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Fukuda, Tatsuo; Kobata, Masaaki; Shobu, Takahisa; Yoshii, Kenji; Kamiya, Junichiro; Iwamoto, Yosuke; Makino, Takahiro*; Yamazaki, Yuichi*; Oshima, Takeshi*; Shirai, Yasuhiro*; et al.
Journal of Applied Physics, 132(24), p.245102_1 - 245102_8, 2022/12
Times Cited Count:1 Percentile:17.38(Physics, Applied)Direct energy conversion has been investigated using Ni/SiC Schottky junctions with the irradiation of monochromatized synchrotron X-rays simulating the gamma rays of Np (30 keV) and Am (60 keV). From current-voltage measurements, electrical energies were obtained for both kinds of gamma rays. The energy conversion efficiencies were found to reach up to 1.6%, which is comparable to those of a few other semiconducting systems reported thus far. This result shows a possibility of energy recovery from nuclear wastes using the present system, judging from the radiation tolerant nature of SiC. Also, we found different conversion efficiencies between the two samples. This could be understandable from hard X-ray photoelectron spectroscopy and secondary ion mass spectroscopy measurements, suggesting the formation of Ni-Si compounds at the interface in the sample with a poor performance. Hence, such combined measurements are useful to provide information that cannot be obtained by electrical measurements alone.
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
Times Cited Count:43 Percentile:96.93(Astronomy & Astrophysics)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.
Thiel, C.*; Tsukamoto, Sumiko*; Tokuyasu, Kayoko; Buylaert, J.-P.*; Murray, A. S.*; Tanaka, Kazuhiro*; Shirai, Masaaki*
Quaternary Geochronology, 29, p.16 - 29, 2015/08
Times Cited Count:11 Percentile:33.8(Geography, Physical)The applicability of both quartz and feldspar luminescence dating was tested on twenty-five samples from a marine succession now forming a cliff at Oga Peninsula, Honshu Island, Japan. The quartz shows thermal instability and linear modulated optically stimulated luminescence (LM-OSL) analysis revealed the dominance of a slow component. When compared with independent age control provided by two marker tephra, the quartz OSL ages grossly underestimated the depositional age. In contrast, potassium (K)-rich feldspar is a suitable dosimeter when measured using post-IR infrared stimulated luminescence (IRSL) at 225C, but it was found that the fading corrected ages calculated using dose rates based on sieved grain-size still underestimate. SEM analyses on the feldspar extracts revealed that the grains are amorphous with small crystalline inclusions; using standard internal dose rate parameters, this would result in a too large dose rate. Three different dose rate scenarios were considered for calculation: (1) sieved grain size (90-180m) and 12.50.5% K. (2) smaller grain size (4020m) and measured K concentration (60.5%), and (3) smaller grain size consistent with the observed crystal dimensions (4020m) and 12.50.5% K. The final dose rate scenario produces fading corrected ages that agree well with independent age control.
Yoshida, Rikiya*; Nakamura, Yoshiaki*; Fukui, Masaki*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Okawa, Mario*; Shin, S.*; Hirai, Masaaki*; Muraoka, Yuji*; et al.
Journal of Physics; Conference Series, 273, p.012021_1 - 012021_4, 2011/02
Times Cited Count:1 Percentile:33.9(Physics, Condensed Matter)Yoshida, Rikiya*; Nakamura, Yoshiaki*; Fukui, Masaki*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Okawa, Mario*; Shin, S.*; Hirai, Masaaki*; Muraoka, Yuji*; et al.
Physical Review B, 82(20), p.205108_1 - 205108_6, 2010/11
Times Cited Count:62 Percentile:88.1(Materials Science, Multidisciplinary)Saito, Kimiaki; Saito, Hidetoshi*; Kunieda, Etsuo*; Narita, Yuichiro*; Myojoyama, Atsushi*; Fujisaki, Tatsuya*; Kawase, Takatsugu*; Kaneko, Katsutaro*; Ozaki, Masahiro*; Deloar, H. M.*; et al.
Joho Shori, 48(10), p.1081 - 1088, 2007/10
no abstracts in English
Saito, Kimiaki; Kunieda, Etsuo*; Narita, Yuichiro*; Kimura, Hideo; Hirai, Masaaki*; Deloar, H. M.*; Kaneko, Katsutaro*; Ozaki, Masahiro*; Fujisaki, Tatsuya*; Myojoyama, Atsushi*; et al.
Radiation Protection Dosimetry, 116(1-4), p.190 - 195, 2005/12
Times Cited Count:2 Percentile:17.6(Environmental Sciences)A dose calculation system for providing accurate dose distribution in a patient body is under developing for supporting radiotherapy using photons and electrons. In this system, a sophisticated human model, a precise accelerator head model, and a Monte Carlo calculation will be utilized to perform realistic simulation. The dose distribution is calculated by this system on the ITBL computer at the dose calculation center, and the related data are transferred through a network. This system is intended to support the quality assurance of current treatments carried out in Japan. Further, this system is planned to apply to advanced radiotherapy. The project started on November 2003 and is scheduled to continue for five years. Prototypes of some parts constituting the system have been already developed, and the fundamental features on the radiation fields have been investigated. On the basis of the fundamental investigation, the final system will be designed and constructed.
Oikawa, Toshihiro; Ushigusa, Kenkichi; Forest, C. B.*; Nemoto, Masahiro; Naito, Osamu; Kusama, Yoshinori; Kamada, Yutaka; Tobita, Kenji; Suzuki, Shingo*; Fujita, Takaaki; et al.
Nuclear Fusion, 40(3Y), p.435 - 443, 2000/03
Times Cited Count:41 Percentile:75.03(Physics, Fluids & Plasmas)no abstracts in English
Oikawa, Toshihiro; Ushigusa, Kenkichi; Forest, C. B.*; Nemoto, Masahiro; Naito, Osamu; Kusama, Yoshinori; Kamada, Yutaka; Tobita, Kenji; Suzuki, Shingo*; Fujita, Takaaki; et al.
Fusion Energy 1998, Vol.2, p.551 - 558, 1998/10
no abstracts in English
Saito, Kimiaki; Kunieda, Etsuo*; Narita, Yuichiro*; Kaneko, Katsutaro*; Hirai, Masaaki*; Oku, Yohei*; Deloar, H. M.*; Fujisaki, Tatsuya*; Myojoyama, Atsushi*; Saito, Hidetoshi*
no journal, ,
no abstracts in English
Kobayashi, Riki; Kaneko, Koji; Wakimoto, Shuichi; Haga, Yoshinori; Matsuda, Tatsuma; Yamamoto, Etsuji; Robert, J.*; Mignot, J.-M.*; Andr, G.*; Matsuda, Masaaki*; et al.
no journal, ,
no abstracts in English
Kobayashi, Riki; Kaneko, Koji; Wakimoto, Shuichi; Haga, Yoshinori; Matsuda, Tatsuma; Yamamoto, Etsuji; Robert, J.*; Mignot, J.-M.*; Andr, G.*; Matsuda, Masaaki*; et al.
no journal, ,
no abstracts in English
Fukuda, Tatsuo; Kobata, Masaaki; Shobu, Takahisa; Yoshii, Kenji; Kamiya, Junichiro; Iwamoto, Yosuke; Makino, Takahiro*; Yamazaki, Yuichi*; Oshima, Takeshi*; Shirai, Yasuhiro*; et al.
no journal, ,
no abstracts in English