Source of chlorine contamination?

[Al Slavin]

W have chlorine present in our UHV chamber, as I can see it with Auger spectroscopy on the silver surface we're studying. The residual gas shows a low pressure (~1 x 10 ^-9 torr) of masses 36 and 38, in about the ratio of 3:1, which looks like chlorine (HCl). Can anyone suggest a source of chlorine in a UHV system? One possible culprit is the dichloromethane we use as a degreaser for new parts. We always follow this by an ultrasonic methanol rinse and assumed that would get rid of any residual dichloromethane.

Another possible source is mineral-fibre "spaghetti" that we use for electrical insulation on wires. I don't know if it might contain chlorine.

If one of the above does outgas chlorine, might it be expected to contaminate our Santovac-5 diffusion-pump oil, so that we would need to change the oil to be rid of the chlorine?

Thanks for suggestions.

Al Slavin

[Ed Kurz]

Do you have a recently refurbished or new ion pump on the system? I
once had Cl contamination from such a case - very heavy when the pump
is first turned on and pressure high and decreasing thereafter. I
suspect they improperly cleaned the pump. Went away after a time but
was a pain.

Ed Kurz

[Alan Slavin]

Ed,  Thanks for the suggestion but no, our main pump is a diffusion pump using Santovac 5 that we've used for years without a problem.  I've replaced dichlomethane as a degreaser with hexane, and the HCl contamination does seem to be going down with repeated baking to 150 C, so maybe just a matter of time. 

Al

[Michel Genet]

A long time ago we discovered that samples stored in a desiccator with silica gel were contaminated by chlorine. I do not know if some of your spare parts or samples were stored in a desiccator and if that can help you.
Best regards,
M. Genet

--

Michel Genet
Université catholique de Louvain (UCL)
Institute of Condensed Matter and Nanosciences (IMCN)
Surface Characterisation platform (SUCH): X-ray photoelectron spectroscopy (XPS)
and
Division Bio & Soft Matter (BSMA) – Surfaces

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B-1348 Louvain-la-Neuve (Belgium)
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e-mail : michel...@uclouvain.be
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5^ème conférence francophone sur les spectroscopies d’électrons
ELSPEC – Louvain-la-Neuve 20-22 mai 2012
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