Electron and ion heating in a high-voltage toroidal theta pinch with parallel or antiparallel bias fields

Rapid heating of electrons and ions has been observed in a high-voltage toroidal theta pinch with initial bias fields either parallel or antiparallel to the fast rising toroidal field. The elimination of rapid end losses has permitted higher electron temperatures to be attained. In contrast to the results of linear theta pinches in which Te≲0.3 Ti, it is now found that Te∼Ti. The ion heating is similar to that observed in the linear case indicating that the effective microinstability heating process is maintained in a toroidal system. Higher temperatures were observed with antiparallel bias fields, but in both cases superthermal electron populations were observed indicating that the turbulent heating process involves electron tail formation.