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Journal Articles

High temperature gas-cooled reactors

Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950$$^{circ}$$C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.

Journal Articles

Fluorescence decay processes following resonant 2p photoexcitation of Ar atoms and clusters studied using a time-resolved fluorescence and photoion coincidence technique

Gejo, Tatsuo*; Ikegami, Takeshi*; Homma, Kenji*; Harries, J.; Tamenori, Yusuke*

Journal of Physics B; Atomic, Molecular and Optical Physics, 46(7), p.075102_1 - 075102_9, 2013/04

 Times Cited Count:3 Percentile:21.46(Optics)

Journal Articles

Beam diagnostics in the J-PARC linac for ACS upgrade

Miura, Akihiko; Sato, Susumu; Tomisawa, Tetsuo; Igarashi, Zenei*; Miyao, Tomoaki*; Ikegami, Masanori*; Toyama, Takeshi*

Proceedings of 10th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators (DIPAC 2011) (Internet), p.50 - 52, 2011/08

J-PARC had developed the beam diagnostic devices for the present J-PARC linac and has used them since the operation start. J-PARC linac began the energy upgrade project since 2009 and 21 ACS cavities will be installed. Because the beam parameters are updated due to the project, new beam diagnostic devices are additionally fabricated and the diagnostic devices at the downstream part where the beam energy will be increased up to 400 MeV by ACS cavities should be developed. In this paper, we introduce the development of the beam diagnostic devices for the project and the new developing devices.

Journal Articles

Stabilization of beam instability due to space-charge effects at J-PARC

Shobuda, Yoshihiro; Chin, Y. H.*; Toyama, Takeshi*; Ikegami, Masanori*

Proceedings of 2009 Particle Accelerator Conference (PAC '09) (DVD-ROM), p.4701 - 4703, 2009/05

The kicker magnet is one of dominant sources of impedances with 3 GeV RCS at J-PARC. It has been considered that this impedance gives us the significant constraint to increase the beam intensity. Recently, the 300 kW beam was accomplished at 3 GeV RCS, while no instability is found. We discuss the space charge effect to stabilize the beam instability.

Journal Articles

Focusing and spectral enhancement of a repetition-rated, laser-driven, divergent multi-MeV proton beam using permanent quadrupole magnets

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:54 Percentile:87.76(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$$times$$8 mm$$^{2}$$ at a distance of 650 mm from the source. This result is in good agreement with a Monte Carlo particle trajectory simulation.

Journal Articles

Beam energy measurement at J-PARC linac

Sato, Susumu; Igarashi, Zenei*; Tomisawa, Tetsuo; Miura, Akihiko; Ueno, Akira; Sako, Hiroyuki; Morishita, Takatoshi; Kondo, Yasuhiro; Shen, G.; Akikawa, Hisashi*; et al.

Proceedings of 5th Annual Meeting of Particle Accelerator Society of Japan and 33rd Linear Accelerator Meeting in Japan (CD-ROM), p.500 - 502, 2008/00

no abstracts in English

Journal Articles

Large displacement of germanium atoms in crystalline Ge$$_2$$Sb$$_2$$Te$$_5$$

Shamoto, Shinichi; Yamada, Noboru*; Matsunaga, Toshiyuki*; Proffen, T.*; Richardson, J. W.*; Chung, J.-H.*; Egami, Takeshi*

Applied Physics Letters, 86(8), p.081904_1 - 081904_3, 2005/02

 Times Cited Count:47 Percentile:82.45(Physics, Applied)

Local structure of NaCl-type crystalline Ge$$_2$$Sb$$_2$$Te$$_5$$ has been studied by the atomic pair distribution function analysis of pulsed neutron powder diffraction data. We have found the large displacement of germanium atoms in this crystalline phase. Usually, such a large lattice distortion has disadvantage for the electric conductivity. The electronic band structure, however, implies that this significant distortion in addition to the lattice defect at Na site reduces only thermal conductivity, while the highly ordered tellurium atoms at Cl site keep high electric conductivity.

Journal Articles

Local structure of LiNiO$$_2$$ studied by neutron diffraction

Chung, J.-H.*; Proffen, T.*; Shamoto, Shinichi; Ghorayeb, A. M.*; Croguennec, L.*; Tian, W.*; Sales, B. C.*; Jin, R.*; Mandrus, D.*; Egami, Takeshi*

Physical Review B, 71(6), p.064410_1 - 064410_11, 2005/02

 Times Cited Count:65 Percentile:88.95(Materials Science, Multidisciplinary)

LiNiO$$_2$$ (S=1/2) forms a triangular lattice with the possible magnetic frustration, but the exact state of spin correlation has not yet been known. While there is no signature of long-range Jahn-Teller distortion, local JT distortion has been suspected. We have performed neutron diffraction and atomic pair-density function analyses up to unprecedented large distances to discover a number of unusual features, such as anomalous peak broadening, local JT distortion, sharp oxygen-oxygen distance correlations, and inverted temperature dependence of medium range correlation. These observations are best explained by local orbital ordering of Ni$$^{3+}$$ ions into three sublattices. This orbital ordering, however, cannot develop into long-range order because of the strain field it generates, and domains of about 10 nm in size are formed. Domains are susceptible to random pinning by impurities ssite disorderd resulting in the loss of structural long-range order. We suggest that this local orbital ordering is the basis for the complex magnetic properties observed in this compound.

