3D Reconstruction of Plasma Equilibrium using Magnetic Diagnostics on the Compact Toroidal Hybrid

Abstract

Equilibrium reconstruction of magnetically confined plasma for fusion energy research uses magnetohydrodynamic (MHD) theory in combination with experimental diagnostic data to accurately model high temperature plasma discharges. Reconstruction of two dimensional, axisymmetric plasma equilibria are commonly used in many of today’s fusion energy experiments. The ability to reconstruct fully three dimensional plasma equilibria has received less attention, but is becoming increasingly important in stellarator as well as tokamak research. This dissertation describes the process of reconstructing plasma equilibria produced in the Compact Toroidal Hybrid (CTH) device. CTH is a torsatron, a type of stellarator. Stellarators confine plasmas using external magnetic field coils without the requirement of plasma current. Nonetheless, toroidal currents can be driven in CTH, which significantly modifies the equilibrium. Plasma equilibria of current-driven discharges are reconstructed using data from a set of magnetic diagnostics and the V3FIT equilibrium reconstruction code1. The main magnetic diagnostics used consist of several segmented Rogowski coils as well as a movable Hall sensor array. The details of the construction and calibration of each of these diagnostics are described. The reconstructed plasma results are shown and compared with measurements made using the Hall sensor array. Finally, sources of systematic error and the suggested steps for improving the reconstruction process are described.