Field reversed configurations (FRC),1,2,3 as mirror machines have been developed as simple plasma confinement systems. FRC formed by reversing of magnetic field and reconnection and sustained by plasma current. Several mirrors may be linked together with solenoids - tandem mirrors (TM), end losses in the axisymmetric tandem mirror are reduced by ambipolar trapping - ambipolar trap (AT). Power balance of deuterium - helium-3 (D-3He) plasma in a prolate FRC power plant is compared with the power balance for a central cell of D-3He tandem mirror reactor (ambipolar trap). Deuterium - tritium (D-T) ITER4, kinetically stabilized tandem mirror (KSTM)5 and D-3He FRC6 parameters are demonstrated.