and beam yaw andmore » by correcting the dispersion when operating over 6 kA peak current with a longitudinally shaped beam.« less

Generation of High-Power High-Intensity Short X-Ray Free-Electron-Laser Pulses

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

Guetg, Marc W.; Lutman, Alberto A.; Ding, Yuantao

X-ray free-electron lasers combine a high pulse power, short pulse length, narrow bandwidth, and high degree of transverse coherence. Any increase in the photon pulse power, while shortening the pulse length, will further push the frontier on several key x-ray free-electron laser applications including single-molecule imaging and novel nonlinear x-ray methods. This Letter shows experimental results at the Linac Coherent Light Source raising its maximum power to more than 300% of the current limit while reducing the photon pulse length to 10 fs. As a result, this was achieved by minimizing residual transverse-longitudinal centroid beam offsets and beam yaw andmore » by correcting the dispersion when operating over 6 kA peak current with a longitudinally shaped beam.« less

Two-Photon Emission of a Hydrogenlike Atom with Photon Polarization and Electron Spin States Taken into Account

NASA Astrophysics Data System (ADS)

Skobelev, V. V.

2017-02-01

The process of two-photon emission ( Ze)* → ( Ze) + 2 γ of a hydrogenlike atom is considered with spin states of the electron and polarization of the photons taken into account, which had not been done before. A general expression for the probability of the process per unit time has been obtained for different polarization states of the photons with a formulation of hard and soft selection rules for the quantum numbers m and l. It is shown that by virtue of the established specifics of the properties of the two-photon emission process (absence of a Zeeman effect and dependence of the probability on the polarization states of the photons), it can in principle be identified against the background of single-photon emission ( Ze)* → ( Ze) + γ, despite the presence of additional small factors: 1) α = e 2/ ћc ≈ 1/137 of the perturbation theory in e, and 2) the square of the atomic expansion parameter ( Zα)2 in the expression for the probability.

Long-term, correlated emittance decrease in intense, high-brightness induction linacs

NASA Astrophysics Data System (ADS)

Carlsten, Bruce E.

1999-09-01

Simulations of high-brightness induction linacs often show a slow, long-term emittance decrease as the beam is matched from the electron gun into the linac. Superimposed on this long-term decrease are rapid emittance oscillations. These effects can be described in terms of correlations in the beam's radial phase space. The rapid emittance oscillations are due to transverse plasma oscillations, which stay nearly in phase for different radial positions within the beam. The initial emittance, just after the electron gun, is dominated by nonlinear focusing within the gun introduced by the anode exit hole. Due to the large space-charge force of an intense electron beam, the focusing of the beam through the matching section introduces an effective nonlinear force (from the change in the particles' potential energies) which counteracts the nonlinearities from the electron gun, leading to an average, long-term emittance decrease. Not all of the initial nonlinearity is removed by the matching procedure, and there are important consequences both for emittance measurements using solenoid focal length scans and for focusing the electron beam to a target.

Quantum dot single-photon switches of resonant tunneling current for discriminating-photon-number detection

PubMed Central

Weng, Qianchun; An, Zhenghua; Zhang, Bo; Chen, Pingping; Chen, Xiaoshuang; Zhu, Ziqiang; Lu, Wei

2015-01-01

Low-noise single-photon detectors that can resolve photon numbers are used to monitor the operation of quantum gates in linear-optical quantum computation. Exactly 0, 1 or 2 photons registered in a detector should be distinguished especially in long-distance quantum communication and quantum computation. Here we demonstrate a photon-number-resolving detector based on quantum dot coupled resonant tunneling diodes (QD-cRTD). Individual quantum-dots (QDs) coupled closely with adjacent quantum well (QW) of resonant tunneling diode operate as photon-gated switches- which turn on (off) the RTD tunneling current when they trap photon-generated holes (recombine with injected electrons). Proposed electron-injecting operation fills electrons into coupled QDs which turn “photon-switches” to “OFF” state and make the detector ready for multiple-photons detection. With proper decision regions defined, 1-photon and 2-photon states are resolved in 4.2 K with excellent propabilities of accuracy of 90% and 98% respectively. Further, by identifying step-like photon responses, the photon-number-resolving capability is sustained to 77 K, making the detector a promising candidate for advanced quantum information applications where photon-number-states should be accurately distinguished. PMID:25797442

Quantum dot single-photon switches of resonant tunneling current for discriminating-photon-number detection.

PubMed

Weng, Qianchun; An, Zhenghua; Zhang, Bo; Chen, Pingping; Chen, Xiaoshuang; Zhu, Ziqiang; Lu, Wei

2015-03-23

Low-noise single-photon detectors that can resolve photon numbers are used to monitor the operation of quantum gates in linear-optical quantum computation. Exactly 0, 1 or 2 photons registered in a detector should be distinguished especially in long-distance quantum communication and quantum computation. Here we demonstrate a photon-number-resolving detector based on quantum dot coupled resonant tunneling diodes (QD-cRTD). Individual quantum-dots (QDs) coupled closely with adjacent quantum well (QW) of resonant tunneling diode operate as photon-gated switches- which turn on (off) the RTD tunneling current when they trap photon-generated holes (recombine with injected electrons). Proposed electron-injecting operation fills electrons into coupled QDs which turn "photon-switches" to "OFF" state and make the detector ready for multiple-photons detection. With proper decision regions defined, 1-photon and 2-photon states are resolved in 4.2 K with excellent propabilities of accuracy of 90% and 98% respectively. Further, by identifying step-like photon responses, the photon-number-resolving capability is sustained to 77 K, making the detector a promising candidate for advanced quantum information applications where photon-number-states should be accurately distinguished.

Compact x-ray source based on burst-mode inverse Compton scattering at 100 kHz

DOE PAGES

Graves, W.  S.; Bessuille, J.; Brown, P.; ...

2014-12-01

A design for a compact x-ray light source (CXLS) with flux and brilliance orders of magnitude beyond existing laboratory scale sources is presented. The source is based on inverse Compton scattering of a high brightness electron bunch on a picosecond laser pulse. The accelerator is a novel high-efficiency standingwave linac and rf photoinjector powered by a single ultrastable rf transmitter at X-band rf frequency. The high efficiency permits operation at repetition rates up to 1 kHz, which is further boosted to 100 kHz by operating with trains of 100 bunches of 100 pC charge, each separated by 5 ns. Themore » entire accelerator is approximately 1 meter long and produces hard x rays tunable over a wide range of photon energies. The colliding laser is a Yb:YAG solid-state amplifier producing 1030 nm, 100 mJ pulses at the same 1 kHz repetition rate as the accelerator. The laser pulse is frequency-doubled and stored for many passes in a ringdown cavity to match the linac pulse structure. At a photon energy of 12.4 keV, the predicted x-ray flux is 5 × 10¹¹ photons/second in a 5% bandwidth and the brilliance is 2 × 10¹² photons/(sec mm² mrad² 0.1%) in pulses with rms pulse length of 490 fs. The nominal electron beam parameters are 18 MeV kinetic energy, 10 microamp average current, 0.5 microsecond macropulse length, resulting in average electron beam power of 180 W. Optimization of the x-ray output is presented along with design of the accelerator, laser, and x-ray optic components that are specific to the particular characteristics of the Compton scattered x-ray pulses.« 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.

Unified theory of quantized electrons, phonons, and photons out of equilibrium: A simplified ab initio approach based on the generalized Baym-Kadanoff ansatz

NASA Astrophysics Data System (ADS)

de Melo, Pedro Miguel M. C.; Marini, Andrea

2016-04-01

We present a full ab initio description of the coupled out-of-equilibrium dynamics of photons, phonons, and electrons. In the present approach, the quantized nature of the electromagnetic field as well as of the nuclear oscillations is fully taken into account. The result is a set of integrodifferential equations, written on the Keldysh contour, for the Green's functions of electrons, phonons, and photons where the different kinds of interactions are merged together. We then concentrate on the electronic dynamics in order to reduce the problem to a computationally feasible approach. By using the generalized Baym-Kadanoff ansatz and the completed collision approximation, we introduce a series of efficient but controllable approximations. In this way, we reduce all equations to a set of decoupled equations for the density matrix that describe all kinds of static and dynamical correlations. The final result is a coherent, general, and inclusive scheme to calculate several physical quantities: carrier dynamics, transient photoabsorption, and light emission, all of which include, at the same time, electron-electron, electron-phonon, and electron-photon interactions. We further discuss how all these observables can be easily calculated within the present scheme using a fully atomistic ab initio approach.

Ultrafast terahertz electrodynamics of photonic and electronic nanostructures

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

Luo, Liang

This thesis summarizes my work on using ultrafast laser pulses to study Terahertz (THz) electrodynamics of photonic and electronic nanostructures and microstructures. Ultrafast timeresolved (optical, NIR, MIR, THz) pump-probe spectroscopy setup has been successfully built, which enables me to perform a series of relevant experiments. Firstly, a novel high e ciency and compact THz wave emitter based on split-ring-resonators has been developed and characterized. The emitter can be pumped at any wavelength by tailoring the magnetic resonance and could generate gapless THz waves covering the entire THz band. Secondly, two kinds of new photonic structures for THz wave manipulation havemore » been successfully designed and characterized. One is based on the 1D and 2D photo-imprinted di ractive elements. The other is based on the photoexcited double-split-ring-resonator metamaterials. Both structures are exible and can modulate THz waves with large tunability. Thirdly, the dark excitons in semiconducting singlewalled carbon nanotubes are studied by optical pump and THz probe spectroscopy, which provides the rst insights into the THz responses of nonequilibrium excitonic correlations and dynamics from the dark ground states in carbon nanotubes. Next, several on-going projects are brie y presented such as the study of ultrafast THz dynamics of Dirac fermions in topological insulator Bi 2Se 3 with Mid-infrared excitation. Finally, the thesis ends with a summary of the completed experiments and an outlook of the future plan.« less

Multichannel Dosimeter and α-Al2O3:C Optically Stimulated Luminescence (OSL) Fiber Sensors for Use in Radiation Therapy—Evaluation With Photon Beams

NASA Astrophysics Data System (ADS)

Magne, Sylvian; de Carlan, Loïc; Bordy, Jean-Marc; Isambert, Aurélie; Bridier, André; Ferdinand, Pierre

2011-04-01

A multichannel OSL fiber optic dosimeter based on optically stimulated luminescence (OSL) of alumina is proposed for online in vivo dosimetry (IVD) in radiation therapy (RT). Two types of dosimetric-grade Al2O3:C crystals are compared and show different behavior according to manufacturing process. Metrological validations have been performed with a Saturne 43 LINAC in reference conditions at CEA LIST LNHB (French Ionizing Radiation Reference Laboratory). The dose response of OSL integrals under photon beam irradiation (6, 12, and 20 MV) show sublinearity behavior modeled by second-order equations and exhibit a small energy dependence (between 0.7% and 1.4%), explained by a modified intermediate cavity model adapted to a LINAC photon spectrum. Preclinical tests at Institut Gustave Roussy (IGR) prove that a proper design for a PMMA build-up cap leads to a low dependence vs photon beam orientation (± 1.5% and ± 0.9%) and vs field size in view of surface measurements.

Quantum State Transfer from a Single Photon to a Distant Quantum-Dot Electron Spin

NASA Astrophysics Data System (ADS)

He, Yu; He, Yu-Ming; Wei, Yu-Jia; Jiang, Xiao; Chen, Kai; Lu, Chao-Yang; Pan, Jian-Wei; Schneider, Christian; Kamp, Martin; Höfling, Sven

2017-08-01

Quantum state transfer from flying photons to stationary matter qubits is an important element in the realization of quantum networks. Self-assembled semiconductor quantum dots provide a promising solid-state platform hosting both single photon and spin, with an inherent light-matter interface. Here, we develop a method to coherently and actively control the single-photon frequency bins in superposition using electro-optic modulators, and measure the spin-photon entanglement with a fidelity of 0.796 ±0.020 . Further, by Greenberger-Horne-Zeilinger-type state projection on the frequency, path, and polarization degrees of freedom of a single photon, we demonstrate quantum state transfer from a single photon to a single electron spin confined in an InGaAs quantum dot, separated by 5 m. The quantum state mapping from the photon's polarization to the electron's spin is demonstrated along three different axes on the Bloch sphere, with an average fidelity of 78.5%.

Comparison between TG-51 and TG-21: Calibration of photon and electron beams in water using cylindrical chambers.

PubMed

Cho, S H; Lowenstein, J R; Balter, P A; Wells, N H; Hanson, W F

2000-01-01

A new calibration protocol, developed by the AAPM Task Group 51 (TG-51) to replace the TG-21 protocol, is based on an absorbed-dose to water standard and calibration factor (N(D,w)), while the TG-21 protocol is based on an exposure (or air-kerma) standard and calibration factor (N(x)). Because of differences between these standards and the two protocols, the results of clinical reference dosimetry based on TG-51 may be somewhat different from those based on TG-21. The Radiological Physics Center has conducted a systematic comparison between the two protocols, in which photon and electron beam outputs following both protocols were compared under identical conditions. Cylindrical chambers used in this study were selected from the list given in the TG-51 report, covering the majority of current manufacturers. Measured ratios between absorbed-dose and air-kerma calibration factors, derived from the standards traceable to the NIST, were compared with calculated values using the TG-21 protocol. The comparison suggests that there is roughly a 1% discrepancy between measured and calculated ratios. This discrepancy may provide a reasonable measure of possible changes between the absorbed-dose to water determined by TG-51 and that determined by TG-21 for photon beam calibrations. The typical change in a 6 MV photon beam calibration following the implementation of the TG-51 protocol was about 1%, regardless of the chamber used, and the change was somewhat smaller for an 18 MV photon beam. On the other hand, the results for 9 and 16 MeV electron beams show larger changes up to 2%, perhaps because of the updated electron stopping power data used for the TG-51 protocol, in addition to the inherent 1% discrepancy presented in the calibration factors. The results also indicate that the changes may be dependent on the electron energy.

Polarized γ source based on Compton backscattering in a laser cavity

NASA Astrophysics Data System (ADS)

Yakimenko, V.; Pogorelsky, I. V.

2006-09-01

We propose a novel gamma source suitable for generating a polarized positron beam for the next generation of electron-positron colliders, such as the International Linear Collider (ILC), and the Compact Linear Collider (CLIC). This 30-MeV polarized gamma source is based on Compton scattering inside a picosecond CO2 laser cavity generated from electron bunches produced by a 4-GeV linac. We identified and experimentally verified the optimum conditions for obtaining at least one gamma photon per electron. After multiplication at several consecutive interaction points, the circularly polarized gamma rays are stopped on a target, thereby creating copious numbers of polarized positrons. We address the practicality of having an intracavity Compton-polarized positron source as the injector for these new colliders.

The response of a radiophotoluminescent glass dosimeter in megavoltage photon and electron beams.

