Vacuum chamber air intake problem

[captoro]

hello,

I have build a vacuum chamber out of an acrylic cylinder.
I can get down to 50 micron but if I turn off the vacuum motor the chamber does not keep its atmosphere (air getting in)
What i did is add a high quality valve between the chamber and motor. Sunk everything in an oil bath. Turn off the valve and quickly disconnect the hose from the motor vacuum and sink that in the oil bath too.
Now everything is submerge and My sensor indicates that air is coming in ! slowly goes from 50 micron to 600 micron then it stays there
Any thoughts about this would be appreciated??

thanks

ken

 

[ZapperZ]

All materials outgas! This is especially true if the stuff you use inside vacuum are not clean (as in free of hydrocarbons, etc.)

Zz.

 

[captoro]

Its a PVC tube with acrylic plates on the end. Very solid, but I guess its not good for outgassing.
What are the possibility ?
1) cleaning the container ? soap is ok ?
2) USING different material ?
3) add a coating of some sort in the inside ?

Ken

 

[ZapperZ]

I'm not sure what you intend to do or what vacuum level you wish to achieve.

Note that even in the most stringent system, one keeps the vacuum pumps running all the time if one wants to maintain such vacuum levels. A few applications such as PMTs where the tubes are sealed are the exceptions, but those usually are made under very clean conditions (or they were cleaned after assembly or during processing).

PVC tubes are never meant to be used to maintain good vacuum.

Zz.

 

[captoro]

I want to get 500mTorr or just around, i can keep this with the vacuum running. The problem with that is I also want to insert Argon gas inside, so I cannot keep the motor (vacuum) running.

I was thinking coating the inside with resin or some other material.
what do you think??

ken

 

[Bender0601]

Zz is correct, everything has to be clean. Free of finger prints, oil, dirty or any other contamination. The vacuum pump should be left on. Resin isn't a good substance in vacuum. Any kinda resin will outgas and you'll never be able to obtain a steady pressure let alone deep enough vacuum.
You should use IPA alcohol for cleaning. Soap will leave a film and some contamination.
What purpose are you building this for? What process are you looking at doing? What pressures are you looking to achieve? Are you sputtering because you using Ar? Just wondering :)

Bender

 

[captoro]

I am trying to replicate a patent, but they use glass, but it is very costly for me.
I am looking to obtain a steady 500 micron. Have not use Ar yet . but as soon as I can get stability, I will. !
I will go to the pharmacy and get some alcohol, see what it does

K