The magnitude of sawtooth crash events in multiple and quasi-single helicity states in a reversed-field-pinch plasma
2005 (English)In: Physics of Plasmas, ISSN 1070-664X, Vol. 12, no 8, 082507- p.Article in journal (Refereed) Published
Factors affecting the magnitude of sawtooth crashes in soft x-ray (SXR) signals (I-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 , 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 , 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-SXR)/I-SXR], is well correlated with the m (poloidal mode number)=0 mode amplitude in the postcrash phase. It is also shown that Delta(I-SXR)/I-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-SXR)/I-SXR is smaller when E-parallel to (the parallel electric field at the plasma surface) is approximately zero in the precrash phase rather than E-parallel to being negative.
Place, publisher, year, edition, pages
2005. Vol. 12, no 8, 082507- p.
Fusion, Plasma and Space Physics
IdentifiersURN: urn:nbn:se:kth:diva-71784DOI: 10.1063/1.2000887ISI: 000231310800032OAI: oai:DiVA.org:kth-71784DiVA: diva2:487001
QC 201201312012-01-312012-01-312012-01-31Bibliographically approved