Vacuum chamber air intake problem

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Discussion Overview

The discussion revolves around the challenges of maintaining a vacuum in a homemade vacuum chamber constructed from acrylic and PVC materials. Participants explore issues related to outgassing, contamination, and the feasibility of achieving specific vacuum levels while also considering the introduction of Argon gas.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Ken reports that his vacuum chamber does not maintain its vacuum level after turning off the vacuum motor, with pressure rising from 50 microns to 600 microns.
  • Zz suggests that all materials outgas, particularly if they are not clean, which may contribute to the pressure increase.
  • Ken considers cleaning the container, using different materials, or applying a coating to reduce outgassing.
  • Zz emphasizes that PVC tubes are not suitable for maintaining good vacuum and notes that vacuum pumps typically need to remain operational to sustain low pressures.
  • Ken expresses a desire to achieve a vacuum level of around 500 mTorr while also wanting to introduce Argon gas, which complicates the situation since the vacuum motor cannot remain on during this process.
  • Bender agrees with Zz about the importance of cleanliness and warns against using resin for coating, as it may outgas and hinder achieving a stable vacuum. Bender also questions the intended application and process related to Argon gas usage.
  • Ken mentions he is trying to replicate a patent that uses glass, which is cost-prohibitive for him, and he aims for a steady 500 micron vacuum.

Areas of Agreement / Disagreement

Participants generally agree on the importance of cleanliness and the challenges posed by outgassing. However, there are differing opinions on the suitability of materials and methods for achieving the desired vacuum levels, indicating unresolved issues and competing views.

Contextual Notes

Participants have not reached a consensus on the best materials or methods to use for maintaining vacuum, and there are unresolved questions about the specific requirements for the intended application.

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

Zz.
 
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
 
Last edited:
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.
 
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
 
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
 
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
 

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