Low-Pressure Gas Effects on the Potency of an Electron Beam Against Ceramic Cloth

An 8-kv electron beam with a current in the neighborhood of 100 mA from the Ukrainian space welding \“Universal Hand Tool\” (UHT) burned holes in Nextel AF-62 ceramic cloth designed to withstand temperatures up to 1,427 C. The burnthrough time was on the order of 8 scc at standoff distances between UHT and cloth ranging from 6-24 in. At both closer (2 in.) and farther (48 in.) standoff distances the potency of the beam against the cloth declined and the burnthrough time went up significantly. Prior to the test it had been expected that the beam would lay down a static charge on the cloth and be deflected without damaging the cloth. The burnthrough is thought to be an effect of partial transmission of beam power by a stream of positive ions generated by the high-voltage electron beam from contaminant gas in the \“vacuum\” chamber. A rough quantitative theoretical computation appears to substantiate this possibility.