PubMed

Araki, Fujio; Ohno, Takeshi

2014-12-01

This study investigated the response of a radiophotoluminescent glass dosimeter (RGD) in megavoltage photon and electron beams. The RGD response was compared with ion chamber measurements for 4-18 MV photons and 6-20 MeV electrons in plastic water phantoms. The response was also calculated via Monte Carlo (MC) simulations with EGSnrc/egs_chamber and Cavity user-codes, respectively. In addition, the response of the RGD cavity was analyzed as a function of field sizes and depths according to Burlin's general cavity theory. The perturbation correction factor, PQ, in the RGD cavity was also estimated from MC simulations for photon and electron beams. The calculated and measured RGD energy response at reference conditions with a 10 × 10 cm(2) field and 10 cm depth in photons was lower by up to 2.5% with increasing energy. The variation in RGD response in the field size range of 5 × 5 cm(2) to 20 × 20 cm(2) was 3.9% and 0.7%, at 10 cm depth for 4 and 18 MV, respectively. The depth dependence of the RGD response was constant within 1% for energies above 6 MV but it increased by 2.6% and 1.6% for a large (20 × 20 cm(2)) field at 4 and 6 MV, respectively. The dose contributions from photon interactions (1 - d) in the RGD cavity, according to Burlin's cavity theory, decreased with increasing energy and decreasing field size. The variation in (1 - d) between field sizes became larger with increasing depth for the lower energies of 4 and 6 MV. PQ for the RGD cavity was almost constant between 0.96 and 0.97 at 10 MV energies and above. Meanwhile, PQ depends strongly on field size and depth for 4 and 6 MV photons. In electron beams, the RGD response at a reference depth, dref, varied by less than 1% over the electron energy range but was on average 4% lower than the response for 6 MV photons. The RGD response for photon beams depends on both (1 - d) and perturbation effects in the RGD cavity. Therefore, it is difficult to predict the energy dependence of RGD response by

Design of photon converter and photoneutron target for High power electron accelerator based BNCT.

PubMed

Rahmani, Faezeh; Seifi, Samaneh; Anbaran, Hossein Tavakoli; Ghasemi, Farshad

2015-12-01

An electron accelerator, ILU-14, with current of 10 mA and 100 kW in power has been considered as one of the options for neutron source in Boron Neutron Capture Therapy (BNCT). The final design of neutron target has been obtained using MCNPX to optimize the neutron production. Tungsten in strip shape and D2O in cylindrical form have been proposed as the photon converter and the photoneutron target, respectively. In addition calculation of heat deposition in the photon target design has been considered to ensure mechanical stability of target. The results show that about 8.37×10(12) photoneutron/s with average energy of 615 keV can be produced by this neutron source design. In addition, using an appropriate beam shaping assembly an epithermal neutron flux of the order of 1.24×10(8) cm(-2) s(-1) can be obtained for BNCT applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

An MCNP-based model for the evaluation of the photoneutron dose in high energy medical electron accelerators.

PubMed

Carinou, Eleutheria; Stamatelatos, Ion Evangelos; Kamenopoulou, Vassiliki; Georgolopoulou, Paraskevi; Sandilos, Panayotis

The development of a computational model for the treatment head of a medical electron accelerator (Elekta/Philips SL-18) by the Monte Carlo code mcnp-4C2 is discussed. The model includes the major components of the accelerator head and a pmma phantom representing the patient body. Calculations were performed for a 14 MeV electron beam impinging on the accelerator target and a 10 cmx10 cm beam area at the isocentre. The model was used in order to predict the neutron ambient dose equivalent at the isocentre level and moreover the neutron absorbed dose distribution within the phantom. Calculations were validated against experimental measurements performed by gold foil activation detectors. The results of this study indicated that the equivalent dose at tissues or organs adjacent to the treatment field due to photoneutrons could be up to 10% of the total peripheral dose, for the specific accelerator characteristics examined. Therefore, photoneutrons should be taken into account when accurate dose calculations are required to sensitive tissues that are adjacent to the therapeutic X-ray beam. The method described can be extended to other accelerators and collimation configurations as well, upon specification of treatment head component dimensions, composition and nominal accelerating potential.

Out-of-field in vivo dosimetry using TLD in SABR for primary kidney cancer involving mixed photon fields.

PubMed

Lonski, P; Keehan, S; Siva, S; Pham, D; Franich, R D; Taylor, M L; Kron, T

2017-05-01

To assess out-of-field dose using three different variants of LiF thermoluminescence dosimeters (TLD) for ten patients who underwent stereotactic ablative body radiotherapy (SABR) for primary renal cell carcinoma (RCC) and compare with treatment planning system (TPS) dose calculations. Thermoluminescent dosimeter (TLD) measurements were conducted at 20, 30, 40 and 50cm from isocentre on ten patients undergoing SABR for primary RCC. Three types of high-sensitivity LiF:Mg,Cu,P TLD material with different 6 Li/ 7 Li isotope ratios were used. Patient plans were calculated using Eclipse Anisotropic Analytical Algorithm (AAA) for clinical evaluation and recalculated using Pencil Beam Convolution (PBC) algorithm for comparison. Both AAA and PBC showed diminished accuracy for photon doses at increasing distance out-of-field. At 50cm, measured photon dose was 0.3cGy normalised to a 10Gy prescription on average with only small variation across all patients. This is likely due to the leakage component of the out-of-field dose. The 6 Li-enriched TLD materials showed increased signal attributable to additional neutron contribution. LiF:Mg,Cu,P TLD containing 6 Li is sensitive enough to measure out-of-field dose 50cm from isocentre however will over-estimate the photon component of out-of-field dose in high energy treatments due to the presence of thermal neutrons. 7 Li enriched materials which are insensitive to neutrons are therefore required for accurate photon dosimetry. Neutron signal has been shown here to increase with MUs and is higher for patients treated using certain non coplanar beam arrangements. Further work is required to convert this additional neutron signal to dose. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

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.

The water-water cycle as alternative photon and electron sinks.

PubMed

Asada, K

2000-10-29

The water-water cycle in chloroplasts is the photoreduction of dioxygen to water in photosystem I (PS I) by the electrons generated in photosystem II (PS II) from water. In the water-water cycle, the rate of photoreduction of dioxygen in PS I is several orders of magnitude lower than those of the disproportionation of superoxide catalysed by superoxide dismutase, the reduction of hydrogen peroxide to water catalysed by ascorbate peroxidase, and the reduction of the resulting oxidized forms of ascorbate by reduced ferredoxin or catalysed by either dehydroascorbate reductase or monodehydroascorbate reductase. The water-water cycle therefore effectively shortens the lifetimes of photoproduced superoxide and hydrogen peroxide to suppress the production of hydroxyl radicals, their interactions with the target molecules in chloroplasts, and resulting photoinhibition. When leaves are exposed to photon intensities of sunlight in excess of that required to support the fixation of CO2, the intersystem electron carriers are over-reduced, resulting in photoinhibition. Under such conditions, the water-water cycle not only scavenges active oxygens, but also safely dissipates excess photon energy and electrons, in addition to downregulation of PS II and photorespiration. The dual functions of the water-water cycle for protection from photoinhibition under photon excess stress are discussed, along with its functional evolution.

Experimental determination of the effective point of measurement of cylindrical ionization chambers for high-energy photon and electron beams.

PubMed

Huang, Yanxiao; Willomitzer, Christian; Zakaria, Golam Abu; Hartmann, Guenther H

2010-01-01

Measurements of depth-dose curves in water phantom using a cylindrical ionization chamber require that its effective point of measurement is located at the measuring depth. Recommendations for the position of the effective point of measurement with respect to the central axis valid for high-energy electron and photon beams are given in dosimetry protocols. According to these protocols, the use of a constant shift P(eff) is currently recommended. However, this is still based on a very limited set of experimental results. It is therefore expected that an improved knowledge of the exact position of the effective point of measurement will further improve the accuracy of dosimetry. Recent publications have revealed that the position of the effective point of measurement is indeed varying with beam energy, field size and also with chamber geometry. The aim of this study is to investigate whether the shift of P(eff) can be taken to be constant and independent from the beam energy. An experimental determination of the effective point of measurement is presented based on a comparison between cylindrical chambers and a plane-parallel chamber using conventional dosimetry equipment. For electron beams, the determination is based on the comparison of halfvalue depth R(50) between the cylindrical chamber of interest and a well guarded plane-parallel Roos chamber. For photon beams, the depth of dose maximum, d(max), the depth of 80% dose, d(80), and the dose parameter PDD(10) were used. It was again found that the effective point of measurement for both, electron and photon beams Dosimetry, depends on the beam energy. The deviation from a constant value remains very small for photons, whereas significant deviations were found for electrons. It is therefore concluded that use of a single upstream shift value from the centre of the cylindrical chamber as recommended in current dosimetry protocols is adequate for photons, however inadequate for accurate electron beam dosimetry.

Unraveling the role of photons and electrons upon their chemical interaction with photoresist during EUV exposure

NASA Astrophysics Data System (ADS)

Pollentier, Ivan; Vesters, Yannick; Petersen, John S.; Vanelderen, Pieter; Rathore, Atish; de Simone, Danilo; Vandenberghe, Geert

2018-03-01

The interaction of 91.6 eV EUV photons with photoresist - in particular chemically amplified resist (CAR) - is different than exposure at 193 nm and 248 nm wavelengths. The latter is understood well and it is known that photons interact with electrons in the resist's molecular valence orbitals (for chemically amplified resist (CAR) the photon interacts with the photo acid generator (PAG), which leads to a deprotection reaction on a polymer after a thermal catalytic reaction during a post-exposure-bake.). At EUV however, more steps are involved in the radiolysis process between the absorption of the photon and the final chemical modification. These are related to the generation of primary electrons and their decay to lower energy secondary electrons, and most of this steps are not well understood. In this paper, the reaction products from EUV and low energy electron exposure are examined using Residual Gas Analysis (RGA), which measures and analyzes the outgassing products related to the ongoing reactions. This investigation is applied firstly on a model CAR where details of the resist chemical constituents were known prior to testing. The measurement not only resolved information on the expected acid related reactions from the PAG and protection groups, but also exhibited direct scission reactions of the polymer, where some of them lead to polymerization reactions. Moreover, the measurement quantifies the balance between the different ongoing reactions, which were confirmed by contrast curve measurements. Based on learnings on the model resist, applied the measurement technique to commercial resists, where actual resist chemistry composition is not known. Despite that, it was found that information could be deduced to distinguish between acid related ongoing reactions and direct scission of reaction on the base polymer and quantify their relation. Moreover, different generations of commercial resists based on similar chemistry platform were investigated, which

Strong coupling of a single electron in silicon to a microwave photon

NASA Astrophysics Data System (ADS)

Mi, X.; Cady, J. V.; Zajac, D. M.; Deelman, P. W.; Petta, J. R.

2017-01-01

Silicon is vital to the computing industry because of the high quality of its native oxide and well-established doping technologies. Isotopic purification has enabled quantum coherence times on the order of seconds, thereby placing silicon at the forefront of efforts to create a solid-state quantum processor. We demonstrate strong coupling of a single electron in a silicon double quantum dot to the photonic field of a microwave cavity, as shown by the observation of vacuum Rabi splitting. Strong coupling of a quantum dot electron to a cavity photon would allow for long-range qubit coupling and the long-range entanglement of electrons in semiconductor quantum dots.

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

Photon spectrum and absorbed dose in brain tumor.

PubMed

Vega-Carrillo, Hector Rene; Silva-Sanchez, Angeles; Rivera-Montalvo, Teodoro

2016-11-01

Using Monte Carlo methods a BOMAB phantom inside a treatment hall with a brain tumor nearby the pituitary gland was treated with photons produced by a Varian 6MV linac. The photon spectrum and the absorbed dose were calculated in the tumor, pituitary gland and the head. The treatment beam was collimated to illuminate only the tumor volume; however photons were noticed in the gland. Photon fluence reaching the tumor is and 15.7 times larger than the fluence in the pituitary gland, on the other hand the absorbed dose in the tumor is 37.1 times larger than the dose in the gland because photons that reach the pituitary gland are scattered, by the head and the tumor, through Compton effect. Copyright © 2016 Elsevier Ltd. All rights reserved.

MCMEG: Simulations of both PDD and TPR for 6 MV LINAC photon beam using different MC codes

NASA Astrophysics Data System (ADS)

Fonseca, T. C. F.; Mendes, B. M.; Lacerda, M. A. S.; Silva, L. A. C.; Paixão, L.; Bastos, F. M.; Ramirez, J. V.; Junior, J. P. R.

2017-11-01

The Monte Carlo Modelling Expert Group (MCMEG) is an expert network specializing in Monte Carlo radiation transport and the modelling and simulation applied to the radiation protection and dosimetry research field. For the first inter-comparison task the group launched an exercise to model and simulate a 6 MV LINAC photon beam using the Monte Carlo codes available within their laboratories and validate their simulated results by comparing them with experimental measurements carried out in the National Cancer Institute (INCA) in Rio de Janeiro, Brazil. The experimental measurements were performed using an ionization chamber with calibration traceable to a Secondary Standard Dosimetry Laboratory (SSDL). The detector was immersed in a water phantom at different depths and was irradiated with a radiation field size of 10×10 cm2. This exposure setup was used to determine the dosimetric parameters Percentage Depth Dose (PDD) and Tissue Phantom Ratio (TPR). The validation process compares the MC calculated results to the experimental measured PDD20,10 and TPR20,10. Simulations were performed reproducing the experimental TPR20,10 quality index which provides a satisfactory description of both the PDD curve and the transverse profiles at the two depths measured. This paper reports in detail the modelling process using MCNPx, MCNP6, EGSnrc and Penelope Monte Carlo codes, the source and tally descriptions, the validation processes and the results.

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.

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.

Shielding evaluation and acceptance testing of a prefabricated, modular, temporary radiation therapy treatment facility

PubMed Central

Ezzell, Gary A.

2004-01-01

We have recently commissioned a temporary radiation therapy facility that is novel in two aspects: it was constructed using modular components, and the LINAC was installed in one of the modular sections before it was lifted into position. Additional steel and granular fill was added to the modular sections on‐site during construction. The building will be disassembled and removed when no longer needed. This paper describes the radiation shielding specifications and survey of the facility, as well as the ramifications for acceptance testing occasioned by the novel installation procedure. The LINAC is a Varian 21EX operating at 6 MV and 18 MV. The radiation levels outside the vault satisfied the design criteria, and no anomalous leakage was detected along the joints of the modular structure. At 18 MV and 600 monitor units (MU) per minute, the radiation level outside the primary barrier walls was 8.5μSv/h of photons; there were no detectable neutrons. Outside the direct‐shielded door, the levels were 0.4μSv/h of photons and 3.0μSv/h of neutrons. The isocentricity of the accelerator met the acceptance criteria and was not affected by its preinstallation into an integrated baseframe and subsequent transport to the building site. PACS numbers: 87.52.Df, 87.52.Ga PMID:15738926

Review of biomaterials for electronics and photonics

NASA Astrophysics Data System (ADS)

Ouchen, Fahima; Rau, Ileana; Kajzar, François; Heckman, Emily; Grote, James G.

