Dave is correct here. That is why I keep the fusor in the 100 micron range under vacuum all the time. For an operating session, I start the pump and now I am down to D2 bleed in and fusion pressures in a few minutes, long before the large mechanical pump has started to warm up. (maybe 10 minutes.) I am usually fusing in under 30 minutes. Long runs rarely exceed and hour and the pump by that time is getting quite warm. However, at 2 hours total run time, the big pump body is almost too hot to touch.
It must be realized that at this time a lot of oil backstreaming is occuring and the oil vapor is getting into the trap, but at least it is stoped there. Such oil vapor is miniscule in quantity compared to a pump down from air water load, however.
Created on Wednesday, April 18, 2001 5:29 PM EDT by Richard Hull