MHD simulations of small ELMs at low triangularity in ASDEX Upgrade

被引：20

作者：

Cathey, A. ^{[1
]}

Hoelzl, M. ^{[1
]}

Harrer, G. ^{[2
]}

Dunne, M. G. ^{[1
]}

Huijsmans, G. T. A. ^{[3
,4
]}

Lackner, K. ^{[1
]}

Pamela, S. J. P. ^{[5
]}

Wolfrum, E. ^{[1
]}

Guenter, S. ^{[1
]}

机构：

[1] Max Planck Inst Plasma Phys, D-85748 Garching, Germany

[2] TU Wien, Inst Appl Phys, A-1040 Vienna, Austria

[3] CEA, IRFM, F-13108 St Paul Les Durance, France

[4] Eindhoven Univ Technol, NL-5600 MB Eindhoven, Netherlands

[5] Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England

来源：

PLASMA PHYSICS AND CONTROLLED FUSION | 2022年 / 64卷 / 05期

关键词：

small ELMs; non-linear MHD; macroscopic instabilities; DIAMAGNETIC STABILIZATION; MODES; INSTABILITIES; TRANSPORT; STABILITY;

D O I：

10.1088/1361-6587/ac5b4b

中图分类号：

O35 [流体力学]; O53 [等离子体物理学];

学科分类号：

070204 ; 080103 ; 080704 ;

摘要：

The development of small and no-ELM regimes for ITER is a high priority topic due to the risks associated with type-I ELMs. By considering non-linear extended magnetohydrodynamic (MHD) simulations of the ASDEX Upgrade tokamak with the JOREK code, we probe a regime that avoids type-I ELMs completely, provided that the separatrix density is high enough. The dynamics of the pedestal in this regime are observed to be qualitatively similar to the so-called quasi-continuous exhaust regime in several ways. Repetitive type-I ELMs are substituted by roughly constant levels of outward transport, caused by peeling-ballooning modes (with dominant ballooning characteristics) which are localised in the last 5% of the confined region (in normalised poloidal flux). The simulated low triangularity plasma transitions to a type-I ELMy H-mode if the separatrix density is sufficiently reduced or if the input heating power is sufficiently increased. The stabilising factors that play a role in the suppression of the small ELMs are also investigated by analysing the simulations, and the importance of including diamagnetic effects in the simulations is highlighted. By considering a scan in the pedestal resistivity and by comparing the poloidal velocity of the modes to theoretical estimates for ideal and resistive modes, we identify the underlying instabilities as resistive peeling-ballooning modes. Decreasing the resistivity below experimentally-relevant conditions (i.e. going towards ideal MHD), the peeling-ballooning modes that constrain the pedestal below the type-I ELM stability boundary display sharply decreasing growth rates.

引用

页数：15

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