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Journal Articles

Measurements of displacement cross sections of metals for 120-GeV proton beam irradiation

Iwamoto, Yosuke; Matsuda, Hiroki*; Meigo, Shinichiro; Yonehara, Katsuya*; Pellemoine, F.*; Liu, Z.*; Lynch, K.*; Yoshida, Makoto*; Yabuuchi, Atsushi*; Yoshiie, Toshimasa*; et al.

Nuclear Instruments and Methods in Physics Research B, 557, p.165543_1 - 165543_8, 2024/12

 Times Cited Count:0 Percentile:0.00(Instruments & Instrumentation)

The number of displacements per atom is widely used as an indicator of irradiation damage to materials in proton accelerator facilities. Experiments have been carried out on protons below 3 GeV to verify the dpa of metallic materials. However, the dpa for high-energy protons above 3 GeV has not been measured. In order to validate the displacement cross sections of metals in the high-energy region, the electrical resistivity changes of aluminium, copper and tungsten wires at a temperature of 8 K were measured using protons with energy of 120 GeV. The results show that the conventional irradiation damage model of PHITS overestimates the experimental data. On the other hand, the calculation results using the athermal recombination correction model were in agreement with the experimental data.

Journal Articles

Development of a forward Monte Carlo based weight-window generator using the history-counter function in PHITS

Sato, Tatsuhiko; Hashimoto, Shintaro; M$'a$rquez Dami$'a$n, J. I.*; Niita, Koji*

Nuclear Instruments and Methods in Physics Research B, 557, p.165535_1 - 165535_8, 2024/12

 Times Cited Count:0 Percentile:0.00(Instruments & Instrumentation)

Journal Articles

Overview of PHITS Ver.3.34 with particular focus on track-structure calculation

Ogawa, Tatsuhiko; Hirata, Yuho; Matsuya, Yusuke; Kai, Takeshi; Sato, Tatsuhiko; Iwamoto, Yosuke; Hashimoto, Shintaro; Furuta, Takuya; Abe, Shinichiro; Matsuda, Norihiro; et al.

EPJ Nuclear Sciences & Technologies (Internet), 10, p.13_1 - 13_8, 2024/11

The latest updates on PHITS, a versatile radiation transport code, focusing specifically on track-structure models are presented. Track structure calculations are methods used to simulate the movement of charged particles while explicitly considering each atomic reaction. Initially developed for radiation biology, these calculation methods aimed to analyze the radiation-induced damage to DNA and chromosomes. Several track-structure calculation models, including PHITS-ETS, PHITS-ETS for Si, PHITS-KURBUC, ETSART, and ITSART, have been developed and implemented to PHITS. These models allow users to study the behavior of various particles at the nano-scale across a wide range of materials. Furthermore, potential applications of track-structure calculations have also been proposed so far. This collection of track-structure calculation models, which encompasses diverse conditions, opens up new avenues for research in the field of radiation effects.

Journal Articles

Monte Carlo simulation study on the dose and dose-averaged linear energy transfer distributions in carbon ion radiotherapy

Ishikawa, Akihisa; Koba, Yusuke*; Furuta, Takuya; Chang, W.*; Yonai, Shunsuke*; Matsumoto, Shinnosuke*; Hashimoto, Shintaro; Hirai, Yuta*; Sato, Tatsuhiko

Radiological Physics and Technology, 17(2), p.553 - 560, 2024/06

Journal Articles

Experimental and computational verifications of the dose calculation accuracy of PHITS for high-energy photon beam therapy

Kuga, Naoya*; Shiiba, Takuro*; Sato, Tatsuhiko; Hashimoto, Shintaro; Kuroiwa, Yasuyoshi*

Journal of Nuclear Science and Technology, 61(1), p.136 - 145, 2024/01

 Times Cited Count:2 Percentile:34.39(Nuclear Science & Technology)

