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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

$$^{rm 99m}$$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

A Terrestrial SER Estimation Methodology Based on Simulation Coupled With One-Time Neutron Irradiation Testing

Abe, Shinichiro; Hashimoto, Masanori*; Liao, W.*; Kato, Takashi*; Asai, Hiroaki*; Shimbo, Kenichi*; Matsuyama, Hideya*; Sato, Tatsuhiko; Kobayashi, Kazutoshi*; Watanabe, Yukinobu*

IEEE Transactions on Nuclear Science, 70(8, Part 1), p.1652 - 1657, 2023/08

Single event upsets (SEUs) caused by neutrons is a reliability problem for microelectronic devices in the terrestrial environment. Acceleration tests using white neutron beam provide realistic soft error rates (SERs), but only a few facilities can provide white neutron beam in the world. If single-source irradiation applicable to diverse neutron source can be utilized for the evaluation of the SER in the terrestrial environment, it contributes to solve the shortage of beam time. In this study, we investigated the feasibility of the SER estimation in the terrestrial environment by any one of these measured data with the SEU cross sections obtained by PHITS simulation. It was found that the SERs estimated by our proposed method are within a factor of 2.7 of that estimated by the Weibull function. We also investigated the effect of simplification which reduce the computational cost in simulation to the SER estimation.

Journal Articles

Chiral superconductivity in UTe$$_2$$ probed by anisotropic low-energy excitations

Ishihara, Kota*; Roppongi, Masaki*; Kobayashi, Masayuki*; Imamura, Kumpei*; Mizukami, Yuta*; Sakai, Hironori; Opletal, P.; Tokiwa, Yoshifumi; Haga, Yoshinori; Hashimoto, Kenichiro*; et al.

Nature Communications (Internet), 14, p.2966_1 - 2966_7, 2023/05

 Times Cited Count:1 Percentile:83.24(Multidisciplinary Sciences)

The superconducting symmetry of the heavy fermion uranium-based superconductor UTe$$_2$$ is investigated using low temperature penetration depth measurements. The anisotropic low-energy quasiparticle excitations indicates multiple superconducting components in a chiral complex form. The most consistent is a chiral non-unitary state.

Journal Articles

Anisotropic enhancement of lower critical field in ultraclean crystals of spin-triplet superconductor candidate UTe$$_2$$

Ishihara, Kota*; Kobayashi, Masayuki*; Imamura, Kumpei*; Konczykowski, M.*; Sakai, Hironori; Opletal, P.; Tokiwa, Yoshifumi; Haga, Yoshinori; Hashimoto, Kenichiro*; Shibauchi, Takasada*

Physical Review Research (Internet), 5(2), p.L022002_1 - L022002_6, 2023/04

Lower superconducting critical fields $$H_{rm c1}$$ of UTe$$_2$$ have been determined. Orthorhombic UTe$$_2$$ has magnetic easy axis along the $$a$$-axis. We found $$H_{rm c1}$$ perpendicular to $$a$$ showed anomalous enhancement. By comparing with anisotropy of upper critical fields, effect of magnetic fluctuations on superconductivity is suggested.

Journal Articles

High-sensitive XANES analysis at Ce L$$_{2}$$-edge for Ce in bauxites using transition-edge sensors; Implications for Ti-rich geological samples

Li, W.*; Yamada, Shinya*; Hashimoto, Tadashi; Okumura, Takuma*; Hayakawa, Ryota*; Nitta, Kiyofumi*; Sekizawa, Oki*; Suga, Hiroki*; Uruga, Tomoya*; Ichinohe, Yuto*; et al.

