Investigation of magnetic reconnection during a sawtooth crash in a high-temperature tokamak plasma

Journal Article · Sat Oct 01 00:00:00 EDT 1994 · Physics of Plasmas; (United States)

DOI:https://doi.org/10.1063/1.870479· OSTI ID:7167139

Yamada, M; Levinton, F M; Pomphrey, N; Budny, R; Manickam, J; Nagayama, Y ^[1]

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1. Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

In this paper a laboratory investigation is made on magnetic reconnection in high-temperature Tokamak Fusion Test Reactor (TFTR) plasmas [[ital Plasma] [ital Physics] [ital and] [ital Controlled] [ital Nuclear] [ital Fusion] [ital Research] 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 51]. The motional Stark effect (MSE) diagnostic is employed to measure the pitch angle profile of magnetic field lines, and hence the [ital q] profile. An analytical expression that relates pitch angle to [ital q] profile is presented for a toroidal plasma with circular cross section. During the crash phase of sawtooth oscillations in plasma discharges, the ECE (electron cyclotron emission) diagnostic measures a fast flattening of the two-dimensional (2-D) electron temperature profile in a poloidal plane, an observation consistent with the Kadomtsev reconnection theory. On the other hand, the MSE measurements indicate that central [ital q] values do not relax to unity after the crash, but increase only by 5%--15%, typically from 0.7 to 0.8. The latter result is in contradiction with the 2-D models of Kadomtsev and/or Wesson. In the present study this puzzle is addressed by a simultaneous analysis of electron temperature and [ital q] profile evolutions. Based on a heuristic model for magnetic reconnection during the sawtooth crash, the small change of [ital q], i.e., partial reconnection, is attributed to the precipitous drop of pressure gradients that drive the instability and the reconnection process, as well as flux conserving plasma dynamics.

• DOE Contract Number: AC02-76CH03073
• OSTI ID: 7167139
• Journal Information: Physics of Plasmas; (United States), Vol. 1:10; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
TOKAMAK DEVICES
MAGNETIC RECONNECTION
SAWTOOTH OSCILLATIONS
ELECTRON TEMPERATURE
PLASMA CONFINEMENT
PLASMA DIAGNOSTICS
PLASMA INSTABILITY
Q-VALUE
STARK EFFECT
CLOSED PLASMA DEVICES
CONFINEMENT
ENERGY
INSTABILITY
OSCILLATIONS
THERMONUCLEAR DEVICES
700310* - Plasma Confinement- (1992-)
700320 - Plasma Diagnostic Techniques & Instrumentation- (1992-)
700340 - Plasma Waves
Oscillations
& Instabilities- (1992-)