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Ogawa, Tatsuhiko; Iwamoto, Yosuke
Nuclear Instruments and Methods in Physics Research B, 549, p.165255_1 - 165255_4, 2024/04
Atomic defect is one of the critical factors that determines the irradiation effects in materials. The atoms are recoiled by the impulse of incoming radiation, which changes the mechanical, electrical and chemical properties of the target materials. Methods to calculate atomic displacement based on nuclear reaction cross sections and Rutherford scattering cross sections were proposed but they were dedicated to calculation of the defect density in macroscopic scale whereas some phenomena are attributed to the topological arrangements of defects in microscopic scale. Application of a track-structure calculation model, ITSART implemented to a general-purpose radiation transport code PHITS for calculation of the topological arrangement of radiation-induced defects is proposed in this study. To verify the defect production calculated by ITSART, DPA (Displacement Per Atom) cross section in Cu was calculated and compared with literature data. The agreement indicates the accuracy of ITSART for calculating atomic displacement. By using the same methodology to a smaller volume, the defects in SiO
exposed to 600 MeV proton beam was calculated. PHITS users can make use of the outputs by forwarding them to other tools, such as molecular dynamics codes, to analyse the further evolution of the defects.
Hirata, Yuho; Kai, Takeshi; Ogawa, Tatsuhiko; Matsuya, Yusuke; Sato, Tatsuhiko
Nuclear Instruments and Methods in Physics Research B, 547, p.165183_1 - 165183_7, 2024/02
Times Cited Count：0 Percentile：0.02(Instruments & Instrumentation)The luminescence efficiency of the phosphors for swift ions is known to decrease because of the quenching effects. To obtain the precise dose distributions using phosphor detectors, understanding the mechanisms of quenching effects is mandatory. Here, we developed a new model for estimating the luminescence intensity of phosphors based on the track-structure modes for arbitrary materials implemented in PHITS. The developed model enabled the simulation of the quenching effects of the BaFBr detector and was verified by comparing the results to the corresponding measured data. The present model is expected to contribute to developing phosphor detectors worldwide.
Murase, Kiyoka*; Kataoka, Ryuho*; Nishiyama, Takanori*; Sato, Kaoru*; Tsutsumi, Masaki*; Tanaka, Yoshimasa*; Ogawa, Yasunobu*; Sato, Tatsuhiko
Space Weather, 21(12), p.e2023SW003651_1 - e2023SW003651_11, 2023/12
Times Cited Count：0 Percentile：0.01(Astronomy & Astrophysics)Comprehensive understandings of their global impact on the atmosphere require whole pictures of spatio-temporal distributions of the ionization due to them. We estimate the altitude profiles of the ionization rate during the space weather event occurred in September 2017 by using the Particle and Heavy Ion Transport code System (PHITS) with input of the particle fluxes obtained by satellites. The estimates are then compared with measurements of the ionization altitude, ionization intensity, and electron density by the radars in the polar region such as the PANSY radar at Syowa Station and the EISCAT in Tromso, Norway. We conclude that the PHITS simulation results reproduce those ionizations measured by ground-based instruments with inputs of observed ionization sources by satellites within a factor of 2.
Hirata, Yuho; Kai, Takeshi; Ogawa, Tatsuhiko; Matsuya, Yusuke*; Sato, Tatsuhiko
Japanese Journal of Applied Physics, 62(10), p.106001_1 - 106001_6, 2023/10
Times Cited Count：2 Percentile：75.57(Physics, Applied)Optimization of semiconductor detector design requires theoretical analysis of the process of radiation conversion to carriers (excited electrons) in semiconductor materials. We, therefore, developed an electron track-structure code that can trace an incident electron trajectory down to a few eV and simulate many excited electron productions in semiconductors, named ETSART, and implemented it into PHITS. The accuracy of ETSART was validated by comparing calculated electron ranges in semiconductor materials with the corresponding data recommended in ICRU Report 37 and obtained from another simulation code. The average energy required to produce a single excited electron (epsilon value) is an important value that describes the characteristics of semiconductor detectors. Using ETSART, we computed the epsilon values in various semiconductors and found that the calculated epsilon values cannot be fitted well with a linear model of the band-gap energy. ETSART is expected to be useful for initial and mechanistic evaluations of electron-hole generation in undiscovered materials.
Sato, Tatsuhiko; Matsuya, Yusuke*; Ogawa, Tatsuhiko; Kai, Takeshi; Hirata, Yuho; Tsuda, Shuichi; Parisi, A.*
Physics in Medicine & Biology, 68(15), p.155005_1 - 155005_15, 2023/07
Times Cited Count：2 Percentile：84.52(Engineering, Biomedical)In this study, we improved the microdosimetric function implemented in PHITS using the latest track-structure simulation codes. The improved function is capable of calculating the probability densities of not only the conventional microdosimetric quantities such as lineal energy but also the numbers of ionization events occurred in a target site, the so-called ionization cluster size distribution, for arbitrary site diameters from 3 nm to 1 um. As a new application of the improved function, we calculated the relative biological effectiveness of the single-strand break and double-strand break yields for proton irradiations using the updated PHITS coupled with the simplified DNA damage estimation model, and confirmed its equivalence in accuracy and its superiority in computational time compared to our previously proposed method based on the track-structure simulation.
