Characteristics of the TFTR limiter H-mode: The transition, ELMs, transport and confinement

Technical Report · Sun Nov 01 00:00:00 EST 1992

DOI:https://doi.org/10.2172/7118517· OSTI ID:7118517

Bush, C E ^[1]; Bretz, N; Nazikian, R; Stratton, B C; Synakowski, E; Ramsey, A T; Scott, S D; Bell, M; Bell, R; Biglari, H; Bitter, M; Darrow, D S; Efthimion, P; Fredrickson, E D; Hill, K; Hsuan, H; Kilpatrick, S; McGuire, K M; Manos, D; Mansfield, D ; Medley, S S; Mueller, D; Park, H; Paul, S; Sabbagh, S; Schivell, J; Thompson, M; Town,

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1. Oak Ridge National Lab., TN (United States)

H-Modes obtained through transitions from the supershot regime have been studied on TFTR. The characteristics of these H-modes are similar to those found on other tokamaks with one main exception, the density prof:des can be highly peaked. In the best cases the enhanced confinement in the core of the initial supershot is retained in the H-mode phase, while the confinement in a broad edge region is enhanced. Thus in TFTR, all of the important physics of H-modes such as transitions, enhanced edge confinement, ELMs and other phenomena are studied in a large circular limiter tokamak with the added feature of centrally peaked density profiles and the advantage of an extensive set of diagnostics. The threshold power for the transition is found to be a linear function of plasma current. Transitions and ELMs are affected by the mix of co-and counter-neutral beam injection (NBI) and by perturbations introduced by pellet injection, gas puffing, and current ramping before and during NBI. Fluctuations near both transition and ELM events have been characterized. High frequency magnetic fluctuations in the range [ge] 100--250 kHz usually decrease during the transition. Microwave scattering spectra of density fluctuations in the plasma edge show a feature at high frequency during the H-mode, which is not observed in the plasma core and which is consistent with an edge poloidal rotation velocity, V[sub [theta]], of [approximately] 10[sup 4] m/s. The fluctuations begin at the transition, propagate in the direction of electron diamagnetic drift, and have modulation correlated with ELMs. Several TFTR H-modes showed a modest improvement in confinement over that of the supershots from which they originated, and an understanding of these may eventually lead to a plasma with the combined advantages of both the supershot and the H-mode. The characteristics and physics of the TFTR H-modes are considered relative to other tokamaks and in light of various theoretical studies.

• Research Organization: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 7118517
• Report Number(s): PPPL-2863; ON: DE93005724
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
TFTR TOKAMAK
H-MODE PLASMA CONFINEMENT
CHARGED-PARTICLE TRANSPORT
CONFINEMENT TIME
EDGE LOCALIZED MODES
ELECTRON DENSITY
ELECTRON TEMPERATURE
FLUCTUATIONS
LIMITERS
NEUTRAL ATOM BEAM INJECTION
BEAM INJECTION
CLOSED PLASMA DEVICES
CONFINEMENT
INSTABILITY
PLASMA CONFINEMENT
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
RADIATION TRANSPORT
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
VARIATIONS
700310* - Plasma Confinement- (1992-)
700330 - Plasma Kinetics
Transport
& Impurities- (1992-)