Neutralizer experiment of KSTAR NBTS system

A general neutralizer experiment was carried out to establish the operational coil current of the bending magnet, the neutralization efficiency of an ion beam with various parameter (beam energy, gas flow rate). Suggested operational coil current which was already studied for the bending magnet, was confirmed through a thermocouple installed at the middle of each ion dump and WFC (water flow calorimetry) system. The calculated optimum coil currents agree with the experimental coil current to penetrate each ion dump. Neutralization efficiency was measured by the WFC system. It depends on the gas flow rate and beam energy and a gas injection more than 800 sccm was needed to attain a equilibrium neutralization. Maximum efficiency was measured at more than 60% at 40 keV and less than 30% at the 80 keV of the hydrogen beam.