2018-03-01

Much work has been done developing and utilizing biomaterials over the last decade. Biomaterials not only includes deoxyribonucleic acid (DNA), but nucleobases and silk. These materials are abundant, inexpensive, non-fossil fuel-based and green. Researchers have demonstrated their potential to enhance the performance of organic and inorganic electronic and photonic devices, such as light emitting diodes, thin film transistors, capacitors, electromagnetic interference shielding and electro-optic modulators. Starting around the year 2000, with only a hand full of researchers, including researchers at the Air Force Research Laboratory (AFRL) and researchers at the Chitose Institute of Technology (CIST), it has grown into a large US, Asia and European consortium, producing over 3400 papers, three books, many book chapters and multiple patents. Presented here is a short overview of the progress in this exciting field of nano bio-engineering.

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.

Ultrafast Science Opportunities with Electron Microscopy

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

Durr, Hermann

X-rays and electrons are two of the most fundamental probes of matter. When the Linac Coherent Light Source (LCLS), the world’s first x-ray free electron laser, began operation in 2009, it transformed ultrafast science with the ability to generate laser-like x-ray pulses from the manipulation of relativistic electron beams. This document describes a similar future transformation. In Transmission Electron Microscopy, ultrafast relativistic (MeV energy) electron pulses can achieve unsurpassed spatial and temporal resolution. Ultrafast temporal resolution will be the next frontier in electron microscopy and can ideally complement ultrafast x-ray science done with free electron lasers. This document describes themore » Grand Challenge science opportunities in chemistry, material science, physics and biology that arise from an MeV ultrafast electron diffraction & microscopy facility, especially when coupled with linac-based intense THz and X-ray pump capabilities.« less

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.

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

DPM, a fast, accurate Monte Carlo code optimized for photon and electron radiotherapy treatment planning dose calculations

NASA Astrophysics Data System (ADS)

Sempau, Josep; Wilderman, Scott J.; Bielajew, Alex F.

2000-08-01

A new Monte Carlo (MC) algorithm, the `dose planning method' (DPM), and its associated computer program for simulating the transport of electrons and photons in radiotherapy class problems employing primary electron beams, is presented. DPM is intended to be a high-accuracy MC alternative to the current generation of treatment planning codes which rely on analytical algorithms based on an approximate solution of the photon/electron Boltzmann transport equation. For primary electron beams, DPM is capable of computing 3D dose distributions (in 1 mm3 voxels) which agree to within 1% in dose maximum with widely used and exhaustively benchmarked general-purpose public-domain MC codes in only a fraction of the CPU time. A representative problem, the simulation of 1 million 10 MeV electrons impinging upon a water phantom of 1283 voxels of 1 mm on a side, can be performed by DPM in roughly 3 min on a modern desktop workstation. DPM achieves this performance by employing transport mechanics and electron multiple scattering distribution functions which have been derived to permit long transport steps (of the order of 5 mm) which can cross heterogeneity boundaries. The underlying algorithm is a `mixed' class simulation scheme, with differential cross sections for hard inelastic collisions and bremsstrahlung events described in an approximate manner to simplify their sampling. The continuous energy loss approximation is employed for energy losses below some predefined thresholds, and photon transport (including Compton, photoelectric absorption and pair production) is simulated in an analogue manner. The δ-scattering method (Woodcock tracking) is adopted to minimize the computational costs of transporting photons across voxels.

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

Two-Photon Absorption of Soft X-Ray Free Electron Laser Radiation by Graphite Near the Carbon K-Absorption Edge

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

Christensen, Steven T; Lam, Royce K.; Raj, Sumana L.

We have examined the transmission of soft X-ray pulses from the FERMI free electron laser through carbon films of varying thickness, quantifying nonlinear effects of pulses above and below the carbon K-edge. At typical of soft X-ray free electron laser intensities, pulses exhibit linear absorption at photon energies above and below the K-edge, ~308 and ~260 eV, respectively; whereas two-photon absorption becomes significant slightly below the K-edge, ~284.2 eV. The measured two-photon absorption cross section at 284.18 eV (~6 x 10-48 cm4 s) is 7 orders of magnitude above what is expected from a simple theory based on hydrogen-like atomsmore » - a result of resonance effects.« less

Two-photon absorption of soft X-ray free electron laser radiation by graphite near the carbon K-absorption edge

NASA Astrophysics Data System (ADS)

Lam, Royce K.; Raj, Sumana L.; Pascal, Tod A.; Pemmaraju, C. D.; Foglia, Laura; Simoncig, Alberto; Fabris, Nicola; Miotti, Paolo; Hull, Christopher J.; Rizzuto, Anthony M.; Smith, Jacob W.; Mincigrucci, Riccardo; Masciovecchio, Claudio; Gessini, Alessandro; De Ninno, Giovanni; Diviacco, Bruno; Roussel, Eleonore; Spampinati, Simone; Penco, Giuseppe; Di Mitri, Simone; Trovò, Mauro; Danailov, Miltcho B.; Christensen, Steven T.; Sokaras, Dimosthenis; Weng, Tsu-Chien; Coreno, Marcello; Poletto, Luca; Drisdell, Walter S.; Prendergast, David; Giannessi, Luca; Principi, Emiliano; Nordlund, Dennis; Saykally, Richard J.; Schwartz, Craig P.

2018-07-01

We have examined the transmission of soft X-ray pulses from the FERMI free electron laser through carbon films of varying thickness, quantifying nonlinear effects of pulses above and below the carbon K-edge. At typical of soft X-ray free electron laser intensities, pulses exhibit linear absorption at photon energies above and below the K-edge, ∼308 and ∼260 eV, respectively; whereas two-photon absorption becomes significant slightly below the K-edge, ∼284.2 eV. The measured two-photon absorption cross section at 284.18 eV (∼6 × 10-48 cm4 s) is 7 orders of magnitude above what is expected from a simple theory based on hydrogen-like atoms - a result of resonance effects.

Electron and photon energy calibration with the ATLAS detector using LHC Run 1 data

DOE PAGES

Aad, G.; Abbott, B.; Abdallah, J.; ...

2014-10-01

This paper presents the electron and photon energy calibration achieved with the ATLAS detector using about 25 fb -1 of LHC proton–proton collision data taken at centre-of-mass energies of √s=7 and 8 TeV. The reconstruction of electron and photon energies is optimised using multivariate algorithms. The response of the calorimeter layers is equalised in data and simulation, and the longitudinal profile of the electromagnetic showers is exploited to estimate the passive material in front of the calorimeter and reoptimise the detector simulation. After all corrections, the Z resonance is used to set the absolute energy scale. For electrons from Zmore » decays, the achieved calibration is typically accurate to 0.05 % in most of the detector acceptance, rising to 0.2 % in regions with large amounts of passive material. The remaining inaccuracy is less than 0.2–1 % for electrons with a transverse energy of 10 GeV, and is on average 0.3 % for photons. The detector resolution is determined with a relative inaccuracy of less than 10 % for electrons and photons up to 60 GeV transverse energy, rising to 40 % for transverse energies above 500 GeV.« less

Design of High Efficiency High Power Electron Accelerator Systems Based on Normal Conducting RF Technology for Energy and Environmental Applications

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

Dolgashev, Valery; Tantawi, Sami

The goal of this project was to perform engineering design studies of three extremely high efficiency electron accelerators with the following parameters [1]: 2 MeV output beam energy and 1 MW average beam power; 10 MeV output energy and 10 MW; 10 MeV output energy and 1 MW. These linacs are intended for energy and environmental applications [2]. We based our designs on normal conducting radio-frequency technology. We have successfully reached this goal where we show rf-to-beam efficiency of 96.7 %, 97.2 %, and 79.6 % for these linacs.

Electron-electron correlation in two-photon double ionization of He-like ions [Counterintuitive electron correlation in two-photon double ionization of He-like ions

DOE PAGES

Hu, S. X.

2018-01-18

Electron correlation plays a crucial role in quantum many-body physics ranging from molecular bonding, strong-field–induced multi-electron ionization, to superconducting in materials. Understanding the dynamic electron correlation in the photoionization of relatively simple quantum three-body systems, such as He and He-like ions, is an important step toward manipulating complex systems through photo-induced processes. Here we have performed ab initio investigations of two-photon double ionization (TPDI) of He and He-like ions [Li +, Be 2+, and C 4+] exposed to intense attosecond x-ray pulses. Results from such fully correlated quantum calculations show weaker and weaker electron correlation effects in TPDI spectra asmore » the ionic charge increases, which is counterintuitive to the belief that the strongly correlated ground state and the strong Coulomb field of He-like ions should lead to more equal-energy sharing in photoionization. Lastly, these findings indicate that the final-state electron–electron correlation ultimately determines their energy sharing in TPDI.« less

Electron-electron correlation in two-photon double ionization of He-like ions [Counterintuitive electron correlation in two-photon double ionization of He-like ions

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

Hu, S. X.

Electron correlation plays a crucial role in quantum many-body physics ranging from molecular bonding, strong-field–induced multi-electron ionization, to superconducting in materials. Understanding the dynamic electron correlation in the photoionization of relatively simple quantum three-body systems, such as He and He-like ions, is an important step toward manipulating complex systems through photo-induced processes. Here we have performed ab initio investigations of two-photon double ionization (TPDI) of He and He-like ions [Li +, Be 2+, and C 4+] exposed to intense attosecond x-ray pulses. Results from such fully correlated quantum calculations show weaker and weaker electron correlation effects in TPDI spectra asmore » the ionic charge increases, which is counterintuitive to the belief that the strongly correlated ground state and the strong Coulomb field of He-like ions should lead to more equal-energy sharing in photoionization. Lastly, these findings indicate that the final-state electron–electron correlation ultimately determines their energy sharing in TPDI.« less

Strong coupling of a single electron in silicon to a microwave photon.

PubMed

Mi, X; Cady, J V; Zajac, D M; Deelman, P W; Petta, J R

2017-01-13

Silicon is vital to the computing industry because of the high quality of its native oxide and well-established doping technologies. Isotopic purification has enabled quantum coherence times on the order of seconds, thereby placing silicon at the forefront of efforts to create a solid-state quantum processor. We demonstrate strong coupling of a single electron in a silicon double quantum dot to the photonic field of a microwave cavity, as shown by the observation of vacuum Rabi splitting. Strong coupling of a quantum dot electron to a cavity photon would allow for long-range qubit coupling and the long-range entanglement of electrons in semiconductor quantum dots. Copyright © 2017, American Association for the Advancement of Science.

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

Realization of a Cascaded Quantum System: Heralded Absorption of a Single Photon Qubit by a Single-Electron Charged Quantum Dot.

PubMed

Delteil, Aymeric; Sun, Zhe; Fält, Stefan; Imamoğlu, Atac

2017-04-28

Photonic losses pose a major limitation for the implementation of a quantum state transfer between nodes of a quantum network. A measurement that heralds a successful transfer without revealing any information about the qubit may alleviate this limitation. Here, we demonstrate the heralded absorption of a single photonic qubit, generated by a single neutral quantum dot, by a single-electron charged quantum dot that is located 5 m away. The transfer of quantum information to the spin degree of freedom takes place upon the emission of a photon; for a properly chosen or prepared quantum dot, the detection of this photon yields no information about the qubit. We show that this process can be combined with local operations optically performed on the destination node by measuring classical correlations between the absorbed photon color and the final state of the electron spin. Our work suggests alternative avenues for the realization of quantum information protocols based on cascaded quantum systems.

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.

Dual crystal x-ray spectrometer at 1.8 keV for high repetition-rate single-photon counting spectroscopy experiments

DOE PAGES

Gamboa, E. J.; Bachmann, B.; Kraus, D.; ...

2016-08-01

The recent development of high-repetition rate x-ray free electron lasers (FEL), makes it possible to perform x-ray scattering and emission spectroscopy measurements from thin foils or gasses heated to high-energy density conditions by integrating over many experimental shots. Since the expected signal may be weaker than the typical CCD readout noise over the region-of-interest, it is critical to the success of this approach to use a detector with high-energy resolution so that single x-ray photons may be isolated. We describe a dual channel x-ray spectrometer developed for the Atomic and Molecular Optics endstation at the Linac Coherent Light Source (LCLS)more » for x-ray spectroscopy near the K-edge of aluminum. The spectrometer is based on a pair of curved PET (002) crystals coupled to a single pnCCD detector which simultaneously measures x-ray scattering and emission in the forward and backward directions. Furthermore, the signals from single x-ray photons are accumulated permitting continuous single-shot acquisition at 120 Hz.« less

Electron-electron correlation in two-photon double ionization of He-like ions

NASA Astrophysics Data System (ADS)

Hu, S. X.

2018-01-01

Electron correlation plays a crucial role in quantum many-body physics ranging from molecular bonding and strong-field-induced multielectron ionization, to superconducting in materials. Understanding the dynamic electron correlation in the photoionization of relatively simple quantum three-body systems, such as He and He-like ions, is an important step toward manipulating complex systems through photoinduced processes. Here we have performed ab initio investigations of two-photon double ionization (TPDI) of He and He-like ions (L i+,B e2 + , and C4 +) exposed to intense attosecond x-ray pulses. Results from such fully correlated quantum calculations show weaker and weaker electron correlation effects in TPDI spectra as the ionic charge increases, which is opposite to the intuition that the absolute increase of correlation in the ground state should lead to more equal energy sharing in photoionization. These findings indicate that the final-state electron-electron correlation ultimately determines the energy sharing of the two ionized electrons in TPDI.

