Measurements and modelling of plasma response field to RMP on the COMPASS tokamak

Abstract

It has been shown on several tokamaks that application of a resonant magnetic perturbation (RMP) field to the plasma can lead to suppression or mitigation of edge-localized mode (ELM) instabilities. Due to the rotation of the plasma in the RMP field reference system, currents are induced on resonant surfaces within the plasma, consequently screening the original perturbation. In this work, the extensive set of 104 saddle loops installed on the COMPASS tokamak is utilized to measure the plasma response field for two n = 2 RMP configurations of different poloidal mode m spectra. It is shown that spatially the response field is in opposite phase to the original perturbation, and that the poloidal profile of the measured response field does not depend on the poloidal profile of the applied RMP. Simulations of the plasma response by the linear MHD code MARS-F (Liu et al 2000 Phys. Plasmas 7 3681) reveal that both of the studied RMP configurations are well screened by the plasma. Comparison of measured plasma response field with the simulated one shows a good agreement across the majority of poloidal angles, with the exception of the midplane low-field side area, where discrepancy is seen.

Nonlinear modeling of forced magnetic reconnection in slab geometry with NIMROD

“…A significant number of numerical studies of FMR explore the magnetic field response to RMP application in 3D toroidal geometries. Studies investigate the linear [32][33][34][35][36][37][38][39][40][41][42] and nonlinear [43][44][45][46][47][48][49][50][51][52][53] field response to RMPs. Each work details studies on the physics of reconnection and flow-screening in tokamaks, and a number of the nonlinear studies discuss the interaction of RMPs with ELMs.…”

Runaway electron experiments at COMPASS in support of the EUROfusion ITER physics research

“…Next, a minor modulation in plasma position due to the feedback system properties proved to produce a well correlated eect between HXR radiation and infrared radiation from the limiter, which directly conrmed that RE interaction with the limiter makes a signicant contribution to the overall HXR radiation intensity [33]. In this subsection, the main results from recent RE experiments with RMP system at COMPASS [52,53] are presented. The work was partly inspired by recent work of the ASDEX Upgrade team in RMP experiments on post-disruption RE beam [54].…”

Mode penetration induced by transient magnetic perturbations

“…A perturbation analysis can be used to determine the ultimate evolution of the island width toward the equi-librium island width w eq defined in Eq. (36). Here, w ≡ w eq + δw is used and the solution of the perturbed version of Eq.…”