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Thanks Tyler and Brian,</div>
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<div style="color: rgb(0, 0, 0);"><font face="Calibri, Arial, Helvetica, sans-serif" size="3">Joe mentioned</font><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> that </span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; font-style: normal; font-variant-caps: normal; color: rgb(0, 0, 0);">old
SLAC setup used two Hewlett Packard HP 34401A multimeters, the</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> </span>
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<span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">current from the Hamamatsu silicone photodiode S1337-101BQ (</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; font-style: normal; font-variant-caps: normal; color: rgb(0, 0, 0);">the
same as the S2281) was typically 50-200microAmp for the</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> </span></p>
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<span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">resistor, using a 5V power supply.</span></p>
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<font face="Calibri, Helvetica, sans-serif">Fernando after looking at the specs pointed out:</font></p>
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<font face="Calibri, Helvetica, sans-serif"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">"</span></p>
<p style="margin:0.0px 0.0px 0.0px 0.0px;font:13.0px 'Helvetica Neue'"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">For the 325 nm line, their offerings range from 2 mW to 100 mW and the photodiode has a responsivity of ~0.15
A/W (@325 nm). The current range is then 300 uA to 15 mA; measuring voltage with a 50 Ohm load, the range is 15 mV to 750 mV and you can easily increase these values with a larger resistor.</span></p>
<p style="margin:0.0px 0.0px 0.0px 0.0px;font:13.0px 'Helvetica Neue'"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> </span></p>
<p style="margin:0.0px 0.0px 0.0px 0.0px;font:13.0px 'Helvetica Neue'"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">For the 442 nm line, their offerings range from 15 mW to 180 mW and the photodiode has a responsivity of ~0.25
A/W (@442 nm). The current range is then 3.75 mA to 45 mA; measuring voltage with a 50 Ohm load, the range is 190 mV to 2.25 V.</span></p>
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<font face="Calibri, Helvetica, sans-serif">Btw. can we add Joe to dsg-eic_dirc mailing list?</font></p>
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<font face="Calibri, Helvetica, sans-serif">Cheers,</font></p>
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<font face="Calibri, Helvetica, sans-serif">Greg</font></p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Tyler Lemon <tlemon@jlab.org><br>
<b>Sent:</b> Tuesday, September 27, 2022 7:47 AM<br>
<b>To:</b> Brian Eng <beng@jlab.org>; Grzegorz Kalicy <gkalicy@jlab.org><br>
<b>Cc:</b> dsg-eic_dirc@jlab.org <dsg-eic_dirc@jlab.org><br>
<b>Subject:</b> Re: [dsg-eic_dirc] Readout for the DIRC QA laser lab</font>
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For transimpedance amplifiers, the more simple, ~$1k option from Thorlabs looks to be their series designed for photodiodes (link below).<br>
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<a href="https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_ID=7083" id="LPNoLPOWALinkPreview">https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_ID=7083</a><br>
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The one "catch" with these is that the maximum rated input current is around 2 mA.</div>
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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.</div>
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Two PDA200C's<br>
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<a href="https://www.thorlabs.com/thorproduct.cfm?partnumber=PDA200C" id="LPNoLPOWALinkPreview_3">https://www.thorlabs.com/thorproduct.cfm?partnumber=PDA200C</a><br>
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One PRO800 with one PDA8000-2<br>
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<a href="https://www.thorlabs.com/thorproduct.cfm?partnumber=PRO800" id="LPNoLPOWALinkPreview_2">https://www.thorlabs.com/thorproduct.cfm?partnumber=PRO800</a><br>
