Implementation of a new function for handling nuclear data of outgoing particles and residual excitation states in PHITS

Furuta, Takuya; Hashimoto, Shintaro; Ogawa, Tatsuhiko; Tanimura, Yoshihiko

Nuclear Instruments and Methods in Physics Research A, 1086, p.171320_1 - 171320_8, 2026/06

https://doi.org/10.1016/j.nima.2026.171320

A new function to incorporate nuclear data libraries with outgoing particles plus residual nuclei in specific excitation states for neutron-induced reactions has been implemented in a Monte Carlo simulation code, Particle and Heavy Ion Transport code System (PHITS). With this function, accurate predictions of outgoing particle spectra and angular distributions according to the nuclear data libraries become possible, while accounting for production of residual nuclei and de-excitation gammas, conserving total energy and momentum in each event. This feature allows users to perform high-precision simulations of detector responses and radiation damage in materials.

Development of Linear Interpolation System for SMK Model parameters Evaluated from Cellular-scale simulation (LISMEC) and its application to BNCT dosimetry

Shigehira, Takafumi*; Watanabe, Tsubasa*; Suzuki, Minoru*; Hirata, Yuho; Ogawa, Tatsuhiko; Fujimura, Atsushi*; Sakurai, Yoshinori*; Sato, Tatsuhiko

Journal of Radiation Research (Internet), 67(2), p.170 - 181, 2026/03

https://doi.org/10.1093/jrr/rraf075

Development and validation of generalized Monte Carlo track-structure simulation model applicable to arbitrary ions in arbitrary materials

Ogawa, Tatsuhiko; Hirata, Yuho; Matsuya, Yusuke; Kai, Takeshi

Computer Physics Communications, 316, p.109758_1 - 109758_15, 2025/11

https://doi.org/10.1016/j.cpc.2025.109758

A track structure simulation model, ITSART Ver.2, has been developed to simulate the transport of arbitrary ions in arbitrary materials, accounting for every atomic interaction on an event-by-event basis. Unlike conventional track structure models, which are typically designed for therapeutic particle beams or bio-molecular targets, ITSART Ver.2 uniquely enables track structure calculations for any ion-material combination across an energy range from 10 eV/n to 1 TeV/n. To validate the developed model, the energy-angular distributions of secondary electrons, ion stopping ranges, radial dose distributions, and microscopic dose distributions calculated by ITSART Ver.2 were benchmarked against literature data. The unique features of ITSART Ver.2, including kinetic modeling of secondary electrons above 1 keV, modeling of secondary electron angular distribution, consideration of momentum transfer to target atoms, and interface with an atomic de-excitation model, resulted in calculations that were consistent with the benchmarking data. Furthermore, this benchmarking calculation demonstrated that ITSART Ver.2 can reproduce target-specific quantities such as Auger electron production and penumbra radial dose, which cannot be simulated with conventional codes that approximate the target as water. The capability of ITSART Ver.2 to perform track structure calculations under unconventional conditions paves the way for simulating various irradiation eff ects, such as reactor material irradiation damage, semiconductor device degradation, and other complex interactions.

Prediction of composite neutron source spectra by combination of JENDL-5 and PHITS

Ogawa, Tatsuhiko

Annals of Nuclear Energy, 216, p.111256_1 - 111256_12, 2025/06

https://doi.org/10.1016/j.anucene.2025.111256

A novel robust method has been developed to simulate the performance of composite neutron sources composed of an alpha-emitting actinide and a light nucleus with low neutron separation energy. This method is based on the JENDL-5 cross-section data library and the Monte-Carlo radiation transport code PHITS. In contrast to previously devised methods, this approach can predict various quantities of the sources, such as actinide grain size dependence, absolute neutron emission intensity, energy spectra of neutrons and parasitic photons, neutron multiplicity, and time structure, with little approximation. The accurate calculation of stopping power of alpha rays in actinide grains and light elements, as well as the use of (,n) reaction evaluated cross sections, which is one of the unique features of PHITS Ver.3.34 and its later versions, are the essences of the method. This method allows for the calculation of quantities important for practical applications, such as detection signal frequency, coincidence event rate, and the impact of parasitic gamma-rays.

A Benchmark for Monte Carlo simulation of photoneutron fields from electron accelerators

Sari, A.*; Meleshenkovskii, I.*; Ogawa, Tatsuhiko; Tran, K.-T.*; Jinaphanh, A.*; Jouanne, C.*; Zoia, A.*

