Measurement of helium lines in the edge plasma of the JIPP T-IIU tokamak

UV-visible spectra of neutral and low-ionized impurities are observed in the edge plasma of the JIPP T-IIU tokamak. To study recombination processes, helium was introduced into the deuterium plasma as a trace element. The line intensities of He I from the n = 3, 4, 5 levels were compared with a calculation of the collisional radiative (CR) model. The line intensity distributions were deviated from the CR model, particularly for the lines from n = 3. It seems that the double charge transfer process is one of the dominant recombination processes for He in the edge plasma.