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Si observed by X-ray absorption spectroscopyNakai, Hirohito*; Ebihara, Takao*; Tsutsui, Satoshi*; Mizumaki, Masaichiro*; Kawamura, Naomi*; Michimura, Shinji*; Inami, Toshiya; Nakamura, Toshiyuki*; Kondo, Akihiro*; Kindo, Koichi*; et al.
Journal of the Physical Society of Japan, 82(12), p.124712_1 - 124712_5, 2013/12
Times Cited Count：9 Percentile：53.5(Physics, Multidisciplinary)The temperature and magnetic field dependences of Yb valence were observed in the heavy fermion compoundYbRhSi by X-ray absorption spectroscopy. The measurements revealed that the Yb valence decreases with decreasing temperature in the range from 200 to 2 K and increases with increasing magnetic field in the range from 0 to 33 T without showing an abrupt change in the Yb valence. The Yb valence is in the range from 2.92 to 2.96 depending on temperature and magnetic field. With respect to the valence being 2.92 at 0 T and 2.93 at 33 T in 2 K, YbRhSi is a valence fluctuation compound and does not reach the integer trivalent state at high magnetic field. These results endorse the conventional knowledge that the valence of Yb is very close to the integer value of 3+, decreases with decreasing temperature, and becomes closer to 3+ with increasing magnetic field.
Okano, Yasushi; Yamano, Hidemasa; Fujita, Satoshi; Kubo, Shigenobu; Sakai, Takaaki; Nakai, Ryodai
Proceedings of 8th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-8) (USB Flash Drive), 9 Pages, 2012/12
General safety approaches are developed for next generation SFR based on the fundamental safety characteristics with incorporating lessons learned from the TEPCO's Fukushima Daiichi accidents. The fundamental characteristics are: reactivity, coolant pressure, sub-cool margin, ultimate heat sink, and sodium properties. These points are considered to derive general safety approach related to fundamental function. The key is to apply passive safety for prevention/mitigation of severe accident in design extension condition (DEC) with balancing active safety systems - passive mechanism should be built-in design for reactor shutdown and decay heat removal especially for DEC in order to enhance diversity to the engineered safety systems utilized for design basis accident. For containment integrity, the potentials of pressure/temperature increases via sodium leak and of significant mechanical energy release by re-criticality in the course of the CDA should be eliminated.
Ogura, Koichi; Shizuma, Toshiyuki; Hayakawa, Takehito; Yogo, Akifumi; Nishiuchi, Mamiko; Orimo, Satoshi; Sagisaka, Akito; Pirozhkov, A. S.; Mori, Michiaki; Kiriyama, Hiromitsu; et al.
Japanese Journal of Applied Physics, 51(4), p.048003_1 - 048003_2, 2012/04
Times Cited Count：2 Percentile：8.9(Physics, Applied)A proton beam driven by a repetitive high-intensity-laser is utilized to induce a 
Li(p,n)Be nuclear reaction. The total activity of Be are evaluated by two different methods. The activity obtained measuring the decay 
-rays after 1912 shots at 1 Hz is 1.7
0.2 Bq. This is in good agreement with 1.60.3 Bq evaluated from the proton energy distribution measured using a time-of-flight detector and the nuclear reaction cross-sections. We conclude that the production of activity can be monitored in real time using the time-of-flight-detector placed inside a diverging proton beam coupled with a high-speed signal processing system.
Watahiki, Masatoshi; Akai, Masanori; Nakai, Koji; Iemura, Keisuke; Yoshino, Masanori*; Hirano, Hiroshi*; Kitamura, Akihiro; Suzuki, Kazunori
Nihon Genshiryoku Gakkai Wabun Rombunshi, 11(1), p.101 - 109, 2012/02
Gloveboxes used for plutonium fuel development and fabrication are eventually dismantled for replacement or decommissioning. Since equipment interior and the inner surface of gloveboxes are contaminated in radioactive materials, glovebox dismantling work is performed by workers wearing an air fed suit with mechanical tools in a plastic enclosure system to control the spread of contamination. Various improvements of enclosure system are implemented including modification of the rooms to decontaminate and undress the air fed suit and introduction of inflammable filter and safety film near the size reduction workspace against fire. We describe the countermeasures deployed in the enclosure system against potential hazards and how these devices work in the real dismantling activities.