Nuclear Instruments and Methods in Physics Research A, 1072, p.170168_1 - 170168_17, 2025/03

https://doi.org/10.1016/j.nima.2024.170168

Electron accelerators cover a wide range of applications, from nuclear waste package assay and security-related tasks to radiation therapy. High-energy photons produced by electron Bremsstrahlung radiation might induce photonuclear reactions emitting secondary neutrons. In this paper, we perform a two-stage benchmark for Monte Carlo simulation of photoneutron fields from electron accelerators operating in the 4-20 MeV range. On the one hand, we benchmark three independently developed Monte Carlo codes, i.e., MCNP, TRIPOLI-4; and PHITS, using ENDF7u photonuclear data from the ENDF/B-VII.1 library. On the other hand, we benchmark two photonuclear data sub-libraries, i.e., ENDF7u and JENDL-5, as well as nuclear reaction models, using the PHITS code. Errors in ENDF7u for W-184 and Ta-181 cause unphysical shapes of the photoneutron energy spectra with the three codes. Questionable behaviors are also found with JENDL-5, which calls for further examinations in this recently released library. For the cases of heavy water and beryllium, the photoneutron energy spectra obtained with MCNP6 is invalidated. We identified that the problem stems from wrong treatment of the reference frame in using the ACE data files by MCNP and previous versions of PHITS. Results obtained for tungsten and tantalum show that photoneutrons are overall emitted in an isotropic manner. However, results obtained for heavy water and beryllium display different tendencies. This investigation should help Monte Carlo code users to refine the current validity domain of the latest releases of MCNP6, PHITS and TRIPOLI-4 for the simulation of photoneutrons.

Compendium on Monte Carlo simulation of photoneutrons in the Giant Dipole Resonance energy range; The First five elements

Garnaud, L.*; Ogawa, Tatsuhiko; 7 of others*

EPJ Web of Conferences, 302, p.07004_1 - 07004_14, 2024/10

https://doi.org/10.1051/epjconf/202430207004

Photoneutrons, produced by photonuclear reactions, appear in diverse applications using high-energy gamma sources, electron accelerators, or nuclear reactors. Monte Carlo particle-transport codes typically simulate their emission, characterize their fields, and evaluate their impact on nuclear systems. This work aims to compile a compendium on photoneutron simulation using MCNP6, PHITS, and TRIPOLI-4. Each code runs with both ENDF/B-VIII.0 and JENDL-5 nuclear data libraries. We investigate photoneutron fields from 50 naturally isotopic elements, ranging from reaction energy threshold up to 30 MeV (the Giant Dipole Resonance regime). These fields are characterized by photoneutron current, energy spectrum, and angular distribution. This paper details results for the initial five elements: deuterium, beryllium, carbon, nitrogen, and oxygen, ordered by increasing atomic number. This compendium will serve as a valuable resource for users to understand code capabilities and limitations, for developers to improve neutron-emitting photonuclear reaction sampling, and for all photoneutron researchers, including nuclear data evaluators and experimental physicists.

Development and application of PHITS track structure calculations to elucidate the response mechanisms of radiation detectors

Hirata, Yuho; Kai, Takeshi; Ogawa, Tatsuhiko; Matsuya, Yusuke; Sato, Tatsuhiko

Hoshasen Kagaku (Internet), (118), p.21 - 28, 2024/10

https://radiation-chemistry.org/kaishi/118pdf/RC118.pdf

Accurate dose evaluation by radiation detectors is crucial for the safe use of radiation. However, with certain types of radiation, the output from detectors can be nonlinear relative to the dose, thereby hindering correct dose assessments. To address these issues, it is vital to theoretically analyze the mechanisms affecting detector outputs. The radiation transport code PHITS includes a track structure analysis mode that precisely tracks radiation behavior. This review paper introduces the newly developed Electron Trajectory Structure Analysis Mode for Arbitrary Materials (ETSART), which facilitates the tracking of electron beams in various detector materials. Additionally, we present an example of phosphor quenching under ion beam irradiation, as analyzed using the PHITS track structure mode.

Numerical intercomparison of PHITS and Geant4 Monte Carlo codes for fast neutron inelastic scattering applications

Meleshenkovskii, I.*; Van den Brandt, K.*; Ogawa, Tatsuhiko; Datema, C.*; Mauerhofer, E.*

European Physical Journal Plus (Internet), 139, p.565_1 - 565_9, 2024/07

https://doi.org/10.1140/epjp/s13360-024-05372-z

Fast neutron inelastic scattering is a promising non-destructive assay technique for various analytical applications. As an active neutron interrogation technique, its performance is a function of various different factors and parameters that require optimization. Monte Carlo simulation codes are indispensable for such tasks. However, the internal simulation routines implemented in such codes can rely on different physical models that can yield discrepancies in the simulation results. In this work we conduct an intercomparison of PHITS and Geant4 codes performance in application to fast neutron inelastic scattering simulations. The goal of this paper is twofold. First, we explain the differences in code configuration with respect to gamma and neutron transport, as well as internal simulation routines. Second, we conduct a performance assessment of the two codes using two different measurement configurations. One configuration consisted of a source of gamma-rays in a broad energy range (100 keV - 9000 keV) and a CeBr detector. The other configuration consisted of a monoenergetic 2.5 MeV fast neutron source, Fe, Nd, Dy, B targets and a CeBr detector. Selected simulation configurations were chosen with a goal to compare the performance differences in neutron energy distribution, produced prompt gamma-rays and energy deposition in CeBr detector between the two codes. Results of our study reveal a good coherence of both codes performance in the application of fast neutron inelastic scattering simulations. The simulation geometries and observed differences are described in detail.

Development of a model for evaluating the luminescence intensity of phosphors based on the PHITS track-structure simulation

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

https://doi.org/10.1016/j.nimb.2023.165183

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.

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

https://doi.org/10.1080/00223131.2023.2275736

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.