Abstract: An alkali metal thermal to electric converter (AMTEC) cell of the type employing an alkali metal flowing between a hot end of the AMTEC cell and a cold end of AMTEC cell. The AMTEC cell being separated into a low-pressure zone and a high-pressure zone and comprising a condenser communicating with the low-pressure zone for condensing alkali metal vapor migrating through the low-pressure zone from the solid electrolyte structure, a return channel coupled to the condenser for directing the condensed alkali metal from the condenser toward the hot end of the AMTEC cell, an evaporator coupled to the return channel and communicating with the high-pressure zone for evaporating the condensed alkali metal into the high-pressure zone, the evaporator including an evaporation surface, and a solid electrolyte structure separating the low-pressure zone and the high pressure zone and having alkali metal simultaneously existing in a vapor and liquid state in its interior.