This study aims to verify the accuracy of PHITS in terms of photon and electron transport and provide essential data for its application in clinical dosimetry in high-energy photon beam therapy. Percentage depth dose (PDD), beam profiles, and output factor (OPF) in a water phantom with various field sizes created by a Clinac 21EX linear accelerator were measured using an ionization chamber. Experimental setups were precisely reproduced by PHITS version 3.24, and the percentage differences (%Diff) between the measured and calculated data were evaluated. The average %Diff of PDDs obtained from PHITS and measurement were within 10% and 2% in the build-up and fall-off regions, respectively. For beam profiles, the average %Diff in the plateau region was within 3%; the differences between the calculated and measured distances from the central axis to 50% dose level were within 2 mm. These differences were lower than their tolerance levels. The consistency between the PHITS and EGSnrc was better; their %Diff was within 1% in most cases. The concurrence between the PHITS and measurement shown in this study demonstrates the potential clinical application of PHITS in high-energy photon beam therapy, given its similar dose calculation accuracy compared with EGSnrc.

Journal Articles

Development of nuclear de-excitation model EBITEM Ver.2

Ogawa, Tatsuhiko; Hashimoto, Shintaro; Sato, Tatsuhiko

Journal of Nuclear Science and Technology, 61(1), p.68 - 73, 2024/01

 Times Cited Count:1 Percentile:34.39(Nuclear Science & Technology)

The gamma de-excitation model of the general-purpose radiation transport code Particle and Heavy Ion Transport code System (PHITS), called the Evaluated Nuclear Structure Data File (ENSDF-)-Based Isomeric Transition and isomEr production Model (EBITEM) has been upgraded with focus on precise neutron capture reaction simulation. The first de-excitation subsequent to neutron capture of numerous nuclei, which was formerly simulated by a model based on the single particle model, is calculated using the Evaluated Gamma Activation File (EGAF). The database used for further de-excitation, ENSDF, retrieved in 2013, was replaced with Reference Input Parameter Library 3 (RIPL-3) to consider internal conversion. The internal conversion process was interfaced with the atomic de-excitation model to assess the emission of Auger electrons and fluorescent X-rays. The spectra of gamma-rays from neutron capture reactions calculated by the upgraded EBITEM correlate better with the evaluated cross section data than those of the previous version.

Journal Articles

Recent improvements of the Particle and Heavy Ion Transport code System; PHITS version 3.33

Sato, Tatsuhiko; Iwamoto, Yosuke; Hashimoto, Shintaro; Ogawa, Tatsuhiko; Furuta, Takuya; Abe, Shinichiro; Kai, Takeshi; Matsuya, Yusuke; Matsuda, Norihiro; Hirata, Yuho; et al.

Journal of Nuclear Science and Technology, 61(1), p.127 - 135, 2024/01

 Times Cited Count:80 Percentile:99.96(Nuclear Science & Technology)

The Particle and Heavy Ion Transport code System (PHITS) is a general-purpose Monte Carlo radiation transport code that can simulate the behavior of most particle species with energies up to 1 TeV (per nucleon for ions). Its new version, PHITS3.31, was recently developed and released to the public. In the new version, the compatibility with high-energy nuclear data libraries and the algorithm of the track-structure modes have been improved. In this paper, we summarize the upgraded features of PHITS3.31 with respect to the physics models, utility functions, and application software introduced since the release of PHITS3.02 in 2017.

Journal Articles

Isotopic composition of enriched $$^{100}$$Mo for production of medical $$^{rm 99m}$$Tc by $$^{100}$$Mo($$p,2n$$)$$^{rm 99m}$$Tc

Hashimoto, Shintaro; Nagai, Yasuki*

Journal of the Physical Society of Japan, 92(12), p.124202_1 - 124202_11, 2023/12

