Argon or Dry N2 for venting a small Ultra High Vacuum chamber

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Discussion Overview

The discussion revolves around the choice of inert gas for venting a small Ultra High Vacuum (UHV) chamber, specifically comparing Argon and dry Nitrogen. Participants explore the implications of gas purity, cost, and the impact on vacuum system performance.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Experimental/applied

Main Points Raised

  • One participant, Dave, suggests that Argon may provide higher purity due to its density, which could exclude air more effectively, but raises concerns about its compatibility with ion pumps and getters.
  • Another participant, Patrick, indicates a preference for dry Nitrogen based on personal experience, noting that the choice of seals and bakeout methods may significantly affect vacuum performance.
  • A third participant mentions the cost of Argon being significantly higher than that of dry Nitrogen, which could be a consideration for those on a budget.
  • Dave later comments on the pricing of Argon and Nitrogen in his area, suggesting that they are similarly priced, with Argon being about 40% more expensive, and questions whether previous comparisons were made between different purity levels of the gases.
  • Dave concludes that he will choose Nitrogen for his application.

Areas of Agreement / Disagreement

Participants express differing opinions on the choice of gas, with no consensus reached. Some favor dry Nitrogen for its cost-effectiveness and compatibility, while others highlight the potential benefits of Argon in terms of purity.

Contextual Notes

Participants mention factors such as the type of seals and valves used, as well as the method of bakeout, which may influence the effectiveness of the chosen gas in the high vacuum regime. There is also uncertainty regarding the purity levels of the gases being compared.

Who May Find This Useful

This discussion may be useful for individuals involved in vacuum technology, particularly those working with UHV chambers and considering options for inert gas venting.

dreens
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TL;DR
Curious whether people have a preferred gas for venting UHV.
Hi there,

I have a small, few liter UHV chamber that frequently needs to be vented and rebaked. I want to shorten my bake time, so I’ve obtained a glove box to allow me to vent, work and close back up under inert gas.

i’m curious if people have a preference between Argon and dry Nitrogen. I suspect the argon will provide higher purity by virtue of being heavier and excluding air from my glove box more effectively. But I also suspect that the residual argon will be more challenging for my ion pump and non evaporator getter combo to pump, compared with the nitrogen.

Thanks for any thoughts.
Dave
 
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Dry N2 seems to be the preferred choice in my experience for the reasons you mentioned. Though I should mention that the seals and valves you use (conflat or viton) and the method of bakeout you are employing are going to have a bigger impact once you get into the high vacuum regime. Anyways, I highly recommend reading these articles by Phil Danielson for info https://www.normandale.edu/departme...lection/articles/conditioning-vacuum-chambers.

-Patrick
 
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Price is also a factor here, if your budget is tight. Neglecting shipping and handling fees, argon is something like ~5x more expensive.
 
Thanks all. I really like that article series by Phil Danielson. It tickles me every time he refers to us, the readers, as “vacuum practitioners” or “practitioners of high vacuum”. Seems to happen at least once near the beginning of all his articles, and I wouldn’t want it any other way.

It’s funny, at least here in MA, Argon and N2 are similarly priced. Argon is about 40% more. Either are available at ultra high purity or research grade, the latter being about 5x the price relative to the former for either gas. I wonder if you could’ve been seeing a comparison between more pure Argon and less pure N2, Twigg?

Anyways, I’m going with N2, for what it’s worth.

Cheers,
Dave
 

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