Analytica Chimica Acta, 1240, p.340755_1 - 340755_9, 2023/02

 Times Cited Count:1 Percentile:34.31(Chemistry, Analytical)

no abstracts in English

Journal Articles

Free-surface flow simulations with floating objects using lattice Boltzmann method

Watanabe, Seiya*; Kawahara, Jun*; Aoki, Takayuki*; Sugihara, Kenta; Takase, Shinsuke*; Moriguchi, Shuji*; Hashimoto, Hirotada*

Engineering Applications of Computational Fluid Mechanics, 17(1), p.2211143_1 - 2211143_23, 2023/00

In tsunami inundations or slope disasters of heavy rain, a lot of floating debris or driftwood logs are included in the flows. The damage to structures from solid body impacts is more severe than the damage from the water pressure. In order to study free-surface flows that include floating debris, developing a high-accurate simulation code of free-surface flows with high performance for large-scale computations is desired. We propose the single-phase free-surface flow model based on the cumulant lattice Boltzmann method coupled with a particle-based rigid body simulation. The discrete element method calculates the contact interaction between solids. An octree-based AMR (Adaptive Mesh Refinement) method is introduced to improve computational accuracy and time-to-solution. High-resolution grids are assigned near the free surfaces and solid boundaries. We conducted two kinds of tsunami flow experiments in the 15 and 70 m water tanks at Hachinohe Institute of Technology and Kobe University to validate the accuracy of the proposed model. The simulation results have shown good agreement with the experiments for the drifting speed, the number of trapped wood pieces, and the stacked angles.

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, 10 Pages, 2023/00

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

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, 9 Pages, 2023/00

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

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:0 Percentile:49.94(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

Axial U(1) symmetry at high temperatures in $$N_f=2+1$$ lattice QCD with chiral fermions

Aoki, Shinya*; Aoki, Yasumichi*; Fukaya, Hidenori*; Hashimoto, Shoji*; Kanamori, Issaku*; Kaneko, Takashi*; Nakamura, Yoshifumi*; Rohrhofer, C.*; Suzuki, Kei

Proceedings of Science (Internet), 396, p.332_1 - 332_7, 2022/07

The axial U(1) anomaly in high-temperature QCD plays an important role to understand the phase diagram of QCD. The previous works by JLQCD Collaboration studied high-temperature QCD using 2-flavor dynamical chiral fermions such as the domain-wall fermion and reweighted overlap fermion. We extend our simulations to QCD with 2+1-flavor dynamical quarks, where the masses of the up, down, and strange quarks are near the physical point, and the temperatures are close to or higher than the pseudocritical temperature. In this talk, we will present the results for the Dirac spectrum, topological susceptibility, axial U(1) susceptibility, and hadronic collelators.

Journal Articles

What is chiral susceptibility probing?

Aoki, Shinya*; Aoki, Yasumichi*; Fukaya, Hidenori*; Hashimoto, Shoji*; Rohrhofer, C.*; Suzuki, Kei

Proceedings of Science (Internet), 396, p.050_1 - 050_9, 2022/07

In the early days of QCD, the axial $$U(1)$$ anomaly was considered as a trigger for the breaking of the $$SU(2)_Ltimes SU(2)_R$$ symmetry through topological excitations of gluon fields. However, it has been a challenge for lattice QCD to quantify the effect. In this work, we simulate QCD at high temperatures with chiral fermions. The exact chiral symmetry enables us to separate the contribution from the axial $$U(1)$$ breaking from others among the susceptibilities in the scalar and pseudoscalar channels. Our result in two-flavor QCD indicates that the chiral susceptibility, which is conventionally used as a probe for $$SU(2)_Ltimes SU(2)_R$$ breaking, is actually dominated by the axial $$U(1)$$ breaking at temperatures $$Tge 165$$ MeV.

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:32 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.

Journal Articles

Mesospheric ionization during substorm growth phase

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:0 Percentile:24.42(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.

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:3 Percentile:73.26(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:0 Percentile:48.58(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

The Japan Health Physics Society Guideline on Dose Monitoring for the Lens of the Eye

Yokoyama, Sumi*; Tsujimura, Norio; Hashimoto, Makoto; Yoshitomi, Hiroshi; Kato, Masahiro*; Kurosawa, Tadahiro*; Tatsuzaki, Hideo*; Sekiguchi, Hiroshi*; Koguchi, Yasuhiro*; Ono, Koji*; et al.

