Design for detecting recycling muon after muon-catalyzed fusion reaction in solid hydrogen isotope target

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

https://doi.org/10.1016/j.fusengdes.2021.112712

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.

First isolation and analysis of caesium-bearing microparticles from marine samples in the Pacific coastal area near Fukushima Prefecture

Miura, Hikaru*; Ishimaru, Takashi*; Ito, Yukari*; Kuribara, Yuichi; Otosaka, Shigeyoshi*; Sakaguchi, Aya*; Misumi, Kazuhiro*; Tsumune, Daisuke*; Kubo, Atsushi*; Higaki, Shogo*; et al.

Scientific Reports (Internet), 11, p.5664_1 - 5664_11, 2021/03

https://doi.org/10.1038/s41598-021-85085-w

For the first time, we isolated and investigated seven CsMPs (radioactive caesium-bearing microparticles) from marine particulate matter and sediment. From the elemental composition, the Cs/Cs activity ratio, and the Cs activity per unit volume results, we inferred that the five CsMPs collected from particulate matter were emitted from Unit 2 of the FDNPP, whereas the two CsMPs collected from marine sediment were possibly emitted from Unit 3. The presence of CsMPs can cause overestimation of the solid-water distribution coefficient of Cs in marine sediments and particulate matter and a high apparent radiocaesium concentration factor for marine biota. CsMPs emitted from Unit 2, which were collected from the estuary of a river that flowed through a highly contaminated area, may have been deposited on land and then transported by the river. By contrast, CsMPs emitted from Unit 3 were possibly transported eastward by the wind and deposited directly onto the ocean surface.

Effect of the soft X-rays on highly hydrogenated diamond-like carbon films

Kanda, Kazuhiro*; Yokota, Kumiko*; Tagawa, Masahito*; Tode, Mayumi; Teraoka, Yuden; Matsui, Shinji*

Japanese Journal of Applied Physics, 50(5), p.055801_1 - 055801_3, 2011/05

https://doi.org/10.1143/JJAP.50.055801

Recently, the irradiation of soft X-ray synchrotron radiation (SR) to highly-hydrogenated diamond-like-carbon (H-DLC) films in vacuum results in the desorption of hydrogen and the increase of film density, hardness and refractive index. In this study, we investigated SR irradiation effects on the H-DLC with different hydrogen contents. The H-DLC thin films were deposited on an Si wafer with 200 nm thickness by an amplitude-modulated radio frequency plasma chemical vapor deposition method. The SR irradiation was carried out at NewSUBARU BL6. The SR has a continuous spectrum from IR to soft X-ray, which is lower than 1 keV. The hydrogen content dependence on SR dose was estimated using elastic recoil detection analysis (ERDA) and Rutherford backscattering (RBS) techniques. The hydrogen content was kept constant in the low-hydrogenated DLC film, while that in the high-hydrogenated DLC film decreased exponentially with soft X-ray dose.

Synchrotron radiation photoelectron spectroscopy and near-edge X-ray absorption fine structure study on oxidative etching of diamond-like carbon films by hyperthermal atomic oxygen

Tagawa, Masahito*; Yokota, Kumiko*; Kitamura, Akira*; Matsumoto, Koji*; Yoshigoe, Akitaka; Teraoka, Yuden; Kanda, Kazuhiro*; Niibe, Masahito*

Applied Surface Science, 256(24), p.7678 - 7683, 2010/10

https://doi.org/10.1016/j.apsusc.2010.06.030

Surface structural changes of a hydrogenated diamond-like carbon (DLC) film exposed to a hyperthermal atomic oxygen beam were investigated by Rutherford backscattering spectroscopy (RBS), synchrotron radiation photoelectron spectroscopy (SR-PES), and near-edge X-ray absorption fine structure (NEXAFS). It was confirmed that the DLC surface was oxidized and etched by high-energy collisions of atomic oxygen. RBS and real-time mass-loss data showed a linear relationship between etching and atomic oxygen fluence. SR-PES data suggested that the oxide layer was restricted to the topmost surface of the DLC film. NEXAFS data were interpreted to mean that the sp structure at the DLC surface was selectively etched by collisions with hyperthermal atomic oxygen, and an sp-rich region remained at the topmost DLC surface. The formation of an sp-rich layer at the DLC surface led to surface roughening and a reduced erosion yield relative to the pristine DLC surface.

