Abstract
This paper studies the energy-balance characteristics of an ultra low-q (ULQ) confinement concept, and shows the possibility of the Ohmic-Heating ignition. The ULQ equilibrium considered here has the safety factor q in the intermediate range 0< q< 1 lying between tokamaks (1<q) and reversed-field pinches (q< 0 in a peripheral region). Our calculation of the energy balance is based on the experimental observation in the REPUTE-1 experiments, however, assumes a lot to consider the reactor-parameter regime. The aim of this paper is to provide a reasonable direction of researches on engineering bases. Our basic findings are as follows. There is a possibility of the Ohmic-Heating ignition for a compact and high-power density ULQ system with minor radius s 1 m, major radius ≤s 4 m, toroidal field= 8-10 T, and the total wall loading 12.5 MW/m2. To ignite ULQ plasma, temporal control of the plasma density in the start-up phase is important, and Zeff should be greater than 2 to increase the net input power.
