By a proper usage of ECRH heating in minimum-B tandem mirror plugs, thermal barriers can be created which thermally insulate hot-plug electrons from both the central cell and the outside environment. This arrangement can be utilized in an axisymmetric, outboard anchor plug arrangement or a minimum-B plug. In the axisymmetric arrangement, ICRF can serve as a pump for preventing ions from accumulating in the thermal-barrier potential depression whereas, in the minimum-B plug, unconfined drift orbits should prevent such an accumulation.