The 110-GHz Electron Cyclotron Range of Frequency System on JT-60U: Design and Operation

Ikeda, Yoshitaka; Kasugai, Atsushi; Moriyama, S.; Kajiwara, K.; Seki, M.; Tsuneoka, M.; Takahashi, Koji; Anno, K.; Hamamatsu, K.; Hiranai, S.; Ikeda, Y.; Imai, T.; Sakamoto, K.; Shimono, M.; Shinozaki, S.; Terakado, M.; Yamamoto, T.; Yokokura, K.; Fujii, T.

doi:10.13182/fst02-a239

Cited by 30 publications

(13 citation statements)

References 21 publications

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“…Since the transmission line on the JT-60 ECRF system was designed for achieving 1 MW for 5 s, the active cooling of the waveguides was not sufficient for longer pulse operation. Moreover, the diameter of the waveguides was relatively small (31.75 mm) in order to reduce the mode conversion loss due to misalignment of the long (approximately 60 m) transmission line [31]. However, waveguides with a diameter of 31.75 mm have higher power density and smaller heat capacity than those with a diameter of 63.5 mm used for demonstrating the long-pulse operation of 800 s at 1 MW for ITER in JAEA [11,12].…”

Section: Transmission Linementioning

confidence: 99%

Progress of high-power and long-pulse ECRF system development in JT-60

Kobayashi¹,

Isayama²,

Yokokura³

et al. 2011

Nucl. Fusion

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A new gyrotron operation technique to increase oscillation efficiency was developed using the JT-60 electron cyclotron range of frequency (ECRF) system. In order to increase the efficiency without a significant increase in the anode leakage current by trapped electrons that limits the efficiency of gyrotrons with a collector potential depression technology, we actively optimized the electron pitch factor by controlling only the anode voltage within ∼0.1 s after the start of the gyrotron operation, and a high-efficiency oscillation in the so-called hard-self-excitation region was achieved from the start of the oscillation. As an application of this technique in the JT-60 ECRF system, the gyrotron output power of 1.5 MW for 4 s, which is the longest pulse length in the world at an output power of 1.5 MW, was recorded with a successful reduction in the collector heat load by 20% as compared with the conventional operation. The reduced collector heat load at the 1.5 MW operation was acceptable for a steady-state operation. Further progress was made with respect to the expansion of the long-pulse capability of the ECRF system. A new gyrotron with an improved mode converter was developed in order to demonstrate a reduction in the stray radiation in the gyrotron; such radiation has thus far hindered long-pulse operations by causing an unacceptable heat load. We confirmed that the stray radiation was reduced to 1/3 of that of the original gyrotron; this reduced heat load is acceptable for steady-state operation. A conditioning operation of the improved gyrotron proceeds up to 31 s at 1 MW. This progress significantly contributes to an enhancement in the high-power and long-pulse capability of the ECRF system used in JT-60SA, where a total output power of 9 MW for 100 s is planned.

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Section: Transmission Linementioning

confidence: 99%

Progress of high-power and long-pulse ECRF system development in JT-60

Kobayashi¹,

Isayama²,

Yokokura³

et al. 2011

Nucl. Fusion

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“…This suppresses the parasitic oscillation and improves the beam quality [3]. As a result of this improvement, the pulse duration reached 4 s at 1.2 MW.…”

Section: Gyrotron Operation For a Long Pulsementioning

confidence: 90%

Development and contribution of rf heating and current drive systems to long pulse, high performance experiments in JT-60U

Moriyama¹,

Seki²,

Terakado³

et al. 2005

Fusion Engineering and Design

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“…In JT-60U, NTM stabilization has been performed since the installation of the first 110 GHz gyrotron in 1999 [7], and stabilization by real-time mirror steering [8], preemptive stabilization [9] and simulation with the TOPICS code [10][11][12] have been performed.…”

Section: Introductionmentioning

confidence: 99%

Advanced Tokamak Research in JT-60U and JT-60SA

Isayama

2010

Plasma and Fusion Research

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Results of experiment in JT-60U and design study in JT-60SA (Super Advanced) are described focusing on the development of advanced tokamak. In JT-60U, a high-integrated performance plasma with the normalized beta β N = 2.6, confinement enhancement factor H H98(y,2) = 1.0-1.1 and bootstrap current fraction f BS = 0.4 has been sustained for 25 s (14 times current diffusion time (τ R )). Neoclassical tearing mode (NTM) with the poloidal mode number m = 2 and the toroidal mode number n = 1 has been stabilized with modulated electron cyclotron current drive (ECCD) in synchronization with the mode frequency (∼5 kHz). A high-beta plasma exceeding the ideal MHD limit without conducting wall has been sustained for 5 s (∼3τ R ) by suppressing resistive wall mode (RWM). In addition, two new instabilities in the high-beta regime, Energetic particle driven Wall Mode (EWM) and RWM precursor, have been observed. In JT-60SA, exploration of full non-inductive steady-state operation with current drive by neutral beams and electron cyclotron waves is planned. In addition, NTM control with ECCD and RWM suppression with external coils are planned.

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The 110-GHz Electron Cyclotron Range of Frequency System on JT-60U: Design and Operation

Cited by 30 publications

References 21 publications

Progress of high-power and long-pulse ECRF system development in JT-60

Progress of high-power and long-pulse ECRF system development in JT-60

Development and contribution of rf heating and current drive systems to long pulse, high performance experiments in JT-60U

Advanced Tokamak Research in JT-60U and JT-60SA

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