Constantini, J.-M.*; Ogawa, Tatsuhiko; Gourier, D.*
Journal of Physics; Condensed Matter, 35(28), p.285701_1 - 285701_12, 2023/04
Times Cited Count：0 Percentile：0(Physics, Condensed Matter)A novel analysis of luminescence is presented on the basis of virtual photon spectra (VPS) produced by charged particles (electrons or ions) passing by luminescent species such as defects or impurities, in wide band-gap ionic-covalent solids. The electron-energy dependence of experimental luminescence spectra of sapphire (
-AlO
) is discussed in relation to the computed VPS for the primary and secondary electrons. The experimental luminescence spectra of -AlO are also analyzed in this framework for protons and helium ions in the MeV energy range. The variations of stopping power are consistent with the variation of the number of emitted VPs. The decay of luminescence yield versus ion stopping power is discussed on the basis of the variation of the computed VPS, and ionization and excitation induced by primary ions and secondary electrons. This decay is accounted for by a decrease of the yield of low-energy secondary electrons with the subsequent VP emission.
Constantini, J.-M.*; Ogawa, Tatsuhiko
Quantum Beam Science (Internet), 7(1), p.7_1 - 7_16, 2023/03
Sputtering, emission of constituent atoms or molecules of materials induced by irradiation, is regarded as one of standard engineering techniques. According to some experimental data, emission of atoms whose direction is anti-parallel to incident radiation momentum was found among the sputtered atoms. Based on the standard approach, the thermal-spike model, atoms are evaporated by equillibrated thermal canonical ensemble resulted in by heat propagation therefore emission must be isotropic. Inspired by the fact that ionizations induced by ion irradiation are arranged linearly along the ion path, and the electric repulsion force between the ionizations tend to be parallel to irradiation axis, we developed an alternative approach in this study to explain the anisotropic emission. Using the spatial configuration of the irradiation-induced positive ions calculated by track-structure calculation code RITRACKS, the momentum of ions driven by the electric force was calculated. The calculated result explains the inverse jet of ions in case of 1 MeV proton and 1 MeV/u carbon ion irradiation to water. Moreover, the calculated sputtering yield also agrees with earlier experimental data.
Iwamoto, Yosuke; Tsuda, Shuichi; Ogawa, Tatsuhiko
Frontiers in Energy Research (Internet), 11, p.1085264_1 - 1085264_11, 2023/01
Times Cited Count：0 Percentile：0.02(Energy & Fuels)This review describes experimental data useful for validation of radiation shielding design in advanced reactor systems such as nuclear fusion and accelerator-driven subcritical systems (ADS) and calculations using the PHITS code and JENDL-4.0/HE. The relevant experiments have been conducted mainly in Japan and include (1) neutron spectra in iron shields using 14 MeV neutron sources, (2) leakage neutron spectra from spherical piles of various materials using 14 MeV neutron sources, (3) neutron spectra after penetration through shields using several tens of MeV neutron sources, (4) neutron spectra produced from the target by high-energy heavy-ion bombardment, and (5) induced radioactivity in concrete using heavy-ion nuclear reaction product particles as a source. Throughout, the experimental and calculated values were agreed well. These experimental data are also useful for the validation of all radiation transport calculation codes used in the design of advanced reactor systems.
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, 9 Pages, 2023/00
Times Cited Count：5 Percentile：98.08(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.
Ogawa, Tatsuhiko; Hirata, Yuho; Matsuya, Yusuke; Kai, Takeshi
Isotope News, (784), p.13 - 16, 2022/12
Track-structure calculation, a method to simulate every secondary electron production reaction explicitly, has been extensively used as an important techniques in various fields such as radiation biology, material irradiation effect, and radiation detection. However, it requires the dielectric function of the target materials, which is not well known except for liquid water. Therefore we developed a model to perform track-structure calculation based on a systematic formula of secondary electron production cross section and that of stopping power. The model can therefore perform track-structure calculation regardless of the availability of dielectric function measurement data. Stopping range, and energy deposition radial distribution calculated by this model agreed well with the earlier experimental data and calculation by precedent codes. The lineal energy in tissue-equivalent gas calculated by this model agreed with measurement data taken from literature, showing distinct difference from that in liquid water. This model was implemented to PHITS Ver3.25, the general-purpose radiation transport simulation code of JAEA, being distributed to users as the first track-structure calculation model applicable to arbitrary materials available in general-purpose transport code.