 Times Cited Count:0 Percentile:0.00(Physics, Multidisciplinary)

$$^{rm 99m}$$Tc, which is a daughter nuclide of $$^{99}$$Mo, is used worldwide for medical imaging. However, there is a problem with the supply of $$^{rm 99m}$$Tc ($$^{99}$$Mo) due to the replacement of aging reactors. A method to produce $$^{rm 99m}$$Tc by irradiating $$^{100}$$Mo with protons using medical cyclotrons has been proposed. In this study, we presented a method to determine individual excitation functions for Mo($$p,x$$)Tc using measured excitation functions for $$^{nat}$$Mo($$p,x$$)Tc. The method was validated by comparing estimated radionuclide purities of $$^{rm 99m}$$Tc in enriched $$^{100}$$Mo samples using the determined excitation functions with measured ones. In this study, we found that the content of $$^{97}$$Mo, $$^{96}$$Mo, and $$^{95}$$Mo should be low in order to produce $$^{rm 99m}$$Tc with high radionuclide purity. The results of this study play an important role in discussion of the required Mo compositions in enriched $$^{100}$$Mo, taking into account the constraints of each facility.

Journal Articles

Development of the DICOM-based Monte Carlo dose reconstruction system for a retrospective study on the secondary cancer risk in carbon ion radiotherapy

Furuta, Takuya; Koba, Yusuke*; Hashimoto, Shintaro; Chang, W.*; Yonai, Shunsuke*; Matsumoto, Shinnosuke*; Ishikawa, Akihisa*; Sato, Tatsuhiko

Physics in Medicine & Biology, 67(14), p.145002_1 - 145002_15, 2022/07

 Times Cited Count:6 Percentile:65.89(Engineering, Biomedical)

Carbon ion radiotherapy has an advantage over conventional radiotherapy such that its superior dose concentration on the tumor helps to reduce unwanted dose to surrounding normal tissues. Nevertheless, a little dose to normal tissues, which is a potential risk of secondary cancer, is still unavoidable. The Monte Carlo simulation is a good candidate for the tool to assess secondary cancer risk, including the contributions of secondary particles produced by nuclear reactions. We therefore developed a new dose reconstruction system implementing PHITS as the engine. In this system, the PHITS input is automatically created from the DICOM data sets recorded in the treatment planning. The developed system was validated by comparing to experimental dose distribution in water and treatment plan on an anthropomorphic phantom. This system will be used for retrospective studies using the patient data in National Institute for Quantum and Science and Technology.

Journal Articles

Transport model comparison studies of intermediate-energy heavy-ion collisions

Walter, H.*; Colonna, M.*; Cozma, D.*; Danielewicz, P.*; Ko, C. M.*; Kumar, R.*; Ono, Akira*; Tsang, M. Y. B*; Xu, J.*; Zhang, Y.-X.*; et al.

Progress in Particle and Nuclear Physics, 125, p.103962_1 - 103962_90, 2022/07

 Times Cited Count:81 Percentile:95.92(Physics, Nuclear)

Transport models are the main method to obtain physics information on the nuclear equation of state and in-medium properties of particles from low to relativistic-energy heavy-ion collisions. The Transport Model Evaluation Project (TMEP) has been pursued to test the robustness of transport model predictions to reach consistent conclusions from the same type of physical model. To this end, calculations under controlled conditions of physical input and set-up were performed by the various participating codes. These included both calculations of nuclear matter in a periodic box, which test individual ingredients of a transport code, and calculations of complete collisions of heavy ions. Over the years, five studies were performed within this project. They show, on one hand, that in box calculations the differences between the codes can be well understood and a convergence of the results can be reached. These studies also highlight the systematic differences between the two families of transport codes, known under the names of Boltzmann-Uehling-Uhlenbeck (BUU) and Quantum Molecular Dynamics (QMD) type codes. On the other hand, there still exist substantial differences when these codes are applied to real heavy-ion collisions. The results of transport simulations of heavy-ion collisions will have more significance if codes demonstrate that they can verify benchmark calculations such as the ones studied in these evaluations.

