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

[Tyler Lemon]

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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