Hirata, Yuho; Kai, Takeshi; Ogawa, Tatsuhiko; Matsuya, Yusuke; Sato, Tatsuhiko
Japanese Journal of Applied Physics, 61(10), p.106004_1 - 106004_6, 2022/10
Times Cited Count：5 Percentile：67.2(Physics, Applied)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.
Ogawa, Tatsuhiko; Litaize, O.*; Mancusi, D.*; Chebboubi, A.*; Serot, O.*
European Physical Journal A, 58(8), p.153_1 - 153_9, 2022/08
Times Cited Count：1 Percentile：33.4(Physics, Nuclear)The Monte-Carlo code FIFRELIN was originally developed for the simulation of first chance fission of fissile nuclei. It can predict fission observables such as fragment yields and neutron yields accurately by using experimental data and databases. However, FIFRELIN cannot calculate remnant dose and decay heat considering delayed decay of fission fragments. Moreover, FIFRELIN can predict the energy spectra of neutrons and gammas but further transport calculation required generation of heavy external files. In this study, FIFRELIN was interfaced to radiation transport code PHITS to perform burn up calculation and particle transport calculation. Owing to the burn up calculation, decay heat and remnant dose were calculated for given irradiation condition and cooling period. Interface of particle transport calculation by PHITS and FIFRELIN can perform particle transport simulation based on the source term calculated by FIFRELIN.
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
Times Cited Count：7 Percentile：91.6(Nuclear Science & Technology)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.
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：48 Percentile：96.94(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.
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
Times Cited Count：1 Percentile：22.72(Astronomy & Astrophysics)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.
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
Times Cited Count：15 Percentile：80.59(Biology)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.
Ogawa, Tatsuhiko; Hirata, Yuho; Matsuya, Yusuke; Kai, Takeshi
Scientific Reports (Internet), 11(1), p.24401_1 - 24401_10, 2021/12
Times Cited Count：14 Percentile：76.83(Multidisciplinary Sciences)Track-structure calculation, a method to simulate every secondary electron production reaction explicitly, has been extensively used as an important techniques in various fields such as radiation biology, material irradiation effect, and radiation detection. However, it requires the dielectric function of the target materials, which is not well known except for liquid water. Therefore we developed a model to perform track-structure calculation based on a systematic formula of secondary electron production cross section and that of stopping power. The model can therefore perform track-structure calculation regardless of the availability of dielectric function measurement data. Stopping range, and energy deposition radial distribution calculated by this model agreed well with the earlier experimental data and calculation by precedent codes. The lineal energy in tissue-equivalent gas calculated by this model agreed with measurement data taken from literature, showing distinct difference from that in liquid water. This model was implemented to PHITS Ver3.25, the general-purpose radiation transport simulation code of JAEA, being distributed to users as the first track-structure calculation model applicable to arbitrary materials available in general-purpose transport code.
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.
Meleshenkovskii, I.*; Ogawa, Tatsuhiko; Sari, A.*; Carrel, F.*; Boudergui, K.*
Nuclear Instruments and Methods in Physics Research B, 483, p.5 - 14, 2020/11
Times Cited Count：4 Percentile：45.45(Instruments & Instrumentation)For the purpose of fissile material detection, the technique to observe neutrons ejected from photo-fission induced by bremsstrahlung X-rays is being developed. This technique is advantageous in the sense that the machine can be compact compared to conventional neutron generators. However, photo-fission reaction cross sections are generally smaller than those of neutron-induced fission cross sections therefore optimization of the beam line is of high importance. In this study, we investigated the factors necessary to be optimized by using Monte-Carlo transport codes MCNP and PHITS. It was found that high-Z materials are advantageous to effectively produce bremsstrahlung X-rays but photons produce neutrons by secondary (
,n) reactions resulting in mixing of prompt and delayed fission reactions. Moreover, secondary neutrons are produced not only inside the target but also in the materials surrounding the target. Therefore it is necessary to select elements whose neutron separation energy is high to suppress parasitic secondary neutrons.
Constantini, J.-M.*; Seo, P.*; Yasuda, Kazuhiro*; Bhuian, AKM S. I.*; Ogawa, Tatsuhiko; Gourier, D.*
Journal of Luminescence, 226, p.117379_1 - 117379_10, 2020/10
Times Cited Count：5 Percentile：42.02(Optics)Cathodo-luminescence is used for detection of lattice defects, in particular oxygen vacancies in ceramics induced by electrons. However, how oxygen vacancy production efficiency depends on sample temperature, incoming electron flux, and electron energy was not clear. In this study, oxygen vacancies were made in the specimens of CeO by irradiation of 400-1250 keV electrons and the cathodoluminescence from thus induced vacancies were observed by photo-fiber probe combined with CCD. As the result, the dependence of luminescence intensity on specimen temperature depends on the carrier trapping frequency and luminescence efficiency while luminescence center production/annihilation speed determines the dependency on the incoming electron flux. Moreover, radiation transport calculation conducted by the particle transport simulation code PHITS indicates that the number of electrons above the defect production threshold energy is vital to explain incoming electron energy dependence.
