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Eric Burgett - One of the best experts on this subject based on the ideXlab platform.
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measured neutron spectra and dose equivalents from a mevion single room passively scattered proton system used for craniospinal irradiation
International Journal of Radiation Oncology Biology Physics, 2016Co-Authors: Rebecca M Howell, Eric Burgett, Daniel Isaacs, Samantha Price G Hedrick, Michael P Reilly, L Rankine, K Grantham, Stephanie M Perkins, Eric E KleinAbstract:Purpose To measure, in the setting of typical passively scattered proton craniospinal irradiation (CSI) treatment, the secondary neutron spectra, and use these spectra to calculate dose equivalents for both internal and external Neutrons delivered via a Mevion single-room compact proton system. Methods and Materials Secondary neutron spectra were measured using extended-range Bonner spheres for whole brain, upper spine, and lower spine proton fields. The detector used can discriminate Neutrons over the entire range of the energy spectrum encountered in proton therapy. To separately assess internally and externally generated Neutrons, each of the fields was delivered with and without a phantom. Average neutron energy, total neutron fluence, and ambient dose equivalent [H* (10)] were calculated for each spectrum. Neutron dose equivalents as a function of depth were estimated by applying published neutron depth–dose data to in-air H* (10) values. Results For CSI fields, neutron spectra were similar, with a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate continuum between the evaporation and thermal peaks. Neutrons in the evaporation peak made the largest contribution to dose equivalent. Internal Neutrons had a very low to negligible contribution to dose equivalent compared with external Neutrons, largely attributed to the measurement location being far outside the primary proton beam. Average energies ranged from 8.6 to 14.5 MeV, whereas fluences ranged from 6.91 × 10 6 to 1.04 × 10 7 n/cm 2 /Gy, and H* (10) ranged from 2.27 to 3.92 mSv/Gy. Conclusions For CSI treatments delivered with a Mevion single-gantry proton therapy system, we found measured neutron dose was consistent with dose equivalents reported for CSI with other proton beamlines.
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secondary neutron spectrum from 250 mev passively scattered proton therapy measurement with an extended range bonner sphere system
Medical Physics, 2014Co-Authors: Rebecca M Howell, Eric BurgettAbstract:Purpose: Secondary Neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on Neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. Methods: The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. Results: The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the Neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from Neutrons with energies ≥20 MeV. Conclusions: The authors measured a neutron spectrum for external Neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to Neutrons over the entire energy range being measured, i.e., thermal to 250 MeV. The authors used the neutron fluence spectrum to demonstrate experimentally the contribution of Neutrons with different energies to the total dose equivalent and in particular the contribution of high-energy Neutrons (≥20 MeV). These are valuable reference data that can be directly compared with Monte Carlo and experimental data in the literature.
Rebecca M Howell - One of the best experts on this subject based on the ideXlab platform.
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measured neutron spectra and dose equivalents from a mevion single room passively scattered proton system used for craniospinal irradiation
International Journal of Radiation Oncology Biology Physics, 2016Co-Authors: Rebecca M Howell, Eric Burgett, Daniel Isaacs, Samantha Price G Hedrick, Michael P Reilly, L Rankine, K Grantham, Stephanie M Perkins, Eric E KleinAbstract:Purpose To measure, in the setting of typical passively scattered proton craniospinal irradiation (CSI) treatment, the secondary neutron spectra, and use these spectra to calculate dose equivalents for both internal and external Neutrons delivered via a Mevion single-room compact proton system. Methods and Materials Secondary neutron spectra were measured using extended-range Bonner spheres for whole brain, upper spine, and lower spine proton fields. The detector used can discriminate Neutrons over the entire range of the energy spectrum encountered in proton therapy. To separately assess internally and externally generated Neutrons, each of the fields was delivered with and without a phantom. Average neutron energy, total neutron fluence, and ambient dose equivalent [H* (10)] were calculated for each spectrum. Neutron dose equivalents as a function of depth were estimated by applying published neutron depth–dose data to in-air H* (10) values. Results For CSI fields, neutron spectra were similar, with a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate continuum between the evaporation and thermal peaks. Neutrons in the evaporation peak made the largest contribution to dose equivalent. Internal Neutrons had a very low to negligible contribution to dose equivalent compared with external Neutrons, largely attributed to the measurement location being far outside the primary proton beam. Average energies ranged from 8.6 to 14.5 MeV, whereas fluences ranged from 6.91 × 10 6 to 1.04 × 10 7 n/cm 2 /Gy, and H* (10) ranged from 2.27 to 3.92 mSv/Gy. Conclusions For CSI treatments delivered with a Mevion single-gantry proton therapy system, we found measured neutron dose was consistent with dose equivalents reported for CSI with other proton beamlines.
