Kataoka, Ryuho*; Sato, Tatsuhiko; Kato, Chihiro*; Kadokura, Akira*; Kozai, Masayoshi*; Miyake, Shoko*; Murase, Kiyoka*; Yoshida, Rihito*; Tomikawa, Yoshihiro*; Munakata, Kazuoki*
Journal of Space Weather and Space Climate (Internet), 12, p.37_1 - 37_11, 2022/11
Solar modulation of galactic cosmic rays around the solar minimum in 2019-2020 looks different in the secondary neutrons and muons observed at the ground. To compare the solar modulation of primary cosmic rays in detail, we have to remove the possible seasonal variations caused by the atmosphere and surrounding environment. As such surrounding environment effects, we evaluate the snow cover effect on neutron count rate and the atmospheric temperature effect on muon count rate both simultaneously observed at Syowa Station in the Antarctic (69.01 S, 39.59 E). The corrected muon count rate starts decreasing in late 2019, earlier than the corrected neutron count rate which starts decreasing in early 2020, possibly indicating the rigidity dependent solar modulation in the heliosphere.
Iwamoto, Yosuke; Sato, Tatsuhiko
PLOS ONE (Internet), 17(11), p.e0276364_1 - e0276364_16, 2022/11
The displacement damage dose (DDD) has been used as an index to determine the lifetime of semiconductor devices used in space radiation environments. Recently, a new index, effective DDD, has been proposed, which takes into account the defect generation efficiency of materials obtained from molecular dynamics simulations. In this study, we developed a method to calculate both conventional and effective DDD for typical semiconductor materials such as SiC, InAs, GaAs, and GaN in the PHITS code. As a result, in the arsenic compounds InAs and GaAs, the number of defects increases due to amorphization and the effective DDD is larger than the conventional DDD, while in SiC the relationship is reversed due to defect recombination. The improved PHITS can be used to calculate the effective DDD of semiconductors in cosmic ray environments, and PHITS can make a significant contribution to the evaluation of radiation damage of new semiconductor devices in space.
Matsuya, Yusuke; Kai, Takeshi; Parisi, A.*; Yoshii, Yuji*; Sato, Tatsuhiko
Physics in Medicine & Biology, 67(21), p.215017_1 - 215017_13, 2022/11
Proton beam therapy allows to irradiate tumor volumes with reduced side effects on normal tissues with respect to X-ray radiotherapy. Biological effects such as cell killing after proton beam irradiations depend on the proton kinetic energy, which is intrinsically related in the early DNA damage induction. As such, the estimation of DNA damage yields based on Monte Carlo simulations is a research topic of worldwide interest. In this study, we investigate the possibility of applying a simple model developed for electron to proton without any modification. The yields of single-strand breaks (SSB), double-strand breaks (DSB) and the complex DSB were assessed as a function of the proton kinetic energy. The PHITS-based estimation accurately reproduced the experimental and simulated yields of various DNA damage types induced by protons with linear energy transfer (LET) up to about 30 keV/m. These results suggest that current DNA damage model implemented in PHITS is sufficient for estimating DNA lesion yields induced after protons irradiation except for lower energies than MeV.
Hirata, Yuho; Kai, Takeshi; Ogawa, Tatsuhiko; Matsuya, Yusuke; Sato, Tatsuhiko
Japanese Journal of Applied Physics, 61(10), p.106004_1 - 106004_6, 2022/10
Some radiation effects such as pulse-height defects and soft errors can cause problems in silicon (Si) devices. Local energy deposition in microscopic scales is essential information to elucidate the mechanism of these radiation effects. We, therefore, developed an electron track-structure model, which can simulate local energy deposition down to nano-scales, dedicated to Si and implemented it into PHITS. Then, we verified the accuracy of our developed model by comparing the ranges and depth-dose distributions of electrons obtained from this study with the corresponding experimental values and other simulated results. As an application of the model, we calculated the mean energies required to create an electron-hole pair, the so-called epsilon value. We found that the threshold energy for generating secondary electrons reproducing the epsilon value is 2.75 eV, consistent with the corresponding data deduced from past theoretical and computational studies. Since the magnitudes of the radiation effects on Si devices largely depend on the epsilon value, the developed code is expected to contribute to precisely understanding the mechanisms of pulse-height defects and semiconductor soft errors.