Kitamura, Akihiro; Nakai, Koji; Namekawa, Takashi; Watahiki, Masatoshi
Nuclear Engineering and Design, 241(7), p.2614 - 2623, 2011/07
Times Cited Count：5 Percentile：38.51(Nuclear Science & Technology)We developed a remote control system to display recreated three dimensional information of workspace from measured data obtained by laser rangefinder and to operate manipulator arm remotely. In order to evaluate the effectiveness and usefulness of developed system, we implemented remote handling experiments using mock up equipment and compared the performances of remote operation conducted by the present control system with that by the usual camera based control system. Impressions of operator on the performance of each system are collected and NASA TLX tests are conducted. It was observed that the present system reduced workload stresses and reinforced visual information during remote operation.
Iemura, Keisuke; Nakai, Koji; Watahiki, Masatoshi; Kitamura, Akihiro; Suzuki, Kazunori; Aoki, Yoshikazu
Dekomisshoningu Giho, (43), p.2 - 9, 2011/03
Plutonium fuel fabrication facility is constructed in 1972 and it is almost 40 years of age and equipment and components comprises the facility start degrading. Therefore we need to start dismantling gloveboxes from old ones first and at the same time to maintain the facility components and structures and gloveboxes as necessary. Also, since waste storage space is limited in the site, we effectively use open spaces generated after removing gloveboxes and equipment as temporal waste storage space. After shipping these wastes from the facility, final characterization of the facility will be conducted and demolition of the facility will be take place.
Sagisaka, Akito; Pirozhkov, A. S.; Mori, Michiaki; Yogo, Akifumi; Ogura, Koichi; Orimo, Satoshi; Nishiuchi, Mamiko; Ma, J.*; Kiriyama, Hiromitsu; Kanazawa, Shuhei; et al.
NIFS-PROC-85, p.30 - 33, 2011/02
The experiment of proton generation is performed for developing the laser-driven ion source. We observe proton signals in the laser-plasma interaction by using a thin-foil target. To get higher energy protons the size of the preformed plasma is reduced by changing the laser contrast level. In the high-contrast laser pulse case the maximum energy of the protons generated at rear side of the target increases.
Sagisaka, Akito; Pirozhkov, A. S.; Mori, Michiaki; Yogo, Akifumi; Ogura, Koichi; Orimo, Satoshi; Nishiuchi, Mamiko; Ma, J.*; Kiriyama, Hiromitsu; Kanazawa, Shuhei; et al.
Reza Kenkyu, 38(9), p.702 - 705, 2010/09
High-intensity laser and thin-foil interactions produce high-energy particles, hard X-ray, high-order harmonics, and terahertz (THz) radiation. A proton beam driven by a high-intensity laser has received attention as a compact ion source for medical applications. In this study we have tested simultaneous generation of protons and THz radiation from a thin-foil target. We use a Ti:sapphire laser system (J-KAREN) at JAEA. A laser beam is focused by an off-axis parabolic mirror at the thin-foil target. We observed the high-energy proton in the rear side of the target and THz radiation in the reflected direction. Next, high energy protons are observed by reducing the size of preformed plasma.
Sakaki, Hironao; Nishiuchi, Mamiko; Hori, Toshihiko; Bolton, P.; Yogo, Akifumi; Ogura, Koichi; Sagisaka, Akito; Pirozhkov, A. S.; Orimo, Satoshi; Kondo, Kiminori; et al.
Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.312 - 315, 2010/08
The beam transport test is carried out through the test beam line of the laser-driven proton accelerator which consists of the phase rotation cavity, PMQ, and bending magnet. The laser system used is J-KAREN at JAEA. The final transmitted bunch duration and transverse profile are well predicted by the PARMILA particle transport code by assuming relatively low initial current of the proton beam. The most probable explanation for this is the space charge neutralization by the laser-plasma-electrons.
Nishiuchi, Mamiko; Sakaki, Hironao; Hori, Toshihiko; Bolton, P.; Ogura, Koichi; Sagisaka, Akito; Yogo, Akifumi; Mori, Michiaki; Orimo, Satoshi; Pirozhkov, A. S.; et al.
