[dsg-hallb_rich] [EXTERNAL] Re: d0 results for mirrors 5 and 5C

[Tyler Lemon]

Hi Marco,

Okay, we'll repeat the tests.

I do have some questions, though.

For the procedure, it says to determine the exposure time by testing various exposures until the maximum CCD counts is ~850. This is what we did with the latest measurements. If when we repeat the tests with 0.5-ms exposure times, and the CCD counts are significantly less than 850 for what we determine to be the smallest image size by eye, should we still continue the tests?

Also, there is a trim potentiometer on the light source that I'm guessing will slightly vary the brightness of the source. Should we use that to slightly increase the source brightness if we are at significantly lower CCD counts with 0.5-ms exposure?

Lastly (this is mainly just out of curiosity) for the tests, is there a reason the light source is red?

Like you said, we can talk about it in the meeting, but I wanted to ask the questions now in case the answers need some thinking time.

-Tyler
________________________________
From: Marco Mirazita <Marco.Mirazita at lnf.infn.it>
Sent: Thursday, October 7, 2021 11:43 AM
To: Tyler Lemon <tlemon at jlab.org>
Cc: dsg-hallb_rich at jlab.org <dsg-hallb_rich at jlab.org>
Subject: Re: [dsg-hallb_rich] [EXTERNAL] Re: d0 results for mirrors 5 and 5C

Hi Tyler,
in your measurements you used an exposition time variable from 2 to 3.5
ms, at least by reading the name of the files.
This is definitely bigger than the value of 0.5 ms we used for the
RICH-1 mirrors.
I would ask you to repeat the measurement with 0.5 ms exposition time.
There could be also some issue with the alignment, since the image on
the CCD seems to be moving with Z.
We can discuss about this point tomorrow at the meeting.
I have posted my slides for tomorrow on the RICH wiki if you want to
have a look now.
Marco


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