Comparison of linac-based fractionated stereotactic radiotherapy and tomotherapy treatment plans for intra-cranial tumors

NASA Astrophysics Data System (ADS)

Jang, Bo Shim; Suk, Lee; Sam, Ju Cho; Sang, Hoon Lee; Juree, Kim; Kwang, Hwan Cho; Chul, Kee Min; Hyun Do, Huh; Rena, Lee; Dae, Sik Yang; Young, Je Park; Won, Seob Yoon; Chul, Yong Kim; Soo, Il Kwon

2010-11-01

This study compares and analyzes stereotactic radiotherapy using tomotherapy and linac-based fractionated stereotactic radiotherapy in the treatment of intra-cranial tumors, according to some cases. In this study, linac-based fractionated stereotactic radiotherapy and tomotherapy treatment were administered to five patients diagnosed with intra-cranial cancer in which the dose of 18-20 Gy was applied on 3-5 separate occasions. The tumor dosing was decided by evaluating the inhomogeneous index (II) and conformity index (CI). Also, the radiation-sensitive tissue was evaluated using low dose factors V1, V2, V3, V4, V5, and V10, as well as the non-irradiation ratio volume (NIV). The values of the II for each prescription dose in the linac-based non-coplanar radiotherapy plan and tomotherapy treatment plan were (0.125±0.113) and (0.090±0.180), respectively, and the values of the CI were (0.899±0.149) and (0.917±0.114), respectively. The low dose areas, V1, V2, V3, V4, V5, and V10, in radiation-sensitive tissues in the linac-based non-coplanar radiotherapy plan fell into the ranges 0.3%-95.6%, 0.1%-87.6%, 0.1%-78.8%, 38.8%-69.9%, 26.6%-65.2%, and 4.2%-39.7%, respectively, and the tomotherapy treatment plan had ranges of 13.6%-100%, 3.5%-100%, 0.4%-94.9%, 0.2%-82.2%, 0.1%-78.5%, and 0.3%-46.3%, respectively. Regarding the NIV for each organ, it is possible to obtain similar values except for the irradiation area of the brain stem. The percentages of NIV 10%, NIV20%, and NIV30%for the brain stem in each patient were 15%-99.8%, 33.4%-100%, and 39.8%-100%, respectively, in the fractionated stereotactic treatment plan and 44.2%-96.5%, 77.7%-99.8%, and 87.8%-100%, respectively, in the tomotherapy treatment plan. In order to achieve higher-quality treatment of intra-cranial tumors, treatment plans should be tailored according to the isodose target volume, inhomogeneous index, conformity index, position of the tumor upon fractionated stereotactic radiosurgery, and radiation

Intra-operative 3D guidance and edema detection in prostate brachytherapy using a non-isocentric C-arm

PubMed Central

Jain, A.; Deguet, A.; Iordachita, I.; Chintalapani, G.; Vikal, S.; Blevins, J.; Le, Y.; Armour, E.; Burdette, C.; Song, D.; Fichtinger, G.

2015-01-01

Purpose Brachytherapy (radioactive seed insertion) has emerged as one of the most effective treatment options for patients with prostate cancer, with the added benefit of a convenient outpatient procedure. The main limitation in contemporary brachytherapy is faulty seed placement, predominantly due to the presence of intra-operative edema (tissue expansion). Though currently not available, the capability to intra-operatively monitor the seed distribution, can make a significant improvement in cancer control. We present such a system here. Methods Intra-operative measurement of edema in prostate brachytherapy requires localization of inserted radioactive seeds relative to the prostate. Seeds were reconstructed using a typical non-isocentric C-arm, and exported to a commercial brachytherapy treatment planning system. Technical obstacles for 3D reconstruction on a non-isocentric C-arm include pose-dependent C-arm calibration; distortion correction; pose estimation of C-arm images; seed reconstruction; and C-arm to TRUS registration. Results In precision-machined hard phantoms with 40–100 seeds and soft tissue phantoms with 45–87 seeds, we correctly reconstructed the seed implant shape with an average 3D precision of 0.35 mm and 0.24 mm, respectively. In a DoD Phase-1 clinical trial on six patients with 48–82 planned seeds, we achieved intra-operative monitoring of seed distribution and dosimetry, correcting for dose inhomogeneities by inserting an average of over four additional seeds in the six enrolled patients (minimum 1; maximum 9). Additionally, in each patient, the system automatically detected intra-operative seed migration induced due to edema (mean 3.84 mm, STD 2.13 mm, Max 16.19 mm). Conclusions The proposed system is the first of a kind that makes intra-operative detection of edema (and subsequent re-optimization) possible on any typical non-isocentric C-arm, at negligible additional cost to the existing clinical installation. It achieves a

Projection imaging of photon beams by the Cerenkov effect

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

Glaser, Adam K.; Davis, Scott C.; McClatchy, David M.

2013-01-15

Purpose: A novel technique for beam profiling of megavoltage photon beams was investigated for the first time by capturing images of the induced Cerenkov emission in water, as a potential surrogate for the imparted dose in irradiated media. Methods: A high-sensitivity, intensified CCD camera (ICCD) was configured to acquire 2D projection images of Cerenkov emission from a 4 Multiplication-Sign 4 cm{sup 2} 6 MV linear accelerator (LINAC) x-ray photon beam operating at a dose rate of 400 MU/min incident on a water tank with transparent walls. The ICCD acquisition was gated to the LINAC sync pulse to reduce background lightmore » artifacts, and the measurement quality was investigated by evaluating the signal to noise ratio and measurement repeatability as a function of delivered dose. Monte Carlo simulations were used to derive a calibration factor for differences between the optical images and deposited dose arising from the anisotropic angular dependence of Cerenkov emission. Finally, Cerenkov-based beam profiles were compared to a percent depth dose (PDD) and lateral dose profile at a depth of d{sub max} from a reference dose distribution generated from the clinical Varian ECLIPSE treatment planning system (TPS). Results: The signal to noise ratio was found to be 20 at a delivered dose of 66.6 cGy, and proportional to the square root of the delivered dose as expected from Poisson photon counting statistics. A 2.1% mean standard deviation and 5.6% maximum variation in successive measurements were observed, and the Monte Carlo derived calibration factor resulted in Cerenkov emission images which were directly correlated to deposited dose, with some spatial issues. The dose difference between the TPS and PDD predicted by Cerenkov measurements was within 20% in the buildup region with a distance to agreement (DTA) of 1.5-2 mm and {+-}3% at depths beyond d{sub max}. In the lateral profile, the dose difference at the beam penumbra was within {+-}13% with a DTA of 0

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.

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

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

Observation of quantum entanglement between a photon and a single electron spin confined to an InAs quantum dot

NASA Astrophysics Data System (ADS)

Schaibley, John; Burgers, Alex; McCracken, Greg; Duan, Luming; Berman, Paul; Steel, Duncan; Bracker, Allan; Gammon, Daniel; Sham, Lu

2013-03-01

A single electron spin confined to a single InAs quantum dot (QD) can serve as a qubit for quantum information processing. By utilizing the QD's optically excited trion states in the presence of an externally applied magnetic field, the QD spin can be rapidly initialized, manipulated and read out. A key resource for quantum information is the ability to entangle distinct QD spins. One approach relies on intermediate spin-photon entanglement to mediate the entanglement between distant QD spin qubits. We report a demonstration of quantum entanglement between a photon's polarization state and the spin state of a single electron confined to a single QD. Here, the photon is spontaneously emitted from one of the QD's trion states. The emitted photon's polarization along the detection axis is entangled with the resulting spin state of the QD. By performing projective measurements on the photon's polarization state and correlating these measurements with the state of the QD spin in two different bases, we obtain a lower bound on the entanglement fidelity of 0.59 (after background correction). The fidelity bound is limited almost entirely by the timing resolution of our single photon detector. The spin-photon entanglement generation rate is 3 ×103 s-1. Supported by: NSF, MURI, AFOSR, DARPA, ARO.

Digital front end electronics design for the EUSO photon detector

NASA Astrophysics Data System (ADS)

Musico, P.; Pallavicini, M.; Petrolini, A.; Pratolongo, F.

2003-09-01

In this paper we will present the design status of the Digital Front End Electronic system (DFEE), that will be used for the EUSO photon detector. The DFEE is able to count the single photoelectrons coming form the detector for a given time period, store the numbers in a memory buffer and read them out after a trigger, using a serial communication line. Because of space, mass and power consumption constraints, the system will be implemented in an ASIC using a deep submicron technology. The actual design follows the original ideas of the system, though adding several new functionalities. A fully functional prototype chip has been submitted for fabrication in fall 2002. Extensive tests will be performed on it both with bench instrumentations and with the real sensor (the multi anode photomultiplier Hamamatsu R7600-M64), expecting significant results by early Summer 2003. Future work is needed to convert the design into a more robust RAD-hard technology, suitable for space applications and to include in the final die an additional circuit used to optimize the performances at high photons rates: the Analog Front End Electronics (AFEE). Moreover the base board used to house the multi anode photomultipliers is presented: it is the back-bone of the microcell and will be the basic block used to build up the EUSO focal surface.

A diamond detector in the dosimetry of high-energy electron and photon beams.

PubMed

Laub, W U; Kaulich, T W; Nüsslin, F

1999-09-01

A diamond detector type 60003 (PTW Freiburg) was examined for the purpose of dosimetry with 4-20 MeV electron beams and 4-25 MV photon beams. Results were compared with those obtained by using a Markus chamber for electron beams and an ionization chamber for photon beams. Dose distributions were measured in a water phantom with the detector connected to a Unidos electrometer (PTW Freiburg). After a pre-irradiation of about 5 Gy the diamond detector shows a stability in response which is better than that of an ionization chamber. The current of the diamond detector was measured under variation of photon beam dose rate between 0.1 and 7 Gy min(-1). Different FSDs were chosen. Furthermore the pulse repetition frequency and the depth of the detector were changed. The electron beam dose rate was varied between 0.23 and 4.6 Gy min(-1) by changing the pulse-repetition frequency. The response shows no energy dependence within the covered photon-beam energy range. Between 4 MeV and 18 MeV electron beam energy it shows only a small energy dependence of about 2%, as expected from theory. For smaller electron energies the response increases significantly and an influence of the contact material used for the diamond detector can be surmised. A slight sublinearity of the current and dose rate was found. Detector current and dose rate are related by the expression i alpha Ddelta, where i is the detector current, D is the dose rate and delta is a correction factor of approximately 0.963. Depth-dose curves of photon beams, measured with the diamond detector, show a slight overestimation compared with measurements with the ionization chamber. This overestimation is compensated for by the above correction term. The superior spatial resolution of the diamond detector leads to minor deviations between depth-dose curves of electron beams measured with a Markus chamber and a diamond detector.

Experimental studies of 7-cell dual axis asymmetric cavity for energy recovery linac

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

Konoplev, Ivan V.; Metodiev, K.; Lancaster, A. J.

High average current, transportable energy recovery linacs (ERLs) can be very attractive tools for a number of applications including next generation high-luminosity, compact light sources. Conventional ERLs are based on an electron beam circulating through the same set of rf cavity cells. This leads to an accumulation of high-order modes inside the cavity cells, resulting in the development of a beam breakup (BBU) instability, unless the beam current is kept below the BBU start current. This limits the maximum current which can be transported through the ERL and hence the intensity of the photon beam generated. It has recently beenmore » proposed that splitting the accelerating and decelerating stages, tuning them separately and coupling them via a resonance coupler can increase the BBU start current. The paper presents the first experimental rf studies of a dual axis 7-cell asymmetric cavity and confirms the properties predicted by the theoretical model. The field structures of the symmetric and asymmetric modes are measured and good agreement with the numerical predictions is demonstrated. The operating mode field flatness was also measured and discussed. A novel approach based on the coupled mode (Fano-like) model has been developed for the description of the cavity eigenmode spectrum and good agreement between analytical theory, numerical predictions and experimental data is shown. Finally, numerical and experimental results observed are analyzed, discussed and a good agreement between theory and experiment is demonstrated.« less

Experimental studies of 7-cell dual axis asymmetric cavity for energy recovery linac

DOE PAGES

Konoplev, Ivan V.; Metodiev, K.; Lancaster, A. J.; ...

2017-10-10

High average current, transportable energy recovery linacs (ERLs) can be very attractive tools for a number of applications including next generation high-luminosity, compact light sources. Conventional ERLs are based on an electron beam circulating through the same set of rf cavity cells. This leads to an accumulation of high-order modes inside the cavity cells, resulting in the development of a beam breakup (BBU) instability, unless the beam current is kept below the BBU start current. This limits the maximum current which can be transported through the ERL and hence the intensity of the photon beam generated. It has recently beenmore » proposed that splitting the accelerating and decelerating stages, tuning them separately and coupling them via a resonance coupler can increase the BBU start current. The paper presents the first experimental rf studies of a dual axis 7-cell asymmetric cavity and confirms the properties predicted by the theoretical model. The field structures of the symmetric and asymmetric modes are measured and good agreement with the numerical predictions is demonstrated. The operating mode field flatness was also measured and discussed. A novel approach based on the coupled mode (Fano-like) model has been developed for the description of the cavity eigenmode spectrum and good agreement between analytical theory, numerical predictions and experimental data is shown. Finally, numerical and experimental results observed are analyzed, discussed and a good agreement between theory and experiment is demonstrated.« less

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

Femtosecond Electron and Photon Pulses Facility in Thailand

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

Rimjaem, S.; Thongbai, C.; Jinamoon, V.

Femtosecond electron and photon pulses facility has been established as SURIYA project at the Fast Neutron Research Facility (FNRF). Femtosecond electron bunches can be generated from a system consisting of an RF gun with a thermionic cathode, an alpha magnet as an magnetic bunch compressor, and a linear accelerator as a post acceleration section. Femtosecond electron pulses can be used directly or used as a source to produce equally short electromagnetic (EM) radiation pulses via certain kind of radiation production processes. At SURIYA project, we are interested especially in production of radiation in Far-infrared (FIR) regime. At these wavelengths, themore » radiation from femtosecond electron pulses is emitted coherently resulting in high intensity radiation. Overview of the facility, the generation of femtosecond electron bunches, the theoretical background of coherent transition radiation and the recent experimental results will be presented and discussed in this paper.« 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.

The response of a radiophotoluminescent glass dosimeter in megavoltage photon and electron beams

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

Araki, Fujio, E-mail: f-araki@kumamoto-u.ac.jp; Ohno, Takeshi

Purpose: This study investigated the response of a radiophotoluminescent glass dosimeter (RGD) in megavoltage photon and electron beams. Methods: The RGD response was compared with ion chamber measurements for 4–18 MV photons and 6–20 MeV electrons in plastic water phantoms. The response was also calculated via Monte Carlo (MC) simulations with EGSnrc/egs-chamber and Cavity user-codes, respectively. In addition, the response of the RGD cavity was analyzed as a function of field sizes and depths according to Burlin’s general cavity theory. The perturbation correction factor, P{sub Q}, in the RGD cavity was also estimated from MC simulations for photon and electronmore » beams. Results: The calculated and measured RGD energy response at reference conditions with a 10 × 10 cm{sup 2} field and 10 cm depth in photons was lower by up to 2.5% with increasing energy. The variation in RGD response in the field size range of 5 × 5 cm{sup 2} to 20 × 20 cm{sup 2} was 3.9% and 0.7%, at 10 cm depth for 4 and 18 MV, respectively. The depth dependence of the RGD response was constant within 1% for energies above 6 MV but it increased by 2.6% and 1.6% for a large (20 × 20 cm{sup 2}) field at 4 and 6 MV, respectively. The dose contributions from photon interactions (1 − d) in the RGD cavity, according to Burlin’s cavity theory, decreased with increasing energy and decreasing field size. The variation in (1 − d) between field sizes became larger with increasing depth for the lower energies of 4 and 6 MV. P{sub Q} for the RGD cavity was almost constant between 0.96 and 0.97 at 10 MV energies and above. Meanwhile, P{sub Q} depends strongly on field size and depth for 4 and 6 MV photons. In electron beams, the RGD response at a reference depth, d{sub ref}, varied by less than 1% over the electron energy range but was on average 4% lower than the response for 6 MV photons. Conclusions: The RGD response for photon beams depends on both (1 − d) and perturbation effects

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

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.