Sato, Tatsuhiko; Matsuya, Yusuke; Hamada, Nobuyuki*
International Journal of Radiation Oncology, Biology, Physics, 114(1), p.153 - 162, 2022/09
The microdosimetric kinetic model, which was originally developed for estimating cell surviving fractions for various radiations, was improved to be capable of estimating the mean and uncertainty of RBE for skin reactions. The parameter used in the model was independently determined from in vitro measurements of dermal cell survival and in vivo measurements of skin reactions taken from 8 and 23 papers, respectively. Our model quantitatively revealed that RBE for skin reactions tend to be higher than that for dermal cell survival. RBE of various mono-energetic radiations calculated from this model confirmed that the past evaluations made by ICRP and NCRP a few decades ago are still supported by recent experimental data. Conclusions: Our model can play important roles not only in medical physics for avoiding unnecessary skin reactions in particle therapy and BNCT but also in radiation protection for future decision making of the recommended RBE values.
Watabe, Tadashi*; Liu, Y.*; Kaneda, Kazuko*; Sato, Tatsuhiko; Shirakami, Yoshifumi*; Oe, Kazuhiro*; Toyoshima, Atsushi*; Shimosegawa, Eku*; Wang, Y.*; Haba, Hiromitsu*; et al.
International Journal of Molecular Sciences (Internet), 23(16), p.9434_1 - 9434_11, 2022/08
In this study, we compare the therapeutic effect between [At]NaAt and [I]NaI. In vitro analysis of double-stranded DNA break (DSB) and colony formation assay were performed using K1-NIS cells. [At]NaAt induced higher numbers of DSBs and had a reduced colony formation than [I]NaI. In K1-NIS mice, dose-dependent therapeutic effects were observed in both [At]NaAt and [I]NaI. The superior therapeutic effect of [At]NaAt suggests the promising clinical applicability of targeted alpha therapy using [At]NaAt in patients with differentiated thyroid cancer refractory to standard [I]NaI treatment.
Satoh, Daiki; Sato, Tatsuhiko
Journal of Nuclear Science and Technology, 59(8), p.1047 - 1060, 2022/08
In this research, we simulated the neutron-response functions and detection efficiencies of a liquid organic scintillator using the particle and heavy-ion transport code system (PHITS). We incorporated the algorithm and database of the neutron-response simulation code SCINFUL-QMD into PHITS. Then, we updated the total, elastic, and inelastic cross-section data of the hydrogen and carbon nuclei for neutrons and developed a new scorer to analyze the light outputs from a scintillator. The calculation results of the neutron-response functions and the detection efficiencies were compared with results of SCINFUL-QMD, the previous PHITS with the new scorer, and the reported measurements. It was found that the improved PHITS successfully reproduced the results calculated by SCINFUL-QMD, except for around 150 MeV where a discontinuity of detection-efficiency curve was observed in the SCINFUL-QMD values. Our results showed better agreement with the measured data than the results of the previous PHITS. The uncertainties of the detection efficiencies calculated by PHITS using the present extensions were estimated to be approximately 15% for neutrons in the energy region below 100 MeV.
Spiegl, T. C.*; Yoden, Shigeo*; Langematz, U.*; Sato, Tatsuhiko; Chhin, R.*; Noda, Satoshi*; Miyake, Fusa*; Kusano, Kanya*; Schaar, K.*; Kunze, M.*
Journal of Geophysical Research; Atmospheres, 127(13), p.e2021JD035658_1 - e2021JD035658_21, 2022/07
The abundance of cosmogenic isotopes in natural archives carries important information about the complex pathways from their source in the upper atmosphere to their deposition via atmospheric transport processes. Here, we use a new modelling framework to (a) estimate the Be production yield for the 774 CE/775 event, (b) evaluate the performance of our model framework by comparing the model results to four ice core records and (c) investigate the atmospheric pathways with a state-of-the-art climate model in detail. The results give new constraints regarding the seasonal timing of the event, underpin the role of the background conditions in the stratosphere, and highlight regional variations in the cosmogenic surface flux.
Hirata, Yuho; Sato, Tatsuhiko; Watanabe, Kenichi*; Ogawa, Tatsuhiko; Parisi, A.*; Uritani, Akira*
Journal of Nuclear Science and Technology, 59(7), p.915 - 924, 2022/07
The reliability of dose assessment with radiation detectors is an important feature in various fields, such as radiotherapy, radiation protection, and high-energy physics. However, many detectors irradiated by high linear energy transfer (LET) radiations exhibit decreased efficiency called the quenching effect. This quenching effect depends not only on the particle LET but strongly on the ion species and its microscopic pattern of energy deposition. Recently, a computational method for estimating the relative efficiency of luminescence detectors was proposed following analysis of microdosimetric specific energy distributions simulated using the particle and heavy ion transport code system (PHITS). This study applied the model to estimate the relative optically stimulated luminescence (OSL) efficiency of BaFBr:Eu detectors. Additionally, we measured the luminescence intensity of BaFBr:Eu detectors exposed to He, C and Ne ions to verify the calculated data. The model reproduced the experimental data in the cases of adopting a microdosimetric target diameter of approximately 30-50 nm. The calculated relative efficiency exhibit ion-species dependence in addition to LET. This result shows that the microdosimetric calculation from specific energy is a successful method for accurately understanding the results of OSL measurements with BaFBr:Eu detectors irradiated by various particles.