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<a href="https://www.thorlabs.com/thorproduct.cfm?partnumber=PDA8000-2" id="LPNoLPOWALinkPreview_4">https://www.thorlabs.com/thorproduct.cfm?partnumber=PDA8000-2</a><br>
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Do you all have any records or anything on the current seen from the photodiodes from previous tests?</div>
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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).</div>
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-Tyler<br>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> Brian Eng <beng@jlab.org><br>
<b>Sent:</b> Monday, September 26, 2022 5:03 PM<br>
<b>To:</b> Grzegorz Kalicy <gkalicy@jlab.org><br>
<b>Cc:</b> Tyler Lemon <tlemon@jlab.org>; dsg-eic_dirc@jlab.org <dsg-eic_dirc@jlab.org><br>
<b>Subject:</b> Re: [dsg-eic_dirc] Readout for the DIRC QA laser lab</font>
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<div class="x_PlainText">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.<br>
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You can do a simple resistor, but you'll most likely run into noise/speed issues.<br>
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At the very least if you wanted to make a circuit yourself you'd want to do something with an op-amp.<br>
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Here's some slides with a pretty good overview of the issues with reading out a photodiode:<br>
<a href="https://e2e.ti.com/cfs-file/__key/CommunityServer.Discussions.Components.Files/14/4370.PhotodiodeAmplifers.pdf">https://e2e.ti.com/cfs-file/__key/CommunityServer.Discussions.Components.Files/14/4370.PhotodiodeAmplifers.pdf</a><br>
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And some circuit diagrams:<br>
<a href="https://www.ti.com/lit/an/sboa061/sboa061.pdf">https://www.ti.com/lit/an/sboa061/sboa061.pdf</a><br>
<a href="https://ww1.microchip.com/downloads/en/Appnotes/01494A.pdf">https://ww1.microchip.com/downloads/en/Appnotes/01494A.pdf</a><br>
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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.<br>
<br>
> On Sep 26, 2022, at 4:40 PM, Grzegorz Kalicy <gkalicy@jlab.org> wrote:<br>
> <br>
> Hi Tyler,<br>
> <br>
> Thanks a lot for quick feedback!<br>
> <br>
> 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:<br>
> <a href="https://www.thorlabs.com/drawings/d3c75d389e4cb97e-309FEEC9-C8A5-6AE6-44C9015816931D45/SM1PD2A-SpecSheet.pdf">
https://www.thorlabs.com/drawings/d3c75d389e4cb97e-309FEEC9-C8A5-6AE6-44C9015816931D45/SM1PD2A-SpecSheet.pdf</a>
<br>
> ?<br>
> 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?<br>
> <br>
> If we would indeed switch to voltage, what would you suggest? And you were right about reading out two channels.<br>
> <br>
> Cheers,<br>
> <br>
> Greg<br>
> From: Tyler Lemon <tlemon@jlab.org><br>
> Sent: Monday, September 26, 2022 12:22 PM<br>
> To: Grzegorz Kalicy <gkalicy@jlab.org>; dsg-eic_dirc@jlab.org <dsg-eic_dirc@jlab.org><br>
> Subject: Re: Readout for the DIRC QA laser lab<br>
> <br>
> Hi Greg,<br>
> <br>
> That is something that I can help out with.<br>
> <br>
> 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.<br>
> <br>
> With that, something like a Keithley Model 6482, dual-channel picoammeter could be helpful.
<br>
> <br>
> 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.<br>
> It's base cost is ~$6,500 according to their website<br>
> <br>
> Does this fit into what you're looking for in terms of "quick" and "relatively cheap"?<br>
> <br>
> <br>
> -Tyler<br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> From: Grzegorz Kalicy <gkalicy@jlab.org><br>
> Sent: Monday, September 26, 2022 1:24 PM<br>
> To: Tyler Lemon <tlemon@jlab.org><br>
> Subject: Readout for the DIRC QA laser lab<br>
> <br>
> Hi Tyler,<br>
> <br>
> 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?<br>
> <br>
> Cheers,<br>
> <br>
> Greg<br>
> _______________________________________________<br>
> dsg-eic_dirc mailing list<br>
> dsg-eic_dirc@jlab.org<br>
> <a href="https://mailman.jlab.org/mailman/listinfo/dsg-eic_dirc">https://mailman.jlab.org/mailman/listinfo/dsg-eic_dirc</a><br>
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