Alternating Current Tokamak Reactor with Long Pulses

Alternating current (ac) tokamak operation in the reactor parameter range is studied by considering the volt-second consumption, A simple condition for obtaining ac operation with nearly constant pulse length is given by L_p/R_p < T_{d, ss} (L_p is the plasma inductance, R_p is the plasma resistance, and T_{d, ss} is the discharge length in the standard operation), assuming time-independent plasma parameters. The discharge length for ac operation is shorter than for standard operation and is given by where is the total transformer flux and is the plasma inductive flux. Alternating current operation is found to be advantageous in a large reactor having a large ohmic transformer flux satisfying . The superconducting magnetic energy storage system is proposed as an attractive power supply for ac operation in a large reactor.