Journal Articles

Benchmark study of particle and heavy-ion transport code system using shielding integral benchmark archive and database for accelerator-shielding experiments

Iwamoto, Yosuke; Hashimoto, Shintaro; Sato, Tatsuhiko; Matsuda, Norihiro; Kunieda, Satoshi; $c{C}$elik, Y.*; Furutachi, Naoya*; Niita, Koji*

Journal of Nuclear Science and Technology, 59(5), p.665 - 675, 2022/05

 Times Cited Count:18 Percentile:90.59(Nuclear Science & Technology)

A benchmark study of PHITS3.24 has been conducted using neutron-shielding experiments listed in the Shielding Integral Benchmark Archive and Database. Five neutron sources were selected, which are generated from (1) 43- and 68-MeV proton-induced reaction on a thin lithium target, (2) 52-MeV proton-induced reaction on a thick graphite target, (3) 590-MeV proton-induced reaction on a thick lead target, (4) 500-MeV proton-induced reaction on a thick tungsten target, and (5) 800-MeV proton-induced reaction on a thick tantalum target. For all cases, overall agreements in the results are satisfactory when using the JENDL-4.0/HE to simulate neutron- and proton-induced reactions up to 200 MeV. However, discrepancies using PHITS default settings are observed in the results. For an accurate neutron-shielding design for accelerator facilities, using JENDL-4.0/HE in the particle and heavy-ion transport code system calculation is favorable.

Journal Articles

Estimated isotopic compositions of Yb in enriched $$^{176}$$Yb for producing $$^{177}$$Lu with high radionuclide purity by $$^{176}$$Yb($$d,x$$)$$^{177}$$Lu

Nagai, Yasuki*; Kawabata, Masako*; Hashimoto, Shintaro; Tsukada, Kazuaki; Hashimoto, Kazuyuki*; Motoishi, Shoji*; Saeki, Hideya*; Motomura, Arata*; Minato, Futoshi; Ito, Masatoshi*

Journal of the Physical Society of Japan, 91(4), p.044201_1 - 044201_10, 2022/04

 Times Cited Count:3 Percentile:42.95(Physics, Multidisciplinary)

Recently, $$^{177}$$Lu is considered as one of the most important medical RIs for treating neuroendocrine tumors. A plan to produce $$^{177}$$Lu with high purity by using enriched $$^{176}$$Yb samples with irradiation of deuteron beams in accelerators has been discussed. However, since the other Yb isotopes contained in the Yb sample interacts with deuterons, Lu isotopes other than $$^{177}$$Lu are produced as impurities. Since the purity of $$^{177}$$Lu is important for medical use, a method to evaluate the impurity of Lu has been required. In this study, we proposed a new method to estimate production yields of each Lu isotopes in Yb samples with arbitrary isotopic compositions by using excitation functions of Yb($$d,x$$)Lu reactions and the particle transport calculation code PHITS. The method plays an important role in discussing the isotopic composition of enriched samples to produce high-purity $$^{177}$$Lu using accelerators.

Journal Articles

Large scale production of $$^{64}$$Cu and $$^{67}$$Cu via the $$^{64}$$Zn(n, p)$$^{64}$$Cu and $$^{68}$$Zn(n, np/d)$$^{67}$$Cu reactions using accelerator neutrons

Kawabata, Masako*; Motoishi, Shoji*; Ota, Akio*; Motomura, Arata*; Saeki, Hideya*; Tsukada, Kazuaki; Hashimoto, Shintaro; Iwamoto, Nobuyuki; Nagai, Yasuki*; Hashimoto, Kazuyuki*

Journal of Radioanalytical and Nuclear Chemistry, 330(3), p.913 - 922, 2021/12

 Times Cited Count:7 Percentile:66.21(Chemistry, Analytical)

Both $$^{64}$$Cu and $$^{67}$$Cu are promising radionuclides in nuclear medicine. Production yields of these radionuclides were quantified by irradiating 55.4 g of natural zinc with accelerator neutrons. Clinically suitable $$^{64}$$Cu and $$^{67}$$Cu yields were estimated by experimental based numerical simulations using 100 g of enriched $$^{64}$$Zn and $$^{68}$$Zn, respectively, and elevated neutron fluxes from 40 MeV, 2 mA deuterons. A combined thermal- and resin-separation method was developed to isolate $$^{64}$$Cu and $$^{67}$$Cu from zinc, resulting in 73% separation efficiency and 97% zinc recovery. Such methods can provide large scale production of $$^{64}$$Cu and $$^{67}$$Cu for clinical applications.

