High oxide-ion conductivity in Si-deficient La(Si[])O apatite without interstitial oxygens due to the overbonded channel oxygens

Fujii, Kotaro*; Yashima, Masatomo*; Hibino, Keisuke*; Shiraiwa, Masahiro*; Fukuda, Koichiro*; Nakayama, Susumu*; Ishizawa, Nobuo*; Hanashima, Takayasu*; Ohara, Takashi

Journal of Materials Chemistry A, 6(23), p.10835 - 10846, 2018/06

https://doi.org/10.1039/C8TA02237B

Simulation of discharge in insulating gas from initial partial discharge to growth of a stepped leader using the percolation model

Sasaki, Akira; Kato, Susumu*; Takahashi, Eiichi*; Kishimoto, Yasuaki*; Fujii, Takashi*; Kanazawa, Seiji*

Japanese Journal of Applied Physics, 55(2), p.026101_1 - 026101_10, 2016/02

https://doi.org/10.7567/JJAP.55.026101

A percolation model of discharge, which can reproduce stochastic behaviors of initial partial discharge to the growth of a stepped leader, is presented. The model uses macroscopic cells, from which a network of electric circuits is defined, and the spatial and temporal evolutions of the electric field and current in the discharge medium are calculated. For each cell, one of two states, either insulator or conductor, which corresponds to neutral gas or ionized plasmas, respectively, is decided. The decision is made on the basis of probability for each calculation cell at each time step, taking the effects of local electric field and current, which enhance ionization and sustain the discharge channel, respectively, into account. The stochastic behavior of discharge is discussed, in conjunction with the characteristic feature of ionization, that is, the ionization occurs not only ahead of the streamer tip where the electric field is enhanced but randomly in the discharge medium.

Investigation on cause of malfunction of Wide Range Monitor (WRM) in High Temperature engineering Test Reactor (HTTR); Sample tests and destructive tests

Shinohara, Masanori; Motegi, Toshihiro; Saito, Kenji; Haga, Hiroyuki; Sasaki, Shinji; Katsuyama, Kozo; Takada, Kiyoshi*; Higashimura, Keisuke*; Fujii, Junichi*; Ukai, Takayuki*; et al.

JAEA-Technology 2012-032, 29 Pages, 2012/11

JAEA-Technology-2012-032.pdf:6.57MB

An event, in which one of WRMs were disabled to detect the neutron flux in the reactor core, occurred during the period of reactor shut down of HTTR in March, 2010. The actual life time of WRM was unexpectedly shorter than the past developed life time. Investigation of the cause of the outage of WRM toward the recovery of the life time up to the past developed life is one of the issues to develop the technology basis of HTGR. Then, two experimental investigations were carried out to reveal the cause of the malfunction by specifying the damaged part causing the event in the WRM. One is an experiment using a mock-up sample test which strength degradation on assembly accuracy and heat cycle to specify the damaged part in the WRM. The other is a destructive test in FMF to specify the damaged part in the WRM. This report summarized the results of the destructive test and the experimental investigation using the mock-up to reveal the cause of malfunction of WRM.

Neutron-capture cross-sections of Cm and Cm measured with an array of large germanium detectors in the ANNRI at J-PARC/MLF

Kimura, Atsushi; Fujii, Toshiyuki*; Fukutani, Satoshi*; Furutaka, Kazuyoshi; Goko, Shinji*; Hara, Kaoru; Harada, Hideo; Hirose, Kentaro; Hori, Junichi*; Igashira, Masayuki*; et al.

Journal of Nuclear Science and Technology, 49(7-8), p.708 - 724, 2012/07

https://doi.org/10.1080/00223131.2012.693887

Measurements of neutron capture cross sections at J-PARC/MLF/ANNRI, 2

Hori, Junichi*; Fujii, Toshiyuki*; Fukutani, Satoshi*; Furusaka, Michihiro*; Furutaka, Kazuyoshi; Goko, Shinji*; Harada, Hideo; Hiraga, Fujio*; Igashira, Masayuki*; Kamiyama, Takashi*; et al.

JAEA-Conf 2011-002, p.29 - 34, 2011/09

https://jopss.jaea.go.jp/pdfdata/JAEA-Conf-2011-002.pdf

The neutron capture cross sections of Zr, Tc and Pd have been measured relative to the B(n,) standard cross section by the neutron time-of-flight (TOF) method. Neutron capture rays were measured with a 4 Ge spectrometer as a part of the Accurate Neutron-Nucleus Reaction measurement Instrument (ANNRI) installed at the neutron Beam Line No.4 (BL04) of the Material and Life science experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC). This paper presents the preliminary results.

Study of neutron capture reactions using the 4 Ge spectrometer

Harada, Hideo; Goko, Shinji*; Kimura, Atsushi; Ota, Masayuki*; Oshima, Masumi; Kitatani, Fumito; Toh, Yosuke; Furutaka, Kazuyoshi; Kin, Tadahiro; Koizumi, Mitsuo; et al.

