Application of high performance inverter circuit to plasma generation and heating in fusion devices

We have constructed a rf power source using static induction transistor (SIT) inverters to generate high heat flux plasmas in the diverter plasma simulator, NAGDIS-II. Since the SIT can enlarge the operating frequency range of the high power inverter above 1 MHz with output power of several tens of kW, SIT inverters can be used to generate rf plasmas and to heat plasmas by exciting low frequency plasma waves, such as Alfven waves and ion cyclotron waves in plasma devices. The rf conversion efficiency of a SIT inverter with matched load is ≫85% for frequencies up to 1.2 MHz. The third harmonic antenna current is found to be less than -30 dB. Using four sets of inverter power supplies, we can generate more than 56 kW in continuous rf power or 80 kW in 1 s pulses to produce high heat flux plasmas in the diverter plasma simulator. © 1998 American Institute of Physics.