Evidence for molecular-assisted recombination of He+ from particle balance measurements in helium-hydrogen mixture plasmas in PISCES-A

Cai, Laizhong; Tynan, George R.; Hollmann, Eric M.
October 2008
Physics of Plasmas;Oct2008, Vol. 15 Issue 10, p102505
Academic Journal
Particle balance measurements of He+ ions in He/H mixture plasma are performed by using wall probes, plunging probes, and spectroscopy. The measurements indicate that radial loss to the chamber wall is the dominant ion sink; nevertheless, a missing ion sink is observed as the plasma hydrogen fraction is increased. This sink term is attributed to hydrogen-mediated recombination of He+ ions, so-called molecular-assisted recombination (MAR). Independent evidence for MAR (acting on hydrogen ions, however) is seen in anomalously large Hα/Hγ ratios at the cold plasma edge.


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