The magnitude of sawtooth crash events in multiple and quasi-single helicity states in a reversed-field-pinch plasma
- National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)
Factors affecting the magnitude of sawtooth crashes in soft x-ray (SXR) signals (I{sub SXR}) have been studied using data from high-{theta} (pinch parameter) discharges in the toroidal pinch experiment TPE-1RM20 reversed-field pinch device [Y. Yagi et al., J. Plasma Fusion Research 69, 700 (1993)]. In TPE-1RM20, discharges with a high {theta} that are free of large sawteeth (improved high-{theta} mode discharges), spontaneously appeared [Y. Hirano et al., Nucl. Fusion 36, 721 (1996)] among typical conventional discharges exhibiting large sawtooth crashes. The reason for the spontaneous appearance of sawtooth-free discharges has been unclear. It is shown that the normalized magnitude of the SXR crashes, [{delta}(I{sub SXR})/I{sub SXR}], is well correlated with the m (poloidal mode number)=0 mode amplitude in the postcrash phase. It is also shown that {delta}(I{sub SXR})/I{sub SXR} is smaller when the quasi-single helicity state precedes the crash rather than when the multiple-helicity state precedes the crash, and {delta}(I{sub SXR})/I{sub SXR} is smaller when E{sub parallel} (the parallel electric field at the plasma surface) is approximately zero in the precrash phase rather than E{sub parallel} being negative.
- OSTI ID:
- 20764467
- Journal Information:
- Physics of Plasmas, Vol. 12, Issue 8; Other Information: DOI: 10.1063/1.2000887; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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