Journal Articles

Implementation of simplified stochastic microdosimetric kinetic models into PHITS for application to radiation treatment planning

Sato, Tatsuhiko; Hashimoto, Shintaro; Inaniwa, Taku*; Takada, Kenta*; Kumada, Hiroaki*

International Journal of Radiation Biology, 97(10), p.1450 - 1460, 2021/10

 Times Cited Count:13 Percentile:85.93(Biology)

The stochastic microdosimetric kinetic (SMK) model is one of the most sophisticated and precise models used in the estimation of the relative biological effectiveness of carbon-ion radiotherapy (CRT) and boron neutron capture therapy (BNCT). Through the introduction of Taylor expansion (TE) or fast Fourier transform (FFT), we developed two simplified SMK models and implemented them into the Particle and Heavy Ion Transport code System (PHITS). This study enables the instantaneous calculation of the equieffective dose for CRT and BNCT, considering their cellular-scale dose heterogeneities. Treatment-planning systems that use the improved PHITS as a dose-calculation engine are under development.

Journal Articles

Technical Note: Validation of a material assignment method for a retrospective study of carbon-ion radiotherapy using Monte Carlo simulation

Chang, W.*; Koba, Yusuke*; Furuta, Takuya; Yonai, Shunsuke*; Hashimoto, Shintaro; Matsumoto, Shinnosuke*; Sato, Tatsuhiko

Journal of Radiation Research (Internet), 62(5), p.846 - 855, 2021/09

 Times Cited Count:3 Percentile:27.95(Biology)

With the aim of developing a revaluation tool of treatment plan in carbon-ion radiotherapy using Monte Carlo (MC) simulation, we propose two methods; one is dedicated to identify realistic-tissue materials from a CT image with satisfying the well-calibrated relationship between CT numbers and stopping power ratio (SPR) provided by TPS, and the other is to estimate dose to water considering the particle- and energy-dependent SPR between realistic tissue materials and water. We validated these proposed methods by computing depth dose distribution in homogeneous and heterogeneous phantoms composed of human tissue materials and water irradiated by a 400 MeV/u carbon beam with 8 cm SOBP using a MC simulation code PHITS and comparing with results of conventional treatment planning system (TPS). Our result suggested that use of water as a surrogate of real tissue materials, which is adopted in conventional TPS, is inadequate for dose estimation from secondary particles because their production rates cannot be scaled by SPR of the primary particle in water. We therefore concluded that the proposed methods can play important roles in the reevaluation of the treatment plans in carbon-ion radiotherapy.

Journal Articles

Total cross section model with uncertainty evaluated by KALMAN

Hashimoto, Shintaro; Sato, Tatsuhiko

EPJ Web of Conferences, 239, p.03015_1 - 03015_4, 2020/09

 Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)

Particle transport simulation codes based on the Monte Carlo technique have been successfully applied to shielding calculations in accelerator facilities. Estimation of not only statistical uncertainties, which depend on the number of trials, but also systemic uncertainties, which are caused by uncertainty of total cross section models, is required to confirm the reliability of the simulation results. We evaluated unclear quantities of internal parameters included in the total cross section model by the KALMAN code, which is based on the least squares technique, comparing with experimental data of the total cross section. The uncertainties in the total cross sections obtained by the new model are comparable to the experimental errors. In the present study, the systematic uncertainty included in the simulation results can be estimated by performing the transport calculations with variation of the internal parameters within their unclear quantities.

