[dsg-eic_dirc] EIC DIRC Exit light study

[Grzegorz Kalicy]

Hi Tyler,

Thanks a lot for the study, we had a discussion with our German collaborators about it and they had a similar feeling that we should be fine with cutting it out as a background. Having said that I think it is now way brighter than 58 Lumins that are required.

Cheers,

Greg
________________________________
From: dsg-eic_dirc <dsg-eic_dirc-bounces at jlab.org> on behalf of Tyler Lemon via dsg-eic_dirc <dsg-eic_dirc at jlab.org>
Sent: Thursday, September 28, 2023 4:02 PM
To: dsg-eic_dirc at jlab.org <dsg-eic_dirc at jlab.org>
Subject: [dsg-eic_dirc] EIC DIRC Exit light study

Hi Beni and Greg,

Since Monday's meeting, I have been thinking of ways to help us resolve the exit light problem.

In the meeting, you mentioned that we can't treat the exit light like a background light noise and subtract it from measurements because the light is AC powered.

After thinking more on this and about the exit light's behavior when you press it's test button, I started to think that this is not true, so I did a few tests.

The results of these tests are covered in the attached PowerPoint since I wanted to be able to explain my thought process and thought slides would be a better format.

A brief, three sentence summary is:
I set up one of the test station photodiodes with a 10-kΩ resistor in series, pointed the photodiode at the red LEDs through the sign's lettering, and observed the response of the photodiode by measuring the voltage drop across the resistor.
No changes in the voltage were seen for the red light from the EXIT sign.
With this, I think that the red light from the exit sign can be treated as a background noise and subtracted off of any measurement.

Since it is a lot of info, we can discuss it more in Monday's DSG - EIC DIRC meeting.

-Tyler


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