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
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.
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
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.
Murase, Kiyoka*; Kataoka, Ryuho*; Nishiyama, Takanori*; Nishimura, Koji*; Hashimoto, Taishi*; Tanaka, Yoshimasa*; Kadokura, Akira*; Tomikawa, Yoshihiro*; Tsutsumi, Masaki*; Ogawa, Yasunobu*; et al.
Journal of Space Weather and Space Climate (Internet), 12, p.18_1 - 18_16, 2022/06
We identified two energetic electron precipitation (EEP) events during the growth phase of moderate substorms and estimated the mesospheric ionization rate for an EEP event for which the most comprehensive dataset from ground-based and space-born instruments was available. The mesospheric ionization signature reached below 70 km altitude and continued for ~15 min until the substorm onset, as observed by the PANSY radar and imaging riometer at Syowa Station in the Antarctic region. We also used energetic electron flux observed by the Arase and POES 15 satellites as the input for the air-shower simulation code PHITS to quantitatively estimate the mesospheric ionization rate. Combining the cutting-edge observations and simulations, we shed new light on the space weather impact of the EEP events during geomagnetically quiet times, which is important to understand the possible link between the space environment and climate.
Iwamoto, Yosuke; Hashimoto, Shintaro; Sato, Tatsuhiko; Matsuda, Norihiro; Kunieda, Satoshi; elik, Y.*; Furutachi, Naoya*; Niita, Koji*
Journal of Nuclear Science and Technology, 59(5), p.665 - 675, 2022/05
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.
Titarenko, Yu. E.*; Batyaev, V. F.*; Pavlov, K. V.*; Titarenko, A. Yu.*; Malinovskiy, S. V.*; Rogov, V. I.*; Zhivun, V. M.*; Kulevoy, T. V.*; Chauzova, M. V.*; Khalikov, R. S.*; et al.
Nuclear Instruments and Methods in Physics Research A, 1026, p.166151_1 - 166151_9, 2022/03
The paper presents the Hg production cross-sections measured by the direct gamma-spectrometry technique in the samples of lead enriched with isotopes 206, 207 and 208, as well as in the samples of natural lead and bismuth, irradiated by protons of 11 energies in the range from 0.04 to 2.6 GeV. The obtained experimental results are compared with the previous measurements, with the TENDL-2019 data-library evaluations and the simulated data by means of the high-energy transport codes MCNP6.1 (CEM03.03), PHITS (INCL4.6/GEM), Geant4 (INCL++/ABLA) and the nuclear reaction code TALYS.
Griffin, K. T.*; Sato, Tatsuhiko; Funamoto, Sachiyo*; Chizhov, K.*; Domal, S.*; Paulbeck, C.*; Bolch, W.*; Cullings, H. M.*; Egbert, S. D.*; Endo, Akira; et al.
Radiation and Environmental Biophysics, 61(1), p.73 - 86, 2022/03
To evaluate the potential dosimetry improvements that would arise from their use in a Dosimetry System (DS) at RERF, we have evaluated organ doses in the J45 series using the environmental fluence data for twenty generalized survivor scenarios pulled directly from the current DS. The energy- and angle-dependent gamma and neutron fluences were converted to a phase space source term for use in MCNP6, a modern radiation transport code. Overall, the updated phantom series would be expected to provide dose improvements to several important organs, including the active marrow, colon, and stomach wall (up to 20%, 20%, and 15% impact on total dose, respectively). The impacts on dosimetry were especially significant for neutron dose estimates (up to a two-fold difference) and within organs which were unavailable in the previous phantom series, such as the skin, esophagus, and prostate.
Matsuya, Yusuke; Hamada, Nobuyuki*; Yachi, Yoshie*; Satou, Yukihiko; Ishikawa, Masayori*; Date, Hiroyuki*; Sato, Tatsuhiko
Cancers (Internet), 14(4), p.1045_1 - 1045_15, 2022/02
An insoluble cesium-bearing microparticle (Cs-BMP) was discovered after the incident at the Fukushima nuclear power plant. Radiation risk by intake of internal exposure to radioactive cesium is conventionally estimated from organ dose, assuming that soluble cesium is uniformly distributed throughout human body. Meanwhile, such Cs-BMPs are assumed to adhere in the long term to normal tissue, leading to chronic non-uniform exposure. In this study, to clarify the normal tissue effects for Cs-BMP exposure, we investigated the relationship between the inflammatory responses and DNA damage induction. From experiments focusing on the inflammatory signaling pathways such as NF-B p65 and COX-2, compared to the uniform exposure to -rays, NF-B p65 tended to be more activated in the cells proximal to the Cs-BMP, while both NF-B p65 and COX-2 were significantly activated in the distal cells. Experiments with inhibitors for NF-B p65 and COX-2 suggested involvement of such inflammatory responses both in the reduced radiosensitivity of the cells proximal to Cs-BMP and the enhanced radiosensitivity of the cells distal from Cs-BMP. These results suggested that radiation effects for Cs-BMP exposure can differ from that estimated based on conventional uniform exposure to normal tissues.