Physical Review Special Topics; Accelerators and Beams, 13(7), p.071304_1 - 071304_7, 2010/07
Times Cited Count：25 Percentile：79.33(Physics, Nuclear)A laser-driven repetition-rated 1.9 MeV proton beam line composed of permanent quadrupole magnets (PMQs), a radio frequency (rf) phase rotation cavity, and a tunable monochromator is developed to evaluate and to test the simulation of laser-accelerated proton beam transport through an integrated system for the first time. In addition, the proton spectral modulation and focusing behavior of the rf phase rotationcavity device is monitored with input from a PMQ triplet. In the 1.9 MeV region we observe very weakproton defocusing by the phase rotation cavity. The final transmitted bunch duration and transverse profile are well predicted by the PARMILA particle transport code. The transmitted proton beam duration of 6 ns corresponds to an energy spread near 5% for which the transport efficiency is simulated to be 10%. The predictive capability of PARMILA suggests that it can be useful in the design of future higher energy transport beam lines as part of an integrated laser-driven ion accelerator system.
Nishiuchi, Mamiko; Sakaki, Hironao; Hori, Toshihiko; Bolton, P.; Ogura, Koichi; Sagisaka, Akito; Yogo, Akifumi; Mori, Michiaki; Orimo, Satoshi; Pirozhkov, A. S.; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.88 - 90, 2010/05
The concept of a compact ion particle accelerator has become attractive in view of recent progress in laser-driven ion acceleration. We report here the recent progress in the laser-driven proton beam transport at the Photo Medical Research Center (PMRC) at JAEA, which is established to address the challenge of laser-driven ion accelerator development for ion beam cancer therapy.
Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05
Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.
Yogo, Akifumi; Kiriyama, Hiromitsu; Mori, Michiaki; Esirkepov, T. Z.; Ogura, Koichi; Sagisaka, Akito; Orimo, Satoshi; Nishiuchi, Mamiko; Pirozhkov, A. S.; Nagatomo, Hideo*; et al.
European Physical Journal D, 55(2), p.421 - 425, 2009/11
Times Cited Count：3 Percentile：20.28(Optics)We demonstrate the laser-ion acceleration from a near-critical density plasma, when amplified spontaneous emission (ASE) was used to convert a solid foil target into the lower-density target. In this work, a direct comparison is made by changing the ASE intensity by factor 3 in order to investigate the target density-dependency of the laser-ion acceleration. The beam direction of high-energy component is successfully controlled by modifying the target density. The near-critical density plasma can be a favorable target to control the beam direction to be dependent on its energy.
Suzuki, Masayuki; Kiriyama, Hiromitsu; Daito, Izuru; Okada, Hajime; Nakai, Yoshiki; Orimo, Satoshi; Sato, Masatoshi*; Tamaoki, Yoshinori*; Yoshii, Takehiro*; Maeda, Junya*; et al.
Applied Physics B, 97(2), p.379 - 382, 2009/10
Times Cited Count：7 Percentile：37.48(Optics)We report the highest energy broadband laser pulses at a center wavelength of 1030 nm based on optical parametric chirped-pulse amplification (OPCPA). We have demonstrated amplification of 1030 nm femtosecond laser pulses from a broadband Yb oscillator to over 6.5 mJ with a total gain of greater than 10 achieved in a single pass through only 56 mm of gain material at a 10 Hz repetition rate. The amplified spectral bandwidth of 10.8 nm affords recompression to a 230 fs pulse duration following amplification. As an alternative to the regenerative amplifier (RA) this system is one of the more promising candidates for realizing compact, high intensity, direct diode pumped, high repetition rate femtosecond Yb:YAG chirped-pulse amplification (CPA) in laser systems.
Sagisaka, Akito; Daido, Hiroyuki; Pirozhkov, A. S.; Mori, Michiaki; Yogo, Akifumi; Ogura, Koichi; Orimo, Satoshi; Nishiuchi, Mamiko; Ma, J.-L.; Kiriyama, Hiromitsu; et al.
