Dave Mckay's Urbana Info

Some information from Dave McKay how to make a good vacuum, from an e-mail on Jan 26, 2009

1)In Brian's view, Duniway and MDC are just a cheaper version of
Varian and he would not trust them for valves, pumps or ti-sub
cartridges, although he has had numerous problems with Varian
electronics in the past

Joseph's Response:
I hear from the people at Kimball Physics that they are now buying ion
pumps from Duniway. I've also heard horror stories about Varian ion
pumps from two groups.

My take on this is that it depends on the particular product you are
talking about, because Varian stamps its name on products made in
different factories all over the world. Valves, for instance, could be
made by a better place than the ion pump factory? Indeed we have had
terrible issues with the Duniway TSP now, and next time I would try
varian for that. Having no other information, sure, let's buy future
valves from Varian.

2) Brian's cleaning procedure: degreaser (ie. alconox, but they use
simple green here), DI water rinse, acetone then spectroscopic grade
methanol as the last step (No DI water as the last step). Although, he
would agree that a good bake probably makes the cleaning steps largely
irrelevant.

3) Baking procedure (from Dave Wineland's lab), 350 with turbo (about a
week) then cool down to 80C and outgas ion gauges, ti-subs, etc. and
turn on ion pump, valve off turbo then back up to 300C for another
week with just the ion pump

Joseph's Response:
YES! I completely agree. If this information has somehow gotten
lost… we should do this kind of double bake. It was what we did for
the last chip experiment bake, for instance. An ion-pump only bake is
considered critical in a number of labs.

4) Ben also mentioned that he heard nickel gaskets damaged vacuum knife
edges (couldn't remember where he heard that from though)

5) Brian mentioned that he felt the RGA would limit the attainable
pressure to the low 11's based on "what he has heard"

6) Brian has heard that the limiting pressure in glass based systems is
due to diffusion of helium through the glass…I wonder if this will
limit our pressure because of the really thin imaging window (it
probably helps that its crystal sapphire)

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