Spectroscopic Measurement of Neutral Particle Influx Ratio on EAST

The spectra of HeI (587.6 nm), Hα (656.28 nm) and Dα (656.1 nm) of the helium discharges as well as the normal deuterium discharges have been measured with two optical spec- troscopic multi-channel analysis (OMA) systems on the experimental advanced superconducting tokamak (EAST). The influx ratio of the sum of H and D to He spectral lines and the influx ratio of H to D are given. In this way the ratio of hydrogen/deuterium ion (S/XB)_H/D to (S/XB)_He as well as (S/XB)_H/D is not very sensitive to the variation in the edge density and temperature. The low-density helium discharges are operated in order to reduce the recycling hydrogen fluxes; however, the effect is not obvious. The possible reason is that the number of helium discharges is not enough and the content of hydrogen in the wall is still very abundant, which is caused by frequent wall conditionings and the vacuum leakage. The H/(H+D) ratio decreases quickly after one lithium coating and reduces to less than 10% using several accumulated lithium wall conditioning. It is found that the deposited He atoms on the carbon wall will remain at a low level after several D2 discharges.