CCD/Dewar contamination

[AlasaMorph]

Posted to CCD-world:
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Hi

 As Paul already mentioned we went thru extensive vacuum baking/cycling with 
the turbo pump, whilst the dewar was hot to get rid of contamination on our 
Loral CCDs. As you may recall this contamination resulted in a drastic 
reduction of QE after flooding and on cooling. I have to own up and say that 
one dewar - with a CCD int it went to about 110C, by accident! It damned well 
cured the contamination and DIDNT release the bump bonds on the chip!! After 
that I did the cycling at 80C, with equally good results. I decided the 
contamination we had was probably water vapour, not the exotic stuff you are 
getting. Is there anything in the dewar whicch could have got contaminated w/o 
you knowing. I saw one of our electronics guys using 'light oil' to coax the 
maganin wires into a sleave we were using to connect the cryostat connector to 
the chip. I 'suggested' he do it again w/o the oil!
   I am not sure whether baking  at the temp. I quoted above would have solved 
a problem like yoy have or for instance another problem we had - vacuum grease
deposists on an optical surface - that was a complete dismatle and clean.. Long 
job, both quantifying and solving!! Though like you we had a mass spectrometer
(at the University of Loughborough) to identify the culprit

Aloha (er just got back from Hawaii and Im STILL 12 hours out of sync!!!!) 
still truckin!!

Paddy


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