Journal of Radiation Protection and Research, 47(1), p.1 - 7, 2022/03

Background: In Japan, new regulations that revise the dose limit for the lens of the eye (the lens), operational quantities, and measurement positions for the lens dose were enforced in April 2021. Based on the international safety standards, national guidelines, the results of the Radiation Safety Research Promotion Fund of the Nuclear Regulatory Authority, and other studies, the Working Group of Radiation Protection Standardization Committee, the Japan Health Physics Society (JHPS) developed a guideline for radiation dose monitoring for the lens. Materials and Methods: The Working Group of the JHPS discussed the criteria of non-uniform exposure and the management criteria set to not exceed the dose limit for the lens. Results and Discussion: In July 2020, the JHPS guideline was published. The guideline consists of three parts: main text, explanations, and 26 questions. In the questions, the corresponding answers were prepared, and specific examples were provided to enable similar cases to be addressed. Conclusion: With the development of guideline on radiation dose monitoring of the lens, radiation managers and workers will be able to smoothly comply with revised regulations and optimise radiation protection.

Journal Articles

Role of the axial $$U(1)$$ anomaly in the chiral susceptibility of QCD at high temperature

Aoki, Shinya*; Aoki, Yasumichi*; Fukaya, Hidenori*; Hashimoto, Shoji*; Rohrhofer, C.*; Suzuki, Kei

Progress of Theoretical and Experimental Physics (Internet), 2022(2), p.023B05_1 - 023B05_12, 2022/02

 Times Cited Count:5 Percentile:83.18(Physics, Multidisciplinary)

The chiral susceptibility, or the first derivative of the chiral condensate with respect to the quark mass, is often used as a probe for the QCD phase transition since the chiral condensate is an order parameter of $$SU(2)_L times SU(2)_R$$ symmetry breaking. However, the chiral condensate also breaks the axial $$U(1)$$ symmetry, which is usually not studied as it is already broken by the anomaly and apparently has little impact on the transition. We investigate the susceptibilities in the scalar and pseudoscalar channels in order to quantify how much the axial $$U(1)$$ breaking contributes to the chiral phase transition. Employing a chirally symmetric lattice Dirac operator and its eigenmode decomposition, we separate the axial $$U(1)$$ breaking effects from others. Our result in two-flavor QCD indicates that both of the connected and disconnected chiral susceptibilities are dominated by axial $$U(1)$$ breaking at temperatures $$Tgeq 190$$ MeV after the quadratically divergent constant is subtracted.

Journal Articles

Development of guidelines on radiation protection for the lens of the eye in Japan

Yokoyama, Sumi*; Iwai, Satoshi*; Tsujimura, Norio; Hashimoto, Makoto; Yoshitomi, Hiroshi; Kato, Masahiro*; Kurosawa, Tadahiro*; Tatsuzaki, Hideo*; Sekiguchi, Hiroshi*; Koguchi, Yasuhiro*; et al.

Proceedings of 15th International Congress of the International Radiation Protection Association (IRPA-15) (Internet), 8 Pages, 2022/00

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:4 Percentile:73.26(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

Dynamics of radiocaesium within forests in Fukushima; Results and analysis of a model inter-comparison

Hashimoto, Shoji*; Tanaka, Taku*; Komatsu, Masabumi*; Gonze, M.-A.*; Sakashita, Wataru*; Kurikami, Hiroshi; Nishina, Kazuya*; Ota, Masakazu; Ohashi, Shinta*; Calmon, P.*; et al.

Journal of Environmental Radioactivity, 238-239, p.106721_1 - 106721_10, 2021/11

 Times Cited Count:8 Percentile:58.13(Environmental Sciences)

This study was aimed at analysing performance of models for radiocesium migration mainly in evergreen coniferous forest in Fukushima, by inter-comparison between models of several research teams. The exercise included two scenarios of countermeasures against the contamination, namely removal of soil surface litter and forest renewal, and a specific konara oak forest scenario in addition to the evergreen forest scenario. All the models reproduced trend of time evolution of radiocesium inventories and concentrations in each of the components in forest such as leaf and organic soil layer. However, the variations between models enlarged in long-term predictions over 50 years after the fallout, meaning continuous field monitoring and model verification/validation is necessary.

383 (Records 1-20 displayed on this page)