Measurements of displacement cross sections of metals for 120-GeV proton beam irradiation

Iwamoto, Yosuke; Matsuda, Hiroki*; Meigo, Shinichiro; Yonehara, Katsuya*; Pellemoine, F.*; Liu, Z.*; Lynch, K.*; Yoshida, Makoto*; Yabuuchi, Atsushi*; Yoshiie, Toshimasa*; et al.

Nuclear Instruments and Methods in Physics Research B, 557, p.165543_1 - 165543_8, 2024/12

https://doi.org/10.1016/j.nimb.2024.165543

The number of displacements per atom is widely used as an indicator of irradiation damage to materials in proton accelerator facilities. Experiments have been carried out on protons below 3 GeV to verify the dpa of metallic materials. However, the dpa for high-energy protons above 3 GeV has not been measured. In order to validate the displacement cross sections of metals in the high-energy region, the electrical resistivity changes of aluminium, copper and tungsten wires at a temperature of 8 K were measured using protons with energy of 120 GeV. The results show that the conventional irradiation damage model of PHITS overestimates the experimental data. On the other hand, the calculation results using the athermal recombination correction model were in agreement with the experimental data.

Measurements of displacement cross section of tungsten under 389-MeV proton irradiation and thermal damage recovery

Iwamoto, Yosuke; Yoshida, Makoto*; Matsuda, Hiroki; Meigo, Shinichiro; Satoh, Daiki; Yashima, Hiroshi*; Yabuuchi, Atsushi*; Shima, Tatsushi*

Materials Science Forum, 1024, p.95 - 101, 2021/03

https://doi.org/10.4028/www.scientific.net/MSF.1024.95

To predict the lifetime of target materials in high-energy radiation environments at spallation neutron sources, radiation transport codes such as PHITS are used to calculate the displacements per atom (DPA) value. In this work, to validate calculated DPA values of tungsten, we implemented 0.25-mm-diameter wire sample of tungsten in a proton irradiation device with a Gifford-McMahon cryocooler and measured the defect-induced electrical resistivity changes related to the displacement cross section using 389-MeV protons at 10 K. As well as our previous results for aluminum and copper, calculated results with defect production efficiencies provided good agreements with experimental data. Based on measurements of recovery of the defects through annealing, about 85% of the damage remained at 60 K, and the same tendency is observed in other experimental result for reactor neutron irradiation.

Status of JAEA-AMS-MUTSU

Kuwabara, Jun; Kinoshita, Naoki; Tobinai, Kazuhito; Matsuno, Satoru; Oyokawa, Atsushi; Seki, Takeo; Yabuuchi, Noriaki

Dai-28-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.77 - 79, 2015/12

A Tandetron AMS system (JAEA-AMS-MUTSU) at Mutsu Office, Aomori Research and Development Center, Sector of Decommissioning and Radioactive Waste Management, JAEA, installed in 1997, has composed of 3 MV tandem accelerator and two beam lines (carbon and iodine). Status of the JAEA-AMS-MUTSU and trouble of ion source caused by deterioration of optical fiber cable are reported.

Irradiation effect of swift heavy ion for ZrCuAl bulk glassy alloy

Onodera, Naoto*; Ishii, Akito*; Ishii, Koji*; Iwase, Akihiro*; Yokoyama, Yoshihiko*; Saito, Yuichi; Ishikawa, Norito; Yabuuchi, Atsushi*; Hori, Fuminobu*

Nuclear Instruments and Methods in Physics Research B, 314, p.122 - 124, 2013/11

https://doi.org/10.1016/j.nimb.2013.04.034

It has been reported that heavy ion irradiation causes softening in some cases of Zr-based bulk metallic glass alloys. However, the fundamental mechanisms of such softening have not been clarified yet. In this study, ZrCuAl bulk glassy alloys were irradiated with heavy ions of 10 MeV I at room temperature. Positron annihilation measurements have performed before and after irradiation to investigate changes in free volume. We discuss the relationship between the energy loss and local open volume change after 10 MeV I irradiation compared with those obtained for 200 MeV Xe and 5 MeV Al. The energy loss analysis in ion irradiation for the positron lifetime has revealed that the decreasing trend of positron lifetime is well expressed as a function of total electronic energy deposition rather than total elastic energy deposition. It means that the positron lifetime change by the irradiation has a relationship with the inelastic collisions with electrons during heavy ion irradiation.

Location and size of nanoscale free-volume holes in crosslinked-polytetrafluoroethylene-based graft-type polymer electrolyte membranes determined by positron annihilation lifetime spectroscopy

Sawada, Shinichi; Yabuuchi, Atsushi*; Maekawa, Masaki; Kawasuso, Atsuo; Maekawa, Yasunari

Radiation Physics and Chemistry, 87, p.46 - 52, 2013/06

https://doi.org/10.1016/j.radphyschem.2013.02.016

The location and size of nanoscale free-volume holes (nanoholes) in graft-type polymer electrolyte membranes (PEMs), which were prepared by radiation-induced graft polymerization (grafting) of styrene into crosslinked-polytetrafluoroethylene (cPTFE) films and subsequent sulfonation, was investigated using positron annihilation lifetime (PAL) spectroscopy. The PAL spectra of the PEMs indicated the existence of two types of ortho-positronium (o-Ps) species, corresponding to nanoholes with volumes of 0.11 and 0.38 nm, respectively. Comparison of the PAL data of the PEMs with that of the precursor original cPTFE and polystyrene-grafted films demonstrated the probability that the smaller holes were located in both the PTFE crystalline phases and the poly(styrene sulfonic acid) graft regions, whereas the larger holes are potentially localized in the PTFE amorphous phases.