Selective etching of hydrogenated diamond-like carbon thin films by hyperthermal oxygen atomic beams

Tagawa, Masahito*; Yokota, Kumiko*; Kitamura, Akira*; Matsumoto, Koji*; Yamada, Noriko*; Kanda, Kazuhiro*; Niibe, Masahito*; Yoshigoe, Akitaka; Teraoka, Yuden; Belin, M.*; et al.

no journal, , 

Degradation of hydrogenated diamond -like carbon surfaces in space environments by action of high speed atomic oxygen beams has been investigated in laboratory environments. The HDLC was prepared on Si substrates by a plasma CVD method. High speed oxygen atomic beams were generated by a laser detonation method. The HDLC surfaces irradiated by the oxygen atomic beams were analyzed by Synchrotron Radiation Photoemission Spectroscopy (SRPES), Ratherford Backscattering Spectroscopy (RBS), Elastic Recoil Detection Analysis (ERDA), Near-Edge X-ray Absorption Fine Structure (NEXAFS). Although chemical bonding states of oxygen atoms were maintained as they were even after the oxygen atomic beam irradiation, concentrations of carbon and hydrogen were decreased. The sp/sp ratio was also decreased. Consequently, carbon atoms in the sp state were selectively etched out with hydrogen atoms by chemical reactions with oxygen atomic beams.

Hydrogen desorption process from hydrogenated diamond-like carbon film by irradiation of soft X-ray

Kanda, Kazuhiro*; Teraoka, Yuden; Tode, Mayumi; Matsui, Shinji*

no journal, , 

In order to investigate soft X-ray irradiation effects for a diamond-like carbon (DLC) film, thermal desorption spectra (TDS) were observed for a hydrogenated DLC film and a soft X-ray irradiated (300 mAh) hydrogenated DLC film. The temperature elevation rate was 87.5 K/min and the temperature range was from 373 K to 1073 K. In the case of TDS for hydrogen molecules, a large peak was observed around 470 K in the hydrogenated DLC film. The peak, however, was not observed in the non-irradiated hydrogenated DLC film. The elastic recoil analysis showed a large decrease of hydrogen in the X-ray irradiated (300 mAh) sample. We concluded on the basis of these observations that hydrogen molecules desorb by soft X-ray irradiation of 300 mAh.

Effect of VUV exposures to the hydrogenated diamond-like carbon films

Yokota, Kumiko*; Tagawa, Masahito*; Furuyama, Yuichi*; Kanda, Kazuhiro*; Tode, Mayumi; Yoshigoe, Akitaka; Teraoka, Yuden

no journal, , 

In this study, hydrogen desorption from highly-hydrogenated diamond-like-carbon (DLC) containing 54% hydrogen via vacuum ultraviolet light irradiation was investigated and compared to that of soft X-ray irradiation. An elastic recoil detection analysis (ERDA) spectrum showed the decrease of hydrogen up to 0.5 micrometer depth with increasing the dose of vacuum ultraviolet light. On the other hand, an ERDA spectrum for the soft X-ray irradiation revealed that the decrease of hydrogen from a whole depth, that is, hydrogen desorption reactions took place remarkably comparing to the vacuum ultraviolet light irradiation. In both cases, the thickness of DLC film did not change at all. These facts showed that a depth profile of hydrogen desorption via light excitation depended considerably on wavelength.

Hydrogen desorption processes from DLC films by soft X-ray irradiation

Kanda, Kazuhiro*; Tagawa, Masahito*; Yokota, Kumiko*; Tode, Mayumi; Teraoka, Yuden; Matsui, Shinji*

no journal, , 

In this study, hydrogen desorption processes from highly-hydrogenated DLC films have been investigated by thermal desorption mass stectrometry (TDS) and elastic recoil detection analysis (ERDA). The soft X-ray irradiation was performed at BL-6 in NewSUBARU. The white light is containing infra red to 1000 eV X-ray. The TDS measurements were performed using the thermal desorption measurement system at BL23SU in SPring-8. Although a large peak was observed at around 470 K in the non-X-ray-irradiated DLC film, the peak almost disappeared after irradiation of 300 mAhr synchrotron radiation. ERDA measurements resulted in no change of hydrogen content for lowly-hydrogenated DLC film instead of large decrease of hydrogen for highly-hydrogenated DLC film depending on soft X-ray dose. Hydrogen molecules, which are seen in a TDS spectrum as a low temperature peak, desorb by soft X-ray irradiation so that density and reflective index are changed.

Evaluation of Stability of biologically-relevant molecules in interplanetary environment; Ground simulation and space experimental plan

Kobayashi, Kensei*; Kawamoto, Yukinori*; Okabe, Takuto*; Sarker, P. K.*; Obayashi, Yumiko*; Kaneko, Takeo*; Mita, Hajime*; Kanda, Kazuhiro*; Yoshida, Satoshi*; Narumi, Issei

no journal, , 

no abstracts in English

Protection of materials from O-atom collision in low earth orbit using thin oxide film growth in space

Yokota, Kumiko*; Yoshigoe, Akitaka; Teraoka, Yuden; Kanda, Kazuhiro*; Furuyama, Yuichi*; Matsumoto, Koji*; Tagawa, Masahito*

no journal, ,