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secondary neutron spectrum from 250 mev passively scattered proton therapy measurement with an extended range bonner sphere system
Medical Physics, 2014Co-Authors: Rebecca M Howell, Eric BurgettAbstract:Purpose: Secondary Neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on Neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. Methods: The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. Results: The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the Neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from Neutrons with energies ≥20 MeV. Conclusions: The authors measured a neutron spectrum for external Neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to Neutrons over the entire energy range being measured, i.e., thermal to 250 MeV. The authors used the neutron fluence spectrum to demonstrate experimentally the contribution of Neutrons with different energies to the total dose equivalent and in particular the contribution of high-energy Neutrons (≥20 MeV). These are valuable reference data that can be directly compared with Monte Carlo and experimental data in the literature.
K Kanda - One of the best experts on this subject based on the ideXlab platform.
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A fundamental study on hyper-thermal Neutrons for neutron capture therapy.
Physics in medicine and biology, 1994Co-Authors: Yoshinori Sakurai, T Kobayashi, K KandaAbstract:The utilization of hyper-thermal Neutrons, which have an energy spectrum with a Maxwellian distribution at a higher temperature than room temperature (300 K), was studied in order to improve the thermal neutron flux distribution at depth in a living body for neutron capture therapy. Simulation calculations were carried out using a Monte Carlo code 'MCNP-V3' in order to investigate the characteristics of hyper-thermal Neutrons, i.e. (i) depth dependence of the neutron energy spectrum, and (ii) depth distribution of the reaction rate in a water phantom for materials with 1/ nu neutron absorption. It is confirmed that hyper-thermal neutron irradiation can improve the thermal neutron flux distribution in the deeper areas in a living body compared with thermal neutron irradiation. When hyper-thermal Neutrons with a 3000 K Maxwellian distribution are incident on a body, the reaction rates of 1/ nu materials such as 14N, 10B, etc. are about twice that observed for incident thermal Neutrons at 300 K, at a depth of 5 cm. The limit of the treatable depth for tumours having 30 ppm 10B is expected to be about 1.5 cm greater by utilizing hyper-thermal Neutrons at 3000 K compared with the incidence of thermal Neutrons at 300 K.
Sara A Pozzi - One of the best experts on this subject based on the ideXlab platform.
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neutron angular distribution in plutonium 240 spontaneous fission
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2016Co-Authors: Matthew J Marcath, Shaun D Clarke, Tony H Shin, Paolo Peerani, Sara A PozziAbstract:Abstract Nuclear safeguards applications require accurate fission models that exhibit prompt neutron anisotropy. In the laboratory reference frame, an anisotropic neutron angular distribution is observed because prompt fission Neutrons carry momentum from fully accelerated fission fragments. A liquid organic scintillation detector array was used with pulse shape discrimination techniques to produce neutron-neutron cross-correlation time distributions and angular distributions from spontaneous fission in a 252 Cf, a 0.84 g 240 Pu eff metal, and a 1.63 g 240 Pu eff metal sample. The effect of cross-talk, estimated with MCNPX-PoliMi simulations, is removed from neutron-neutron coincidences as a function of the angle between detector pairs. Fewer coincidences were observed at detector angles near 90°, relative to higher and lower detector angles. As light output threshold increases, the observed anisotropy increases due to spectral effects arising from fission fragment momentum transfer to emitted Neutrons. Stronger anisotropy was observed in Cf-252 spontaneous fission prompt Neutrons than in Pu-240 Neutrons.
