Injection performance prediction of the upgraded neutral beam on EAST

Abstract

The neutral beams(NB) on EAST are being upgraded according to the scheme that the beamline located on Port F will be moved to Port D and adjusted clockwise injection to counterclockwise injection(top view), while the beamline on Port A is unchanged with counterclockwise injection. The two beamlines are modified to counterclockwise injection consistent with the direction of plasma current (co-IP) instead of the primarily balanced-injection (co-IP and counter-IP). The two coming co-IP beamlines are expected to play important roles in plasma heating, neutron emission and current drive in EAST operating scenarios. The injection performances after the beam upgrade are predicted by the simulation codes ONETWO/NUBEAM and TRANSP/NUBEAM to model the discharges on EAST. After the beamlines are upgraded, the bulk ions are heated to a high temperature above 3.2 keV, which is much higher than that in the previous experiments. The orbit loss drops sharply by 83 % and the external charge exchange loss drops by 50 % after the beamline upgrade. The neutron rate induced by the upgraded beamline is greatly enhanced to the order of 1014/s with co-IP injection as opposed to the balanced-injection, and it is also heightened with the increases of plasma density and beam power. The simulation results show that it leads to a significant improvement of the beam-driven current and provides a practical condition for EAST to carry out long pulse and steady-state experiments. The assessment on the injection capabilities of the upgraded neutral beams is an important guiding reference to the subsequent EAST experiments.