Development of High-Power, Long-Pulse Gyrotrons and Its Application for High Electron Temperature, EBWH and ECCD Experiments on LHD

Journal Article · Fri Dec 23 00:00:00 EST 2011 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3665016· OSTI ID:21612520

Yoshimura, Y; Kubo, S; Shimozuma, T; Igami, H; Takahashi, H; Nishiura, M; Ito, S; Kobayashi, S; Mizuno, Y; Okada, K; Takita, Y; Mutoh, T; Yamada, H; Komori, A ^[1]; Kariya, T; Imai, T ^[2]; Marushchenko, Nikolai B; Turkin, Yuri ^[3]

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1. National Institute for Fusion Science, Toki (Japan)
2. University of Tsukuba, Tsukuba (Japan)
3. Max-Planck-Institut for Plasmaphysik, Greifswald (Germany)

To sustain plasmas with higher parameters and with longer pulse duration in LHD, ECH system has been upgraded by introducing newly developed 77 GHz gyrotrons. The designed output power and operation duration time are over 1 MW for several seconds and 0.3 MW for continuous operation, respectively. Owing to the upgrade of gyrotrons and improved power supply operation procedure, total injection power of EC-waves to LHD increased up to 3.7 MW at the last LHD experimental campaign in 2010.Application of the high-power 77 GHz EC-waves of 3.4 MW as focused beams to the center of plasma with low line-average electron density of {approx}0.2x10{sup 19} m{sup -3} causes highly steep electron temperature profile and the central electron temperature reached up to 20 keV, which highly exceeds the former record of 15 keV. At higher density region of 1x10{sup 19} m{sup -3}, central electron temperature reached 8.6 keV.Additional electron Bernstein wave heatings, O-X-B and slow X-B heatings, using a 77 GHz ECH system caused clear increase in plasma stored energy even for the high-density plasmas over plasma cutoff (>7.35x10{sup 19} m{sup -3}) sustained with NBI. For the O-X-B scenario, the 77 GHz EC-wave was obliquely injected from low-field side in O-mode polarization, aiming at the point where high mode-conversion efficiency was expected. For realizing slow X-B scenario, new inner-vessel mirrors were installed in LHD just close to a helical coil, that is, at the high-field side (HFS) region. Using the inner-vessel mirror, X-mode waves were injected from HFS, showing evident increase in plasma stored energy.Oblique injection of long-pulse 0.77 MW/8 s 77 GHz wave with various N{sub ||} clearly demonstrated ECCD in LHD. The EC-driven current changes its direction with the sign of N{sub ||}, and the highest EC-driven current reached up to 42 kA.

• OSTI ID: 21612520
• Journal Information: AIP Conference Proceedings, Vol. 1406, Issue 1; Conference: 9. topical conference on radio frequency power in plasmas, Newport (United States), 1-3 Jun 2011; Other Information: DOI: 10.1063/1.3665016; (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANTENNAS
BERNSTEIN MODE
ECR CURRENT DRIVE
ECR HEATING
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELECTRONS
GHZ RANGE
HYPERFINE STRUCTURE
KEV RANGE
LHD DEVICE
MICROWAVE AMPLIFIERS
MODE CONVERSION
PLASMA
PLASMA DENSITY
PLASMA WAVES
POLARIZATION
PULSES
STORED ENERGY
AMPLIFIERS
CLOSED PLASMA DEVICES
ELECTRICAL EQUIPMENT
ELECTRONIC EQUIPMENT
ELEMENTARY PARTICLES
ENERGY
ENERGY RANGE
EQUIPMENT
FERMIONS
FREQUENCY RANGE
HEATING
HIGH-FREQUENCY HEATING
LEPTONS
MICROWAVE EQUIPMENT
NON-INDUCTIVE CURRENT DRIVE
OSCILLATION MODES
PHYSICAL PROPERTIES
PLASMA HEATING
THERMODYNAMIC PROPERTIES
THERMONUCLEAR DEVICES