I recently finished building a little vacuum system for fusors and other similar equipment. It's small, and not exactly professional-grade, but it uses up a lot of parts and supplies I have had sitting around a long time doing nothing. Utimate vacuum so far is around 1E-6 torr.
At the center of this setup is an Edwards EO50/60 diffusion pump (air cooled, 20 mL DC705 oil, 50 l / s). The backing / roughing pump is an Edwards E2M1. The rest of the parts compliment consists of four KF-25 bellows valves (including the high-vacuum throttle valve), two thermocouple gauges (DV6 and DV3 equivalent), a Penning gauge, a needle leak valve, and a variety of stock and custom QF-25 fittings. The DP heater (200 W) is run from a light dimmer. A foreline anti-backstreaming trap is made by pushing a tight 6" roll of copper Chore-Boy mesh into a KF-25 bellows hose. Another anti-backstreaming feature is the needle leak valve, which can be used to hold foreline pressure in a Knudsen flow regime. It draws intake air through a zeolite filter. The whole thing is supported on a frame that is mostly pieces of sheet steel and angle stock screwed together. Most of the piping (including that on the HV side) is regular copper water pipe with "external" soft-silver-solder joints.
Here are some specs I calculated:
Conductance, high vacuum leg: 5 l / s
O-ring permeation loading, high vacuum leg: 2 nTorr l / s
Conductance, foreline components: 1.5 l / s
Thus, effective speed at the vacuum port (currently blanked off) is about 4.5 l / s. For deuterium, I'd expect it might be significantly higher because the diff pump speed rises significantly for the lighter gases.
In the pics you can see the the thing in operation, with high vacuum at about 4E-6 mbar (3E-6 torr) and the foreline at just under 200 mtorr as set with the needle leak valve. I had just given up trying to teflon-tape seal the high-vacuum side TC tube into its 1/8" NPT socket because of a leak, and I had gone ahead and Torr-Sealed the thing right in. Last night, the Penning gauge was kissing the 10-7 range.
Certainly, one could get by with less on such a system, but it is pretty versatile: I can swap out roughing pumps while leaving the diff pump on, for example; I can open the high-vacuum side while leaving the pumps on; and between the heater and the high-vacuum valve it appears I have a pretty decent throttling capability.
-Carl
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2006-06-04 19:36 "New" high vacuum system 
(Carl Willis) [Latest: 2006-06-12 10:41]
(Michael Kan)