The answer to some of these is "it depends"...but:
1) what kind of connection should be used for the gas inlets, (NPT + teflon tape or epoxy ? ISO KF + welded tube?)
The latter is cleaner. My cross-field device (Gow) uses 1/8 NPT and epoxy. Perfectly adequate.
2) On the gas inlets, should I have a shut off valve + leak valve, in order to be free to disconnect everything from the fusor ? Or a leak valve is sufficient ?
Leak valves are control valves and control valves are not usually guaranteed to be shutoff valves. Better is to use both, especially if you stand to lose some valuable process gas.
3) What about using NW10 connections for gas inlets ? (cheaper an less space taken on the chamber surface + smaller holes to drill) Is the NW25 recommended for pump connection because of possible conductance problems?
NW10s aren't really that common. NW16 is more prevalent. NW25 or NW40 are good sizes for the pump connection.
4) Planning to use my little diffusion pump (NW50) has anyone played with reducing it to NW25 or NW10 ? Can I use a "straight" reducer or is it better a conical one ? (conductance)
No big difference. In the other thread on the Hummer SEM sample coater the turbo has a constricted inlet (acts as a fixed throttle valve) to provide pressure drop and to minimize the amount of gas needed to get to a given pressure. Pump down will be a bit slower but for a small, reasonably tight chamber, no big deal.
Steve
Created on Friday, March 16, 2001 8:43 PM EDT by Steve Hansen