skip to main content

This content will become publicly available on November 22, 2017

Title: Experimental studies of high-confinement mode plasma response to non-axisymmetric magnetic perturbations in ASDEX Upgrade

Here, the interaction of externally applied small non-axisymmetric magnetic perturbations (MP) with tokamak high-confinement mode (H-mode) plasmas is reviewed and illustrated by recent experiments in ASDEX Upgrade. The plasma response to the vacuum MP field is amplified by stable ideal kink modes with low toroidal mode number n driven by the H-mode edge pressure gradient (and associated bootstrap current) which is experimentally evidenced by an observable shift of the poloidal mode number m away from field alignment (m = qn, with q being the safety factor) at the response maximum. A torque scan experiment demonstrates the importance of the perpendicular electron flow for shielding of the resonant magnetic perturbation, as expected from a two-fluid MHD picture. Two significant effects of MP occur in H-mode plasmas at low pedestal collisionality, $$\nu _{\text{ped}}^{\ast}\leqslant 0.4$$ : (a) a reduction of the global plasma density by up to $$61 \% $$ and (b) a reduction of the energy loss associated with edge localised modes (ELMs) by a factor of up to 9. A comprehensive database of ELM mitigation pulses at low $${{\nu}^{\ast}}$$ in ASDEX Upgrade shows that the degree of ELM mitigation correlates with the reduction of pedestal pressure which in turn is limited and defined by the onset of ELMs, i. e. a modification of the ELM stability limit by the magnetic perturbation.
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [4] ;  [1]
  1. Max-Planck-Institut fur Plasmaphysik, Garching (Germany)
  2. Culham Science Centre, Oxon (United Kingdom)
  3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  4. Culham Science Centre, Oxon (United Kingdom); Univ. of York, York (United Kingdom)
Publication Date:
OSTI Identifier:
1340288
Grant/Contract Number:
633053; AC02-09CH11466
Type:
Accepted Manuscript
Journal Name:
Plasma Physics and Controlled Fusion
Additional Journal Information:
Journal Volume: 59; Journal Issue: 1; Journal ID: ISSN 0741-3335
Publisher:
IOP Science
Research Org:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org:
USDOE
Contributing Orgs:
The ASDEX Upgrade Team; The DIII-D Team; The Eurofusion MST1 Team
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamak; ASDEX Upgrade; magnetic perturbation; high-confinement mode; edge-localised mode; ELM mitigation; ELM suppression; dynamic ergodic divertor; error field correction; resistive wall modes; high-beta; impurity transport; saddle coils; diii-d; discharges