Author Topic: Column window leaks  (Read 163 times)

wrigke

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Column window leaks
« on: March 11, 2019, 03:11:53 pm »
-----Original Message-----
> From: Philipp.POEML@ec.europa.eu <Philipp.POEML@ec.europa.eu>
> Sent: Monday, March 11, 2019 12:31 PM
> To: sx50-users@lists.wisc.edu
> Subject: RE: [sx50-users] SX100 Ion Pump problems
>
> All,
>
> just wanted to sum up on this.
>
> We indeed had a P10 leak. It was pretty evident after closing the P10 gas. Weird, normally we do this check quite often.
>
> Anyway, it was not a window. It was the counter. The window was good. But some screws on the counter were not super tight. I do not know why. Maybe some rubber seals went soft over the years and the counter became untight?
>
> After checking all screws on the counter the leak was gone.
>
> Unfortunate was, that just two weeks before we had already checked all the P10 tubing in that spectrometer, because we were suspecting a leak. But we only checked the tubing, not the counter itself.... Argh.
>
> Then the Ar must have found somehow a way into the gun. This is a bit weird too and somewhat a long story.
>
> Since vacuum in the chamber was great we did not think that a spectro window was not tight. But after a few days we wanted to play a bit with our crystals, because we had changed the setup of our counter shieldings.
>
> Venting the specs it turned out that there was indeed a leak, because the vacuum in the chamber became bad too.
>
> After looking around for some time, we noticed something really stupid: There was half a spectro window stuck in spectro 4, and another window was sitting on top! We do not know how long this has been the case, because nobody noticed during normal operation something was wrong. The next two weeks we spent trying to remove this half counter window. This was extremely tricky, because it had been pushed by the second window too far inside and was sitting behind the metallic tube where normally the o-ring of the spectro window sits. After all, our workshop made a nice tool, and eventually the window came out.
>
> Somehow, while fitting the window removal tool, this window must have become unscrewed, one of us pulled it out, looked through it, just saw "window gone" and pushed a new window in... OMG!
>
> Anyway, half window removed, but we still have something like a leak. What would you do in this case? We put blind plugs everywhere and the leak is still there. So it must be leaking at one o-ring of a blind plug. BTW, the same for the mylar windows, of course, which we want to use for crystal adjustments.
>
> So for now, we have applied just a little bit of ultra-high vacuum grease to the o-rings of spectro 1 and 4 windows and the vacuum is MUCH better. It is still pumping down.
>
> Any other suggestions for getting the chamber tight when venting the spectros?
>
> Hope you enjoyed our little story with the half window...
>
> Cheers
> Philipp


On 3/11/2019 12:38 PM, Karen E. Wright wrote:
> Hi Philipp,
>
> I know you and I have similar instruments, so I will offer this observation of my column windows:  The machining of the area where the column windows goes is REALLY bad.  Every time I pull a column window there are metal filings stuck to the O ring.  I have gotten in the habit of cleaning the machined area where the window will sit with long cotton swabs dipped in ethanol.  This usually takes many cotton swabs for each window opening.  I then use a small amount of high vacuum grease on the window O ring.  This process typically works very well and now my chamber vacuum is about an order of magnitude lower than before I used this process.
>
> Good luck!
>
> Karen


>