Q-profile reconstruction during the current ramp at TEXTOR for current diffusion measurements, assessment of methods and measurements

Abstract

The safety factor q in a tokamak is closely linked with stability and transport properties of the plasma, and therefore it is desirable to be able to measure and understand the evolution of this quantity. In this work an attempt was made to reconstruct the q-profile evolution during the current ramp at TEXTOR, with the ultimate goal of comparing measurements with simulations in order to validate physical models of e.g. the plasma conductivity. Two methods were investigated: -A numerical equilibrium solver, which attempts to interpret the plasma equilibrium from limited input data-Spectral Motional Stark Effect (MSE) measurements, whereby beam emission spectra of injected hydrogen molecules are related to the magnetic field at the point of emissionBoth methods were found to yield unreliable results on the q-profile. Further analysis of the methods identified sources of error and culprits which were not previously taken into account.

Date of Award	31 Aug 2013
Original language	English
Supervisor	M.F.M. de Bock (Supervisor 1)