CCD-world: Re: cleaning

[Peter Conroy]

The following was posted to CCD-world:

Dear CCD World.

I to have had to clean a SITe 1024 chip that was contaminated when a
Leybold turbopump stopped running but the backing pump kept running
probably while the chip was still a little cold.  The chip had droplets of
oil on the surface that acted as microlenses and produced some very strange
pictures.

I found that isopropyl did not dissolve the backing pump oil but reagent
grade petroleum spirit did. I used a wash bottle filled with the pet
spirit, held the chip, in a shorted socket, vertical under a fume hood and
gently washed the oil down to one corner with a fine jet of spirit. You can
shake the remaining drop from the corner of the metal chip package. Pet
spirit dries very quickly, you will not need to blow dry the chip. I washed
the chip about four times to remove the last trace of oil scum and used
about 100ml of pet spirit. I found that I needed to clean the inside of the
Dewar or a thin fresh layer of oil would appear on the CCD with each
pump/cool cycle.

This proces did not seem to effect the chip coating, it is still black. The
chip has been in service for about one year sence cleaning. I must admit to
not checking with SITe before attempting this process, you may wish to do so.

Regards 
------------------------------------------------------------------------------
>Michael Lesser wrote:
>
>> We have good luck cleaning with a spray of isopropyl alcohol.  It helps if
>> the IPA is dry (not open to the air very much).  Just spray the CCD and dry
>> off as fast as possible with clean air or nitrogen (preferable ionized
>> nitrogen).
>>
>> -Mike
>>
>
>Thanks for the information.
>Before trying to follow your suggestion,
>I'd like to know what if I fail to clean the isoprophyl alcohol & oil
>composition from the CCD fast enough. Is it harmful to the
>coating? What precautions do I need before spraying the alcohol
>to the CCD? Still I am not sure of the nature of the "liquid-drops"
>on the CCD.
>
>Thanks,
>Byeong-Gon

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Peter Conroy - Senior Draftsman - Design Office
Mt Stromlo Observatory -  Canberra Australia
Private Bag  Weston Creek PO ACT 2611 Australia
Email - conroy at mso.anu.edu.au
Phone - 61 02 6279 8022   Fax - 61 02  6249 0233 
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