[Dsg-rich] Reflectivity test station - alignment tests

[Valery Kubarovsky]

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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