Influence of distant scatterer on air kerma measurement in the evaluation of diagnostic X-rays using Monte Carlo simulation

Tominaga, Masahide*; Nagayasu, Yukari*; Sasaki, Motoharu*; Furuta, Takuya; Hayashi, Hiroaki*; Oita, Masataka*; Nishiyama, Yuichi*; Haga, Akihiro*

Radiological Physics and Technology, 14(4), p.381 - 389, 2021/12

https://doi.org/10.1007/s12194-021-00641-3

Due to recent advance of diagnostic radiology, the increase of diagnostic radiation exposure to patient becomes problem. Diagnostic Reference Levels has been released to optimized the radiation exposure to patients in Japan recently. The evaluation of entrance surface dose (ESD) is recommended to assess the dose level for general X-ray examination. The ESD can be easily evaluated by multiplying the backscatter factor of the patient body on the free-in-air air kerma. The air kerma free-in-air value used to estimate ESD may contain X-rays scattered from obstacles located at the time of measurement, which may induce non-minor error in assessments. We therefore studied the influence of scattered X-rays on air kerma measurement under various environments (distances, field sizes, and materials). It was found that the dependence on the X-ray energy and field size was different for different materials. The X-ray contamination can be ignored for all the materials when the distance to the scatterer exceeds 35 cm.

Repeatability and reproducibility of measurements of low dissolved radiocesium concentrations in freshwater using different pre-concentration methods

Kurihara, Momo*; Yasutaka, Tetsuo*; Aono, Tatsuo*; Ashikawa, Nobuo*; Ebina, Hiroyuki*; Iijima, Takeshi*; Ishimaru, Kei*; Kanai, Ramon*; Karube, Jinichi*; Konnai, Yae*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 322(2), p.477 - 485, 2019/11

https://doi.org/10.1007/s10967-019-06696-2

We assessed the repeatability and reproducibility of methods for determining low dissolved radiocesium concentrations in freshwater in Fukushima. Twenty-one laboratories pre-concentrated three of 10 L samples by five different pre-concentration methods (prussian-blue-impregnated filter cartridges, coprecipitation with ammonium phosphomolybdate, evaporation, solid-phase extraction disks, and ion-exchange resin columns), and activity of radiocesium was measured. The z-scores for all of the Cs results were within 2, indicating that the methods were accurate. The relative standard deviations (RSDs) indicating the variability in the results from different laboratories were larger than the RSDs indicating the variability in the results from each separate laboratory.

Multiple-wavelength neutron holography with pulsed neutrons

Hayashi, Koichi*; Oyama, Kenji*; Happo, Naohisa*; Matsushita, Tomohiro*; Hosokawa, Shinya*; Harada, Masahide; Inamura, Yasuhiro; Nitani, Hiroaki*; Shishido, Toetsu*; Yubuta, Kunio*

Science Advances (Internet), 3(8), p.e1700294_1 - e1700294_7, 2017/08

http://doi.org/10.1126/sciadv.1700294

Performance of a total absorption clover detector for measurements of neutron-rich nuclei far from the -stability line

Hayashi, Hiroaki*; Shibata, Michihiro*; Asai, Masato; Osa, Akihiko; Sato, Tetsuya; Koizumi, Mitsuo; Kimura, Atsushi; Oshima, Masumi*

Nuclear Instruments and Methods in Physics Research A, 747, p.41 - 51, 2014/05

https://doi.org/10.1016/j.nima.2014.02.012

To measure -decay energy of short-lived fission products with good accuracy and high efficiency, we have developed a new total absorption clover detector and demonstrated its performance. Using a large-volume clover-type Ge detector having a through-hole in its center, we could measure total absorption spectra of + rays with extremely high efficiency and high energy resolution, and could determine values with 30 keV accuracy. Using this detector, we have determined the values of Eu and Gd for the first time, and of Eu and Gd with better accuracies. In addition, we have observed a new isomeric state in Gd, and determined its half-life and excitation energy.

High-energy electron generation via laser wakefield acceleration

Kando, Masaki; Mori, Michiaki; Kotaki, Hideyuki; Hayashi, Yukio; Nishimura, Hiroaki*

Osaka Daigaku Reza Enerugigaku Kenkyu Senta Heisei-23-Nendo Kyodo Riyo, Kyodo Kenkyu Seika Hokokusho, p.13 - 14, 2012/03

This paper reports collaboration work between JAEA and Osaka University on the high energy electron acceleration using the LFEX laser. At JAEA we have examined the conditions for generating stable electrons with a 4-TW laser. We used Ar gas, which was found by us to produce stabler electrons and measured reproducibility at 4.0 TW and 3.6 TW. We found that there is a density threshold; the reproducibility becomes almost 100% when the density is larger than the threshold. We also noticed that the threshold value decreases as increasing the laser power. In addition, we report on the status of a sampling calorimeter, which will be used in the future laser acceleration experiments with LFEX.

