Progress of divertor simulation research toward the realization of detached plasma using a large tandem mirror device

Nakashima, Yosuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Oki, Kensuke*; Sakamoto, Mizuki*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; Imai, Tsuyoshi*; et al.

Journal of Nuclear Materials, 463, p.537 - 540, 2015/08

https://doi.org/10.1016/j.jnucmat.2014.12.063

Development of a high power gyrotron operating at 28 and 35 GHz

Kariya, Tsuyoshi*; Minami, Ryutaro*; Imai, Tsuyoshi*; Eguchi, Taku*; Sakamoto, Keishi; Mitsunaka, Yoshika*; Numakura, Tomoharu*; Endo, Yoichi*

Plasma and Fusion Research (Internet), 8, p.1205107_1 - 1205107_2, 2013/10

https://doi.org/10.1585/pfr.8.1205107

Development of multi-purpose MW gyrotrons for fusion devices

Minami, Ryutaro*; Kariya, Tsuyoshi*; Imai, Tsuyoshi*; Numakura, Tomoharu*; Endo, Yoichi*; Nakabayashi, Hidetaka*; Eguchi, Taku*; Shimozuma, Takashi*; Kubo, Shin*; Yoshimura, Yasuo*; et al.

Nuclear Fusion, 53(6), p.063003_1 - 063003_7, 2013/06

https://doi.org/10.1088/0029-5515/53/6/063003

Achievement of robust high-efficiency 1 MW oscillation in the hard-self-excitation region by a 170 GHz continuous-wave gyrotron

Sakamoto, Keishi; Kasugai, Atsushi; Takahashi, Koji; Minami, Ryutaro*; Kobayashi, Noriyuki; Kajiwara, Ken

Nature Physics, 3(6), p.411 - 414, 2007/06

https://doi.org/10.1038/nphys599

The first 1 MW quasi-continuous wave generation is demonstrated at 170 GHz gyrotron of TE31,8 resonator mode with outstanding efficiency of greater than 55 percent. The robust high efficiency oscillation is obtained in a hard self-excitation region with an active control of gyrotron parameters. Furthermore, a novel nonlinear process is found that the desired TE31,8 mode is excited as a parasitic mode of an adjacent TE30,8 mode and finally the TE31,8 dominates a system. This effect extends a substantial soft self-excitation region of the desired mode significantly.

Upgrade program of ECRH system for GAMMA10

Imai, Tsuyoshi*; Tatematsu, Yoshinori*; Numakura, Tomoharu*; Sakamoto, Keishi; Minami, Ryutaro*; Watanabe, Osamu*; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Kamata, Yasuhiro*; Machida, Norihito*; et al.

Fusion Science and Technology, 51(2T), p.208 - 212, 2007/02

https://doi.org/10.13182/FST07-A1352

no abstracts in English

Characteristics of 28 GHz gyrotron for ECRH on GAMMA10

Kamata, Yasuhiro*; Imai, Tsuyoshi*; Tatematsu, Yoshinori*; Watanabe, Osamu*; Minami, Ryutaro*; Saito, Teruo*; Sakamoto, Keishi; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Machida, Norihito*; et al.

Fusion Science and Technology, 51(2T), p.412 - 414, 2007/02

https://doi.org/10.13182/FST07-A1419

no abstracts in English

Long pulse operation of 170 GHz ITER gyrotron by beam current control

Kasugai, Atsushi; Minami, Ryutaro; Takahashi, Koji; Kobayashi, Noriyuki; Sakamoto, Keishi

Fusion Engineering and Design, 81(23-24), p.2791 - 2796, 2006/11

https://doi.org/10.1016/j.fusengdes.2006.07.077

In JAEA (Japan Atomic Energy Agency, formerly JAERI), development of 170 GHz, 1 MW, CW gyrotron for ITER has been carried out. Key technologies for ITER gyrotron such as a diamond window, a depressed collector for high efficiency operation and a stable operation at 170 GHz/1 MW with higher mode TE31,8 have been developed. By integration of these key technologies, gyrotron performance of 0.5 MW/ 100 sec and 0.9 MW/ 9.2 sec were demonstrated. Hence, next target is a demonstration of long pulse operation. One of the issues which prevent the pulse extension is large beam current decrease due to so called the emission cooling of a cathode. During the operation, the oscillation mode shift from TE31,8 to TE30,8 was caused by the current decrease. Then, the magnetic field of the cavity should be increased to avoid the downshift of the oscillation mode, however, the efficiency decreases and the parasitic oscillation appears in a quasi-optical mode converter. To suppress the beam current decrease and to demonstrate the long pulse operation of the high power gyrotron, pre-programming control of the cathode heater power was applied and the long pulse experiment was carried out to sustain the beam current. As a result, stable electron beam of 1000 s, which is required for ITER operation, was demonstrated without oscillation, and pre-programming control directed the effectiveness for constant beam current. Moreover, in the experiment of the long pulse oscillation with oscillation, the pre-programming control suppressed the beam current decrease. Up to now, stable long pulse operation of 8 minutes with 0.2 MW output power was obtained. The output energy of the oscillation is maximum value in the 170GHz ITER gyrotron. Since overheating due to stray radiation inside the gyrotron limit the pulse extension, long pulse operation with high power output will be achieved by enhancement of the cooling and reduction of stray radiation due to modification of a built-in mode converter.

The Designs of high efficiency launcher of quasi-optical mode converter for high power gyrotrons

Minami, Ryutaro; Kasugai, Atsushi; Takahashi, Koji; Kobayashi, Noriyuki*; Mitsunaka, Yoshika*; Sakamoto, Keishi

International Journal of Infrared and Millimeter Waves, 27(1), p.13 - 24, 2006/01

https://doi.org/10.1007/s10762-006-9078-7

no abstracts in English

Development of high power gyrotron for CW operation

Minami, Ryutaro; Kasugai, Atsushi; Takahashi, Koji; Kobayashi, Noriyuki; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Hayashi, Kenichi*; Sakamoto, Keishi

Shingaku Giho, 105(498), p.39 - 42, 2005/12

no abstracts in English

Development of long pulse and high power 170 GHz gyrotron

Sakamoto, Keishi; Kasugai, Atsushi; Minami, Ryutaro; Takahashi, Koji; Kobayashi, Noriyuki*

Journal of Physics; Conference Series, 25, p.8 - 12, 2005/00

https://doi.org/10.1088/1742-6596/25/1/002

The present status of ITER gyrotron development of JAERI is reported. Up to now, we demonstrated 100 sec operation at 0.5 MW level power output. On the other hand, some issues were recognized for CW operation, i.e., the beam current decreased as pulse duration expanded. And the large amount of stray RF of 170 GHz exists in the gyrotron. Former, pre-programming control of the heater power of electron gun was introduced to keep the beam current constant. Latter, the inner surface of the radiator was optimized to minimize the diffraction, and loss was reduced by 1/5. Prior to the RF pulse extension, we tried an electron beam test without RF oscillation. As a result, the constant beam current was demonstrated up to 1000 sec.