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

Technical Report · Thu Sep 01 00:00:00 EDT 1994

DOI:https://doi.org/10.2172/10182651· OSTI ID:10182651

Yamada, M; Pomphrey, N; Budney, R; Macickam, J ^[1]; Levinton, F ^[2]; Nagayama, Y ^[3]

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1. Princeton Univ., NJ (United States). Plasma Physics Lab.
2. Fusion Physics and Technology, Torrance, CA (United States)
3. Tsukuba Univ., Ibaraki (Japan)

This paper reports on a recent laboratory investigation on magnetic reconnection in high temperature tokamak plasmas. The motional stark effect(MSE) diagnostic is employed to measure the pitch angle of magnetic field lines, and hence the q profile. An analytical expression that relates pitch angle to q profile has been developed for a toroidal plasma with circular cross section. During the crash phase of sawtooth oscillations in the plasma discharges, the ECE (electron cyclotron emission) diagnostic measures a fast flattening of the 2-D electron temperature profile in a poloidal plane, an observation consistent with the Kadomtsev reconnection theory. On the other hand motional the MSE measurements indicate that central q values do not relax to unity after the crash, but increase only by 5-10%, typically from 0.7 to 0.75. The latter result is in contradiction with the models of Kadomtsev and/or Wesson. The present study addresses this puzzle by a simultaneous analysis of electron temperature and q profile evolutions. Based on a heuristic model for the magnetic reconnection during the sawtooth crash, the small change of q, i.e. partial reconnection, is attributed to the precipitous drop of pressure gradients which drive the instability and the reconnection process as well as flux conserving plasma dynamics.

• Research Organization: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 10182651
• Report Number(s): PPPL-3004; ON: DE94018788; TRN: 94:018978
• Resource Relation: Other Information: PBD: Sep 1994
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
TFTR TOKAMAK
MAGNETIC RECONNECTION
STARK EFFECT
ELECTRON TEMPERATURE
SAWTOOTH OSCILLATIONS
PLASMA DIAGNOSTICS
ELECTRON CYCLOTRON-RESONANCE
PRESSURE GRADIENTS
PLASMA INSTABILITY
700430
700340
MAGNET COILS AND FIELDS
PLASMA WAVES, OSCILLATIONS, AND INSTABILITIES