Performances of inert gas glow discharges for reductions of fuel hydrogen retention and helium retention

In order to clarify the effects of inert gas discharges on the reduction of fuel hydrogen retention, the inert gas discharge has to be similarly conducted in the same apparatus with the same conditions. In the present experiment, first, the hydrogen glow discharge was conducted to measure the fuel hydrogen retention. During the discharge, the amount of retained hydrogen was measured by a technique of residual gas analysis. The inert gas discharges, He, Ne and Ar discharges, then, were carried out after the hydrogen discharge to measure the amount of removed hydrogen. The fractions of removed hydrogen after the He, Ne and Ar discharges were 0.8, 0.3 and 0.1, respectively. The projected range of helium ion is comparable with that of the hydrogen ion, so that the helium impact desorption well removed the hydrogen. The sputter-etching rate of argon is significantly high, so that the wall surface is quickly covered by the deposited layer. Thus, the removal ratio of the Ar discharge becomes lower than that of the He or Ne discharge. The H2, Ne or Ar discharge was carried out after the He discharge to reduce the helium retention. It was found that the Ne and Ar discharges significantly reduced the helium retention, although the H2 discharge little reduced the helium retention. The reduction of the Ne discharge was larger than that of the Ar discharge. The amounts of the retained He, Ne and Ar were a few times, two orders and three orders of magnitude smaller than that of hydrogen.