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Improved Fission Neutron Data Base for Active Interrogation of Actinides
2013Co-Authors: Sara A Pozzi, J. Bart Czirr, Robert C. Haight, Michael Kovash, Pavel TsvetkovAbstract:This project will develop an innovative neutron detection system for active interrogation measurements. Many active interrogation methods to detect fissionable material are based on the detection of Neutrons from fission induced by fast Neutrons or high-energy gamma rays. The energy spectrum of the fission Neutrons provides data to identify the fissionable isotopes and materials such as shielding between the fissionable material and the detector. The proposed path for the project is as follows. First, the team will develop new neutron detection systems and algorithms by Monte Carlo simulations and bench-top experiments. Next, They will characterize and calibrate detection systems both with monoenergetic and white neutron sources. Finally, high-fidelity measurements of neutron emission from fissions induced by fast Neutrons will be performed. Several existing fission chambers containing U-235, Pu-239, U-238, or Th-232 will be used to measure the neutron-induced fission neutron emission spectra. The challenge for making confident measurements is the detection of Neutrons in the energy ranges of 0.01 – 1 MeV and above 8 MeV, regions where the basic data on the neutron energy spectrum emitted from fission is least well known. In addition, improvements in the specificity of neutron detectors are required throughout the complete energy range: theymore » must be able to clearly distinguish Neutrons from other radiations, in particular gamma rays and cosmic rays. The team believes that all of these challenges can be addressed successfully with emerging technologies under development by this collaboration. In particular, the collaboration will address the area of fission neutron emission spectra for isotopes of interest in the advanced fuel cycle initiative (AFCI).« less
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mcnpx polimi for nuclear nonproliferation applications
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2012Co-Authors: Sara A Pozzi, Shaun D Clarke, W J Walsh, E C Miller, J L Dolan, Marek Flaska, B M Wieger, Andreas Enqvist, Enrico Padovani, John MattinglyAbstract:This paper describes the use of the Monte Carlo code MCNPX-PoliMi for nuclear-nonproliferation applications, with particular emphasis on the simulation of spontaneous and neutron-induced nuclear fission. New models for the outgoing Neutrons and gamma rays emitted in spontaneous and induced fission are described. For spontaneous fission, the models include prompt neutron energy distributions that depend on the number of Neutrons emitted in the individual fission events. For neutron-induced fission, due to lack of data, the prompt neutron energy distributions are independent of the number of Neutrons emitted in the individual fission events. Gamma rays are sampled independently of the Neutrons. Code validation is performed on well-characterized mixed-oxide fuel and plutonium-oxide samples.
Masatsugu Akiyama - One of the best experts on this subject based on the ideXlab platform.
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Study of epithermal neutron columns for boron neutron capture therapy
Progress in Nuclear Energy, 1998Co-Authors: Yoshiaki Oka, Masatsugu AkiyamaAbstract:Abstract Optimal neutron energy for boron neutron capture therapy for treating brain tumors was studied. Epithermal Neutrons gave lower dose at the brain surface and pentrated deeper than thermal Neutrons. An epithermal neutron column and a reactor facility for boron neutron capture therapy were conceptually studied. Layers of alminum and heavy water whose volume ratio 85 15 were effective in decreasing fast Neutrons while maintaining a high epithermal neutron level. An epithermal neutron column was experimentally developed at YAYOI reactor. It has been used for fundamental study of BNCT and radiation biology, although the beam intensity was not high enough to treat the patients due to the low reactor power.
