First observation of O

Kondo, Yosuke*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; Baba, Hidetada*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.

Nature, 620(7976), p.965 - 970, 2023/08

https://doi.org/10.1038/s41586-023-06352-6

no abstracts in English

Multiple mechanisms in proton-induced nucleon removal at 100 MeV/nucleon

Pohl, T.*; Sun, Y. L.*; Obertelli, A.*; Lee, J.*; Gmez-Ramos, M.*; Ogata, Kazuyuki*; Yoshida, Kazuki; Cai, B. S.*; Yuan, C. X.*; Brown, B. A.*; et al.

Physical Review Letters, 130(17), p.172501_1 - 172501_8, 2023/04

https://doi.org/10.1103/PhysRevLett.130.172501

We report on the first proton-induced single proton- and neutron-removal reactions from the neutron deficient O nucleus with large Fermi-surface asymmetry at 100 MeV/nucleon. Our results provide the first quantitative contributions of multiple reaction mechanisms including the quasifree knockout, inelastic scattering, and nucleon transfer processes. It is shown that the inelastic scattering and nucleon transfer, usually neglected at such energy regime, contribute about 50% and 30% to the loosely bound proton and deeply bound neutron removal, respectively.

Flow-induced vibration evaluation of primary hot-leg piping in advanced loop-type sodium-cooled fast reactor for demonstration

Yamano, Hidemasa; Xu, Y.*; Sago, Hiromi*; Hirota, Kazuo*; Baba, Takeo*

Proceedings of 2016 International Congress on Advances in Nuclear Power Plants (ICAPP 2016) (CD-ROM), p.1029 - 1038, 2016/04

This study conducted the flow-induced vibration evaluation of the primary hot-leg piping in the demonstration reactor design of advanced loop-type sodium-cooled fast reactor in order to confirm the integrity of the piping. Following the description of the primary hot-leg piping design and a design guideline of the flow-induced vibration evaluation, this paper describes mainly the flow-induced vibration evaluation and thereby the integrity assessment. In the fatigue evaluation for the flow-induced vibration, the pipe stresses considering the stress concentration factor and so on, at representative locations were less than the design fatigue limit. Therefore, this evaluation confirmed the integrity of the primary hot-leg piping in the demonstration reactor.

Orientation effect of organic semiconducting polymer revealed using Photo-Electron Emission Microscope (PEEM)

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Hirao, Norie; Honda, Mitsunori; Izumi, Toshinori; Ikeura, Hiromi*

Photon Factory Activity Report 2013, Part B, P. 546, 2014/00

The molecular orientation is one of the important factors for controlling various properties in organic semiconductor materials. Films are usually heterogeneous. Thus they exist as a mixture of microscopic domains which have a variety of orientation directions. Therefore, it is essential to observe selectively microscopic domains with different orientation direction. In this work, we have developed the photoelectron emission microscope (PEEM) system combined with the linearly polarized vacuum ultraviolet (VUV) light or synchrotron radiation (SR) X-rays. PEEM images for poly(3-hexylthiophene), P3HT thin films were observed under synchrotron X-ray irradiation with linearly polarization. In conclusion, it was found that PEEM with polarized synchrotron can be a powerful tool that gives information of molecular orientation in nano-meter scale.

Microdosimetric evaluation of the neutron field for BNCT at Kyoto University Reactor by using the PHITS code

Baba, Hiromi*; Onizuka, Yoshihiko*; Nakao, Minoru*; Fukahori, Mai*; Sato, Tatsuhiko; Sakurai, Yoshinori*; Tanaka, Hiroki*; Endo, Satoru*

Radiation Protection Dosimetry, 143(2-4), p.528 - 532, 2011/02

https://doi.org/10.1093/rpd/ncq511

The PHITS simulation were performed to reproduce the geometrical setup of an experiment that measured the microdosimetric energy distributions at the Kyoto University Reactor (KUR) where two types of tissue equivalent proportional counters (TEPC) were used, one with A-150 wall alone and another with a 50 ppm boron loaded A-150 wall. It was found that the PHITS code is a useful tool for the simulation of the energy deposited in tissue in BNCT based on the comparisons with experimental results.