Influence of oversized elements (Hf, Zr, Ti and Nb) on the thermal stability of vacancies in type 316L stainless steels

Yabuuchi, Atsushi*; Maekawa, Masaki; Kawasuso, Atsuo

Journal of Nuclear Materials, 430(1-3), p.190 - 193, 2012/11

https://doi.org/10.1016/j.jnucmat.2012.07.005

Study on defects in H ion implanted B2 type Fe-Al alloy using slow positron beam

Komagata, Eiichi*; Kawasuso, Atsuo; Yabuuchi, Atsushi*; Maekawa, Masaki; Batchuluun, C.*; Yasuda, Keisuke*; Ishigami, Ryoya*; Kume, Kyo*; Iwase, Akihiro*; Hori, Fuminobu*

Physics Procedia, 35, p.75 - 79, 2012/00

https://doi.org/10.1016/j.phpro.2012.06.014

Fe48-at.% Al alloy were implanted with 50 keV H ions to the fluence of 310 and 110 /cm at room temperature. Positron annihilation Doppler broadening and lifetime measurements for these alloys have been carried out using slow positron beam apparatus with an energy range of 0.2 to 30.2 keV. The positron annihilation S-parameter decreased by H ion irradiation. Also the positron lifetimes for hydrogen deposited region in the alloy decreased by the irradiation. These results show that implanted H atoms were trapped by vacancy type defects.

Spin-polarized positron annihilation measurements of polycrystalline Fe, Co, Ni, and Gd based on Doppler broadening of annihilation radiation

Kawasuso, Atsuo; Maekawa, Masaki; Fukaya, Yuki; Yabuuchi, Atsushi; Mochizuki, Izumi

Physical Review B, 83(10), p.100406_1 - 100406_4, 2011/03

https://doi.org/10.1103/PhysRevB.83.100406

The Doppler broadening of annihilation radiation (DBAR) spectra of Fe, Co, Ni and Gd polycrystals measured using spin-polarized positrons from a Ge-Ga source in magnetic fields exhibited clear asymmetry upon field reversal. The differential DBAR spectra between field-up and field-down conditions were qualitatively reproduced in calculations considering polarization of positrons and electrons. The magnitudes of the field-reversal asymmetry for the Fe, Co and Ni samples was approximately proportional to the effective magnetization. The magnetic field dependence of the DBAR spectrum for the Fe sample showed hysteresis that is similar to a magnetization curve. These results demonstrate that spin-polarized positron annihilation spectroscopy will be useful in studying magnetic substances.

Fabrication of diluted magnetic semiconductor crystals by ion-implantation technique

Yabuuchi, Atsushi; Maekawa, Masaki; Kawasuso, Atsuo; Entani, Shiro; Matsumoto, Yoshihiro; Sakai, Seiji; Yamamoto, Shunya

JAEA-Review 2010-065, JAEA Takasaki Annual Report 2009, P. 131, 2011/01

https://doi.org/10.11484/jaea-review-2010-065

Ion implantation technique is expected to be useful in fabrication of diluted magnetic semiconductors (DMS) that require high concentration magnetic atom doping without a secondary phase formation. However, ion implantation surely introduces irradiation-induced vacancies into crystals. Recent calculation studies have suggested a presence of vacancies affect the magnetic properties in DMS. In this study, magnetic ions were implanted into compound semiconductor crystals by using ion implantation. N-type ZnO(0001) crystals were implanted with 380 keV maximum energy Cr ions to a dose of 110 ions/cm. After ion implantation, isochronal annealing in steps of 30 min/100 C was performed. From the measurement results, irradiation-induced vacancies were annealed out at 900 C. From XRD measurements after annealing at 1100 C, no secondary phase peaks were observed. However, from SQUID measurement, a clear magnetic hysteresis was not observed.

Production of highly spin-polarized positron source

Kawasuso, Atsuo; Maekawa, Masaki; Fukaya, Yuki; Yabuuchi, Atsushi

JAEA-Review 2010-065, JAEA Takasaki Annual Report 2009, P. 176, 2011/01

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2010-065.pdf

We attempt to produce the Ge-Ga radioisotope as a highly spin-polarized positron source. We irradiated 20 MeV or 25 MeV proton beam for Ga targets. We confirmed the production of Ge-Ga radioisotopes by a nuclear reaction of Ga(p,2n)Ge. From the magnetic field dependence of two- self-annihilation intensity of positronium in a fused silica, we determined the spin polarization of emitted positrons to be more than 80% as theoretically predicted using the positron helicity.