Journal Articles

Estimation of reliable displacements-per-atom based on athermal-recombination-corrected model in radiation environments at nuclear fission, fusion, and accelerator facilities

Iwamoto, Yosuke; Meigo, Shinichiro; Hashimoto, Shintaro

Journal of Nuclear Materials, 538, p.152261_1 - 152261_9, 2020/09

 Times Cited Count:25 Percentile:93.83(Materials Science, Multidisciplinary)

The displacements-per-atom (dpa) is widely used as an exposure unit to predict the operating lifetime of materials in radiation environments. Because the athermal-recombination-corrected dpa (arc-dpa) model is a more realistic model than the standard Norgertt-Robinson-Torrens (NRT) model, new evaluation of radiation damage will be performed using the arc-dpa model as a standard. In this work, the recent arc-dpa model of various materials are incorporated in PHITS, and the rescaling factors (NRT-dpa/arc-dpa) over a wide energy range are reported. For neutron incidences with the energy spectrum determined in selected nuclear facilities and proton incidences with energies of 600 MeV-50 GeV, the rescaling factor for each material is independent of these irradiation conditions with almost the same value for each material. Our findings will be beneficial for rescaling the NRT-dpa model used for radiation damage applications over a wide energy region.

Journal Articles

Anomalous radioisotope production for $$^{68}$$ZnO using polyethylene by accelerator neutrons

Tsukada, Kazuaki; Nagai, Yasuki*; Hashimoto, Shintaro; Minato, Futoshi; Kawabata, Masako*; Hatsukawa, Yuichi*; Hashimoto, Kazuyuki*; Watanabe, Satoshi*; Saeki, Hideya*; Motoishi, Shoji*

Journal of the Physical Society of Japan, 89(3), p.034201_1 - 034201_7, 2020/03

 Times Cited Count:2 Percentile:18.96(Physics, Multidisciplinary)

We found anomalously large yields of $$^{67}$$Ga, $$^{66}$$Ga, $$^{rm 69m}$$Zn and $$^{64}$$Cu by neutron irradiation on a $$^{68}$$ZnO sample in a polyethylene shield. Neutron beams are generated from the $$^{9}$$Be($$d,n$$) reaction for 50 MeV deuterons. The yields obtained were more than 20 times larger than those in the unshielded sample. On the other hand, the yields of $$^{67}$$Ga, $$^{66}$$Ga, $$^{rm 69m}$$Zn and $$^{64}$$Cu from a metallic $$^{68}$$Zn sample and the yields of $$^{67}$$Cu, $$^{65}$$Ni and $$^{65}$$Zn from the $$^{68}$$ZnO and $$^{68}$$Zn samples were almost insensitive to the shield conditions. This finding would provide us a unique capability of accelerator neutrons to simultaneously produce a large amount of several radioisotopes, including proton induced reaction products, by using a single sample. The experimental data were compared with the yields estimated by using the Particle and Heavy Ion Transport code System and the result was discussed.

Journal Articles

International Conference on Nuclear Data for Science and Technology (ND2019), 3; Evaluation and theory

Nakayama, Shinsuke; Iwamoto, Osamu; Iwamoto, Nobuyuki; Hashimoto, Shintaro

Kaku Deta Nyusu (Internet), (123), p.53 - 59, 2019/06

The 2019 International Conference on Nuclear Data for Science and Technology (ND2019) was held at the China National Convention Center on May 19-24, 2019. The series of the ND conferences are the largest conferences in nuclear data research field that are held every three years. In this paper, as a part of the conference reports of ND2019, the authors gave summaries of the presentations on nuclear data evaluation and theory conducted at the conference.

Journal Articles

Estimation method of systematic uncertainties in Monte Carlo particle transport simulation based on analysis of variance

Hashimoto, Shintaro; Sato, Tatsuhiko

Journal of Nuclear Science and Technology, 56(4), p.345 - 354, 2019/04

 Times Cited Count:7 Percentile:55.95(Nuclear Science & Technology)

Particle transport simulations based on the Monte Carlo method have been applied to shielding calculations. Estimation of not only statistical uncertainty related to the number of trials but also systematic one induced by unclear physical quantities is required to confirm the reliability of calculated results. In this study, we applied a method based on analysis of variance to shielding calculations. We proposed random- and three-condition methods. The first one determines randomly the value of the unclear quantity, while the second one uses only three values: the default value, upper and lower limits. The systematic uncertainty can be estimated adequately by the random-condition method, though it needs the large computational cost. The three-condition method can provide almost the same estimate as the random-condition method when the effect of the variation is monotonic. We found criterion to confirm convergence of the systematic uncertainty as the number of trials increases.

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