Contamination of PPtF CCD's

[Preben Noerregaard]

Hi Derek
We, - and others, have had some experiences that PPtF chips
tends to loose their sensitivity when kept in vacuum at room
temperature. It looks like the oxygen disappears from the
surface.
Keeping the chip in dry air for a few hours and then pump
the dewar down again, will recharge the surface and the QE
is OK again.
Regards, Preben

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Preben Noerregaard
Copenhagen University Observatory
Juliane Maries Vej 30,  DK 2100 Copenhagen O
Tel: +45 35 32 59 44, Fax: +45 35 32 59 89
email: preben at astro.ku.dk
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