Pulsed muon facility of J-PARC MUSE

Shimomura, Koichiro*; Koda, Akihiro*; Pant, A. D.*; Sunagawa, Hikaru*; Fujimori, Hiroshi*; Umegaki, Izumi*; Nakamura, Jumpei*; Fujihara, Masayoshi; Tampo, Motonobu*; Kawamura, Naritoshi*; et al.

Interactions (Internet), 245(1), p.31_1 - 31_6, 2024/12

https://doi.org/10.1007/s10751-024-01863-8

Present status of J-PARC MUSE

Shimomura, Koichiro*; Koda, Akihiro*; Pant, A. D.*; Natori, Hiroaki*; Fujimori, Hiroshi*; Umegaki, Izumi*; Nakamura, Jumpei*; Tampo, Motonobu*; Kawamura, Naritoshi*; Teshima, Natsuki*; et al.

Journal of Physics; Conference Series, 2462, p.012033_1 - 012033_5, 2023/03

https://doi.org/10.1088/1742-6596/2462/1/012033

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

https://doi.org/10.1051/swsc/2022012

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.

Time evolution calculation of muon catalysed fusion; Emission of recycling muons from a two-layer hydrogen film

Yamashita, Takuma*; Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.

Fusion Engineering and Design, 169, p.112580_1 - 112580_5, 2021/08

https://doi.org/10.1016/j.fusengdes.2021.112580

A muon () having 207 times larger mass of electron and the same charge as the electron has been known to catalyze a nuclear fusion between deuteron (d) and triton (t). These two nuclei are bound by and form a muonic hydrogen molecular ion, dt. Due to the short inter-nuclear distance of dt, the nuclear fusion, d +t + n + 17.6 MeV, occurs inside the molecule. This reaction is called muon catalyzed fusion (CF). Recently, the interest on CF is renewed from the viewpoint of applications, such as a source of high-resolution muon beam and mono-energetic neutron beam. In this work, we report a time evolution calculation of CF in a two-layered hydrogen isotope target.

Enhancement of element production by incomplete fusion reaction with weakly bound deuteron

Wang, H.*; Otsu, Hideaki*; Chiga, Nobuyuki*; Kawase, Shoichiro*; Takeuchi, Satoshi*; Sumikama, Toshiyuki*; Koyama, Shumpei*; Sakurai, Hiroyoshi*; Watanabe, Yukinobu*; Nakayama, Shinsuke; et al.

Communications Physics (Internet), 2(1), p.78_1 - 78_6, 2019/07

https://doi.org/10.1038/s42005-019-0165-1

Searching for effective pathways for the production of proton- and neutron-rich isotopes through an optimal combination of reaction mechanism and energy is one of the main driving forces behind experimental and theoretical nuclear reaction studies as well as for practical applications in nuclear transmutation of radioactive waste. We report on a study on incomplete fusion induced by deuteron, which contains one proton and one neutron with a weak binding energy and is easily broken up. This reaction study was achieved by measuring directly the cross sections for both proton and deuteron for Pd at 50 MeV/u via inverse kinematics technique. The results provide direct experimental evidence for the onset of a cross-section enhancement at high energy, indicating the potential of incomplete fusion induced by loosely-bound nuclei for creating proton-rich isotopes and nuclear transmutation of radioactive waste.

Estimation of the vertical distribution of radiocesium in soil on the basis of the characteristics of -ray spectra obtained via aerial radiation monitoring using an unmanned helicopter

Ochi, Kotaro; Sasaki, Miyuki; Ishida, Mutsushi*; Hamamoto, Shoichiro*; Nishimura, Taku*; Sanada, Yukihisa

International Journal of Environmental Research and Public Health, 14(8), p.926_1 - 926_14, 2017/08

https://doi.org/10.3390/ijerph14080926

After the Fukushima Daiichi Nuclear Power Plant accident, the vertical distribution of radiocesium in soil has been investigated to better understand the behavior of radiocesium in the environment. The typical method used for measuring the vertical distribution of radiocesium is troublesome because it requires collection and measurement of the activity of soil samples. In this study, we established a method of estimating the vertical distribution of radiocesium by focusing on the characteristics of -ray spectra obtained via aerial radiation monitoring using an unmanned helicopter. In this method, the change in the ratio of direct rays to scattered rays at various depths in the soil was utilized to quantify the vertical distribution of radiocesium. The results show a positive correlation between the abovementioned and the actual vertical distributions of radiocesium measured in the soil samples.

Numerical simulation of muon beam behavior in solid hydrogen

Konishi, Ren*; Okutsu, Kenichi*; Kino, Yasushi*; Sasaki, Kyosuke*; Nakashima, Ryota*; Yamashita, Takuma*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; et al.

no journal, , 

Muon catalyzed fusion (CF) is a cyclic reaction where a negatively charged muon itself acts like a catalyst of nuclear fusion between hydrogen isotopes. In this work, we used PHITS code to simulate the behavior of the low-energy muon in a thin layer of the solid hydrogen.

Numerical simulation of energy and angular distributions of scattered muons and bremsstrahlung photons in muon-catalyzed fusion experiment

Konishi, Ren*; Okutsu, Kenichi*; Kino, Yasushi*; Sasaki, Kyosuke*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; et al.

no journal, , 

We are attempting to observe regenerative muons emitted from the surface of a solid hydrogen thin film by muon-catalyzed fusion by irradiating the film with muons that have the same charge as electrons and 207 times the mass of electrons. The main background factors in detecting regenerative muons are scattered muons from the accelerator, which are slowed down to the same level as regenerative muons by the target, and bremsstrahlung generated by the components of the device. The results show that there is little scattering within the solid hydrogen, and that the dominant slowing down process is at the Al foil upstream of the solid hydrogen target. The energy distribution of Bremsstrahlung at the X-ray detection position will be reported.

Multiphysics behavior in HTGRs with high power density, 2; Feasibility study

Takamatsu, Kuniyoshi; Okita, Shoichiro; Tachibana, Yukio; Nishimura, Yosuke*; Okamoto, Koji*

no journal, , 

In this study, accident analyses of high-power density HTGRs adopting SiC-matrixed fuel compacts and feasibility study were conducted. Specifically, for the feasibility study, rapid depressurization accidents were analyzed using the two-dimensional unsteady heat transfer analysis code for safety evaluation of HTGRs. As a result of the rapid depressurization accident analyses, the fuel temperature and RPV temperature distributions in the HTGRs with high-power density were clarified, and it was confirmed that the maximum fuel temperature does not exceed 1400C. In other words, even if a rapid depressurization accident occurs, the high-power density HTGRs adopting SiC-matrixed fuel compacts will be able to have excellent passive safety features.

Time evolution calculation of muon catalyzed fusion by the Runge-Kutta method

Yamashita, Takuma*; Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.

no journal, , 

A muon () having 207 times larger mass of electron and the same charge as the electron has been known to catalyze a nuclear fusion (CF) between deuteron (d) and triton (t). In this work, we have solved simultaneous reaction rate equations by the 4th-order Runge-Kutta method for the jointed CF cycles in the two layers (H/D and D/T). The T concentration to maximize the intensities of fusion neutrons and muons emitted to the vacuum will be discussed.