Hidetoshi Ohshita

Local Structural Analysis by Using Atomic Pair Distribution Function on Mixed Valence Compound LiMn2O4

Katsuaki Kodama1, Naoki Igawa1, Shin-ichi Shamoto1, Kazutaka Ikeda2, Hidetoshi Ohshita2, Naokatsu Kaneko2, Toshiya Otomo2, Kentaro Suzuya3, Akinori Hoshikawa4, and Toru Ishigaki4 1Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan 2Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan 3J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan 4 Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Tokai, Ibaraki 319-1106, Japan

New Neutron Beam Monitor Based on GEM

The high-intensity neutron total diffractometer (NOVA) constructed in BL21 of MLF [1] in J-PARC is one of the world’s most intense diffractometers. Since NOVA can observe structural changes in a very short time, it is a very powerful system for in-situ measurements. Because a time-slice measurement is usually performed in in-situ measurements, NOVA has to monitor the amount of incident neutrons with high accuracy. Therefore, an incident neutron beam monitor with the ability to monitor high counts is one of the key components of NOVA. We had already developed a two-dimensional neutron detector with a Gas Electron Multiplier (GEM) [2] as the incident neutron beam monitor of NOVA [3]. The GEM-based detector is a good neutron detector, but its electronics is obsolete and it is becoming more difficult to offer it as a new purchase. To overcome this problem, we developed a new neutron beam monitor (nGEM), which is an upgraded system that follows the basic design concept of the GEM-based detector. The nGEM is a gas-flow radiation detector that can measure charged particles from a n( 10 B, ) 7 Li nuclear reaction. The nGEM has a compact body of dimensions 524 mm × 254 mm × 50 mm. An Application Specific Integrated Circuit (ASIC) for pulse shaping and a Field Programmable Gate Array (FPGA) for online processing are also installed in the onboard electronics of the nGEM, which is able to transfer data directly to a PC via a network. The thermal neutron efficiency of the nGEM depends on the thickness of an ■■■ JPS Conf. Proc. , 036019 (2015)

Local Lattice Distortion Caused by Short-range Charge Ordering in Transition Metal Oxides

Katsuaki Kodama1, Naoki Igawa1, Shin-ichi Shamoto1, Kazutaka Ikeda2, Hidetoshi Ohshita2, Naokatsu Kaneko2, Toshiya Otomo2, Kentaro Suzuya3, Akinori Hoshikawa4, and Toru Ishigaki4 1Quantum Beam Science Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan 2Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan 3J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan 4 Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Tokai, Ibaraki 319-1106, Japan

Performance of a neutron beam monitor with a GEM for the high-intensity total diffractometer at J-PARC

We are developing a neutron beam monitor with a gas electron multiplier (GEM) for the high-intensity total diffractometer at J-PARC. In order to analyze the basic characteristics of the GEM-based detector, a neutron irradiation test was carried out at J-PARC. The wavelength-spectrum distribution obtained from the test is consistent with the calculations, and the beam profiles agree with the simple Monte Carlo (MC) simulation. Therefore we found that as a neutron beam monitor, the GEM-based detector has good two-dimensional imaging ability.