First observation of a nuclear -state of a hypernucleus,

Yoshimoto, Masahiro*; Fujita, Manami; Hashimoto, Tadashi; Hayakawa, Shuhei; Ichikawa, Yudai; Ichikawa, Masaya; Imai, Kenichi*; Nanamura, Takuya; Naruki, Megumi; Sako, Hiroyuki; et al.

Progress of Theoretical and Experimental Physics (Internet), 2021(7), p.073D02_1 - 073D02_19, 2021/07

https://doi.org/10.1093/ptep/ptab073

Evaluation of dark current profile for prediction of voltage holding capability on multi-aperture multi-grid accelerator for ITER

Nishikiori, Ryo; Kojima, Atsushi; Hanada, Masaya; Kashiwagi, Mieko; Watanabe, Kazuhiro; Umeda, Naotaka; Tobari, Hiroyuki; Yoshida, Masafumi; Ichikawa, Masahiro; Hiratsuka, Junichi; et al.

Plasma and Fusion Research (Internet), 11, p.2401014_1 - 2401014_4, 2016/03

https://doi.org/10.1585/pfr.11.2401014

One of critical issues for high-energy high-current beam acceleration in ITER and JT-60SA is the high voltage holding which is dominated by vacuum discharges. The past results suggest that vacuum discharge occurs beyond the threshold of the dark current. The dark current can be derived from F-N theory where electric field enhancement factor beta is included. Though, beta could only be evaluated from the experiment previously. Therefore, the method to decide beta without experiment is required. This time dark currents were measured at three different areas to compare beta in different electric field. As a result, the effective electric field E, where E is average electric field, were found to be almost constant for different areas although the beta is largely different. By applying E, beta can be evaluated analytically, leading to the analytical prediction of the dark current and voltage holding capability without the measurements.

Time evolution of negative ion profile in a large cesiated negative ion source applicable to fusion reactors

Yoshida, Masafumi; Hanada, Masaya; Kojima, Atsushi; Kashiwagi, Mieko; Umeda, Naotaka; Hiratsuka, Junichi; Ichikawa, Masahiro; Watanabe, Kazuhiro; Grisham, L. R.*; Tsumori, Katsuyoshi*; et al.

Review of Scientific Instruments, 87(2), p.02B144_1 - 02B144_4, 2016/02

https://doi.org/10.1063/1.4938406

Time evolution of spatial profile of negative ion production during an initial conditioning phase has been experimentally investigated in the JT-60 negative ion source. Up to 0.4 g Cs injection, there is no enhancement of the negative ion production and no observation of the Cs emission signal in the source, suggesting the injected Cs is mainly deposited on the water-cooled wall near the nozzle. After 0.4 g Cs injection, enhancement of the negative ion production appeared only at the central segment of the PG. The calculation of the Cs neutral/ion trajectories implied that a part of Cs was ionized near the nozzle and was transported to this area. The expansion of the area of the surface production was saturated after ~2 g Cs injection corresponding to 6000 s discharge time. From the results, it is found that Cs ionization and its transport plays an important role for the negative ion production.

Development of the negative ion beams relevant to ITER and JT-60SA at Japan Atomic Energy Agency

Hanada, Masaya; Kojima, Atsushi; Tobari, Hiroyuki; Nishikiori, Ryo; Hiratsuka, Junichi; Kashiwagi, Mieko; Umeda, Naotaka; Yoshida, Masafumi; Ichikawa, Masahiro; Watanabe, Kazuhiro; et al.

Review of Scientific Instruments, 87(2), p.02B322_1 - 02B322_4, 2016/02

https://doi.org/10.1063/1.4934584

In International Thermo-nuclear Experimental Reactor (ITER) and JT-60 Super Advanced (JT-60 SA), the D ion beams of 1 MeV, 40 A and 0.5 MeV, 22 A are required to produce 3600 s and 100 s for the neutral beam injection, respectively. In order to realize such as powerful D ion beams for long duration time, Japan Atomic Energy Agency (JAEA) has energetically developed cesium (Cs)-seeded negative ion sources (CsNIS) and electro-static multi-aperture and multi-stage accelerators (MAMuG accelerator) which are chosen as the reference design of ITER and JT-60 SA. In the development of the CsNIS, a 100s production of the H ion beam has been demonstrated with a beam current of 15 A by modifying the JT-60 negative ion source. At the higher current, the long pulse production of the negative ions has been tried by the mitigation of the arcing in the plasma inside the ion source. As for the long pulse acceleration of the negative ions in the MAMuG accelerator, the beam steering angle has been controlled to reduce the power loading of the acceleration grids A pulse duration time has been significantly extended from 0.4 s to 60 s at reasonable beam power for ITER requirement. The achieved pulse duration time is limited by the capacity of the power supplies in the test stand. In the range of 60 s, there are no degradations of beam optics and voltage holding capability in the accelerator. It leads to the further extension of the pulse duration time at higher power density. This paper reports the latest results of development on the negative ion source and accelerator at JAEA.

