Measurement of edge plasma parameters at KSTAR using a combination of Lithium and Deuterium Beam Emission Spectroscopy

A 60 keV neutral Lithium beam system was designed and built up for beam emission spectroscopy measurement of edge plasma on KSTAR. The measurement will be the complementary of the heating beam based emission spectroscopy system which was built up in 2012, using the same observation system with different interference filters. The electron density and its fluctuation, thus the density distribution, the transport and different turbulent modes can be measured using the accelerated Lithium beam based emission spectroscopy system [1,2]. A new thermionic ion source is developed with SiC heater to emit around 4mA ion current. The ion optic is following the original 2 steps design with small modifications to reach about 2 cm beam diameter in the plasma. The newly developed ion gun system is built up first in the Wigner RMI for detailed testing of every beam parameter. The maximum 60 keV beam energy with 4 mA ion current were successfully reached at KSTAR which is sufficient for beam emission spectroscopy measurements. A newly developed Sodium vapour neutralizer neutralizes the accelerated ion beam at around 260-280 C degrees even at long (<20s) discharges. The base of the newly developed Li-BES system and the first results are discussed in this paper.