Helium release from tritium occluders in Zetatron tubes

Helium release rates from the gas reservoirs in Zetatron tubes were measured at room temperature and after operation of the reservoirs at elevated temperatures. The average ratios of the quantities of 3He released as free gas to the total quantities of 3He that were generated within the reservoirs were equal to 0.0003, 0.003 and 0.006 at 230C, 3500C and 5000C, respectively. Quantities of 3He that were released from the reservoirs were independent of the duty cycles, which were varied from 5 min/week to 16 h/day. During normal operation, Zetatron target films release three times as much 3He as that which is released from the reservoirs. The combined gas load from the tritium occluders causes the 3He partial pressure within Zetatron tubes to increase at a rate of about 4 Pa per year. Due to contamination of the ion beam by 3He+, the neutron outputs of generators using Zetatron tubes are predicted to decrease to 60% of the initial yield after one year of storage