bschwand wrote:
Hi everybody,

I want to build a device similar in some ways to a vacuum chamber. It
should be able to be filled with various gases, a various pressures. In
the chamber, there will be some electrical device. As the device runs,
I want to mesure different things: how the heat produced is eliminated
depending on the type of gas, its pressure, how is EM radiation
released inside, etc.

So basically I need a gas tight enclosure, probably stainless steel or
some other non-reactive metal, with some gas ports on it to fill and
empty it (no problem), a door to swap the device inside (no problem),
some ports for electrical connections (problem).

I do not know how to make an electrically insulated, vacuum and heat
resistant electrical port.
Don't make it, buy it. What you want is a Kovar feedthrough. These
have a piece of Kovar rod that passes through a piece of ceramic
insulator, which also serves as the vacuum seal.
The material of the port needs to be as
inert and heat resistant as possible, it can not release gases or any
contaminant under vacuum (thus drilling a hole in the chamber, putting
a rod through and sealing it with epoxy or any resin won't work). I
thought of using glass, but I can not fuse the glass to the metal
because of the different thermal expansion rate of glass and metal.
This is exactly why Kovar was developed. It matches the thermal
expansion of glass and ceramic materials, and also wets the glass,
providing a strong mechanical bond. it is what is used to make the
connections through vacuum tubes. If this is a hobby project, you
can salvage the base of an all-glass vacuum tube or CRT.

Jon