Journal of the Korean Physical Society, 59(2), p.1547 - 1552, 2011/08

https://doi.org/10.3938/jkps.59.1547

For the improvement of the accuracy on the neutron capture cross sections, a 4 Ge spectrometer was developed. The 4 Ge spectrometer is a unique tool due to its superior energy resolution for studying properties on neutron capture reactions, not only capture cross sections but also resonance identification, -ray intensity distribution, and spin-parity assignment. For example, its performance on the resonance identification was demonstrated using a Ag sample. On the measurement of a -ray intensity distribution for each resonance, the results of U will be shown. Using the 4 Ge spectrometer, the measurements of neutron capture cross sections were started at the J-PARC/MLF/ANNRI. The preliminary results on the measurements of neutron capture cross sections will be discussed mainly based on measurements of neutron capture cross sections for Am, together with related techniques.

The "Study on nuclear data by using a high intensity pulsed neutron source for advanced nuclear system" nuclear data project and the characteristics of the neutron beam line for the capture cross section experiments at J-PARC

Kiyanagi, Yoshiaki*; Kino, Koichi*; Furusaka, Michihiro*; Hiraga, Fujio*; Kamiyama, Takashi*; Kato, Kiyoshi*; Igashira, Masayuki*; Katabuchi, Tatsuya*; Mizumoto, Motoharu*; Oshima, Masumi; et al.

Journal of the Korean Physical Society, 59(2), p.1781 - 1784, 2011/08

https://doi.org/10.3938/jkps.59.1781

The project of the comprehensive nuclear data research for the development of the advanced reactor systems had been executed successfully by eight organizations from 2005 to 2009. In this project, we constructed the pulsed neutron beamline that was aimed to obtain neutron capture cross-sections of long-lived fission products and minor actinides accurately. The energy spectra, spatial distributions, and pulses of the beam were studied by measurements and simulation calculations, and they were found to be consistent with those of the beamline design. In this paper, we present the overview of the project and the properties of the neutron beam provided by this beam line.

Measurement of neutron capture cross section ratios of Cm resonances using NNRI

Goko, Shinji*; Kimura, Atsushi; Harada, Hideo; Oshima, Masumi; Ota, Masayuki*; Furutaka, Kazuyoshi; Kin, Tadahiro; Kitatani, Fumito; Koizumi, Mitsuo; Nakamura, Shoji; et al.

Journal of Nuclear Science and Technology, 47(12), p.1097 - 1100, 2010/12

https://doi.org/10.3327/jnst.47.1097

To obtain the accurate nuclear data of minor actinides required for a nuclear transmutation system or an innovative nuclear fuel cycle system, measurement of neutron-capture cross section of Cm was performed using NNRI installed at beam line No.4 (BL04) of MLF in J-PARC. Using "4 Ge spectrometer" that is a component of NNRI, neutron time of flight spectra and prompt ray spectra were measured. Then neutron-capture cross section ratios of Cm resonances were derived and compared with the evaluated values of JENDL-3.3. The previous experimental data was measured using a nuclear explosion as a pulsed neutron source, and the present result is the first time in the world that such measurements have been carried out at an accelerator facility. By developing techniques for more detailed analysis and improvement of the experimental conditions, the absolute values of capture cross section are expected to be obtained.

Characterization of electron self-injection in laser wake field acceleration due to the parametric resonance

Zhidkov, A.*; Koga, J. K.; Hosokai, Tomonao*; Fujii, Takashi*; Oishi, Yuji*; Nemoto, Koshichi*; Kodama, Ryosuke*

Physics of Plasmas, 17(8), p.083101_1 - 083101_6, 2010/08

https://doi.org/10.1063/1.3458669

A Novel technique for monitoring the reproducibility of laser tape-target interactions using an X-ray pinhole camera

Ogura, Koichi; Fukumi, Atsushi*; Li, Z.*; Orimo, Satoshi; Sagisaka, Akito; Nishiuchi, Mamiko; Kado, Masataka; Mori, Michiaki; Yogo, Akifumi; Hayashi, Yukio; et al.

Journal of the Vacuum Society of Japan, 52(10), p.570 - 574, 2009/10

https://doi.org/10.3131/jvsj2.52.570

For accurate control of relativistic laser-plasma interaction under the repetitive operation, we have to measure and control the laser irradiation conditions such as laser parameters, the target shooting accuracy and so on as well as measuring proton parameter on each laser shot. The displacement of the laser shooting position on a tape target, that are used in the high energy proton generation using an ultra-short Ti:sapphire laser system, is measured by observing an X-ray image from laser plasma with an X-ray pinhole camera for each laser shot. The displacement of the shooting position on the target is about 20micron and the accuracy of the target positioning is within 20micron which is small enough for present laser focusing optics with an F number of 3.6 (f=179mm). The technique contributes to accurate control of a repetitive laser driven proton accelerators.