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Okay,</div>
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I'll take a look at automating the two integration time measurements</div>
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-Tyler<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Marco Mirazita <Marco.Mirazita@lnf.infn.it><br>
<b>Sent:</b> Thursday, April 28, 2022 12:26 PM<br>
<b>To:</b> Tyler Lemon <tlemon@jlab.org><br>
<b>Cc:</b> dsg-hallb_rich@jlab.org <dsg-hallb_rich@jlab.org><br>
<b>Subject:</b> Re: [dsg-hallb_rich] [EXTERNAL] Re: Mirror reflectivity source around 400nm</font>
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<div class="PlainText">Even better would be to have some overlap between the two measurements
<br>
to be able to check systematics, say the first one up to 450 and the <br>
second one from 350.<br>
Marco<br>
<br>
<br>
Il 2022-04-28 17:30 Marco Mirazita ha scritto:<br>
> Hi Tyler,<br>
> you could split the measurement in two parts, first part up to 400 nm<br>
> with one setting and second part above 400 nm with another setting.<br>
> Marco<br>
> <br>
> <br>
> Il 2022-04-28 16:55 Tyler Lemon ha scritto:<br>
>> Hi Marco Mirazita,<br>
>> <br>
>> Over the past week, I've tried to get measurements with the<br>
>> reflectivity test station at lower wavelengths so we can get data<br>
>> around 400 nm for the RICH mirrors.<br>
>> <br>
>> With the source we have, we can measure ~400 - 600 nm wavelengths if<br>
>> the integration time of the spectrometers is increased. However, as a<br>
>> consequence of the higher integration time, the spectrometer CCD is<br>
>> saturated above ~600 nm. Also, the counts observed around 400 nm is<br>
>> still relatively low. Attached is a plot (NEW reference-AVG.png) of<br>
>> the spectrometer counts of the reference light showing this.<br>
>> <br>
>> This behavior is due to the nature of the quartz-tungsten halogen<br>
>> (QTH) lamp used for the source. While the source does output some<br>
>> light (as specified) down to 360 nm, it has the highest intensity<br>
>> around 850 nm.<br>
>> <br>
>> Looking back at the data from RICH-1, we see the same behavior of the<br>
>> old test station, which also uses a QTH lamp. Attached is a plot<br>
>> (photodiode A by mirror and date.pdf) of current measurements from the<br>
>> control photodiode (the equivalent of the reference light in the new<br>
>> test station) for four mirror measurements taken in 2017 and we see<br>
>> the same general shape as the data from the new test station.<br>
>> <br>
>> With this, it's apparent that the light source in the new test<br>
>> station is comparable to the light source in the old test station.<br>
>> <br>
>> To be able to get more counts at lower wavelengths, we could try<br>
>> getting a filter that only passes the lower wavelength light so we can<br>
>> use higher spectrometer integration times resulting in more counts.<br>
>> Something like the Thorlabs 450-nm cutoff shortpass filter [1] or<br>
>> Newport 450-nm cutoff shortpass filter [2] would be compatible with<br>
>> our source's built-in filter holder.<br>
>> <br>
>> -Tyler<br>
>> <br>
>> <br>
>> Links:<br>
>> ------<br>
>> [1] <br>
>> <a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__www.thorlabs.com_thorproduct.cfm-3Fpartnumber-3DFESH0450&d=DwICAg&c=CJqEzB1piLOyyvZjb8YUQw&r=Ry65GV1L9CI4W-wouYF1Yh0O9PuhLc4ZWUkBi_Op2h8&m=eBTvltLnRWdaj4opfLzlg03ZsIP_RohM4p5I05aADP7UbYASf58bYXuJCj5M6Syx&s=zcAke1YTtfwPG-KUmNVJGfpXA1No1aSDkI1MOgiGJGQ&e=">
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.thorlabs.com_thorproduct.cfm-3Fpartnumber-3DFESH0450&d=DwICAg&c=CJqEzB1piLOyyvZjb8YUQw&r=Ry65GV1L9CI4W-wouYF1Yh0O9PuhLc4ZWUkBi_Op2h8&m=eBTvltLnRWdaj4opfLzlg03ZsIP_RohM4p5I05aADP7UbYASf58bYXuJCj5M6Syx&s=zcAke1YTtfwPG-KUmNVJGfpXA1No1aSDkI1MOgiGJGQ&e=</a>
<br>
>> [2] <br>
>> <a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__www.newport.com_p_10SWF-2D450-2DB&d=DwICAg&c=CJqEzB1piLOyyvZjb8YUQw&r=Ry65GV1L9CI4W-wouYF1Yh0O9PuhLc4ZWUkBi_Op2h8&m=eBTvltLnRWdaj4opfLzlg03ZsIP_RohM4p5I05aADP7UbYASf58bYXuJCj5M6Syx&s=EzRVgEqoTzidU2qCllJyBp2M9gUk-_Pnq3KfiJmT_4w&e=">
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.newport.com_p_10SWF-2D450-2DB&d=DwICAg&c=CJqEzB1piLOyyvZjb8YUQw&r=Ry65GV1L9CI4W-wouYF1Yh0O9PuhLc4ZWUkBi_Op2h8&m=eBTvltLnRWdaj4opfLzlg03ZsIP_RohM4p5I05aADP7UbYASf58bYXuJCj5M6Syx&s=EzRVgEqoTzidU2qCllJyBp2M9gUk-_Pnq3KfiJmT_4w&e=</a>
<br>
>> _______________________________________________<br>
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> <br>
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