Linear MHD stability analysis of post-disruption plasmas in ITER
- PDF / 2,377,263 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 80 Downloads / 185 Views
OKAMAKS
Linear MHD Stability Analysis of Post-Disruption Plasmas in ITER1 K. Aleynikovaa, c, G. T. A. Huijsmansb, and P. Aleynikova a Max-Planck-Institut
für Plasmaphysik, EURATOM Association, Greifswald, D-17491 Germany Organization, St. Paul Lez Durance Cedex, 13115 France c Moscow Institute of Physics and Technology, Institutskii per. 9, Dolgoprudny, Moscow oblast, 141700 Russia e-mail: [email protected] b ITER
Received October 23, 2015; in final form, December 4, 2015
Abstract—Most of the plasma current can be replaced by a runaway electron (RE) current during plasma disruptions in ITER. In this case the post-disruption plasma current profile is likely to be more peaked than the pre-disruption profile. The MHD activity of such plasma will affect the runaway electron generation and confinement and the dynamics of the plasma position evolution (Vertical Displacement Event), limiting the timeframe for runaway electrons and disruption mitigation. In the present paper, we evaluate the influence of the possible RE seed current parameters on the onset of the MHD instabilities. By varying the RE seed current profile, we search for subsequent plasma evolutions with the highest and the lowest MHD activity. This information can be applied to a development of desirable ITER disruption scenario. DOI: 10.1134/S1063780X16050019
1. INTRODUCTION Runaway electrons (REs) can be generated during plasma disruptions in ITER [1, 2]. A large portion of the toroidal current can then be carried by REs, so that a substantial fraction of the magnetic energy would be associated with the RE current. The uncontrolled loss of such REs in ITER must be avoided to minimize the detrimental effects of disruptions. It is therefore important to understand the processes leading to the generation and loss of RE beams, and to develop adequate means to control or suppress the RE beams in ITER. The Disruption Mitigation System (DMS) is being developed in ITER to minimize the possible effects of disruptions [3, 4]. It is known that the current profile can change drastically during disruptions when REs are generated [5]. The post-disruption current profile tends to be more peaked than the pre-disruption one. This is reproduced in the self-consistent modeling of avalanche RE generation and Ohmic current dissipation during the Current Quench (CQ) [5, 6]. On longer timescales, the marginal stability model for the decay of RE current also predicts peaking of the RE current profile [7]. One of the important aspects of such plasma is its MHD stability. Our present MHD stability analysis is based mostly on original models developed by A.B. Mikhailovskii. One of the many contributions of Mikhailovskii has 1 The article is published in the original.
been the development of MHD models for linear analysis of MHD instabilities and waves. The “optimized” formulation of the ideal model has led to the wellknown, and widely used, linear ideal MHD stability code MISHKA-1 [8]. The code was the result of a long-standing collaboration of Mikhailovskii with Kerne
Data Loading...
