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Hello,</div>
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This morning, Mindy and I repeated d0 measurements with mirror 5C taking some of the considerations discussed in last week's collaboration meeting. Below is a (pretty long) summary of what we did.<br>
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The raw data (and also the raw data from previous tests) have been posted at the link below under "October 11, 2021". The files are password protected with the username DSG and password RICH2mirrors<br>
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<a href="https://www.jlab.org/physics/dsg/technical_documentation/hall_b/rich/mirror_data" id="LPlnk906248">https://www.jlab.org/physics/dsg/technical_documentation/hall_b/rich/mirror_data</a></div>
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To maybe give an indicator of how some areas of the mirror surface look, attached is a photo of an area of the surface that looks to not be of very high quality (photo 1).<br>
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The first thing we did was to ensure that the test set up is properly aligned. Results for this are all in the subdirectory "01_realign" This was done by taking the alignment laser pointer and collimators to ensure the beam from the CCD stand is parallel to
the z-axis of the CCD stand (CCD stand set up in attached photo 2, resulting alignment on mirror stand in photo 3). This didn't seem to have any effect on the measurements and gave the same result as before.</div>
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The second thing we did was increasing the intensity of the source light using the sources trim potentiometer. These results are in the subdirectory "02_source-int-adjust". This also did not seem to have a significant effect on the data.</div>
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At this point we tried to cover the edges of the mirror as suggested by Marco C. We did this by cutting a hole in the foam packaging material the mirror is stored in and placing the foam on to the mirror (photo 4). The results for this situation are in the
directory "03_center-only". The results for this situation were not good at all and we did not get a d0-vs-z fit plot that is in line with previous measurements. We'll try this again in the future, but I included the data from this test just as an indicator
that we tried something.<br>
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<span style="font-size:12pt">For all three situations we tried above, we took several background measurements before and after the d0 procedure. In total, throughout the measurement session, we took ~30 backgrounds. I took all of these background files and
plotted their data as histograms, which resulted in a plot of ~30 histograms that all overlap in the same general area of the plot (photo 5).
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Is there any thing else we should try with the d0 measurements? If there is a procedure on how we should polish the source's fiber, please let us know so we can try that.</div>
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In the Friday meeting, we talked about the initial prototype of the spherical mirrors and how those d0 measurements looked. Do we still have that raw data? If so, we can try measuring that mirror again and comparing results to the original measurement to further
verify whether the test station is working as expected.</div>
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Thanks,</div>
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-Tyler<br>
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