High-power and long-pulse gyrotron development in JAERI

Kasugai, Atsushi; Sakamoto, K.; Tsuneoka, M.; Maebara, S.; Nagashima, Takashi; Imai, T.; Kariya, T.; Okazaki, Y.; Shirai, N.; Okamoto, Tadashi; Hayashi, K.; Mitsunaka, Y.; Komuro, M.

doi:10.1016/0920-3796(94)00194-c

Cited by 10 publications

(3 citation statements)

References 12 publications

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“…WGM mode is suitable to satisfy requirements for mode competition avoidance and low cavity surface ohmic loss simultaneously [5]. WGM modes were used in the initial stage of the development of gyrotrons for fusion plasma heating and stable oscillations without mode competition were shown [7,8]. Volume modes were then used to reduce the ohmic loss for the continuous wave (cw) 1 MW class gyrotrons required for the International Thermonuclear Experimental Reactor (ITER) [9].…”

Section: Introductionmentioning

confidence: 99%

Developments for collective Thomson scattering equipment with a sub-THz gyrotron in LHD

et al. 2019

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Plan of collective Thomson scattering (CTS) experiment for the Large Helical Device (LHD) in NIFS with a 303 GHz gyrotron is under way. Use of a sub-THz gyrotron expands the CTS-applicable region of plasma parameters. In LHD, sub-THz CTS can be applied to the high density operation region, plasmas with impurity hole, etc. Moreover, sub-THz CTS is expected to be free from ECE noise. Its "collective" use with 77 GHz and 154 GHz CTS will compose a powerful diagnostic system. A high power sub-THz gyrotron with a frequency of 303 GHz has been developed. Its maximum power is 320 kW. It oscillates in pulse mode and the maximum pulse width is around 100 s, which is sufficient for use in CTS experiments. A whispering gallery mode TE22,2 was adopted for this gyrotron to avoid mode competition. Careful frequency measurement has proved purely single mode oscillation of the TE22,2 mode including turn-on and turn-off phases of the oscillation pulse. This is consistent with mode competition calculations taking account of a finite voltage rise time. A low loss transmission line is necessary for CTS. We have two possibilities. One is a new line with 1.25 inch corrugated waveguides that are optimized for the 300 GHz band. Transmission test with the 303 GHz gyrotron has been carried out and a sufficiently low loss coefficient has been confirmed. The other is to use an existing line with 3.5 inch corrugated waveguides for lower frequencies such as 77 GHz and 154 GHz. Transmission test has been carried out with the 303 GHz gyrotron and a sufficiently low loss coefficient has been confirmed also for 3.5 inch corrugated waveguides. An existing line with 3.5 inch corrugated waveguides will be used in the initial phase of 303 GHz CTS experiment.

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Section: Introductionmentioning

confidence: 99%

Developments for collective Thomson scattering equipment with a sub-THz gyrotron in LHD

et al. 2019

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“…The intensive development of the 170 GHz gyrotron with 1 MW, continuous wave (CW) operation and 50% efficiency has been carried out to satisfy the requirements of the ITER [3][4][5][6]. Japan Atomic Energy Agency (JAEA), formerly JAERI, initiated the development of a highpower gyrotron with the 100 GHz band in order to apply it to fusion devices from 1980s [7]. Several breakthroughs with respect to high-power, long pulse, and high-efficiency operation for the 170 GHz, 1 MW, CW ITER gyrotron have been achieved by JAEA.…”

Section: Introductionmentioning

confidence: 99%

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

Kasugai

Minami

Takahashi

et al. 2006

Fusion Engineering and Design

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“…The mode number was increased to extend the pulse width and the duty ratio by up to 10%. WGM modes were used in the initial development stage for gyrotrons for fusion plasma heating because they oscillate stably without mode competition [6,7]. Volume modes were then used to reduce the ohmic loss for the continuous wave (cw) 1 MW oscillation required for the International Thermonuclear Experimental Reactor (ITER) gyrotron [8].…”

mentioning

confidence: 99%

Development of 300 GHz Band Gyrotron for Collective Thomson Scattering Diagnostics in the Large Helical Device

Saito

Yamaguchi

Tatematsu

et al. 2017

Plasma and Fusion Research

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A 300 GHz pulse gyrotron has been developed for use in collective Thomson scattering (CTS) diagnostics in the Large Helical Device (LHD). Single-mode oscillation power of more than 320 kW was produced. The radiation beam has a Gaussian pattern. The frequency spectrum is very narrow and stable across the pulse width. No competing mode was observed in the oscillation pulse, including during the turn-on and turn-off phases. Collective Thomson scattering (CTS) diagnostics using gyrotrons that operate at around 100 GHz for electron heating have been developed [1,2]. Sub-THz waves are appropriate as power sources because they are almost free from both refraction and/or absorption in plasmas and strong electron cyclotron emissions (ECEs). The probe's wave power should be more than 100 kW to realize a suitable signal-to-noise (SN) ratio [3]. We have thus developed a high power sub-THz gyrotron for use in CTS diagnostics in the Large Helical Device (LHD).The initially developed second harmonic gyrotron demonstrated single mode oscillation that approached 100 kW at 389 GHz. However, a competing fundamental harmonic mode prevented further power enhancements [4]. We subsequently developed a fundamental harmonic prototype gyrotron and used it to verify the design concept for stable single-mode oscillation [5]. Use of the same design concept to produce a whispering gallery mode (WGM) has allowed a gyrotron to be designed and fabricated for use in CTS diagnostics in the LHD.The sub-THz gyrotron for CTS is operated in pulse mode. The designed operating frequency is 303.3 GHz, which corresponds to the minimum for the ECE for standard LHD operation. A moderately high order mode is used to satisfy requirements for mode competition avoidance and low cavity surface ohmic loss simultaneously. The oscillation mode is the TE 22,2 mode, which is a WGM similar to the TE 14,2 mode used in the prototype gyrotron. The mode number was increased to extend the pulse width and the duty ratio by up to 10%.

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High-power and long-pulse gyrotron development in JAERI

Cited by 10 publications

References 12 publications

Developments for collective Thomson scattering equipment with a sub-THz gyrotron in LHD

Developments for collective Thomson scattering equipment with a sub-THz gyrotron in LHD

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

Development of 300 GHz Band Gyrotron for Collective Thomson Scattering Diagnostics in the Large Helical Device

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