Measurement of Neutron Flux at the Initial Phase of Discharge in EAST

Neutron emission in EAST was investigated by a time-resolved monitor systems which consist of four 3He proportion counters and a 235U fission chamber. The D-D neutron flux increased approximately an order of magnitude during the 27 MHz Ion-cyclotron resonance frequency (ICRF) heating, demonstrating that the ICRF wave heated the plasma effectively. In addition in LHW experiment with higher plasma parameters D-D neutrons were also detected. However, a mass of photoneutrons were generated in ohmic discharges with low plasma density. Effect of plasma density on the production of photoneutrons was studied, and it is found that LHW can suppress the runaway electrons and reduce the photoneutrons effectively.