Condition of MeV electron bunch generated from Argon gas-jet target in the self-modulated laser wakefield regime

Mori, Michiaki; Kando, Masaki; Kotaki, Hideyuki; Hayashi, Yukio; Bulanov, S. V.; Koga, J. K.; Kondo, Kiminori; Pirozhkov, A. S.; Nishimura, Hiroaki*; Nagashima, Keisuke

Journal of the Physical Society of Japan, 80(10), p.105001_1 - 105001_2, 2011/09

https://doi.org/10.1143/JPSJ.80.105001

The effects of plasma density and laser power on the energetic electron bunch generation in an Argon (high-Z) gas-jet target in the self modulated laser wakefield acceleration regime were investigated. A vector potential threshold for electron injection was obtained 2.8 through a simple analytical model include two-dimensional laser pulse compression by relativistic self-focusing, and it is similar to that after accounting for three-dimensional laser pulse compression in the standard Laser Wakefield acceleration regime.

Stabilization of laser accelerated electron bunch by the ionization-stage control

Mori, Michiaki; Kando, Masaki; Kotaki, Hideyuki; Hayashi, Yukio; Kawase, Keigo; Bulanov, S. V.; Ogura, Koichi; Pirozhkov, A. S.; Kondo, Kiminori; Sugiyama, Akira; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.4062 - 4064, 2010/05

http://accelconf.web.cern.ch/accelconf/IPAC10/papers/thpec003.pdf

Structure of HIV-1 protease in complex with potent inhibitor KNI-272 determined by high-resolution X-ray and neutron crystallography

Adachi, Motoyasu; Ohara, Takashi; Kurihara, Kazuo; Tamada, Taro; Honjo, Eijiro; Okazaki, Nobuo; Arai, Shigeki; Shoyama, Yoshinari; Kimura, Kaname*; Matsumura, Hiroyoshi*; et al.

Proceedings of the National Academy of Sciences of the United States of America, 106(12), p.4641 - 4646, 2009/03

https://doi.org/10.1073/pnas.0809400106

To further understand the catalytic mechanism and inhibitor recognition of HIV-1 protease, we need to determine the locations of key hydrogen atoms in the catalytic aspartates Asp25 and Asp125. The structure of HIV-1 protease in complex with transition-state analog KNI-272 was determined by combined neutron crystallography at 1.9 resolution and X-ray crystallography at 1.4 resolution. The resulting structural data shows that the catalytic residue Asp25 is protonated and that Asp125 is deprotonated. The proton on Asp25 makes a hydrogen bond with the carbonyl group of the allophenylnorstatine group in KNI-272. The deprotonated Asp125 bonds to the hydroxyl proton of Apns. The results provide direct experimental evidence for proposed aspects of the catalytic mechanism of HIV-1 protease; and can therefore contribute substantially to the development of specific inhibitors for therapeutic application.

Precise intensity measurements in the N(n,)N reaction as a -ray intensity standard up to 11 MeV

Miyazaki, Itaru*; Sakane, Hitoshi*; Takayama, Hirokazu*; Kasaishi, Masafumi*; Tojo, Akinori*; Furuta, Masataka*; Hayashi, Hiroaki*; Suematsu, Osamu*; Narasaki, Hiromichi*; Shimizu, Toshiaki*; et al.

Journal of Nuclear Science and Technology, 45(6), p.481 - 486, 2008/06

https://doi.org/10.3327/jnst.45.481

The intensities of the prompt rays from the N(n,)N reaction have been precisely measured. As the samples, a liquid nitrogen target and a deuterated melamine (CDN) were used. The previous values widely used as intensity standards agreed with those obtained in this study within 4-5% in the 2-11 MeV region, however, showed a monotonous decrease with the increase of -ray energy.

measurements of Pm, Sm, Eu, Gd and Tb using a total absorption BGO detector

Hayashi, Hiroaki*; Akita, Yukinori*; Suematsu, Osamu*; Shibata, Michihiro*; Asai, Masato; Sato, Tetsuya; Ichikawa, Shinichi; Nishinaka, Ichiro; Nagame, Yuichiro; Osa, Akihiko; et al.

European Physical Journal A, 34(4), p.363 - 370, 2007/12

https://doi.org/10.1140/epja/i2006-10522-9

values of Eu and Gd were measured for the first time using a total absorption BGO detector, and the data of Pm, Sm, and Tb obtained previously were reanalyzed. These nuclei were produced by the proton-induced fission of U at the JAEA-Tokai tandem accelerator facility, and separated from the reaction products using an on-line isotope separator. The deduced mass excesses and two-neutron separation energies were compared with those of atomic mass evaluations and theoretical predictions.