Stabilization and onset of sawteeth in TFTR.

Abstract

Measurements from the Tokamak Fusion Test Reactor (TFTR) of the q profile using motional Stark effect polarimetry and the pressure profiles have allowed detailed comparison of both supershots and L-mode discharges to theoretical models describing the stability of sawteeth. In TFTR supershots sawteeth are usually absent, whereas in L-mode discharges they are generally present, and in both cases q(0) is less than 1. It has been found that the ${\mathrm{\ensuremath{\omega}}}^{\mathrm{*}}$-stabilization criterion of the two-fluid collisionless m=1 reconnection mode agrees very well with the presence or absence of sawteeth in TFTR and no beta limits to the sawtooth stabilization have been observed.