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Re: Yet more: diffusion pumps
At 10:46 AM 2/4/96 -0600, you wrote:
>>At 10:07 AM 2/1/96 -1000, you wrote:
>>> >I do believe there some point of decreasing returns.
>>>
>>>
>>>
>>How bout some increasing returns.....In all the diagrams for pumping &
>>bombarding setups I fail to see vacume traps in the systems. I was a
There was a cold trap between
>the diffusion pump and mechanical pump (a welch 1402) and between the dif
>pump and the manifold. Filling the 2nd trap with liquid N2 immediately
>dropped the pressure several DECADES (as in 10-4 to 10-7or8). Both
>pumps' oil remained crystal clear too.
>
>I think the neon industry may be one of the few users of HV technology that
>doesn't use cold traps. I've thought about making one use with neon -
>liquid N2 would undoubtedly clean a dirty mercury tube nicely. But then
>again do I really want to get into this arena of the business?
>
>You can buy liquid N2 here in town by the liter - bring in a thermos bottle
>with a vent drilled into the top. It will keep very long in one of these
>(several days), and it's not very expensive.
>
That's right, our main concern was contamination of the pump oil,
and our lab atmosphere! We just used the dry ice/ethyl alchol
mix (which forms a azeotrophic - SP - mix that has a temp on the
order of -70F) which worked well for us and was less trouble than
liquid nitorgen.
/\/\ike
Belvoir Studios
Chattanooga, TN