[Dsg-rich] RICH - reflectivity test station calibration stability results

[Marco Mirazita]

Hi all,
I did some plots of the data you took, it seems in fact that the system 
is very stable if nobody touches anything. From the plots, we can assume 
about +/-1% systematic uncertainty.
There are a couple of things I forgot to mention in the measurement 
plan:
- Did you ever turn off the lamp after each measurements? Did you take 
note of the voltage supplied to the lamp?
- Did you ever turn off the picoamperometer? Did you redo the zeroing 
before the measurements?
I think we can now move to step 2 of the plan, that I copied below.
Thank you to everybody,
Marco

2) Verification of the stability of the reflectivity measurements using 
the control mirror
Repeat the cycle of calibration and reflectivity mesurerement few times 
during one day:
- align the system for the calibration run
- take calibration data
- install the control mirror and align the system for reflectivity run
- take a reflectivity run
Once the mirror has been installed the first time, it should not be 
touched anymore for the next measurements, the alignment procedures 
should involve only the photodiode B. Again, please take note of the 
times.
==>> For each measurement, take also note of the lamp voltage supply.  
<<==


Il 2017-07-19 13:00 Mindy Leffel ha scritto:
> I see highlighting:
> 
> On 7/18/2017 6:28 PM, Amrit Yegneswaran wrote:
> 
>> good work tyler.
>> 
>> w.r.t. line #8: (see below, i reformatted your e-mail), i don't see
>> any highlighting in the excel sheet.
>> don't understand where you come up with the <1% error you quote?
>> 
>> fix your significant figures, do let excel decide!
>> 
>> w.r.t. line #13: perhaps initially the calibration may be dependent
>> (you didn't take a measurement as soon as you turned it on, did
>> you?), but once the lamp has warmed up, the calibration doesn't
>> change.
>> 
>> finally, calculate the confidence level of your measurement.
>> 
>> amrit
>> 
>> am
>> 
>> w.r.t. #13
>> 
>> -------------------------
>> 
>> FROM: "Tyler Lemon" <tlemon at jlab.org>
>> TO: "dsg-rich" <dsg-rich at jlab.org>
>> SENT: Tuesday, July 18, 2017 4:43:39 PM
>> SUBJECT: [Dsg-rich] RICH - reflectivity test station calibration
>> stability results
>> 
>> Hello Marco Mirazita,
>> 
>> * Attached in "_2017-07-18_calibration_stability_tests.xlsx_" are
>> the results from today's calibration stability of the reflectivity
>> test station.
>> * In the Excel sheet, there is a table of all the raw data for the
>> calibration runs.
>> 
>> * At the end of the data, there are statistics for the data.
>> * For the stability test, we turned on the lamp source at 8:00AM
>> to allow it to heat up.
>> * We aligned the test station's optics for a calibration run and
>> took data on every hour starting at 10:00AM until 4:00PM (total of
>> seven calibration runs).
>> 
>> * After the initial alignment, the dark box was not opened and the
>> position of the photodiodes was not changed.
>> * The results support that the calibration measurements do not
>> vary over the course of a few hours if the test set-up is not
>> modified in any way.
>> * The calibrations for each wavelength has a calculated error of
>> less than 1%, with the exception of the 300nm wavelenth (highlighted
>> in yellow).
>> 
>> * The 300nm-wavelength calibration results from 10:00AM are also
>> highlighted in yellow. This measurement seems to be the source of
>> the larger error for the 300nm wavelength calibration.
>> * Also attached in "_all_calibrations.xlsx_" is data for all
>> calibrations we used for all reflectivity tests, including the ones
>> from today.
>> * The data is arranged in the same way as the stability test
>> results with statistics at the end.
>> 
>> * Using all calibration run data, the calculated error of the
>> calibration is much higher (~10% to ~17%). This most likely is due
>> to the realignment that takes place between calibrations and between
>> the testing of mirrors.
>> * In conclusion, the calibration does not seem to depend on the
>> amount of time the lamp source is on.
>> 
>> * Using the data from all calibrations, the main source of error
>> appears to be the realignment of test station optics.
>> 
>> Best regards,
>> 
>> Tyler
>> 
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> 
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