Lower hybrid current drive experiment with incoherent waves on the HT-2 tokamak

Lower hybrid current drive experiments were carried out in the HT-2 tokamak (major radius 0.44 m) with four sets of an eight-waveguide multijunction launcher and a 2.46 GHz magnetron. The four independent radiofrequency (RF) systems, operating at frequencies differing by 2 MHz each, generated incoherent waves in the plasma. A plasma current of 8.6 kA was sustained during 20 ms by an RF power of 16 kW in a low density plasma. The current drive efficiency was 0.5 × 1018 A.W-1.m -2, which did not decrease with the number of active RF sources. This showed that current drive with incoherent waves is not inferior to that using coherent waves