[Dsg-rich] Reflectivity test station - alignment tests

[Valery Kubarovsky]

> From: "Valery Kubarovsky" <vpk at jlab.org>
> To: "mirazita" <Marco.Mirazita at lnf.infn.it>
> Cc: dsg-rich at jlab.org
> Sent: Thursday, July 20, 2017 10:17:08 AM
> Subject: Re: [Dsg-rich] Reflectivity test station - alignment tests

> Marco,
> I attached the deuterium source spectrum of the lamp that we are using for the
> reflectivity test.
> As you see the intensity of our lamp is order of magnitude HIGHER at low
> wavelength.

> Regards,
> Valery

>> From: "mirazita" <Marco.Mirazita at lnf.infn.it>
>> To: dsg-rich at jlab.org
>> Sent: Thursday, July 20, 2017 9:13:40 AM
>> Subject: Re: [Dsg-rich] Reflectivity test station - alignment tests

>> Hi Tyler,
>> thank you for the data.
>> I attached some analysis of the these data.
>> The phodiode readout variations are much bigger than yesterday, but at
>> the end I estimated a systematic uncertainty on the reflectivity of
>> about +/-2% above 400 nm.
>> This is acceptable.
>> At lower wavelengths, the variations are bigger, but that's because the
>> intensity of the lamp is order of magnitudes smaller.

>> It would be nice if you could redo the same series of measurements on
>> one of the carbon fiber samples.

>> Marco

>> Il 2017-07-19 22:56 Tyler Lemon ha scritto:
>> > Hello,

>> > Attached is an Excel sheet containing the results from today's
>> > alignment tests of the reflectivity tests station. The sheet contains
>> > the three data sets for separate calibration and reflectivity tests of
>> > the control mirror. After the three sets of results, there are
>> > statistics showing the mean photodiode currents, reflectivity, and
>> > percent error for a wavelength.

>> > The procedure for taking each measurements was:

>> > 1.) Align test station to take calibration run.

>> > 2.) Take calibration run.

>> > 3.) Re-align test station to measure mirror.

>> > 4.) Take mirror measurement run.

>> > Between measurements, we noted that the lamp power remained at 10.65V
>> > and 3.84A. We did not turn the lamp or picoampmeter off between
>> > measurements.

>> > The calculations at the end of the data show that there is a higher
>> > error of all measurements compared to yesterday's tests when the test
>> > station was not modified between measurements. Yesterday, the errors
>> > for calibrations were under 1%. Today, the errors for calibrations
>> > were about 6%. There are some exceptions at smaller wavelengths (300nm
>> > - 400nm) where the error for the calibration is greater.

>> > The calculations also show that the control mirror's reflectivity
>> > measurements had an error of about 6% for most wavelengths. Again,
>> > there are some exceptions for reflectivity measurements at smaller
>> > wavelengths (300nm - 420nm) where the error for the reflectivity was
>> > greater. One major exception was that the reflectivity measurement at
>> > 420 nm had an error of ~20%. This measurement is highlighted in orange
>> > in the table.

>> > In conclusion, today's results further support that the main source of
>> > error in the test station is in how repeatable the test station
>> > optics's alignment is between data runs.

>> > Best regards,

>> > Tyler


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