In Reply to: vacuum?????? posted by suryakant asopa on 09/09/03 at 2:38 AM:
Let me try to give you a few brief answers....
1. vacuum chamber, can it be made absolute vacuum? if so how?
No. Any chamber in practice has leaks and outgassing from the chamber's walls. The ultimate pressure depends on the chamber design and used pumps. You can in general reach the pressure about 10-6 torr without great problems, up to 10-8 torr only taking special measures, and 10-14 torr only in very special experiments....
2. will a mild steel chamber be goos enough? and can i paste a pice of glass for viewing the experiment in progress in chamber to the MS chamber?
All depend on your goal, vacuum you want reach and keep during your process, heating, etc. Glass windows are widely used but they must be placed on special flange. There are a lot of methods to install glass window. Once again all depend on your goal, chamber design, etc.
3.what will be the increase in the vacuum temperature, once the chamber is vacuumed?
What do you mean talking about "vacuum temperature"? If you mean the temperature of residual gas it should be practically the same as athmosphere temperature if you have no heaters or processes with heating.
4. a diaphrm type vacuum pump of 25 litres a minute discharge, a good enough vacuum pump for a 40 cubic feet of chamber area?
Well, I suppose it is not good. Basing on my experience I think that for 40 cubic feet chamber (about 4 cubic meters) you need pump with pumping speed about hundreed liters per second and probably not one...
5. do i have to reun the pump continuosly to maintain the vacuum, or once vacuum is created i shut it off?
No. The pressure in the chamber immediately starts to aruse because of leaks and outgassing. You must keep your pump working all the time you need to keep vacuum.