Spectroscopic observation of a helium plasma cooled by a hydrogen gas injection

Abstract

Study of recombining plasmas resulting from a neutral gas injection has been made in a high density steady-state plasma. Recently, the inverted population between He I 1s2p 1 P and 1s3p 1 P due to the selective double electron capture process, He 2+ + H 2 → He * (1s3 l) + 2H +, was observed in a single layer column plasma [S. Namba et al., Fusion Eng. Design 34–35 (1996) 777], when a helium plasma contacts with a hydrogen molecule. Moreover, experimental results which suggest an effect of the vibrational states of hydrogen molecules, He 2+ + H 2 ( ν′) → He * (1s nl; n=3, 4, 5) + 2H +, have been obtained for a double layer column plasma which was generated by a change of helium gas flow rate into the discharge region. The results on the hydrogen gas injection experiments relevant to two plasma conditions are presented.