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Behaviour of runaway electrons in the HL-2A plasmas with LHCD and ECCD

Part of: Energetic Electrons Focus on Fusion

Published online by Cambridge University Press:  26 October 2015

J. X. Zhu ,
L. M. Yao ,
Y. P. Zhang ,
J. W. Yang  and
HL-2A Team
J. X. Zhu*
Affiliation:
School of Physics and Mecha-tronic Engineering, Sichuan University of Arts and Science, Dazhou 635000, China School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
L. M. Yao
Affiliation:
School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
Y. P. Zhang
Affiliation:
Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
J. W. Yang
Affiliation:
Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
*
†Email address for correspondence: [email protected]
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Abstract

The behaviour of runaway electrons have been investigated in lower hybrid current drive (LHCD) and electron cyclotron current drive (ECCD) plasmas as well as the LHCD only plasmas in the HL-2A tokamak. The fast electrons generated by lower hybrid waves (LHWs) and electron cyclotron waves (ECWs) can act as a seed population for runaway electrons. In the LHCD only discharges, a large number of runaway electrons are produced after the termination of lower hybrid (LH) power by conversion of fast electrons into runaway electrons due to the fast electron tail which extends above the runaway critical energy. However, in contrast to LHCD only discharges, during the simultaneous application of LHCD and ECCD discharges, runaway electrons cannot be created by the termination of LH power when the ECCD is on duty. The runaway production is observed to be enhanced until the EC power termination. The loop voltage increase due to the termination of EC power gives rise to a decline in the critical runaway energy, which leads to some of the energetic fast electrons converting into runaway electrons via the acceleration from the toroidal electric field. That is, the fast electrons created by waves can be accelerated into the runaway regime due to the Dreicer process.

Type
Research Article
Information
Journal of Plasma Physics , Volume 81 , Issue 6 , December 2015 , 475810602
Copyright
© Cambridge University Press 2015 

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