Ultra Low-q Discharge and High Temperature Experiments in REPUTE-1

Abstract

The outline and necessity of research in the ultra low-q regime are discussed from the view point of the total understanding of the current carrying systems. The ultra low-q state lies between tokamak and reversed field pinch and has a safety factor profile of 1/ (n+1) <q (r) <1/n, n=1, 2, 3, 4…. In REPUTE-1, the radiation barrier has been overcome and achieved plasma temperatures, Ti and Te, exceed 0.5 keV with electron density of 0.7×10²⁰m^-3. Resistivity anomaly due to m=1 kink activity is observed and considered to be related to a peaked temperature profile with a rather broad current density profile. The plasma resistivity in the ultra low-q regime is proved to be much lower than predicted values and decreases with increasing plasma current.