Enhancement effect in photon-stimulated ion desorption for benzene adsorbed on silicon surfaces observed using angle-dependent technique

Sekiguchi, Tetsuhiro; Ikeura, Hiromi*; Baba, Yuji

Applied Surface Science, 254(23), p.7812 - 7816, 2008/09

BB2008-4109.pdf:0.79MB

https://doi.org/10.1016/j.apsusc.2008.02.091

We have constructed a novel rotatable time-of-flight (TOF) mass detector for desorbed fragment-ions produced by irradiation of synchrotron radiation (SR). This makes the best use of advantages in synchrotron, including variable X-ray energy, linear polarization, and pulsed capability. The detector allows us to measure excitation-energy dependences of desorbing ion yields from solid surfaces in a variety of incident angles of X-ray beams. We propose that this angle-dependent technique provides insights into orientation of chemical bonds lying at the top surface. The present paper reports our recent findings that the mass-patterns and yields of desorbed ions drastically depend on the incident angles less than 10 degrees. The results suggest that direct desorption mechanism prevails in extremely small angles and indirect desorption mechanism induced through collision excitation by secondary electrons is suppressed.

Highly polarized electrons from GaAs-GaAsP and InGaAs-AlGaAs strained-layer superlattice photocathodes

Nishitani, Tomohiro; Nakanishi, Tsutomu*; Yamamoto, Masahiro*; Okumi, Shoji*; Furuta, Fumio*; Miyamoto, Masaharu*; Kuwahara, Makoto*; Yamamoto, Naoto*; Naniwa, Kenichi*; Watanabe, Osamu*; et al.

Journal of Applied Physics, 97(9), p.094907_1 - 094907_6, 2005/05

https://doi.org/10.1063/1.1886888

no abstracts in English

Orientation effect on phot-fragmentation and ion-desorption from the topmost layers of molecular solids

Sekiguchi, Tetsuhiro; Ikeura, Hiromi*; Baba, Yuji

Surface Science, 532-535(1-3), p.1079 - 1084, 2003/06

Using a newly developed rotatable time-of-flight mass spectrometer(R-TOF-MS) and polarized synchrotron radiation, we have investigated orientation effect on fragmentation and desorption pathways occurring at the top-most layers of molecular solids. Reported will be polarization-angle dependencies of TOF mass spectra, high-resolution electron- and ion-NEXAFS in condensed formic acid, formamide and benzene. For condensed formamide(HCOND), marked orientation effect was observed for the enhanced H-yields following C1s * resonance. Direct photodissociation and charge-neutralization play an important role in the effect. For some fragment species, however, the bond scission showed no polarization dependence when dissociation sites were far from core-excited atoms. This is the case for N-D scission and D-desorption following C1s excitation, suggesting that indirect process governs, where secondary electrons would induce the fragmentation.

Element- and orientation-selective photo-decomposition using linearly polarized synchrotron radiation

Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Hiromi*

KEK Proceedings 2001-13, p.24 - 25, 2001/06

no abstracts in English

Inner shell excitation and dissociation of condensed formamide

Ikeura, Hiromi*; Sekiguchi, Tetsuhiro; Kitajima, Yoshinori*; Baba, Yuji

Applied Surface Science, 169-170, p.282 - 286, 2001/01

https://doi.org/10.1016/S0169-4332(00)00671-1

Carbon and nitrogen K-shell excitation and dissociation of condensed formamide at 96 K were studied by near edge X-ray absorption fine structure (NEXAFS) recorded by total electron yield (TEY), total ion yield (TIY) and photon-stimulated desorption (PSD) yield of H+ measurements. It was found that electronic transitions from the C1s or the N1s to the *(C-H) and/or (N-H) enhanced ion yield of H+ from the C-H and/or N-H functional group. This selective dissociation indicates that the corresponding unoccupied molecular orbital has an antibonding character of the C-H and/or N-H. To investigate the molecular orientation of condensed formamide, incidence-angle-dependent TEY-NEXAFS spectra were measured. The CNO plane of the adsorbed formamide molecule is determined to be tilted away from the surface by an averaged angle of about 42 degrees.