Abstract
A 2 MW-2.45 GHz lower hybrid current drive (LHCD) system was designed, fabricated and installed successfully on EAST in 2008 to investigate high performance regimes and achieve a steady-state operation. The system is composed of 20 continuous wave (CW) klystron amplifiers, 4 sets of high voltage power supply, 20 standard rectangle waveguide (American National Standard, WR430) transmission lines with a length of 30 m to 40 m for each, and a multi-junction grill containing 160 active (in groups of 8) and 25 passive sub-waveguides arranged in 5 rows and 4 columns. Fixed phase shifters in sub-waveguides and electronically-controlled digital phase shifters driving each klystron are used to control the radiated power spectrum of the grill. By means of LHCD, a plasma current of 150 kA to 500 kA at a central plasma density of 1 × 1013 cm−3 to 2 × 1013 cm−3 and a toroidal magnetic field of 2.0 T to 2.5 T was achieved. Both a fully non-inductive plasma current of 250 kA lasting up to 23 s and the ramp up were achieved. These results successfully demonstrated the capability of the LHCD system. The system is described in detail and the primary experimental results are presented.