Lower hybrid current drive

Lower hybrid current drive

Lower hybrid current drive (LHCD) (based on Lower hybrid oscillation) is used to supplement the current driven by the Ohmic transformer. The LHCD system is capable of delivering 1.0+ MW of microwave power (planned upgrade to 2 MW or more with addition of a second antenna in 2013) to the plasma at 4.6 GHz. Power is provided by 250 kW klystron microwave amplifiers manufactured by CPI, Inc. Non-inductive operation for up to 0.5 s pulses at 500 kA was achieved. Lower hybrid waves are launched preferentially in the direction opposite the plasma current (i.e. in the direction of electron travel) and deposit energy on electrons moving at approximately three times the thermal velocity via Landau damping. A major area of LHCD research has been in the area of current drive at the high densities (n_e > 10 m) required for a fusion power plant.