Optimizing photon-pair generation electronically using a p-i-n diode incorporated in a silicon microring resonator

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

Savanier, Marc, E-mail: msavanier@eng.ucsd.edu; Kumar, Ranjeet; Mookherjea, Shayan, E-mail: smookherjea@eng.ucsd.edu

Silicon photonic microchips may be useful for compact, inexpensive, room-temperature optically pumped photon-pair sources, which unlike conventional photon-pair generators based on crystals or optical fibers, can be manufactured using CMOS-compatible processes on silicon wafers. It has been shown that photon pairs can be created in simple structures such as microring resonators at a rate of a few hundred kilohertz using less than a milliwatt of optical pump power, based on the process of spontaneous four-wave mixing. To create a practical photon-pair source, however, also requires some way of monitoring the device and aligning the pump wavelength when the temperature varies,more » since silicon resonators are highly sensitive to temperature. In fact, monitoring photodiodes are standard components in classical laser diodes, but the incorporation of germanium or InGaAs photodiodes would raise the cost and fabrication complexity. Here, we present a simple and effective all-electronic technique for finding the optimum operating point for the microring used to generate photon pairs, based on measuring the reverse-biased current in a silicon p-i-n junction diode fabricated across the waveguide that constitutes the silicon microring. We show that by monitoring the current, and using it to tune the pump laser wavelength, the photon-pair generation properties of the microring can be preserved over a temperature range of more than 30 °C.« less

Effects of correlations between particle longitudinal positions and transverse plane on bunch length measurement: a case study on GBS electron LINAC at ELI-NP

NASA Astrophysics Data System (ADS)

Sabato, L.; Arpaia, P.; Cianchi, A.; Liccardo, A.; Mostacci, A.; Palumbo, L.; Variola, A.

2018-02-01

In high-brightness LINear ACcelerators (LINACs), electron bunch length can be measured indirectly by a radio frequency deflector (RFD). In this paper, the accuracy loss arising from non-negligible correlations between particle longitudinal positions and the transverse plane (in particular the vertical one) at RFD entrance is analytically assessed. Theoretical predictions are compared with simulation results, obtained by means of ELEctron Generation ANd Tracking (ELEGANT) code, in the case study of the gamma beam system (GBS) at the extreme light infrastructure—nuclear physics (ELI-NP). In particular, the relative error affecting the bunch length measurement, for bunches characterized by both energy chirp and fixed correlation coefficients between longitudinal particle positions and the vertical plane, is reported. Moreover, the relative error versus the correlation coefficients is shown for fixed RFD phase 0 rad and π rad. The relationship between relative error and correlations factors can help the decision of using the bunch length measurement technique with one or two vertical spot size measurements in order to cancel the correlations contribution. In the case of the GBS electron LINAC, the misalignment of one of the quadrupoles before the RFD between  -2 mm and 2 mm leads to a relative error less than 5%. The misalignment of the first C-band accelerating section between  -2 mm and 2 mm could lead to a relative error up to 10%.

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.

Electron- and photon-stimulated desorption of atomic hydrogen from radiation-modified alkali halide surfaces

NASA Astrophysics Data System (ADS)

Hudson, L. T.; Tolk, N. H.; Bao, C.; Nordlander, P.; Russell, D. P.; Xu, J.

2000-10-01

The desorption yields of excited hydrogen atoms from the surfaces of KCl, KBr, NaCl, NaF, and LiF have been measured as a function of incident photon and electron energy and flux, time of irradiation, dosing pressure of H2 and sample temperature. As these surfaces are exposed to H2 gas during electron or photon bombardment, the fluorescence from excited hydrogen atoms ejected from the surface is monitored. The desorption yields are found to be contingent upon surface damage induced by the incident particle radiation, leading to dissociative adsorption at surface sites containing an excess of alkali metal. A desorption mechanism is presented in which incident electrons or photons induce a valence excitation to a neutral, antibonding state of the surface alkali hydride molecule complex, leading to the desorption of hydrogen atoms possessing several eV of kinetic energy.

Backscatter dose effects for high atomic number materials being irradiated in the presence of a magnetic field: A Monte Carlo study for the MRI linac

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

Ahmad, Syed Bilal

Purpose: To quantify and explain the backscatter dose effects for clinically relevant high atomic number materials being irradiated in the presence of a 1.5 T transverse magnetic field. Methods: Interface effects were investigated using Monte Carlo simulation techniques. We used GPUMCD (v5.1) and GEANT4 (v10.1) for this purpose. GPUMCD is a commercial software written for the Elekta AB, MRI linac. Dose was scored using GPUMCD in cubic voxels of side 1 and 0.5 mm, in two different virtual phantoms of dimensions 20 × 20 × 20 cm and 5 × 5 × 13.3 cm, respectively. A photon beam was generatedmore » from a point 143.5 cm away from the isocenter with energy distribution sampled from a histogram representing the true Elekta, MRI linac photon spectrum. A slab of variable thickness and position containing either bone, aluminum, titanium, stainless steel, or one of the two different dental filling materials was inserted as an inhomogeneity in the 20 × 20 × 20 cm phantom. The 5 × 5 × 13.3 cm phantom was used as a clinical test case in order to explain the dose perturbation effects for a head and neck cancer patient. The back scatter dose factor (BSDF) was defined as the ratio of the doses at a given depth with and without the presence of the inhomogeneity. Backscattered electron fluence was calculated at the inhomogeneity interface using GEANT4. A 1.5 T magnetic field was applied perpendicular to the direction of the beam in both phantoms, identical to the geometry in the Elekta MRI linac. Results: With the application of a 1.5 T magnetic field, all the BSDF’s were reduced by 12%–47%, compared to the no magnetic field case. The corresponding backscattered electron fluence at the interface was also reduced by 45%–64%. The reduction in the BSDF at the interface, due to the application of the magnetic field, is manifested in a different manner for each material. In the case of bone, the dose drops at the interface contrary to the expected increase when no magnetic

A laser-Compton scattering prototype experiment at 100 MeV linac of Shanghai Institute of Applied Physics.

PubMed

Luo, W; Xu, W; Pan, Q Y; Cai, X Z; Chen, J G; Chen, Y Z; Fan, G T; Fan, G W; Guo, W; Li, Y J; Liu, W H; Lin, G Q; Ma, Y G; Shen, W Q; Shi, X C; Xu, B J; Xu, J Q; Xu, Y; Zhang, H O; Yan, Z; Yang, L F; Zhao, M H

2010-01-01

As a prototype of the Shanghai Laser Electron Gamma Source in the Shanghai Synchrotron Radiation Facility, an x-ray source based on laser-Compton scattering (LCS) has been installed at the terminal of the 100 MeV linac of the Shanghai Institute of Applied Physics. LCS x-rays are generated by interactions between Q-switched Nd:yttrium aluminum garnet laser pulses [with wavelength of 1064 nm and pulse width of 21 ns (full width at half maximum)] and electron bunches [with energy of 108 MeV and pulse width of 0.95 ns (rms)] at an angle of 42 degrees between laser and electron beam. In order to measure the energy spectrum of LCS x-rays, a Si(Li) detector along the electron beam line axis is positioned at 9.8 m away from a LCS chamber. After background subtraction, the LCS x-ray spectrum with the peak energy of 29.1+/-4.4|(stat)+/-2.1|(syst) keV and the peak width (rms) of 7.8+/-2.8|(stat)+/-0.4|(syst) keV is observed. Normally the 100 MeV linac operates with the electron macropulse charge of 1.0 nC/pulse, and the electron and laser collision repetition rate of 20 Hz. Therefore, the total LCS x-ray flux of (5.2+/-2.0) x 10(2) Hz can be achieved.

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.

Beam energy spread in FERMI@elettra gun and linac induced by intrabeam scattering

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

Zholents, Alexander A; Zholents, Alexander A; Zolotorev, Max S.

Intrabeam scattering (IBS) of electrons in the pre-cathode area in the electron guns know in the literature as Boersh effect is responsible for a growth of the electron beam energy spread there. Albeit most visible within the electron gun where the electron beam density is large and the energy spread is small, the IBS acts all along the entire electron beam pass through the Linac. In this report we calculate the energy spread induced by IBS in the FERMI@elettra electron gun.

Production and dosimetry of simultaneous therapeutic photons and electrons beam by linear accelerator: A Monte Carlo study

NASA Astrophysics Data System (ADS)

Khledi, Navid; Arbabi, Azim; Sardari, Dariush; Mohammadi, Mohammad; Ameri, Ahmad

2015-02-01

Depending on the location and depth of tumor, the electron or photon beams might be used for treatment. Electron beam have some advantages over photon beam for treatment of shallow tumors to spare the normal tissues beyond of the tumor. In the other hand, the photon beam are used for deep targets treatment. Both of these beams have some limitations, for example the dependency of penumbra with depth, and the lack of lateral equilibrium for small electron beam fields. In first, we simulated the conventional head configuration of Varian 2300 for 16 MeV electron, and the results approved by benchmarking the Percent Depth Dose (PDD) and profile of the simulation and measurement. In the next step, a perforated Lead (Pb) sheet with 1mm thickness placed at the top of the applicator holder tray. This layer producing bremsstrahlung x-ray and a part of the electrons passing through the holes, in result, we have a simultaneous mixed electron and photon beam. For making the irradiation field uniform, a layer of steel placed after the Pb layer. The simulation was performed for 10×10, and 4×4 cm2 field size. This study was showed the advantages of mixing the electron and photon beam by reduction of pure electron's penumbra dependency with the depth, especially for small fields, also decreasing of dramatic changes of PDD curve with irradiation field size.

Isocentric Navigation of Percutaneous Endoscopic Transforaminal Discectomy at the L5/S1 Level in Difficult Puncture Cases: A Technical Note.

PubMed

Fan, Guoxin; Wang, Teng; Hu, Shuo; Guan, Xiaofei; Gu, Xin; He, Shisheng

2017-05-01

Accurate puncture during percutaneous transforaminal endoscopic discectomy at the L5/S1 level in cases with high iliac crest and narrow foramen were difficult, even though the difficulties of foraminoplasty could be overcome by advanced instruments like reamers. The report aimed to describe an isocentric navigation technique with a definite pathway in difficult puncture cases at the L5/S1 level. Technical note. Difficult punctures were defined as over 10 punctures of the needle before obtaining an ideal puncture location by senior surgeons with experience of over 500 percutaneous endoscopic transforaminal discectomy (PETD) cases. A total of 124 punctures were recorded in 11 difficult puncture cases at the L5/S1 level. A definite pathway was created by an isocentric navigation theory, which was based on a surface locator and an arch-guided device. The surface locator was used to rapidly and accurately identify the puncture target with the recognition of the surrounding rods under fluoroscopy. The arch-guided device can ensure that the puncture target always remains at the center of a virtual sphere. We recorded the puncture times, fluoroscopy exposure times, radiation exposure time, operative time, visual analog scale (VAS) score, Japanese Orthopeadic Association (JOA) score, and patient satisfaction. The average puncture times were significantly reduced to 1.27 with the arch-guided device compared with conventional puncture methods (P < 0.05). The average operative time was 90.09 ± 11.00 minutes and the fluoroscopy times were 53.36 ± 5.85. The radiation exposure time was 50.91 ± 5.20 seconds. VAS score of leg and back pain, as well as JOA score, were all significantly improved after surgery (P < 0.05). The excellent and good rate of satisfaction was 90.91%. No major complications, including cerebral fluid leakage, surgical infection, and postoperative nerve root injury, were recorded in this small sample. This was a small-sample study with a short follow-up. The

Single-photon and two-photon excited fluorescence behavior of a novel fluorene-based compound

NASA Astrophysics Data System (ADS)

Ma, Wenbo; Wu, Yiquan; Gu, Donghong; Gan, Fuxi

2005-09-01

A D-π-D type compound, 2,7-bis(4-methoxystyryl)-9,9-bis(2-ethylhexyl)-9H-fluorene (abbreviated as MO-Flu-MO), where electron-donor D is methoxy group andπis fluorene unit, has been synthesized. The molecular structures of the compound were characterized by elemental analyses, EI-MS and FT-IR spectra. UV-Vis spectra in the region 230--1000 nm and single-photon excited fluorescence in tetrahydrofuran (THF) of the compound were measured. It is found that the new compound exhibits strong two-photon excited fluorescence in the region 380--500 nm and moderate two-photon absorption (TPA) value in the femtoseconds regime (TPA cross-section as high as 55×10-50 cm4 s photon-1 with 13fs laser pulses). The results demonstrate that the compound is a promising candidate for two-photon three-dimensional (3D) optical data storage.

Comptonization of thermal photons by relativistic electron beams

NASA Technical Reports Server (NTRS)

Daugherty, Joseph K.; Harding, Alice K.

1989-01-01

This paper presents a numerical calculation of gamma-ray emission produced by Compton scattering of relativistic electron beams on background thermal radiation, which includes spatial dependence of electron energy losses and cyclotron resonance scattering in a strong magnetic field. In the first version, the scattering is described by the fully relativistic Klein-Nishina cross section, but the magnetic field is neglected. In the second version, the scattering is described by the magnetic resonant cross section in the Thomson limit. It is found that when the magnetic field is not included, electron energy losses are important only at higher neutron star surface temperatures (T about 3,000,000 K). In the presence of a strong magnetic field, (10 to the 12th G), resonant scattering greatly increases electron energy losses, making scattering very efficient even at lower surface temperatures. Resulting photon and electron spectra for both cases ae discussed in relation to models for pulsar X-ray and gamma-ray emission.

Nonlinear silicon photonics

NASA Astrophysics Data System (ADS)

Borghi, M.; Castellan, C.; Signorini, S.; Trenti, A.; Pavesi, L.

2017-09-01

Silicon photonics is a technology based on fabricating integrated optical circuits by using the same paradigms as the dominant electronics industry. After twenty years of fervid development, silicon photonics is entering the market with low cost, high performance and mass-manufacturable optical devices. Until now, most silicon photonic devices have been based on linear optical effects, despite the many phenomenologies associated with nonlinear optics in both bulk materials and integrated waveguides. Silicon and silicon-based materials have strong optical nonlinearities which are enhanced in integrated devices by the small cross-section of the high-index contrast silicon waveguides or photonic crystals. Here the photons are made to strongly interact with the medium where they propagate. This is the central argument of nonlinear silicon photonics. It is the aim of this review to describe the state-of-the-art in the field. Starting from the basic nonlinearities in a silicon waveguide or in optical resonator geometries, many phenomena and applications are described—including frequency generation, frequency conversion, frequency-comb generation, supercontinuum generation, soliton formation, temporal imaging and time lensing, Raman lasing, and comb spectroscopy. Emerging quantum photonics applications, such as entangled photon sources, heralded single-photon sources and integrated quantum photonic circuits are also addressed at the end of this review.

