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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：0.01(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.
Okutsu, Kenichi*; Yamashita, Takuma*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
Fusion Engineering and Design, 170, p.112712_1 - 112712_4, 2021/09
Times Cited Count：1 Percentile：27.15(Nuclear Science & Technology)A muonic molecule which consists of two hydrogen isotope nuclei (deuteron (d) or tritium (t)) and a muon decays immediately via nuclear fusion and the muon will be released as a recycling muon, and start to find another hydrogen isotope nucleus. The reaction cycle continues until the muon ends up its lifetime of 2.2 
s. Since the muon does not participate in the nuclear reaction, the reaction is so called a muon catalyzed fusion (CF). The recycling muon has a particular kinetic energy (KE) of the muon molecular orbital when the nuclear reaction occurs. Since the KE is based on the unified atom limit where distance between two nuclei is zero. A precise few-body calculation estimating KE distribution (KED) is also in progress, which could be compared with the experimental results. In the present work, we observed recycling muons after CF reaction.
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
Times Cited Count：2 Percentile：48.75(Nuclear Science & Technology)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.
Nishimura, Shoichiro*; Torii, Hiroyuki*; Fukao, Yoshinori*; Ito, Takashi; Iwasaki, Masahiko*; Kanda, Sotaro*; Kawagoe, Kiyotomo*; Kawall, D.*; Kawamura, Naritoshi*; Kurosawa, Noriyuki*; et al.
Physical Review A, 104(2), p.L020801_1 - L020801_6, 2021/08
Times Cited Count：7 Percentile：81.08(Optics)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
Times Cited Count：7 Percentile：57.83(Physics, Multidisciplinary)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.
Strasser, P.*; Abe, Mitsushi*; Aoki, Masaharu*; Choi, S.*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; et al.
EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01
Times Cited Count：12 Percentile：99.37
-ray spectra obtained via aerial radiation monitoring using an unmanned helicopterOchi, 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
Times Cited Count：4 Percentile：25.63(Environmental Sciences)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.
-ray spectra obtained by airborne radiation monitoringOchi, Kotaro; Sasaki, Miyuki; Ishida, Mutsushi*; Sato, Tomohiko*; Hamamoto, Shoichiro*; Nishimura, Taku*; Sanada, Yukihisa
no journal, ,
A large amount of radiocesium (
Cs & 
Cs) were released into the atmosphere as a result of 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. To estimate the impact of the accident to the environment, dose rate around FDNPP have been measured by MEXT. Dose rate nearby FDNPP, however, still stay high even though decontamination work was carried out, which means it is necessary to develop an effective decontamination method promptly. Information of depth profile of radiocesium in soil is required to realize it, though, most of measurement methods have trouble due to collection and measurement of soil samples. As we have developed the radiation measurement techniques using unmanned aerial vehicle to measure dose rate distribution over wide areas for years, we attempt to establish the estimation method of depth profile of radiocesium in soil based on characteristics of -ray spectra obtained by airborne radiation monitoring in this paper.
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.
CF experiment at J-PARC MLFNatori, Hiroaki*; Doiuchi, Shogo*; Ishida, Katsuhiko*; Kino, Yasushi*; Miyake, Yasuhiro*; Miyashita, Konan*; Nakashima, Ryota*; Nagatani, Yukinori*; Nishimura, Shoichiro*; Oka, Toshitaka; et al.
no journal, ,
A muonic molecule which consists of muon and two hydrogen isotope nuclei (deuteron (d) or tritium (t)) decays immediately via nuclear fusion (
CF) and the muon will be released as a recycling muon. We attempted to use these muons to develop the scanning muon microscope. In this work, we will report the detection of neutron which emits during the CF reaction.
Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
no journal, ,
Muon catalized fusion (CF) is expected to be a high-quality muon beam source for undestructive measurement and a monoenergetic neutron source. In this work, we attemped to observe a released muon after intermolecular nuclear reaction using muonic X-ray.
CF experiment at J-PARC MLFOkutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
no journal, ,
Muon catalized fusion (CF) is expected to be a high-quality muon beam source for undestructive measurement and a monoenergetic neutron source. In this work, we discussed how to observe a kinetic energy distribution of a recycling muon emitted after CF reaction.
Miyashita, Konan*; Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
no journal, ,
To observe a kinetic energy distribution of a recycling muon emitted after CF reaction, it is necessary to guide the recycling muons to a detector. In this work, we simulated the muon transportation using PHITS code and designed an experimental system.
Nakashima, Ryota*; Okutsu, Kenichi*; Kino, Yasushi*; Miyashita, Konan*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
no journal, ,
The recycling muon emitted after the muon catalized fusion (CF) has a kinetic energy between a few keV to 10 keV. To observed the kinetic energy distribution of the recycling muon, we have to guide and inject muons to Ti foil, and measure the muonic X-ray. In this work, we utilized SIMION code to calculate the electric field and the trajectory of muons from deuteron target to Ti foil.
Miyashita, Konan*; Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
no journal, ,
To measure the kinetic energy of a recycling muon, we discussed how to reduce the background radiation and the trajectory of the transported recycling muons by simulation code.
Nakashima, Ryota*; Okutsu, Kenichi*; Kino, Yasushi*; Miyashita, Konan*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
no journal, ,
To detect a recycling muon emitted after muon catalyzed fusion reaction, it is necessary to guide the recycling muons from the target to a detector in a low background area. In this work, we simulated the muon transportation using SIMONS and PHITS codes and designed an experimental system.
Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; 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, such as 
or 
. In this work, we have investigated the shape and characteristic of solid hydrogen isotope target.
Miyashita, Konan*; Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; 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 have designed the shape of the thermal shield to reduce the background noise.
Nakashima, Ryota*; Okutsu, Kenichi*; Kino, Yasushi*; Miyashita, Konan*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.
no journal, ,
We are developing an experimental system to measure the kinetic energy distribution of regenerated muons emitted after muon catalytic nuclear reactions. The trajectory of the regenerated muon emitted from a solid hydrogen target, and the transport efficiency of the regenerated muon and its dependence on the emitted position are calculated/discussed using SIMION code.
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.
Konishi, Ren*; Okutsu, Kenichi*; Kino, Yasushi*; Sasaki, Kyosuke*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Yamashita, Takuma*; Okada, Shinji*; Sato, Motoyasu*; et al.
no journal, ,
When muons are injected into a deuterium thin film target, muon molecules are formed. The muons released after intramolecular fusion (recycling muons) are important for the development of slow muon beams. In this study, corresponding to an experiment in which recycling muons are transported using a coaxial transport tube, the energy distribution of scattered muons, muons after deceleration, and background radiation due to bremsstrahlung by decay electrons and neutrons are analyzed by numerical simulations.
