Error Field Impact on Plasma Boundary in ITER Scenarios

Abstract

Discrepancies in magnetic field maps produced by confinement coils in thermonuclear fusion reactors may drive plasma to lose stability and must be carefully controlled during the whole time evolution of each shot using suitable correction coils. Even when kept below safety thresholds, these error fields (EFs) may alter the geometry of magnetic flux lines, defining the plasma geometry. This paper, using high accuracy 3-D magnetic field computations for confinement coils, addresses the issue of evaluating the effect of EFs on the plasma boundary shape during the shot, modeled as a sequence of equilibrium configurations. In particular, a procedure that can compute the shape perturbations due to given deformations of the coils has been set up and used to carry out an analysis of relationship between the EF and shape perturbations during the time evolution of International Tokamak Experimental Reactor programmed scenario.

Model predictive control of resistive wall mode for ITER

“…Magnetic active feedback RWM control is closely related with error field compensation (EFC) [4]. EFC is intended for the correction of both the static (vacuum) error field due to the imperfections of the main magnetic coils and the varying resonant perturbation of the plasma to the remaining error field, which cannot be fully compensated due to geometry limitations [38,42]. Both EFC and active RWM feedback act on correction coils positioned perpendicularly along the reactor wall, either internally or externally to the vacuum vessel.…”

“…Extensive research of RWMs was carried out in reversed-field pinch (RFP) and tokamak experiments in RFX-mod [11,12,13,14,15], EXTRAP T2R [16,17,18,19,20], HBT-EP [21], DIII-D [4,22,23,8,24,15,25,26,27], NSTX [28,29,30], and JT-60 [6]. Modelling codes, such as VALEN [31,26,27], CarMa [32,33,34,35,36], CarMa0NL [37,38] are generally based on coupling MHD equations for the plasma with the equations describing the currents induced in the conductive wall. RWM control research for ITER [39,40,10] currently relies on modelling.…”