Frontiers of Optoelectronics in China, 2(3), p.299 - 303, 2009/09
High-intensity laser and thin-foil interactions produce high-energy ion, electron, hard X-ray, high-order harmonics, and terahertz (THz) radiation. We have performed the laser and thin-foil interaction experiments using a high-intensity Ti:sapphire laser. We have observed simultaneous generation of proton beam and THz radiation from a thin-foil target. Simultaneous generation of proton beam and UV harmonics is also observed.
Sagisaka, Akito; Pirozhkov, A. S.; Ma, J.-L.; Mori, Michiaki; Yogo, Akifumi; Ogura, Koichi; Orimo, Satoshi; Nishiuchi, Mamiko; Kiriyama, Hiromitsu; Kanazawa, Shuhei; et al.
Journal of Plasma and Fusion Research SERIES, Vol.8, p.464 - 467, 2009/09
We measure the UV harmonics from a thin-foil target by changing the laser pulse duration in the high-energy proton generation. The maximum proton energies are around 1 MeV. In the case of the 
500 fs, the peaks of UV harmonics up to fourth-order clearly appear. The spectra are broadened and shifted at the pulse durations of 100 fs and 30 fs.
Yogo, Akifumi; Daido, Hiroyuki; Mori, Michiaki; Kiriyama, Hiromitsu; Bulanov, S. V.; Bolton, P. R.; Esirkepov, T. Z.; Ogura, Koichi; Sagisaka, Akito; Orimo, Satoshi; et al.
Reza Kenkyu, 37(6), p.449 - 454, 2009/06
The acceleration of protons driven by a high-intensity laser is comprehensively investigated via control of the target density by using ASE just before the time of the main-laser interaction. Two cases were investigated for which the ASE intensity differed by three orders of magnitude: In the low contrast case the beam centre for higher energy protons is shifted closer to the laser-propagation direction of 45
, while the center of lower-energy beam remains near the target normal direction. Particle-in-cell simulations reveal that the characteristic proton acceleration is due to the quasistatic magnetic field on the target rear side with the magnetic pressure sustaining a charge separation electrostatic field.
Ogura, Koichi; Shizuma, Toshiyuki; Hayakawa, Takehito; Yogo, Akifumi; Nishiuchi, Mamiko; Orimo, Satoshi; Sagisaka, Akito; Pirozhkov, A. S.; Mori, Michiaki; Kiriyama, Hiromitsu; et al.
Applied Physics Express, 2(6), p.066001_1 - 066001_3, 2009/05
Times Cited Count：14 Percentile：49.68(Physics, Applied)Protons with energies up to 3.5 MeV have been generated by a 10 Hz compact laser with an intensity of about 10
W/cm
, focused on a 7.5 mm thick polyimide target. These protons were used to induce a nuclear reaction of 
B(p,n)C. A total activity of 11.1 Bq was created after 60-shot laser irradiation. The possibility of thin layer activation (TLA) using a high-intensity ultra-short pulsed laser is discussed.
Yogo, Akifumi; Sato, Katsutoshi; Nishikino, Masaharu; Mori, Michiaki; Teshima, Teruki*; Numasaki, Hodaka*; Murakami, Masao*; Demizu, Yusuke*; Akagi, Takashi*; Nagayama, Shinichi*; et al.
Applied Physics Letters, 94(18), p.181502_1 - 181502_3, 2009/05
Times Cited Count：110 Percentile：94.72(Physics, Applied)Nishiuchi, Mamiko; Daito, Izuru; Ikegami, Masahiro; Daido, Hiroyuki; Mori, Michiaki; Orimo, Satoshi; Ogura, Koichi; Sagisaka, Akito; Yogo, Akifumi; Pirozhkov, A. S.; et al.
Applied Physics Letters, 94(6), p.061107_1 - 061107_3, 2009/02
Times Cited Count：59 Percentile：87.41(Physics, Applied)A pair of conventional permanent magnet quadrupoles is used to focus a 2.4 MeV laser-driven proton beam at a 1 Hz repetition rate. The magnetic field strengths are 55 T/m and 60 T/m for the first and second quadrupoles respectively. The proton beam is focused to a spot size (full width at half maximum) of 2.7
8 mm at a distance of 650 mm from the source. This result is in good agreement with a Monte Carlo particle trajectory simulation.
