Evaluation of indoor air dose rate based on Cs-137 depth distribution in surrounding artificially paved surfaces surveyed 10 years after the Fukushima Daiichi Nuclear Power Plant accident

Kobayashi, Hikaru*; Suto, Masahito*; Otsuki, Kentaro*; Yoshimura, Kazuya; Yoshida, Hiroko*

Japan Architectural Review (Internet), 6(1), p.e12353_1 - e12353_12, 2023/00

https://doi.org/10.1002/2475-8876.12353

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

https://doi.org/10.1038/s41550-020-01271-2

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Characterization of SiO reduction reaction region at void periphery on Si(110)

Yano, Masahiro; Uozumi, Yuki*; Yasuda, Satoshi; Tsukada, Chie*; Yoshida, Hikaru*; Yoshigoe, Akitaka; Asaoka, Hidehito

Japanese Journal of Applied Physics, 57(8S1), p.08NB13_1 - 08NB13_4, 2018/07

https://doi.org/10.7567/JJAP.57.08NB13

Alteration of organic compounds of interstellar origin in the solar system; Simulation experiments on the ground and in space

Kobayashi, Kensei*; Kawamoto, Yukinori*; Sarker, P. K.*; Ono, Keisuke*; Kuwahara, Hideharu*; Obayashi, Yumiko*; Kaneko, Takeo*; Mita, Hajime*; Yabuta, Hikaru*; Yoshida, Satoshi*; et al.

no journal, , 

Tanpopo project; Survival of microbes in outer space

Yokobori, Shinichi*; Kawaguchi, Yuko*; Yang, Y.*; Kawashiri, Narutoshi*; Shiraishi, Keisuke*; Shimizu, Yasuyuki*; Takahashi, Yuta*; Sugino, Tomohiro*; Narumi, Issei; Sato, Katsuya; et al.

no journal, , 

no abstracts in English

Current status of preparation of TANPOPO mission (astrobiology exposure and micrometeoroid capture experiments) and investigation of survivability of microbes in space

Yokobori, Shinichi*; Kawaguchi, Yuko*; Shimizu, Yasuyuki*; Kawashiri, Narutoshi*; Shiraishi, Keisuke*; Sugino, Tomohiro*; Takahashi, Yuta*; Yang, Y.*; Tanigawa, Yoshiaki*; Hashimoto, Hirofumi*; et al.

no journal, , 

no abstracts in English

Study on adsorption reaction of CHCl on Si(100)21 by means of SR-XPS

Tsukada, Chie; Yoshida, Hikaru; Okada, Michio*; Yoshigoe, Akitaka; Yaita, Tsuyoshi

no journal, , 

Cs in clay mineral will be easy to desorb as halide. We should investigate the desorption mechanism. The clay mineral is constructed mainly by oxide with Si and Al. Thus, Si substrate and CHCl are selected as the reaction model materials. The final purpose is to reveal the reaction for CHCl molecular beam on Cs/Si substrate by means of XPS with synchrotron radiation (SR-XPS). As the first step, the purpose in this study is to reveal the adsorption reaction for CHCl molecular beam on Si(100)21 by means of SR-XPS. The CHCl will adsorb at CH and/or Cl group on the Si dimer atom, respectively.

Study on influence of radioactive contamination derived from nuclear power plant accident on building space, 2; Study on measurement method of direction radiation dose rate intended for field survey

Yamamori, Ryo*; Kobayashi, Hikaru*; Honta, Shohei*; Yoshino, Hiroshi*; Nozaki, Atsuo*; Ichijo, Yusuke*; Yoshida, Hiroko*; Furuta, Takuya

no journal, , 

Understanding radiation field is important to predict radiation dose rate in newly constructing buildings in an area widely contaminated by radioactive nuclei. Radiation dose rate at the site is not sufficient, and directional spectra of the radiations are important to consider the shielding effect of the building. Radiation directional spectra can be measured by scintillator partially shielded by lead collimators but the angle of view highly depends on the combination of the scintillator and the collimators. We adopts a method to measure the directional spectra by adopting 3 inch scintillator with placing a plate of lead collimator in front of the scintillator and subtract the values from the spectra measured without lead collimator. We simulates the optimal size of the lead collimator and found that the 15 cm diameter plate placing at 3 cm from the scintillator is the best for our purpose, 90 degree angle of view.

Initial oxidation of copper alloy surfaces with a hyperthermal oxygen molecular beam

Tsuda, Yasutaka*; Makino, Takamasa*; Yoshida, Hikaru; Yoshigoe, Akitaka; Fukuyama, Tetsuya*; Okada, Michio*

no journal, , 

Initial stage of corrosion is one of the central topics in material science. In the present study, we report the results of oxidation on CuPd(111) and CuPt(111) with a hyperthermal O molecular beam (HOMB) with variable incident energies, using X-ray photoemission spectroscopy in conjunction with synchrotron radiation. All experiments were performed using the Surface Reaction Analysis Apparatus constructed in BL23SU at SPring-8. The CuPd(111) and CuPt(111) samples were cleaned by Ar+ sputtering and annealing. The kinetic energy of the HOMB was set to be 2.3 eV. From the uptake curves, it was found that the oxidation of CuPt is less effective than that on CuAu and CuPd. This suppression of the surface reactivity may be caused by the Pt-rich subsurface layer.

Development of -ray directional radiation dose detector with good efficiency for field survey

Yamamori, Ryo*; Kobayashi, Hikaru*; Honta, Shohei*; Yoshino, Hiroshi*; Nozaki, Atsuo*; Ichijo, Yusuke*; Hijikata, Yoshio*; Yoshida, Hiroko*; Furuta, Takuya

no journal, , 

Understanding radiation field is important to predict radiation dose rate in newly constructing buildings in an area widely contaminated by radioactive nuclei. Directional spectra of the radiations are important to consider the shielding effect of the building. We adopts a method to measure the directional spectra by adopting a plate of lead collimator in front of the scintillator and subtract the values from the spectra measured without lead collimator. We investigated a possible weight saving detection system having sufficient detection efficiency. The investigation was carried out for the condition of the collimator radius ( = 10, 15, 20 cm) and the distance between collimator and detector ( = 1, 3, 5 cm). We found that three combinations satisfied the 90 field view and the detection efficiency became better with larger collimator radius. On the other hand, larger collimator radius indicate heavier detection system. Therefore, we developed an optimum detection system for field survey with the 15 cm diameter plate (10kg), the scintillator (3.4kg), and the folder (1.0kg).