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

[Tyler Lemon]

For transimpedance amplifiers, the more simple, ~$1k option from Thorlabs looks to be their series designed for photodiodes (link below).

https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_ID=7083

The one "catch" with these is that the maximum rated input current is around 2 mA.

There are some benchtop options (links below) that allow up to 10 mA, but that also comes with a bigger $2k - $3.5k price tag for reading out two photodiodes.

Two PDA200C's
https://www.thorlabs.com/thorproduct.cfm?partnumber=PDA200C

One PRO800 with one PDA8000-2
https://www.thorlabs.com/thorproduct.cfm?partnumber=PRO800
https://www.thorlabs.com/thorproduct.cfm?partnumber=PDA8000-2



Do you all have any records or anything on the current seen from the photodiodes from previous tests?

The ~12 mA I mentioned earlier was calculated using specs from the laser manufacturer's tests and the photodiode manual. After talking to Brian, 12 mA seems high for photodiodes. I can't really think of a way to actually find out the currents we'll see without setting up the laser (we can't do this yet since the safety documentation is in progress).

-Tyler
________________________________
From: Brian Eng <beng at jlab.org>
Sent: Monday, September 26, 2022 5:03 PM
To: Grzegorz Kalicy <gkalicy at jlab.org>
Cc: Tyler Lemon <tlemon at jlab.org>; dsg-eic_dirc at jlab.org <dsg-eic_dirc at jlab.org>
Subject: Re: [dsg-eic_dirc] Readout for the DIRC QA laser lab

I think Tyler mentioned that particular Keithley because we've used it before for doing small current measurements on silicon sensors for the CLAS12 SVT. I don't know what its availability would be for use in the DIRC test setup.



You can do a simple resistor, but you'll most likely run into noise/speed issues.

At the very least if you wanted to make a circuit yourself you'd want to do something with an op-amp.

Here's some slides with a pretty good overview of the issues with reading out a photodiode:
https://e2e.ti.com/cfs-file/__key/CommunityServer.Discussions.Components.Files/14/4370.PhotodiodeAmplifers.pdf

And some circuit diagrams:
https://www.ti.com/lit/an/sboa061/sboa061.pdf
https://ww1.microchip.com/downloads/en/Appnotes/01494A.pdf



A transimpedance amplifier is what I'd go with rather than spending the time/effort trying to develop a circuit in house, with the caveat that the output of the photodiode needs to verified as most of those don't handle a lot of current. Once it is a voltage output there are all sorts of ways to read that into whatever the DAQ system ends up being.

> On Sep 26, 2022, at 4:40 PM, Grzegorz Kalicy <gkalicy at jlab.org> wrote:
>
> 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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