A coumarin-based two-photon probe for hydrogen peroxide.

PubMed

Zhang, Kai-Ming; Dou, Wei; Li, Peng-Xuan; Shen, Rong; Ru, Jia-Xi; Liu, Wei; Cui, Yu-Mei; Chen, Chun-Yang; Liu, Wei-Sheng; Bai, De-Cheng

2015-02-15

A new fluorescence probe was developed for hydrogen peroxide (H2O2) detection based on donor-excited photo induced electron transfer (D-PET) mechanism, together with the benzil as a quenching and recognizing moiety. The benzil could convert to benzoic anhydride via a Baeyer-Villiger type reaction in the presence of H2O2, followed by hydrolysis of benzoicanhydride to give benzoic acid, and the fluorophore released. The probe was synthesized by a 6-step procedure starting from 4-(diethylamino)salicylaldehyde. A density functional theory (DFT) calculation was performed to demonstrate that the benzil was a fluorescence quencher. The probe was evaluated in both one-photon and two-photon mode, and it exhibited high selectivity toward H2O2 over other reactive oxygen species and high sensitivity with a detection limit of 0.09 μM. Furthermore, the probe was successfully applied to cell imaging of intracellular H2O2 levels with one-photon microscopy and two-photon microscopy. The superior properties of the probe made it of great potential use in more chemical and biological researches. Copyright © 2014 Elsevier B.V. All rights reserved.

The MPGD-based photon detectors for the upgrade of COMPASS RICH-1

NASA Astrophysics Data System (ADS)

Alexeev, M.; Azevedo, C. D. R.; Birsa, R.; Bradamante, F.; Bressan, A.; Büchele, M.; Chiosso, M.; Ciliberti, P.; Dalla Torre, S.; Dasgupta, S.; Denisov, O.; Finger, M.; Finger, M.; Fischer, H.; Gobbo, B.; Gregori, M.; Hamar, G.; Herrmann, F.; Levorato, S.; Maggiora, A.; Makke, A.; Martin, A.; Menon, G.; Steiger, K.; Novy, J.; Panzieri, D.; Pereira, F. A. B.; Santos, C. A.; Sbrizzai, G.; Schopferer, S.; Slunecka, M.; Steiger, L.; Sulc, M.; Tessarotto, F.; Veloso, J. F. C. A.

2017-12-01

The RICH-1 Detector of the COMPASS experiment at CERN SPS has undergone an important upgrade for the 2016 physics run. Four new photon detectors, based on Micro Pattern Gaseous Detector technology and covering a total active area larger than 1.2 m2 have replaced the previously used MWPC-based photon detectors. The upgrade answers the challenging efficiency and stability quest for the new phase of the COMPASS spectrometer physics programme. The new detector architecture consists in a hybrid MPGD combination of two Thick Gas Electron Multipliers and a MicroMegas stage. Signals, extracted from the anode pad by capacitive coupling, are read-out by analog F-E based on the APV25 chip. The main aspects of the COMPASS RICH-1 photon detectors upgrade are presented focussing on detector design, engineering aspects, mass production, the quality assessment and assembly challenges of the MPGD components. The status of the detector commissioning is also presented.

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

PREFACE: XXV International Conference on Photonic, Electronic and Atomic Collisions

NASA Astrophysics Data System (ADS)

Becker, Uwe; Moshammer, Robert; Mokler, Paul; Ullrich, Joachim

2007-07-01

The XXVth ICPEAC in Freiburg marked a notable anniversary in collision physics: half a century ago the first conference in the series of International Conferences on the Physics of Electronic and Atomic Collisions (ICPEAC) was held in New York (1958). Since then, the development of electronic and atomic collision physics has seen tremendous progress. Starting during a time, when this field was regarded as somehow out-of-date, certainly not being in the main stream compared to particle and high-energy physics, it has expanded in a rather exceptional and unforeseen way. Over the years the original scope on electronic, atomic and heavy-ion collision physics was extended substantially to include upcoming expanding fields like synchrotron-radiation and strong-field laser-based atomic and molecular physics giving rise to a change of name to 'Photonic', Electronic and Atomic Collisions (ICPEAC) being used for the first time for the ICPEAC in Santa Fee in 2001. Nowadays, the ICPEAC has opened its agenda even more widely to other fields of atomic and molecular physics, such as interactions with clusters, bio-molecules and surfaces, to cold collisions, coherent control, femto- and attosecond physics and, with the Freiburg conference, to the application of free-electron lasers in the vacuum ultraviolet and soft x-ray regime, a field of potentially huge future impact in essentially all areas of science. In this larger context the XXVth ICPEAC in Freiburg with more than 800 participants set new standards. Representatives from all fields of Atomic, Molecular and Photon-based science came together and had very fruitful, inter-disciplinary discussions. This new forum of collision-based AMP physics will serve as a showcase example of future conferences, bridging not only the gap between different fields of collision physics but also, equally important, between different continents and cultures. The next ICPEAC is going to take place in Kalamazoo in North America, the one after that

Biomimetic Photonic Crystals based on Diatom Algae Frustules

NASA Astrophysics Data System (ADS)

Mishler, Jonathan; Alverson, Andrew; Herzog, Joseph

2015-03-01

Diatom algae are unicellular, photosynthetic microorganisms with a unique external shell known as a frustule. Frustules, which are composed of amorphous silica, exhibit a unique periodic nano-patterning, distinguishing diatoms from other types of phytoplankton. Diatoms have been studied for their distinctive optical properties due to their resemblance of photonic crystals. In this regard, diatoms are not only considered for their applications as photonic crystals, but also for their use as biomimetic templates for artificially fabricated photonic crystals. Through the examination and measurement of the physical characteristics of many scanning electron microscope (SEM) images of diatom frustules, a biomimetic photonic crystal derived from diatom frustules can be recreated and modeled with the finite element method. In this approach, the average geometries of the diatom frustules are used to recreate a 2-dimensional photonic crystal, after which the electric field distribution and optical transmission through the photonic crystal are both measured. The optical transmission is then compared to the transmission spectra of a regular hexagonal photonic crystal, revealing the effects of diatom geometry on their optical properties. Finally, the dimensions of the photonic crystal are parametrically swept, allowing for further control over the transmission of light through the photonic crystal.

SU-E-J-70: Evaluation of Multiple Isocentric Intensity Modulated and Volumetric Modulated Arc Therapy Techniques Using Portal Dosimetry

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

Muralidhar, K Raja; Pangam, S; Kolla, J

2015-06-15

Purpose: To develop a method for verification of dose distribution in a patient during treatment using multiple isocentric Intensity modulated and volumetric modulated arc therapy techniques with portal dosimetry. Methods: Varian True Beam accelerator, equipped with an aS1000 megavoltage electronic portal imaging device (EPID) has an integrated image mode for portal dosimetry (PD). The source-to-imager distance was taken at 150 cm to avoid collision to the table. Fourteen fractions were analyzed for this study. During shift in a single plan from one isocenter to another isocenter, EPID also shifted longitudinally for each field by taking the extent of divergence ofmore » beam into the consideration for EPID distance of 150cm. Patients were given treatment everyday with EPID placed in proper position for each field. Several parameters were obtained by comparing the dose distribution between fractions to fraction. The impact of the intra-fraction and inter-fraction of the patient in combination with isocenter shift of the beams were observed. Results: During treatment, measurements were performed by EPID and were evaluated by the gamma method. Analysis was done between fractions for multiple isocenter treatments. The pass rates of the gamma analysis with a criterion of 3% and 3 mm for the 14 fractions were over 97.8% with good consistency. Whereas maximum gamma exceeded the criteria in few fractions (in<1 cc vol). Average gamma was observed in the criteria of 0.5%. Maximum dose difference and average dose differences were less than 0.22 CU and 0.01 CU for maximum tolerance of 1.0 CU and 0.2 CU respectively. Conclusion: EPID with extended distance is ideal method to verify the multiple isocentric dose distribution in patient during treatment, especially cold and hot spots in junction dose. Verification of shifts as well as the dose differences between each fraction due to inter-fraction and intra-fraction of the patient can be derived.« less

Dosimetric characteristics of a new unshielded silicon diode and its application in clinical photon and electron beams.

PubMed

Griessbach, Irmgard; Lapp, Markus; Bohsung, Jörg; Gademann, Günther; Harder, Dietrich

2005-12-01

Shielded p-silicon diodes, frequently applied in general photon-beam dosimetry, show certain imperfections when applied in the small photon fields occurring in stereotactic or intensity modulated radiotherapy (IMRT), in electron beams and in the buildup region of photon beam dose distributions. Using as a study object the shielded p-silicon diode PTW 60008, well known for its reliable performance in general photon dosimetry, we have identified these imperfections as effects of electron scattering at the metallic parts of the shielding. In order to overcome these difficulties a new, unshielded diode PTW 60012 has been designed and manufactured by PTW Freiburg. By comparison with reference detectors, such as thimble and plane-parallel ionization chambers and a diamond detector, we could show the absence of these imperfections. An excellent performance of the new unshielded diode for the special dosimetric tasks in small photon fields, electron beams and build-up regions of photon beams has been observed. The new diode also has an improved angular response. However, due to its over-response to low-energy scattered photons, its recommended range of use does not include output factor measurements in large photon fields, although this effect can be compensated by a thin auxiliary lead shield.

Non-Hermitian photonics based on parity-time symmetry

NASA Astrophysics Data System (ADS)

Feng, Liang; El-Ganainy, Ramy; Ge, Li

2017-12-01

Nearly one century after the birth of quantum mechanics, parity-time symmetry is revolutionizing and extending quantum theories to include a unique family of non-Hermitian Hamiltonians. While conceptually striking, experimental demonstration of parity-time symmetry remains unexplored in quantum electronic systems. The flexibility of photonics allows for creating and superposing non-Hermitian eigenstates with ease using optical gain and loss, which makes it an ideal platform to explore various non-Hermitian quantum symmetry paradigms for novel device functionalities. Such explorations that employ classical photonic platforms not only deepen our understanding of fundamental quantum physics but also facilitate technological breakthroughs for photonic applications. Research into non-Hermitian photonics therefore advances and benefits both fields simultaneously.

Electron- and Photon-stimulated Desorption of Alkali Atoms from Lunar Sample and a Model Mineral Surface

NASA Technical Reports Server (NTRS)

Yakshinskiy, B. V.; Madey, T. E.

2003-01-01

We report recent results on an investigation of source mechanisms for the origin of alkali atoms in the tenuous planetary atmospheres, with focus on non-thermal processes (photon stimulated desorption (PSD), electron stimulated desorption (ESD), and ion sputtering). Whereas alkaline earth oxides (MgO, CaO) are far more abundant in lunar samples than alkali oxides (Na2O, K2O), the atmosphere of the Moon contains easily measurable concentrations of Na and K, while Ca and Mg are undetected there; traces of Ca have recently been seen in the Moon's atmosphere (10-3 of Na). The experiments have included ESD, PSD and ion sputtering of alkali atoms from model mineral surface (amorphous SiO2) and from a lunar basalt sample obtained from NASA. The comparison is made between ESD and PSD efficiency of monovalent alkalis (Na, K) and divalent alkaline earths (Ba, Ca).The ultrahigh vacuum measurement scheme for ESD and PSD of Na atoms includes a highly sensitive alkali metal detector based on surface ionization, and a time-of-flight technique. For PSD measurements, a mercury arc light source (filtered and chopped) is used. We find that bombardment of the alkali covered surfaces by ultraviolet photons or by low energy electrons (E>4 eV) causes desorption of hot alkali atoms. This results are consistent with the model developed to explain our previous measurements of sodium desorption from a silica surface and from water ice: electron- or photon-induced charge transfer from the substrate to the ionic adsorbate causes formation of a neutral alkali atom in a repulsive configuration, from which desorption occurs. The two-electron charge transfer to cause desorption of divalent alkaline eath ions is a less likely process.The data support the suggestion that PSD by UV solar photons is a dominant source process for alkalis in the tenuous lunar atmosphere.

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

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

Strong coupling of a single electron in silicon to a microwave photon

NASA Astrophysics Data System (ADS)

Mi, Xiao; Cady, Jeffrey; Zajac, David; Petta, Jason

We demonstrate a hybrid circuit quantum electrodynamics (cQED) architecture in which a single electron in a Si/SiGe double quantum dot is dipole-coupled to the electric field of microwave photons in a superconducting cavity. Vacuum Rabi splitting is observed in the cavity transmission when the transition energy of the single-electron charge qubit matches that of a cavity photon, demonstrating that our device is in the strong coupling regime. The achievement of strong coupling is largely facilitated by an exceptionally low charge decoherence rate of 5 MHz and paves the way toward a wide range of cQED experiments with quantum dots, such as non-local qubit interactions, strong spin-cavity coupling and single photon generation . Research sponsored by ARO Grant No. W911NF-15-1-0149, the Gordon and Betty Moore Foundation's EPiQS Initiative through Grant GBMF4535, and the NSF (DMR-1409556 and DMR-1420541).

Controlling Photons, Qubits and their Interactions in Superconducting Electronic Circuits

NASA Astrophysics Data System (ADS)

Wallraff, Andreas

2009-03-01

A combination of ideas from atomic physics, quantum optics and solid state physics allows us to investigate the fundamental interaction of matter and light on the level of single quanta in electronic circuits. In an approach known as circuit quantum electrodynamics, we coherently couple individual photons stored in a high quality microwave frequency resonator to a fully controllable superconducting two-level system (qubit) realized in a macroscopic electronic circuit [1]. In particular, we have recently observed the simultaneous interaction of one, two and three photons with a single qubit. In these experiments, we have probed the quantum nonlinearity of the qubit/light interaction governed by the Jaynes-Cummings hamiltonian, clearly demonstrating the quantization of the radiation field in the on-chip cavity. We have also performed quantum optics experiments with no photons at all. In this situation, i.e. in pure vacuum, we have resolved the renormalization of the qubit transition frequency - known as the Lamb shift - due to its non-resonant interaction with the cavity vacuum fluctuations [3].[4pt] [1] A. Wallraff et al., Nature (London) 431, 162 (2004)[0pt] [2] J. Fink et al., Nature (London) 454, 315 (2008)[0pt] [3] A. Fragner et al., Science 322, 1357 (2008)

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

Electrons and photons at High Level Trigger in CMS for Run II

NASA Astrophysics Data System (ADS)

Anuar, Afiq A.

