Tandem mirror reactors with thermal barriers

Preliminary calculations of Q and magnet designs are presented for three different versions of tandem mirror reactors (TMR) using thermal barriers to enhance plug potentials by auxiliary electron heating. These three versions, called A-cell-barrier TMR, axisymmetric-barrier TMR, and inside-barrier TMR, exhibit reduced plug density (n/sub p/ << 10/sup 19/ m/sup -3/) and less required magnetic mirror field (B/sub mirror approx. = 9 T) compared to TMR designs without thermal barriers. A-cell barrier TMR Q's range from 5 to 25 depending on the central-cell length (L/sub c/ = 100 to 200 m) and peak center-cell beta ..beta../sub c/ (0.3 to 0.7) allowed by MHD stability. Axisymmetric-barrier TMR Q's range from 14 at L/sub c/ = 100 m to 30 at L/sub c/ = 200 m, if peak ..beta../sub c/ = 1. From a global equilibrium model for the inside-barrier TMR, Q values greater than 15 are achieved for ..nu.. = 0.5 in the modified Boltzmann relation for the plug potential. Even higher Q's are obtained using ECRF heating in the barrier to create a hot, mirror-trapped electron population. TMR's burning D-D as a fuel have been analyzed with a modified version of the global equilibrium model and under the assumption of an axisymmetric plug and barrier stabilized by surface magnetic fields. High-barrier mirror ratio is now feasible (R/sub b/ = 30-50), and short barrier length permits Q/sub DD/ values greater than 5