Lower-hybrid current drive and ICRF heating experiments on JT-60U

Conference · Sat Oct 15 00:00:00 EDT 1994 · AIP Conference Proceedings (American Institute of Physics); (United States)

OSTI ID:6922358

Fujii, T; Ushigusa, K; Saigusa, M; Kimura, H; Imai, T; Ikeda, Y; Naito, O; Nemoto, M; Moriyama, S; Seki, M; Kondoh, T; Hamamatsu, K; Sato, M; Yoshino, R; Kamada, Y ^[1]; Campbell, D J ^[2]

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1. Japan Atomic Energy Research Institute, Naka, Ibaraki 311-01 (Japan)
2. JET Joint Undertaking, Abingdon, Oxfordshire OX14 3EA (United Kingdom)

A plasma current of 2 MA is driven by lower hybrid current drive (LHCD) and the maximum CD efficiency of [eta][sub CD]=2.5[times]10[sup 19] m[sup [minus]2] A/W is achieved, which agrees with the previously reported scaling: [eta][sub CD][similar to]12[lt]T[sub e][gt]/(5+Z[sub eff]). The direct loss of launched wave power through energetic electrons is identified by measuring the x-ray signal from the divertor plates. The direct loss power is fairly low (typically [lt]5%) and depends on the slowing down time of energetic electrons accelerated by launched LH waves. This indicates that the slowing down process is dominant compared with loss mechanisms of fast electrons. The radial diffusion coefficient of fast electrons is less than 1 m[sup 2]/s from analyses on change in HX signal on pellet injection and direct lost power by fast electrons. Good coupling characteristics are confirmed for a new large (48[times]4) multijunction launcher. Significantly large loading resistances are obtained with a 2[times]2 phased ICRF antenna, especially [similar to]5 ohms with in-phase current mode even at a big separatrix-wall gap of 29 cm. Efficiency sawtooth stabilization by 2 [omega][sub cH] heating is observed in relatively high-density and low-q region, [l angle]n[sub e][r angle]/P[sub tot][approx]0.8[times]10[sup 19] m[sup [minus]3]/MW at q[sub eff]=4 and I[sub p]=2.4 MA. The maximum sawtooth period is 0.9 sec for ohmic plasmas and 1.7 sec for NBI-heated plasmas at power levels of P[sub IC][approx]3 MW. Combined 2 [omega][sub CH] ICRF (2.5 mW) and NBI (D beam, [similar to]6 MW) heating is carried out for pellet-fueled plasmas. Preliminary results show that the pellet enhanced phase is maintained by 1.4 sec up to sawtooth crash and the energy confinement normalized by heating power is improved by 20% compared with pellet and NBI heating alone.

• OSTI ID: 6922358
• Report Number(s): CONF-9304112-; CODEN: APCPCS
• Journal Information: AIP Conference Proceedings (American Institute of Physics); (United States), Vol. 289:1; Conference: 10. topical conference on radio frequency power in plasmas, Boston, MA (United States), 1-3 Apr 1993; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Fu
JT-60 TOKAMAK
ICR HEATING
ANTENNAS
HARMONICS
LOWER HYBRID CURRENT DRIVE
NEUTRAL ATOM BEAM INJECTION
PLASMA HEATING
POWER LOSSES
BEAM INJECTION
CLOSED PLASMA DEVICES
ELECTRICAL EQUIPMENT
ENERGY LOSSES
EQUIPMENT
HEATING
HIGH-FREQUENCY HEATING
LOSSES
NON-INDUCTIVE CURRENT DRIVE
OSCILLATIONS
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
700350* - Plasma Production
Heating
Current Drive
& Interactions- (1992-)
700460 - Fusion Technology- Heating & Fueling Systems
Fuels- (1992)