2015-12-01

The CMS experiment has been designed with a 2-level trigger system. The first level is implemented using custom-designed electronics. The second level is the so-called High Level Trigger (HLT), a streamlined version of the CMS offline reconstruction software running on a computer farm. For Run II of the Large Hadron Collider, the increase in center-of-mass energy and luminosity will raise the event rate to a level challenging for the HLT algorithms. New approaches have been studied to keep the HLT output rate manageable while maintaining thresholds low enough to cover physics analyses. The strategy mainly relies on porting online the ingredients that have been successfully applied in the offline reconstruction, thus allowing to move HLT selection closer to offline cuts. Improvements in HLT electron and photon definitions will be presented, focusing in particular on: updated clustering algorithm and the energy calibration procedure, new Particle-Flow-based isolation approach and pileup mitigation techniques, and the electron-dedicated track fitting algorithm based on Gaussian Sum Filter.

Black phosphorus-based one-dimensional photonic crystals and microcavities.

PubMed

Kriegel, Ilka; Toffanin, Stefano; Scotognella, Francesco

2016-11-10

The latest achievements in the fabrication of thin layers of black phosphorus (BP), toward the technological breakthrough of a phosphorene atomically thin layer, are paving the way for their use in electronics, optics, and optoelectronics. In this work, we have simulated the optical properties of one-dimensional photonic structures, i.e., photonic crystals and microcavities, in which few-layer BP is one of the components. The insertion of the 5-nm black phosphorous layers leads to a photonic band gap in the photonic crystals and a cavity mode in the microcavity that is interesting for light manipulation and emission enhancement.

TH-C-BRC-03: Emerging Linac Based SRS/SBRT Technologies with Modulated Arc Delivery

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

Ren, L.

2016-06-15

The delivery techniques for SRS/SBRT have been under rapid developments in recent years, which pose new challenges to medical physicists ranging from planning and quality assurance to imaging and motion management. This educational course will provide a general overview of the latest delivery techniques in SRS/SBRT, and discuss the clinical processes to address the challenges of each technique with special emphasis on dedicated gamma-ray based device, robotic x-band linac-based system and conventional C-arm s-band linac-based SRS systems. (1). Gamma-ray based SRS/SRT: This is the gold standard of intracranial SRS. With the advent of precision imaging guidance and frameless patient positioningmore » capabilities, novel stereoscopic CBCT and automatic dose adaption solution are introduced to the Gamma-ray based SRS for the first time. The first North American system has been approved by the US regulatory for patient treatments in the spring of 2016. (2). Robotic SRS/SBRT system: A number of technological milestones have been developed in the past few years, including variable aperture collimator, sequential optimization technique, and the time reduction technique. Recently, a new robotic model allows the option of a multi-leaf collimator. These technological advances have reduced the treatment time and improved dose conformity significantly and could potentially expand the application of radiosurgery for the treatment of targets not previously suitable for robotic SRS/SBRT or fractionated stereotactic radiotherapy. These technological advances have created new demanding mandates on hardware and patient quality assurance (QA) tasks, as well as the need for updating/educating the physicists in the community on these requirements. (3). Conventional Linac based treatments: Modulated arc therapy (MAT) has gained wide popularities in Linac-based treatments in recent years due to its high delivery efficiency and excellent dose conformities. Recently, MAT has been

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

ABOUT the phenomenon produced by the successive jumps of the peripheric electrons, at the absorbtion of the intense photon beam by the metal

NASA Astrophysics Data System (ADS)

Isarie, Claudiu I.; Oprean, Constantin; Marginean, Ion; Nemes, Toderita; Isarie, Ilie V.; Bokor, Corina; Itu, Sorin

2011-03-01

When a photon beam is in impact with a metal, the peripheric electrons which belong to the bombarded material are made jumps, and in the same time, new photons are absorbed by electrons which had not time to come back to the fundamental levels. At a high level concentration of the radiant energy, a peripheral electron, could sequentially absorb more photons and could realize energetic jumps in succesive phase, equivalent with some photons of high energy which have wave-lenght smaller than the incidental photons. After some succesive photon absorbtion of the same electron, in the interval in which it is not activated by new photons, the electron comes back to the fundamental level and delivers the accumulated energy, in photons of higher energy, which have a lower energy than the incident beam. Comming back to the fundamental level, the electrons disturb the electronic cloud of the atom or ion they belong. After a huge number of such phenomenon the electronic cloud which is succesivelly disturbed, produces an oscillation which risez the temperature of the nucleus. The authors have studied the conditions which generated the rise of temperature and multiple radiations at the place where the photons bombard the metal.

Light flavon signals at electron-photon colliders

NASA Astrophysics Data System (ADS)

Muramatsu, Yu; Nomura, Takaaki; Shimizu, Yusuke; Yokoya, Hiroshi

2018-01-01

Flavor symmetries are useful to realize fermion flavor structures in the standard model (SM). In particular, the discrete A4 symmetry is used to realize lepton flavor structures, and some scalars—called flavons—are introduced to break this symmetry. In many models, flavons are assumed to be much heavier than the electroweak scale. However, our previous work showed that a flavon mass around 100 GeV is allowed by experimental constraints in the A4 symmetric model with a residual Z3 symmetry. In this paper, we discuss collider searches for such a light flavon φT. We find that electron-photon collisions at the International Linear Collider have advantages for searching for these signals. In electron-photon collisions, flavons are produced as e-γ →l-φT and decay into two charged leptons. Then, we analyze signals of the flavor-conserving final state τ+τ-e- and the flavor-violating final states τ+μ-μ- and μ+τ-τ- by carrying out numerical simulations. For the former final state, SM background can be strongly suppressed by imposing cuts on the invariant masses of final-state leptons. For the latter final states, SM background is extremely small, because in the SM there are no such flavor-violating final states. We then find that sufficient discovery significance can be obtained, even if flavons are heavier than the lower limits from flavor physics.

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

Dual-energy imaging using a photon counting detector with electronic spectrum-splitting

NASA Astrophysics Data System (ADS)

Bornefalk, Hans; Lundqvist, Mats

2006-03-01

This paper presents a dual-energy imaging technique optimized for contrast-enhanced mammography using a photon counting detector. Each photon pulse is processed separately in the detector and the addition of an electronic threshold near the middle of the energy range of the x-ray spectrum allows discrimination of high and low energy photons. This effectively makes the detector energy sensitive, and allows the acquisition of high- and low-energy images simultaneously. These high- and low-energy images can be combined to dual-energy images where the anatomical clutter has been suppressed. By setting the electronic threshold close to 33.2 keV (the k-edge of iodine) the system is optimized for dual-energy contrast-enhanced imaging of breast tumors. Compared to other approaches, this method not only eliminates the need for separate exposures that might lead to motion artifacts, it also eliminates the otherwise deteriorating overlap between high- and low-energy spectra. We present phantom dual-energy images acquired on a prototype system to illustrate that the technique is already operational, albeit in its infancy. We also present a theoretical estimation of the potential gain in tumor signal-difference-to-noise ratio when using this electronic spectrum-splitting method as opposed to acquiring the high- and low-energy images separately with double exposures with separate x-ray spectra. Assuming ideal energy sensitive photon counting detectors, we arrive at the conclusion that the signal-difference-to-noise ratio could be increased by 145% at constant dose. We also illustrate our results on synthetic images.

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.

On thermalization of electron-positron-photon plasma

NASA Astrophysics Data System (ADS)

Siutsou, I. A.; Aksenov, A. G.; Vereshchagin, G. V.

2015-12-01

Recently a progress has been made in understanding thermalization mechanism of relativistic plasma starting from a non-equilibrium state. Relativistic Boltzmann equations were solved numerically for homogeneous isotropic plasma with collision integrals for two- and three-particle interactions calculated from the first principles by means of QED matrix elements. All particles were assumed to fulfill Boltzmann statistics. In this work we follow plasma thermalization by accounting for Bose enhancement and Pauli blocking in particle interactions. Our results show that particle in equilibrium reach Bose-Einstein distribution for photons, and Fermi-Dirac one for electrons, respectively.

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

Benites, J.; Alumno del Posgrado en CBAP, Universidad Autonoma de Nayarit, Carretera Tepic-Compostela km9. C.P. 63780. Xalisco-Nayarit-Mexico; Vega-Carrillo, H. R.

Neutron spectra and the ambient dose equivalent were calculated inside the bunker of a 15 MV Varian linac model CLINAC iX. Calculations were carried out using Monte Carlo methods. Neutron spectra in the vicinity of isocentre show the presence of evaporation and knock-on neutrons produced by the source term, while epithermal and thermal neutron remain constant regardless the distance respect to isocentre, due to room return. Along the maze neutron spectra becomes softer as the detector moves along the maze. The ambient dose equivalent is decreased but do not follow the 1/r{sup 2} rule due to changes in the neutronmore » spectra.« less

TU-H-BRA-07: Design, Construction, and Installation of An Experimental Beam Line for the Development of MRI-Linac Compatible Electron Accelerator

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

Whelan, B; Keall, P; Holloway, L

Purpose: MRI guided radiation therapy (MRIgRT) is a rapidly growing field; however, Linac operation in MRI fringe fields represents an ongoing challenge. We have previously shown in-silico that Linacs could be redesigned to function in the in-line orientation with no magnetic shielding by adopting an RF-gun configuration. Other authors have also published insilico studies of Linac operation in magnetic fields; however to date no experimental validation data is published. This work details the design, construction, and installation of an experimental beam line to validate our in-silico results. Methods: An RF-gun comprising 1.5 accelerating cells and capable of generating electron energiesmore » up to 3.2MeV is used. The experimental apparatus was designed to monitor both beam current (toroid current monitor), spot size (two phosphor screens with viewports), and generate peak magnetic fields of at least 1000G (three variable current electromagnetic coils). Thermal FEM simulations were developed to ensure coil temperature remained within 100degC. Other design considerations included beam disposal, vacuum maintenance, radiation shielding, earthquake safety, and machine protection interlocks. Results: The beam line has been designed, built, and installed in a radiation shielded bunker. Water cooling, power supplies, thermo-couples, cameras, and radiation shielding have been successfully connected and tested. Interlock testing, vacuum processing, and RF processing have been successfully completed. The first beam on is expected within weeks. The coil heating simulations show that with care, peak fields of up to 1200G (320G at cathode) can be produced using 40A current, which is well within the fields expected for MRI-Linac systems. The maximum coil temperature at this current was 84degC after 6 minutes. Conclusion: An experimental beam line has been constructed and installed at SLAC in order to experimentally characterise RF gun performance in in-line magnetic fields

Out-of-field neutron and leakage photon exposures and the associated risk of second cancers in high-energy photon radiotherapy: current status.

PubMed

Takam, R; Bezak, E; Marcu, L G; Yeoh, E

2011-10-01

Determination and understanding of out-of-field neutron and photon doses in accelerator-based radiotherapy is an important issue since linear accelerators operating at high energies (>10 MV) produce secondary radiations that irradiate parts of the patient's anatomy distal to the target region, potentially resulting in detrimental health effects. This paper provides a compilation of data (technical and clinical) reported in the literature on the measurement and Monte Carlo simulations of peripheral neutron and photon doses produced from high-energy medical linear accelerators and the reported risk and/or incidence of second primary cancer of tissues distal to the target volume. Information in the tables facilitates easier identification of (1) the various methods and measurement techniques used to determine the out-of-field neutron and photon radiations, (2) reported linac-dependent out-of-field doses, and (3) the risk/incidence of second cancers after radiotherapy due to classic and modern treatment methods. Regardless of the measurement technique and type of accelerator, the neutron dose equivalent per unit photon dose ranges from as low as 0.1 mSv/Gy to as high as 20.4 mSv/Gy. This radiation dose potentially contributes to the induction of second primary cancer in normal tissues outside the treated area.

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.

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.

Average stopping powers for electron and photon sources for radiobiological modeling and microdosimetric applications

NASA Astrophysics Data System (ADS)

Vassiliev, Oleg N.; Kry, Stephen F.; Grosshans, David R.; Mohan, Radhe

2018-03-01

This study concerns calculation of the average electronic stopping power for photon and electron sources. It addresses two problems that have not yet been fully resolved. The first is defining the electron spectrum used for averaging in a way that is most suitable for radiobiological modeling. We define it as the spectrum of electrons entering the sensitive to radiation volume (SV) within the cell nucleus, at the moment they enter the SV. For this spectrum we derive a formula that combines linearly the fluence spectrum and the source spectrum. The latter is the distribution of initial energies of electrons produced by a source. Previous studies used either the fluence or source spectra, but not both, thereby neglecting a part of the complete spectrum. Our derived formula reduces to these two prior methods in the case of high and low energy sources, respectively. The second problem is extending electron spectra to low energies. Previous studies used an energy cut-off on the order of 1 keV. However, as we show, even for high energy sources, such as 60Co, electrons with energies below 1 keV contribute about 30% to the dose. In this study all the spectra were calculated with Geant4-DNA code and a cut-off energy of only 11 eV. We present formulas for calculating frequency- and dose-average stopping powers, numerical results for several important electron and photon sources, and tables with all the data needed to use our formulas for arbitrary electron and photon sources producing electrons with initial energies up to  ∼1 MeV.

Circular dichroism measurements at an x-ray free-electron laser with polarization control

NASA Astrophysics Data System (ADS)

Hartmann, G.; Lindahl, A. O.; Knie, A.; Hartmann, N.; Lutman, A. A.; MacArthur, J. P.; Shevchuk, I.; Buck, J.; Galler, A.; Glownia, J. M.; Helml, W.; Huang, Z.; Kabachnik, N. M.; Kazansky, A. K.; Liu, J.; Marinelli, A.; Mazza, T.; Nuhn, H.-D.; Walter, P.; Viefhaus, J.; Meyer, M.; Moeller, S.; Coffee, R. N.; Ilchen, M.

2016-08-01

A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O2 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. An also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.

High-resolution broadband terahertz spectroscopy via electronic heterodyne detection of photonically generated terahertz frequency comb.

PubMed

Pavelyev, D G; Skryl, A S; Bakunov, M I

2014-10-01

We report an alternative approach to the terahertz frequency-comb spectroscopy (TFCS) based on nonlinear mixing of a photonically generated terahertz pulse train with a continuous wave signal from an electronic synthesizer. A superlattice is used as a nonlinear mixer. Unlike the standard TFCS technique, this approach does not require a complex double-laser system but retains the advantages of TFCS-high spectral resolution and wide bandwidth.

Current correlations for the transport of interacting electrons through parallel quantum dots in a photon cavity

NASA Astrophysics Data System (ADS)

Gudmundsson, Vidar; Abdullah, Nzar Rauf; Sitek, Anna; Goan, Hsi-Sheng; Tang, Chi-Shung; Manolescu, Andrei

2018-06-01

We calculate the current correlations for the steady-state electron transport through multi-level parallel quantum dots embedded in a short quantum wire, that is placed in a non-perfect photon cavity. We account for the electron-electron Coulomb interaction, and the para- and diamagnetic electron-photon interactions with a stepwise scheme of configuration interactions and truncation of the many-body Fock spaces. In the spectral density of the temporal current-current correlations we identify all the transitions, radiative and non-radiative, active in the system in order to maintain the steady state. We observe strong signs of two types of Rabi oscillations.

