[dsg-eic_dirc] Readout for the DIRC QA laser lab

[Grzegorz Kalicy]

Hi Tyler,

Thanks a lot for quick feedback!

I think we would like to change readout to voltage, it seems to be easier to handle. One person suggested I need a transimpedance amplifier for that but other said a simple resistor suffices... would it be part of the circuit from page 2 in spec:
https://www.thorlabs.com/drawings/d3c75d389e4cb97e-309FEEC9-C8A5-6AE6-44C9015816931D45/SM1PD2A-SpecSheet.pdf
?
 It seems 5V is required only for pulsed lasers and I have constant wave so we can just ground the cathode. Could we solder these circuits at JLab?

If we would indeed switch to voltage, what would you suggest? And you were right about reading out two channels.

Cheers,

Greg
________________________________
From: Tyler Lemon <tlemon at jlab.org>
Sent: Monday, September 26, 2022 12:22 PM
To: Grzegorz Kalicy <gkalicy at jlab.org>; dsg-eic_dirc at jlab.org <dsg-eic_dirc at jlab.org>
Subject: Re: Readout for the DIRC QA laser lab

Hi Greg,

That is something that I can help out with.

>From the specs of the photodiodes and laser, it looks like the maximum current we can expect (if everything is perfect and everything behaves ideally) is ~12 mA when the 442-nm wavelength is used. It also looks like we'll have two photodiodes to measure at the same time during tests.

With that, something like a Keithley Model 6482, dual-channel picoammeter could be helpful.

This picoammeter has a readout range of 1 fA - 20 mA and also has built-in GPIB and RS-232 interfaces for remote control in addition to a local readout screen.
It's base cost is ~$6,500 according to their website

Does this fit into what you're looking for in terms of "quick" and "relatively cheap"?


-Tyler









________________________________
From: Grzegorz Kalicy <gkalicy at jlab.org>
Sent: Monday, September 26, 2022 1:24 PM
To: Tyler Lemon <tlemon at jlab.org>
Subject: Readout for the DIRC QA laser lab

Hi Tyler,

As I mentioned some time ago I'm trying to avoid unnecessarily complicated readout for photodiodes that we used in original setup in GSI. However, I'm struggling a bit with finding best option (quick, relatively cheap, and useable later for final automatized setup version). Who in DSG I could reach out for advise?

Cheers,

Greg
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