Matsuya, Yusuke; Kai, Takeshi; Sato, Tatsuhiko; Ogawa, Tatsuhiko; Hirata, Yuho; Yoshii, Yuji*; Parisi, A.*; Liamsuwan, T.*
International Journal of Radiation Biology, 98(2), p.148 - 157, 2022/02
When investigating radiation-induced biological effects, it is essential to perform detailed track-structure simulations explicitly by considering each atomic interaction in liquid water (which is equivalent to human tissues) at sub-cellular and DNA scales. The Particle and Heavy Ion Transport code System (PHITS) is a Monte Carlo code which can be used for track structure calculations by employing an original electron track-structure mode (etsmode) and the world-famous KURBUC algorithms (PHITS-KURBUC mode) for protons and carbon ions. In this study, the physical features (i.e., range, radial dose and microdosimetry) of these modes have been verified by comparing to the available experimental data and Monte Carlo simulation results reported in literature. In addition, applying the etsmode to radiobiological study, we estimated the yields of single-strand breaks (SSBs), double-strand breaks (DSBs) and complex DSBs, and evaluated the dependencies of DNA damage yields on incident electron energy. As a result, the simulations suggested that DNA damage types are intrinsically related with the spatial patterns of ionization and electronic excitations and that approximately 500 eV electron can cause much complex DSBs. In this paper, we show the development status of the PHITS track-structure modes and its application to radiobiological research, which would be expected to identify the underlying mechanisms of radiation effects based on physics.
Saito, Susumu*; Wickramasinghe, N. K.*; Sato, Tatsuhiko; Shiota, Daiko*
Earth, Planets and Space (Internet), 73(1), p.57_1 - 57_10, 2021/12
By using an flight trajectory generation algorithm and the global effective dose rate (EDR) distribution calculated WASAVIES, the economic impacts of SEP events on aircraft operation, namely the flight path length, flight time, and fuel consumption, are estimated. The flight path length, flight time, and fuel consumption for a flight route from New York, US to Tokyo, Japan are estimated with constraints in flight routes to avoid the hazard of radiation and compared with those of the reference case without the SEP effects. Setting more flexible constraints in the flight route and generating optimal flight trajectories with minimal economic impacts by fully utilizing the global EDR distribution is the next step.
Ishii, Mamoru*; Shiota, Daiko*; Tao, Chihiro*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Ishii, Takako*; Ichimoto, Kiyoshi*; Kataoka, Ryuho*; Koga, Kiyokazu*; Kubo, Yuki*; et al.
Earth, Planets and Space (Internet), 73(1), p.108_1 - 108_20, 2021/12
We surveyed the relationship between the scale of space weather events and their occurrence rate in Japan and we discussed the social impact of these phenomena during the Project for Solar-Terrestrial Environment Prediction (PSTEP). The information was compiled for domestic users of space weather forecasts for appropriate preparedness against space weather disasters. This paper gives a comprehensive summary of the survey, focusing on the fields of electricity, satellite operations, communication and broadcasting, satellite positioning usage, aviation, human space activity, and daily life on the Earth's surface, using the cutting-edge knowledge of space weather. Quantitative estimations of the economic impact of space weather events on electricity and aviation are also given.
Matsuya, Yusuke; Kai, Takeshi; Ogawa, Tatsuhiko; Hirata, Yuho; Sato, Tatsuhiko
Hoshasen Kagaku (Internet), (112), p.15 - 20, 2021/11
Particle and Heavy Ion Transport code System (PHITS) is a general-purpose Monte Carlo code enabling radiation kinetics, which is often used in diverse research fields, such as atomic energy, engineering, medicine and science. After released in 2010, the PHITS code has been developed to expand its functions and to improve its convenience. In the few years, track-structure mode has been introduced in PHITS that can simulate each atomic interaction by electrons, positions, protons and carbon ions in liquid water. Thanks to the development of track-structure mode, the latest PHITS code enables microscopic dose calculations by decomposing it to the scale of DNA. Aiming at realizing the track-structure mode with high precision, the further developments of electron and ion track-structure mode for arbitrary materials are recently ongoing. This review shows the development history and future prospect of PHITS track-structure mode, which can expect to be further applied to the research fields of atomic physics, radiation chemistry, and quantum life science.