The Japan Health Physics Society Guideline on Dose Monitoring for the Lens of the Eye

Yokoyama, Sumi*; Tsujimura, Norio; Hashimoto, Makoto; Yoshitomi, Hiroshi; Kato, Masahiro*; Kurosawa, Tadahiro*; Tatsuzaki, Hideo*; Sekiguchi, Hiroshi*; Koguchi, Yasuhiro*; Ono, Koji*; et al.

Journal of Radiation Protection and Research, 47(1), p.1 - 7, 2022/03

https://doi.org/10.14407/jrpr.2021.00276

Background: In Japan, new regulations that revise the dose limit for the lens of the eye (the lens), operational quantities, and measurement positions for the lens dose were enforced in April 2021. Based on the international safety standards, national guidelines, the results of the Radiation Safety Research Promotion Fund of the Nuclear Regulatory Authority, and other studies, the Working Group of Radiation Protection Standardization Committee, the Japan Health Physics Society (JHPS) developed a guideline for radiation dose monitoring for the lens. Materials and Methods: The Working Group of the JHPS discussed the criteria of non-uniform exposure and the management criteria set to not exceed the dose limit for the lens. Results and Discussion: In July 2020, the JHPS guideline was published. The guideline consists of three parts: main text, explanations, and 26 questions. In the questions, the corresponding answers were prepared, and specific examples were provided to enable similar cases to be addressed. Conclusion: With the development of guideline on radiation dose monitoring of the lens, radiation managers and workers will be able to smoothly comply with revised regulations and optimise radiation protection.

Investigation of unoccupied electronic states near the fermi level of polysilane using resonant Auger spectroscopy

Ogawa, Hiroshi*; Ikeura, Hiromi*; Sekiguchi, Tetsuhiro

Molecular Crystals and Liquid Crystals, 622(1), p.164 - 169, 2015/11

https://doi.org/10.1080/15421406.2015.1105081

Unoccupied electronic states near the Fermi level of poly(dimethylsilane) were probed using Si 1s X-ray absorption spectroscopy (XAS) and Si KLL resonant Auger spectroscopy (RAS). The measured resonance peaks of XAS spectra near Si K-edge have been assigned in comparison with the discrete variational (DV)-X molecular orbital calculations. The rapid delocalization of Si 1s core-excited electron through the empty conduction band was observed along the polymer chain with the energy dependent RAS measurement, and the electron delocalization time was estimated based on the core-hole clock method.

Thermal evolution of defects in as-grown and electron-irradiated ZnO studied by positron annihilation

Chen, Z. Q.*; Wang, S. J.*; Maekawa, Masaki; Kawasuso, Atsuo; Naramoto, Hiroshi*; Yuan, X. L.*; Sekiguchi, Takashi*

Physical Review B, 75(24), p.245206_1 - 24520_9, 2007/06

https://doi.org/10.1103/PhysRevB.75.245206

Vacancy-type defects in as-grown ZnO single crystals have been identified using positron annihilation spectroscopy. The grown-in defects are supposed to be zinc vacancy V-related defects, and can be easily removed by annealing above 600C. V-related defects are also introduced in ZnO when subjected to 3 MeV electron irradiation with a dose of 5.510 cm. Most of these irradiation-induced V are annealed at temperatures below 200C through recombination with the close interstitials. However, after annealing at around 400C, secondary defects are generated. A detailed analysis of the Doppler broadening measurements indicates that the irradiation introduced defects and the annealing induced secondary defects belong to different species. It is also found that positron trapping by these two defects has different temperature dependences. The probable candidates for the secondary defects are tentatively discussed in combination with Raman scattering studies. After annealing at 700C, all the vacancy defects are annealed out. Cathodoluminescence measurements show that V is not related to the visible emission at 2.3 eV in ZnO, but would rather act as nonradiative recombination centers.

Production and recovery of defects in phosphorus-implanted ZnO

Chen, Z. Q.; Kawasuso, Atsuo; Xu, Y.; Naramoto, Hiroshi; Yuan, X. L.*; Sekiguchi, Takashi*; Suzuki, Ryoichi*; Odaira, Toshiyuki*

Journal of Applied Physics, 97(1), p.013528_1 - 013528_6, 2005/01

https://doi.org/10.1063/1.1821636

Phosphorus ions were implanted into ZnO crystals with energies of 50-380 keV to a dose of 10-10 cm. Positron annihilation measurements show the introduction of vacancy clusters after implantation. These vacancy clusters evolve to microvoids after annealing at a temperature of 600C, and disappear gradually up to 1100C. Raman scattering measurements show the production of oxygen vacancies (V). They are annealed up to 700C accompanying the agglomeration of vacancy clusters. The light emissions of ZnO are suppressed due to the competing nonradiative recombination centers introduced by implantation. Recovery of the light emission occurs above 600C. The vacancy-type defects detected by positrons might be part of the nonradiative recombination centers. Hall measurement shows n-type conductivity for the P-implanted ZnO layer, which suggests that phosphorus is an amphoteric dopant.

Direct vitrification of chloride waste by oxygen plasma

Suzuki, Masaaki*; Sekiguchi, Hidetoshi*; Akatsuka, Hiroshi*; Goto, Takanobu*; Osugi, Takeshi*; Kobayashi, Hiroaki; Nakazawa, Osamu

JNC TY8400 2002-016, 158 Pages, 2002/03

JNC-TY8400-2002-016.pdf:15.93MB

None

Three terminal light emitting device using rare earth doped III-nitride, 4

Kondo, Masaki*; Okada, Hiroshi*; Sekiguchi, Hiroto*; Wakahara, Akihiro*; Sato, Shinichiro; Oshima, Takeshi

no journal, , 

no abstracts in English

Atomic structure and interlayer interactions at the graphene/sapphire interface studied by X-ray standing wave spectroscopy

Entani, Shiro; Sorokin, B. P.*; Avramov, P.; Otomo, Manabu; Matsumoto, Yoshihiro; Narita, Ayumi; Hirao, Norie; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Naramoto, Hiroshi*; et al.

no journal, , 

no abstracts in English

Proton irradiation effects on p- and n-type GaN

Okada, Hiroshi*; Okada, Yuki*; Sekiguchi, Hiroto*; Wakahara, Akihiro*; Sato, Shinichiro; Oshima, Takeshi

no journal, , 

To understand a degradation mechanism of electronic devices in harsh environment, investigation of irradiation damages not only by characterizing whole device, but also by charactrizing each part of the device is important. In this study, proton irradiation effects on p- and n-type GaN on LED structure were investigated by characterizing two-terminal resistances of p- and n-GaN layers on LEDstructure before and after 380 keV proton fluence up to 1 10cm. The resistance of p-GaN after irradiation increased around millionfold while the increase was around one tenth in n-GaN. The result suggests that proton irradiation hardness of GaN-based bipolar device is governed by the hole traps.

Corrosion behavior of Ni-based alloy in molten FLiNaK salt as a fundamental research on molten salt reactors

Ogasawara, Koji*; Sekiguchi, Yuma*; Terai, Takayuki*; Kawamura, Hiroshi*; Tsuchiya, Kunihiko; Watanabe, Takashi*

no journal, , 

no abstracts in English