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

[dreens]

TL;DR Summary

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

 

[yaboi3112]

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

 

[Twigg]

Price is also a factor here, if your budget is tight. Neglecting shipping and handling fees, argon is something like ~5x more expensive.

 

[dreens]

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