Neural plasticity explored by correlative two-photon and electron/SPIM microscopy

NASA Astrophysics Data System (ADS)

Allegra Mascaro, A. L.; Silvestri, L.; Costantini, I.; Sacconi, L.; Maco, B.; Knott, G. W.; Pavone, F. S.

2013-06-01

Plasticity of the central nervous system is a complex process which involves the remodeling of neuronal processes and synaptic contacts. However, a single imaging technique can reveal only a small part of this complex machinery. To obtain a more complete view, complementary approaches should be combined. Two-photon fluorescence microscopy, combined with multi-photon laser nanosurgery, allow following the real-time dynamics of single neuronal processes in the cerebral cortex of living mice. The structural rearrangement elicited by this highly confined paradigm of injury can be imaged in vivo first, and then the same neuron could be retrieved ex-vivo and characterized in terms of ultrastructural features of the damaged neuronal branch by means of electron microscopy. Afterwards, we describe a method to integrate data from in vivo two-photon fluorescence imaging and ex vivo light sheet microscopy, based on the use of major blood vessels as reference chart. We show how the apical dendritic arbor of a single cortical pyramidal neuron imaged in living mice can be found in the large-scale brain reconstruction obtained with light sheet microscopy. Starting from its apical portion, the whole pyramidal neuron can then be segmented and located in the correct cortical layer. With the correlative approach presented here, researchers will be able to place in a three-dimensional anatomic context the neurons whose dynamics have been observed with high detail in vivo.

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.

Data reading with the aid of one-photon and two-photon luminescence in three-dimensional optical memory devices based on photochromic materials

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

Akimov, Denis A; Zheltikov, Aleksei M; Koroteev, Nikolai I

1998-06-30

The problem of nondestructive reading of the data stored in the interior of a photochromic sample was analysed. A comparison was made of the feasibility of reading based on one-photon and two-photon luminescence. A model was proposed for the processes of reading the data stored in photochromic molecules with the aid of one-photon and two-photon luminescence. In addition to photochromic transitions, account was taken of the transfer of populations between optically coupled transitions in molecules under the action of the exciting radiation. This model provided a satisfactory description of the kinetics of decay of the coloured form of bulk samplesmore » of spiropyran and made it possible to determine experimentally the quantum yield of the reverse photoreaction as well as the two-photon absorption cross section of the coloured form. Measurements were made of the characteristic erasure times of the data stored in a photochromic medium under one-photon and two-photon luminescence reading conditions. It was found that the use of two-photon luminescence made it possible to enhance considerably the contrast and localisation of the optical data reading scheme in three-dimensional optical memory devices. The experimental results were used to estimate the two-photon absorption cross section of the coloured form of a sample of indoline spiropyran in a polymethyl methacrylate matrix. (laser applications and other topics in quantum electronics)« less

PHOTON2: A web-based professional development model for photonics technology education

NASA Astrophysics Data System (ADS)

Massa, Nicholas M.; Washburn, Barbara A.; Kehrhahn, Marijke; Donnelly, Judith F.; Hanes, Fenna D.

2004-10-01

In this paper, we present a web-based teacher professional development model for photonics technology education funded by the National Science Foundation Advanced Technology Education (ATE) program. In response to the rapidly growing demand for skilled photonics technicians, the PHOTON2 project will increase the number of high school teachers and community college faculty across the US proficient in teaching photonics technology at their own institutions. The project will also focus on building the capacity of educators to engage in lifelong learning through web-based professional development. Unlike the traditional professional development model whereby educators receive training through intensive short-term workshops, the PHOTON2 project team has developed a pedagogical framework designed specifically for adult learners in which technical content, curriculum development, and learner self-regulatory development are integrated into an active, collaborative, and sustained online learning environment. In Spring 2004, two cohorts of science and technology educators, career/guidance counselors, and industry mentors from eleven states including California, Pennsylvania, Texas, Arizona, Hawaii, and the six New England states commenced participation in the three-year project. Qualitative and quantitative research, focused on individual and environmental factors related to web-based learning, will examine the viability of web-based teacher/faculty professional development in engineering technology education.

Relationship between resist outgassing and EUV witness sample contamination in NXE outgas qualification using electrons and EUV photons

NASA Astrophysics Data System (ADS)

Pollentier, I.; Tirumala Venkata, A.; Gronheid, R.

2014-04-01

EUV photoresists are considered as a potential source of optics contamination, since they introduce irradiation-induced outgassing in the EUV vacuum environment. Therefore, before these resists can be used on e.g. ASML NXE:3100 or NXE:3300, they need to be tested in dedicated equipment according to a well-defined procedure, which is based on exposing a witness sample (WS) in the vicinity of a simultaneously exposed resist as it outgasses. Different system infrastructures are used at multiple sites (e.g. NIST, CNSE, Sematech, EIDEC, and imec) and were calibrated to each other by a detailed test plan. Despite this detailed tool qualifications, a first round robin comparison of identical materials showed inconsistent outgas test results, and required further investigation by a second round robin. Since the resist exposure mode is different at the various locations (some sites are using EUV photons while others use E-gun electrons), this difference has always a point of concern for variability of test results. In this work we compare the outgas test results from EUV photon and electron exposure using the resist materials of the second round robin. Since the imec outgas tester allows both exposure methods on the resist, a within-system comparison is possible and showed limited variation between photon and electron exposure mode. Therefore the system-to-system variability amongst the different outgas test sites is expected to be related to other parameters than the electron/photon exposure mode. Initial work showed that the variability might be related to temperature, E-gun emission excursion, and/or residual outgassing scaled by different wafer areas at the different sites.

Demonstration of Quantum Entanglement between a Single Electron Spin Confined to an InAs Quantum Dot and a Photon

NASA Astrophysics Data System (ADS)

Schaibley, J. R.; Burgers, A. P.; McCracken, G. A.; Duan, L.-M.; Berman, P. R.; Steel, D. G.; Bracker, A. S.; Gammon, D.; Sham, L. J.

2013-04-01

The electron spin state of a singly charged semiconductor quantum dot has been shown to form a suitable single qubit for quantum computing architectures with fast gate times. A key challenge in realizing a useful quantum dot quantum computing architecture lies in demonstrating the ability to scale the system to many qubits. In this Letter, we report an all optical experimental demonstration of quantum entanglement between a single electron spin confined to a single charged semiconductor quantum dot and the polarization state of a photon spontaneously emitted from the quantum dot’s excited state. We obtain a lower bound on the fidelity of entanglement of 0.59±0.04, which is 84% of the maximum achievable given the timing resolution of available single photon detectors. In future applications, such as measurement-based spin-spin entanglement which does not require sub-nanosecond timing resolution, we estimate that this system would enable near ideal performance. The inferred (usable) entanglement generation rate is 3×103s-1. This spin-photon entanglement is the first step to a scalable quantum dot quantum computing architecture relying on photon (flying) qubits to mediate entanglement between distant nodes of a quantum dot network.

Demonstration of quantum entanglement between a single electron spin confined to an InAs quantum dot and a photon.

PubMed

Schaibley, J R; Burgers, A P; McCracken, G A; Duan, L-M; Berman, P R; Steel, D G; Bracker, A S; Gammon, D; Sham, L J

2013-04-19

The electron spin state of a singly charged semiconductor quantum dot has been shown to form a suitable single qubit for quantum computing architectures with fast gate times. A key challenge in realizing a useful quantum dot quantum computing architecture lies in demonstrating the ability to scale the system to many qubits. In this Letter, we report an all optical experimental demonstration of quantum entanglement between a single electron spin confined to a single charged semiconductor quantum dot and the polarization state of a photon spontaneously emitted from the quantum dot's excited state. We obtain a lower bound on the fidelity of entanglement of 0.59±0.04, which is 84% of the maximum achievable given the timing resolution of available single photon detectors. In future applications, such as measurement-based spin-spin entanglement which does not require sub-nanosecond timing resolution, we estimate that this system would enable near ideal performance. The inferred (usable) entanglement generation rate is 3×10(3) s(-1). This spin-photon entanglement is the first step to a scalable quantum dot quantum computing architecture relying on photon (flying) qubits to mediate entanglement between distant nodes of a quantum dot network.

Design of thermal neutron beam based on an electron linear accelerator for BNCT.

PubMed

Zolfaghari, Mona; Sedaghatizadeh, Mahmood

2016-12-01

An electron linear accelerator (Linac) can be used for boron neutron capture therapy (BNCT) by producing thermal neutron flux. In this study, we used a Varian 2300 C/D Linac and MCNPX.2.6.0 code to simulate an electron-photoneutron source for use in BNCT. In order to decelerate the produced fast neutrons from the photoneutron source, which optimize the thermal neutron flux, a beam-shaping assembly (BSA) was simulated. After simulations, a thermal neutron flux with sharp peak at the beam exit was obtained in the order of 3.09×10 8 n/cm 2 s and 6.19×10 8 n/cm 2 s for uranium and enriched uranium (10%) as electron-photoneutron sources respectively. Also, in-phantom dose analysis indicates that the simulated thermal neutron beam can be used for treatment of shallow skin melanoma in time of about 85.4 and 43.6min for uranium and enriched uranium (10%) respectively. Copyright © 2016. Published by Elsevier Ltd.

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.

Entrance and exit dose measurements with semiconductors and thermoluminescent dosemeters: a comparison of methods and in vivo results.

PubMed

Loncol, T; Greffe, J L; Vynckier, S; Scalliet, P

1996-11-01

In order to compare diodes and TLD for in vivo dosimetry, systematic measurements of entrance and exit doses were performed with semiconductor detectors and thermoluminescent dosemeters for brain and head and neck patients treated isocentrically with external photon beam therapy. Scanditronix EDP-20 diodes and 7LiF thermoluminescent chips, irradiated in a 8 MV linac, were studied with similar build-up cap geometries and materials in order to assure an equivalent electronic equilibrium. Identical calibration methodology was applied to both detectors for the dose determination in clinical conditions. For the entrance dose evaluation over 249 field measurements, the ratio of the measured dose to the expected dose, calculated from tabulated tissue maximum ratios, was equal to 1.010 +/- 0.028 (1 s.d.) from diodes and 1.013 +/- 0.041 from thermoluminescent crystals. For the exit dose measurements, these ratios were equal to 0.998 +/- 0.049 and 1.016 +/- 0.070 for diodes and TLDs, respectively, after application of a simple inhomogeneity correction to the calculation of the expected exit dose. Thermoluminescence and semiconductors led to identical results for entrance and exit dose evaluation but TLDs were characterised by a lower reproducibility inherent to the TL process itself and to the acquisition and annihilation procedures.

Electron-impact excitation of He: Dependence of electron-photon coherence parameters on the principal quantum number

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

Hammond, P.; Khakoo, M.A.; McConkey, J.W.

1987-12-01

Measurements are presented representing a complete set of electron-photon polarization correlation parameters for the excitation of n /sup 1/P states of He at an incident energy of 80 eV and an electron scattering angle of 20/sup 0/. The data support the predictions of a recent theoretical paper that these parameters should exhibit little variation with n. However, disagreement in absolute values between experiment and theory indicates the need for additional theoretical input into the problem.

Strong spin-photon coupling in silicon

NASA Astrophysics Data System (ADS)

Samkharadze, N.; Zheng, G.; Kalhor, N.; Brousse, D.; Sammak, A.; Mendes, U. C.; Blais, A.; Scappucci, G.; Vandersypen, L. M. K.

2018-03-01

Long coherence times of single spins in silicon quantum dots make these systems highly attractive for quantum computation, but how to scale up spin qubit systems remains an open question. As a first step to address this issue, we demonstrate the strong coupling of a single electron spin and a single microwave photon. The electron spin is trapped in a silicon double quantum dot, and the microwave photon is stored in an on-chip high-impedance superconducting resonator. The electric field component of the cavity photon couples directly to the charge dipole of the electron in the double dot, and indirectly to the electron spin, through a strong local magnetic field gradient from a nearby micromagnet. Our results provide a route to realizing large networks of quantum dot–based spin qubit registers.

Wavelength-scale photonic-crystal laser formed by electron-beam-induced nano-block deposition.

PubMed

Seo, Min-Kyo; Kang, Ju-Hyung; Kim, Myung-Ki; Ahn, Byeong-Hyeon; Kim, Ju-Young; Jeong, Kwang-Yong; Park, Hong-Gyu; Lee, Yong-Hee

2009-04-13

A wavelength-scale cavity is generated by printing a carbonaceous nano-block on a photonic-crystal waveguide. The nanometer-size carbonaceous block is grown at a pre-determined region by the electron-beam-induced deposition method. The wavelength-scale photonic-crystal cavity operates as a single mode laser, near 1550 nm with threshold of approximately 100 microW at room temperature. Finite-difference time-domain computations show that a high-quality-factor cavity mode is defined around the nano-block with resonant wavelength slightly longer than the dispersion-edge of the photonic-crystal waveguide. Measured near-field images exhibit photon distribution well-localized in the proximity of the printed nano-block. Linearly-polarized emission along the vertical direction is also observed.

A Project of Boron Neutron Capture Therapy System based on a Proton Linac Neutron Source

NASA Astrophysics Data System (ADS)

Kiyanagi, Yoshikai; Asano, Kenji; Arakawa, Akihiro; Fukuchi, Shin; Hiraga, Fujio; Kimura, Kenju; Kobayashi, Hitoshi; Kubota, Michio; Kumada, Hiroaki; Matsumoto, Hiroshi; Matsumoto, Akira; Sakae, Takeji; Saitoh, Kimiaki; Shibata, Tokushi; Yoshioka, Masakazu

At present, the clinical trials of Boron Neutron Capture Therapy (BNCT) are being performed at research reactor facilities. However, an accelerator based BNCT has a merit that it can be built in a hospital. So, we just launched a development project for the BNCT based on an accelerator in order to establish and to spread the BNCT as an effective therapy in the near future. In the project, a compact proton linac installed in a hospital will be applied as a neutron source, and energy of the proton beam is planned to be less than about 10 MeV to reduce the radioactivity. The BNCT requires epithermal neutron beam with an intensity of around 1x109 (n/cm2/sec) to deliver the therapeutic dose to a deeper region in a body and to complete the irradiation within an hour. From this condition, the current of the proton beam required is estimated to be a few mA on average. Enormous heat deposition in the target is a big issue. We are aiming at total optimization of the accelerator based BNCT from the linac to the irradiation position. Here, the outline of the project is introduced and the moderator design is presented.