QE dips in Loral chips

[Paddy Oates]

Hi Folks,
	I posted a message recently to the exploder regarding some rather odd
effects we are seeing in the room temperature measurements of  QE for the Lesser 
thinned Loral 2kx2k CCDs. The data has also been put on the Web at URL-

http://www.ast.cam.ac.uk/~apo/docs/loral.html

The second curve on this page shows a plot of the Loral data showing 2 'dips' at 
390 and 780 nm, there was some suggestion from Mike that the 'dips' were caused 
by oil contamination, possibly back-streaming from our Turbo. I sent
the Turbo back to Balzers and they stated there was no evidence of oil 
contamination PLUS in the meantime we sent one of our chips back to Mike to 
re-measure the response and he also confirms there's no oil either visibly 
on the surface or implied from his QE response measurements.

The data for most recent, cold measurement for our science array is at URL-

http://www.ast.cam.ac.uk/~apo/docs/loral-1.html

and as you will see there is NO evidence of any 'dips'. Whatever it is, appears 
to be temperature dependent!

If you look at the EEV data (RT and cold) at URL -

http://www.ast.cam.ac.uk/~apo/docs/eev.html

you will see from the 3rd curve for device A3409-7-17 that at room temp. there
is no sign of any 'dips' at 390 and 780.

This last nugget is also interesting the 'dips' appear to be separated by x2 in 
wavelength, 390 and 780ish - does this mean anything to anyone. So far we have 
seen it mainly with the Loral CCDs, some small effect with Tek (see the 1st 
figure on the 1st Loral page) and no effect with the EEV CCDs.

We plan to use a monochromator today to do a scan to see if we get the same 
results....

Suggestions, as always, more than welcome...
Anyone heard anything about the meeting at G. Caman yet???

Paddy

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