Quantum dynamics of hydrogen in the iron-based superconductor LaFeAsOD measured with inelastic neutron spectroscopy

Yamaura, Junichi*; Hiraka, Haruhiro*; Iimura, Soshi*; Muraba, Yoshinori*; Bang, J.*; Ikeuchi, Kazuhiko*; Nakamura, Mitsutaka; Inamura, Yasuhiro; Honda, Takashi*; Hiraishi, Masatoshi*; et al.

Physical Review B, 99(22), p.220505_1 - 220505_6, 2019/06

AA2019-0126.pdf:0.9MB

https://doi.org/10.1103/PhysRevB.99.220505

Inelastic neutron scattering was performed for an iron-based superconductor, where most of D (deuterium) replaces oxygen, while a tiny amount goes into interstitial sites. By first-principle calculation, we characterize the interstitial sites for D (and for H slightly mixed) with four equivalent potential minima. Below the superconducting transition temperature Tc = 26 K, new excitations emerge in the range 5-15 meV, while they are absent in the reference system LaFeAsOF. The strong excitations at 14.5 meV and 11.1 meV broaden rapidly around 15 K and 20 K, respectively, where each energy becomes comparable to twice of the superconducting gap. The strong excitations are ascribed to a quantum rattling, or a band motion of hydrogen, which arises only if the number of potential minima is larger than two.

Bipartite magnetic parent phases in the iron oxypnictide superconductor

Hiraishi, Masatoshi*; Iimura, Soshi*; Kojima, Kenji*; Yamaura, Junichi*; Hiraka, Haruhiro*; Ikeda, Kazutaka*; Miao, P.*; Ishikawa, Yoshihisa*; Torii, Shuki*; Miyazaki, Masanori*; et al.

Nature Physics, 10(4), p.300 - 303, 2014/04

https://doi.org/10.1038/nphys2906

Prevention of powder adhesion on substrate using nanoparticle coating

Suzuki, Michitaka*; Yoshikawa, Mao*; Iimura, Kenji*; Satone, Hiroshi*; Ishii, Katsunori

Funtai Kogakkai-Shi, 50(6), p.405 - 409, 2013/06

https://doi.org/10.4164/sptj.50.405

The glass substrate is coated by the silica nanoparticle suspension using dipping or spin coat method and dried in an electric oven. The glass substrate surface is covered with nanoparticle thin layer and the transparent and tiny rugged surface can be produced on a substrate. It was experimentally confirmed to prevent dust adhesion by covering the surface of the glass substrate with nanoparticle. The adhesion force between particle and substrate is measured by the centrifugal method and the relation between the adhesion force and the surface roughness is discussed from experimental and theoretical point of view. The measured and calculated results by Van der Waals force show that adhesion force decreased with the increment of the surface roughness. From the results, nanoparticle coating is very effective to prevent the dust adhesion on the substrate and the various application of nanoparticle coating can be expected.

Status of the design and investigation for hydraulic rabbit irradiation facility

Takita, Kenji; Iimura, Koichi; Tomita, Kenji; Endo, Yasuichi; Kanno, Masaru

UTNL-R-0480, p.7_4_1 - 7_4_6, 2012/03

no abstracts in English

Design of fuel transient test facility system

Hosokawa, Jinsaku; Iimura, Koichi; Ogawa, Mitsuhiro; Tomita, Kenji; Yamaura, Takayuki

JAEA-Technology 2010-018, 269 Pages, 2010/08

JAEA-Technology-2010-018.pdf:5.75MB

At Oarai Research and Development Center, Japan Atomic Energy Agency (JAEA) advances the plan of refurbishing Japan Materials Testing Reactor (JMTR) to start the operation in fiscal 2011. Fuel Transient Test Facility is scheduled to be set up as neutron irradiation test equipment of the light-water reactor fuel that uses JMTR after it operates again. The abnormal transition examination device is the irradiation facilities where the output sudden rise examination that makes the light-water reactor fuel an irradiation sample is done to use it to develop the safety evaluation technology and the damage influence evaluation technology of the light-water reactor fuel that reaches high burn-up. In this report, as for the system design, it is a summary to JMTR among detailed designs of the abnormal transition examination device of the installation schedule.

Dose evaluation of external exposure by direct and skyshine gamma rays of nuclear fuel handling facilities at JMTR

Ogawa, Mitsuhiro; Iimura, Koichi; Tomita, Kenji; Tobita, Masahiro

JAEA-Technology 2009-017, 254 Pages, 2009/05

JAEA-Technology-2009-017.pdf:15.04MB

In JMTR, upgrade of irradiation facilities is advanced to re-operate from 2011 F.Y. In order to irradiate test fuels of high-burnup, external exposure reassessment by direct and skyshine gamma rays of the nuclear fuel handling facility at JMTR was performed. In evaluation method, radiation source of maximum use of the nuclear fuel was calculated by using ORIGEN2 code. Dose equivalent rate for supervised area boundary was calculated by modeling reactor building at using shielding calculation codes QAD-CGGP2 and G33-GP2. As a result of evaluation, it was confirmed that the effective dose equivalent during year was low enough at supervised area boundary of the JMTR site.

Measuring of capping phenomena in powder compaction process using X-ray computed tomography

Suzuki, Michitaka*; Tanaka, Yutaka*; Iimura, Kenji*; Satone, Hiroshi*; Ishii, Katsunori

no journal, , 

The capping phenomenon is one of the important causes of the powder molding trouble. The research of the capping such as how to occur and what kind of condition related to the phenomena is not cleared still now. The packing particles for our tests were 20-150um spherical Alumina granules and the sieved narrow sized granules were also used. The compression tests were performed by a material-tester. The capping region could be detected from X-ray computed tomographic images and the depth of capping area was measured. It's clear that the capping phenomena are easy to occur at small compression displacement in the case of wider size distributed granules 20-150um. It comes from the higher adhesion force between fine powder and the piston or the mold surface. The depth of capping is decreasing with the increase in displacement. In the conclusion, the capping phenomena can be prevented to use coarser mono-sized granules for compression molding.