Foods being better or worse after -irradiation

Chiba, Etsuko*; Iizuka, Tomoko*; Ichikawa, Mariko*; Ukai, Mitsuko*; Kikuchi, Masahiro; Kobayashi, Yasuhiko

Hoshasen To Sangyo, (137), p.29 - 32, 2014/12

no abstracts in English

Verification of the FBR fuel bundle-duct interaction analysis code BAMBOO by the out-of-pile bundle compression test with large diameter pins

Uwaba, Tomoyuki; Ito, Masahiro*; Nemoto, Junichi*; Ichikawa, Shoichi; Katsuyama, Kozo

Journal of Nuclear Materials, 452(1-3), p.552 - 556, 2014/09

https://doi.org/10.1016/j.jnucmat.2014.06.016

The BAMBOO code was verified by results for the out-of-pile bundle compression test with large diameter pin bundle deformation under the bundle-duct interaction (BDI) condition. The pin diameters of were 8.5 mm and 10.4 mm, which are targeted as preliminary fuel pin diameters for the upgraded core of the prototype FBR and for demonstration and commercial FBRs studied in the FaCT project. In the bundle compression test, bundle cross-sectional views were obtained from X-ray computer tomography (CT)images and local parameters of bundle deformation were measured by CT image analyses. In the verification, calculation results of bundle deformation obtained by the BAMBOO code analyses were compared with the experimental results from the CT image analyses. The comparison showed that the BAMBOO code reasonably predicts deformation of large diameter pin bundles under the BDI condition by assuming that pin bowing and cladding oval distortion are the major deformation mechanisms.

Activation analyses of air by deuteron beam at 5-9 MeV

Takahashi, Hiroki; Maebara, Sunao; Sakaki, Hironao; Ichikawa, Masahiro; Suzuki, Hiromitsu; Sugimoto, Masayoshi

Progress in Nuclear Science and Technology (Internet), 4, p.261 - 263, 2014/04

https://doi.org/10.15669/pnst.4.261

An development of accelerator-based neutron irradiation facility is planning to develop materials for a demonstration fusion reactor. To obtain a 14 MeV neutron energy using the neutron-generating D-Li stripping reaction, an injection into liquid lithium flow by a 40 MeV deuteron beam is employed in IFMIF design concept. In the acceleration of deuteron beam, the activation due to the beam loss is critical issue. The activation analyses for the air in an accelerator vault are carried out by PHITS code and DCHAIN code using the experimental data for deuteron induced thick target neutron yield at 5 MeV and 9 MeV for source term.

Coupling cavity designs of the RF input coupler tests for the IFMIF/EVEDA prototype RFQ linac

Maebara, Sunao; Ichikawa, Masahiro

Proceedings of 3rd International Particle Accelerator Conference (IPAC '12) (Internet), p.3284 - 3286, 2013/07

http://accelconf.web.cern.ch/accelconf/IPAC2012/papers/thppc007.pdf

Study on validation method of regional groundwater flow model; Case study for Boso peninsula

Sakai, Ryutaro; Munakata, Masahiro; Kimura, Hideo; Ichikawa, Yasuo*; Nakamura, Masaru*

JAEA-Research 2010-066, 20 Pages, 2011/03

JAEA-Research-2010-066.pdf:2.26MB

In the safety assessment for a geological disposal of radioactive waste, it is important to establish modelling methods and validation methods for regional groundwater flow system in the depth of 3001000m to estimate radionuclide migration to human environment through groundwater flow system. The study discussed application of data and assessment methods for model validation based on multiple indicators such as hydrology, groundwater chemistry, temperature and age of groundwater in case of the Boso Peninsula in Chiba Prefecture where a lot of in-situ data about groundwater was measured. This results show that existing hydrochemical and thermal data are applicable to explain freshwater and saltwater distribution and groundwater flow pattern in case of regional scale. It also indicates that gravitational groundwater is likely to flow into the deep part of fresh-saltwater interface based on the exist of Na-HCO type water above fresh-saltwater interface mixed with meteoric water and that multiple indicators are applicable to evaluate groundwater flow property and groundwater flow boundary in case of site scale region.

Isoscalar giant resonances in the Sn nuclei and implications for the asymmetry term in the nuclear-matter incompressibility

Li, T.*; Garg, U.*; Liu, Y.*; Marks, R.*; Nayak, B. K.*; Madhusudhana Rao, P. V.*; Fujiwara, Mamoru*; Hashimoto, Hisanobu*; Nakanishi, Kosuke*; Okumura, Shun*; et al.

Physical Review C, 81(3), p.034309_1 - 034309_11, 2010/03

https://doi.org/10.1103/PhysRevC.81.034309