Electron density behavior during fast termination phase of post-disruption runaway plasma

Kawano, Yasunori; Nakano, Tomohide; Asakura, Nobuyuki; Tamai, Hiroshi; Isayama, Akihiko; Kondoh, Takashi; Hatae, Takaki; Takenaga, Hidenobu; Ide, Shunsuke

Purazuma, Kaku Yugo Gakkai-Shi, 81(10), p.743 - 744, 2005/10

http://doi.org/10.1585/jspf.81.743

Electron density of post-disruption runaway plasmas in JT-60U has been measured by the tangential CO laser interferometer. Increases in electron density after the first drop of runaway plasma current have been observed during a fast termination phase of the runaway plasma. At the second current drop, an increase in electron density with multiple spikes or oscillation with the period of 1 ms has been found. It is suggested that the increased electron density seems to take part in the shorter current decay time after the second current drop.

Power modulation by changing anode voltage of the 110GHz-gyrotron on JT-60U ECH system

Terakado, Masayuki; Seki, Masami; Shimono, Mitsugu; Igarashi, Koichi*; Mitsunaka, Yoshika*; Isayama, Akihiko; Anno, Katsuto; Ikeda, Yoshitaka

JAERI-Tech 2003-053, 25 Pages, 2003/06

JAERI-Tech-2003-053.pdf:3.23MB

The Electron Cyclotron Range of Frequencies (ECRF) system having four 110 GHz-gyrotrons has been successfully operated on JT-60U to locally heat a plasma (ECH) and drive a plasma current (ECCD) for high plasma performance owing to suppressing MHD activities. For investigation of plasma confinement the ECRF power is intermittently injected into plasmas to evaluate thermal conductivity. We have successfully performed power modulation by changing the anode voltage. The power modulation ratio of 80 % is attained changing the anode voltage by only about 10%. Modulation frequency is from 12 Hz to 500 Hz. The mode converter is heated when oscillation efficiency of the main mode decreases in changing the anode voltage. This seems to be due to the parasitic oscillation at the entrance of the converter. The gyrotron will be able to be protected by monitoring the temperature rise in the converter.

Time-resolved X-ray diffraction study on surface structure and morphology during molecular beam epitaxy growth

Takahashi, Masamitsu; Yoneda, Yasuhiro; Inoue, Hirotane*; Yamamoto, Naomasa*; Mizuki, Junichiro

Journal of Crystal Growth, 251(1-4), p.51 - 55, 2003/04

https://doi.org/10.1016/S0022-0248(02)02375-8

The reflection high energy electron diffraction (RHEED) oscillation has been widely adopted for studies on growth kinetics and dynamics in molecular beam epitaxy (MBE). Recent development in brilliant X-ray source has enabled similar experiments with X-rays, which has great advantage in a straightforward interpretation of results and in a high angular resolution. In general, the diffracted intensity from surface is proportional to the surface structure factor associated with the surface reconstruction, F, multiplied by a damping factor associated with the surface roughness, m. We show that the two factors, F and m, can be obtained separately by measuring diffuse scattering around the two-dimensional Bragg peak during growth.

Development of 972MHz klystron for high-intensity proton accelerator facility

Chishiro, Etsuji; Kobayashi, Tetsuya; Yamazaki, Masayoshi*; Suzuki, Hiroyuki*; Hori, Toshihiko*; Sakamoto, Mitsunori*; Urakata, Hiroto*; Miyake, Setsuo*; Fukuda, Shigeki*; Anami, Shozo*

Proceedings of 21st International Linac Conference, p.455 - 457, 2003/00

In the lilac of the High-Intensity Proton Accelerator Facility, 972MHz klystrons are adopted as the RF source for the acceleration from 190MeV to 400MeV. The klystron is required the RF power of 2.5 MW to drive the ACS accelerator. A prototype klystron was produced, and was evaluated the RF characteristics at the test stand in the JAERI. At the first test, a saturation power of 2.1 MW was obtain on the cathode voltage of 104kV, and an unstable output power causing by a gun oscillation was observed.

NSRR tests under simulated power oscillation conditions of BWRs

Nakamura, Jinichi; Nakamura, Takehiko; Sasajima, Hideo; Suzuki, Motoe; Uetsuka, Hiroshi

HPR-359, Vol.2, p.34_1 - 34_16, 2002/09

In BWR, power oscillations can occur due to the void fraction fluctuation. To investigate the fuel behavior during power oscillation of BWRs, two types of irradiated fuel rods were tested under simulated power oscillation conditions in the Nuclear Safety Research Reactor(NSRR). One is high burnup BWR fuel (56GWd/t) test, with 4 power oscillation cycles, to clarify the behavior of high burnup fuel. The second one is high enriched fuel(20%,25GWd/t) test, with 7 power cycles, to perform the test under high power conditions. The fuel behavior data, such as cladding elongation, fuel stack elongation, cladding temperature, etc. were obtained in these tests. The DNB did not occur in these tests. The PCI was observed through cladding elongation and fuel stack elongation during the power oscillations, but the residual strain of cladding was very small. Fuel behavior under simulated power oscillations is discussed based on in-pile data and PIE data and is compared with FEMAXI-6 and FRAP-T6 calculation.

Technology of the ultra-fast pulse and high-power FELs driven by a superconducting rf linac

Minehara, Eisuke

Oyo Butsuri, 71(2), p.214 - 216, 2002/02

http://joi.jlc.jst.go.jp/JST.Journalarchive/oubutsu1932/71.214

We have developed free-electron lasers driven by a superconducting rf linac to demonstrate a powerful and efficient FEL, and the prototype of the FEL has successfully lased to get 0.1kW as the world-strongest FEL average power in February 1998. Two years after the first lasing, the second world-records of ultra-fast pulse of 250fs, efficiency of 7%, and average and peak power of 2.34kW and 1GW at 22 micron have successfully been obtained using a well-improved FEL and superconducting rf linac driver. The breakthrough of ultra-short pulse, efficiency and power in FELs has been realized using the improved driver performance of high density current and high-quality acceleration, and a discovery of sustained superradiance FEL oscillation. Resultantly, we have been successfully able to demonstrate high-efficiency larger than the theoretical limit and ultra-fast pulse of 3.4cycles, and 250fs. In the text, the novel technology of FELs driven by a superconducting rf linac will be briefly reported.

Study on oscillated flow around excited cylinder using built-in electromagnetic flowmeters

Kondo, Masaya; Anoda, Yoshinari

Emerging Technologies for Fluids, Structures and Fluid-Structure Interaction, 2001 (PVP-Vol.431), p.111 - 117, 2001/07

no abstracts in English

Effect of alternate-vortex on flow-induced in-line oscillation

; Anoda, Yoshinari

Nihon Kikai Gakkai Rombunshu, C, 65(639), p.4252 - 4259, 1999/11

https://doi.org/10.1299/kikaic.65.4252

no abstracts in English

Investigation on natural circulation two-phase flow instability

J.U.Knebel*; Araya, Fumimasa

Proc. of 2nd Japanese-German Symp. on Multi-phase Flow, p.447 - 453, 1997/00

no abstracts in English

Effects of core models and neutron energy group structures on xenon oscillation in large graphite-moderated reactors

Yamashita, Kiyonobu; Harada, Hiro; Murata, Isao; Shindo, Ryuichi; *

Journal of Nuclear Science and Technology, 30(3), p.249 - 260, 1993/03

https://doi.org/10.3327/jnst.30.249

no abstracts in English