In Reply to: welding for vacuum vessels posted by Stefano Marchi on 10/31/00 at 8:42 AM:
This scares me. First, you must have the vessel engineered by a certified pressure(vacuum) vessel engineer. You did not state the size of your chamber but at your pressures, a 1mm thick wall will crumple like stepping on a soda can.
If your wall is 10" x 10", you have 100 square inches. Atmosphere is 14.7 pounds per square inch. Therefore, you would have 1470 pounds exerted against your little 1mm wall.
Buy a chamber or have it engineered by someone qualified.