[vsnet-chat 2105] CCD Cosmic ray hits

[Lew Cook <lcoo@yahoo.com>]

Back about 20 years ago, I got a bucket of chips (not
CCD chips - just integrated circuit chips) for gamma
ray analysis. I found that there was thorium and
uranium in the chips. Both of these trace elements are
radioactive and give rise to a chain of radioactive
decay products. Alpha radiation impinging on a chip
internally can cause errors. Thorium is also used in
some optical glass. 

Ulisse Munari's comment that the coating on a lens
reduced "cosmic ray" hits on a CCD (vsnet-chat 2103)
leads me to suspect that the cosmic rays are actually
locally generated alpha particles originating from the
CCD chip bases (from impurities in the silicon), radon
gas in the atmosphere of the camera, and alpha
particles from other sources near the face of the CCD
chip. The alpha particles will travel only a few
microns in solids and are highly ionizing. 

Does my speculation sound reasonable?




===
Regards, Lew 
- Visit http://home.pacbell.net/cookl 
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