Journal Articles

Developments of the calibration tools for beam position monitor at J-PARC LINAC

Sato, Susumu; Tomisawa, Tetsuo; Akikawa, Hisashi; Ueno, Akira; Lee, S.*; Igarashi, Zenei*; Ikegami, Masanori*; Toyama, Takeshi*; Kamikubota, Norihiko*

Proceedings of 2005 Particle Accelerator Conference (PAC '05) (CD-ROM), p.2777 - 2779, 2005/00

The J-PARC LINAC requires for fine control of beam position to minimize beam loss. So that BPMs need to be calibrated with the accuracy of about a hundred micro-meters. The accuracy of BPMs are calibrated with the calibration tool and real beam. In this paper, details of these developments around BPMs are to be reported.

Journal Articles

Investigation of photo neutralization efficiency of high intensity H$$^{-}$$ beam with Nd:YAG laser in J-PARC

Tomisawa, Tetsuo; Akikawa, Hisashi; Sato, Susumu; Ueno, Akira; Kondo, Yasuhiro; Oigawa, Hiroyuki; Sasa, Toshinobu; Hasegawa, Kazuo; Lee, S.*; Igarashi, Zenei*; et al.

Proceedings of 7th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators (DIPAC 2005), p.275 - 277, 2005/00

The photo neutralization method with Nd:YAG laser for negative hydrogen ions has been expected as an available candidate for the transverse beam profile measurement. The fraction of photo detached electron can also be used for charge exchange procedure to extract very low power proton beam for Transmutation Experimental Facility in J-PARC. The laser system has advantages of maintenance and radiation hardness in high intensity proton accelerators. In order to establish the low power beam extraction system and beam profile monitor, the photo neutralization efficiency must be surveyed in practical beam line with high intensity H$$^{-}$$ beam. In this paper, an experimental set-up and preliminary results of photo neutralization method for intense H$$^{-}$$ beam in J-PARC MEBT1 are described.

Journal Articles

Systematic calibration of beam position monitor at J-PARC LINAC

Sato, Susumu; Tomisawa, Tetsuo; Hiroki, Fumio; Lee, S.*; Igarashi, Zenei*; Ikegami, Masanori*; Ueno, Akira; Kondo, Yasuhiro; Hasegawa, Kazuo; Toyama, Takeshi*; et al.

Proceedings of 1st Annual Meeting of Particle Accelerator Society of Japan and 29th Linear Accelerator Meeting in Japan, p.467 - 469, 2004/08

As a joint project of KEK and JAERI, a MW class of high intensity proton accelerator (J-PARC), consisting of Linac, 3 GeV-RCS, 50 GeV-MR, is under construction. For this accelerator, it is required to minimize the beam loss (typically, lower than0.1$$sim$$1 W/m at the linac). To achieve the requirement, beam trajectory needs to be controlled with accuracy of some 100 $$mu$$m. The first stage of the acceleration (up to 181 MeV during the first stage of construction) is done by linac. The beam position monitor (BPM) in the linac utilizes 4 stripline pickups (50 ohm) on the beam transportation chamber. In this paper, systematic calibration of the BPM is described.

Journal Articles

Systematic calibration of beam position monitor in the high intensity proton accelerator (J-PARC) linac

Sato, Susumu; Igarashi, Zenei*; Lee, S.*; Tomisawa, Tetsuo; Hiroki, Fumio; Kishiro, Junichi; Ikegami, Masanori*; Kondo, Yasuhiro; Hasegawa, Kazuo; Ueno, Akira; et al.

Proceedings of 22nd International Linear Accelerator Conference (LINAC 2004), p.429 - 431, 2004/00

As a joint project of KEK and JAERI, a MW class of high intensity proton accelerator (J-PARC), consisting of Linac, 3 GeV-RCS, 50 GeV-MR, is under construction at Tokai, Japan. For this accelerator, it is required to minimize the beam loss (typically, lower than 0.1$$sim$$1 W/m at the linac). To achieve the requirement, beam trajectory needs to be controlled with accuracy of some 100 micro-meter. The first stage of the acceleration (up to 181 MeV during the first stage of construction) is done by linac. The beam position monitor (BPM) in the linac utilizes 4 strip-line pickups (50 ohm) on the beam transportation chamber. In this paper, systematic calibration of the BPM is described.

Journal Articles

Energetic protons from a few-micron metallic foil evaporated by an intense laser pulse

Matsukado, Koji*; Esirkepov, T. Z.; Kinoshita, Kenichi*; Daido, Hiroyuki; Utsumi, Takayuki*; Li, Z.*; Fukumi, Atsushi*; Hayashi, Yukio; Orimo, Satoshi; Nishiuchi, Mamiko; et al.

Physical Review Letters, 91(21), p.215001_1 - 215001_4, 2003/11

 Times Cited Count:134 Percentile:95.57(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Vibronic mechanism of high-${it Tc}$ superconductivity

Tachiki, Masashi*; Machida, Masahiko; Egami, Takeshi*

Physical Review B, 67(17), p.174506_1 - 174506_12, 2003/05

 Times Cited Count:45 Percentile:85.43(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Structural design for intermediate heat exchanger of the HTTR

Kunitomi, Kazuhiko; Takeda, Takeshi; Shinozaki, Masayuki; Okubo, Minoru; *; Koikegami, Hajime*

Nihon Genshiryoku Gakkai-Shi, 37(4), p.316 - 326, 1995/00

 Times Cited Count:1 Percentile:18.1(Nuclear Science & Technology)

no abstracts in English

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