[dsg-hallb_rich] [EXTERNAL] Re: More d0 tests of mirror 5C

[Marco Mirazita]

Hi Tyler,
one possible reason why you don't the d0 vs z curve when you covered the 
edges of the mirror could be because the white foam you used is 
reflecting the light everywhere. You should use something black.
Marco



Il 2021-10-11 21:00 Tyler Lemon ha scritto:
> Hello,
> 
>  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.
> 
>  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
> 
> 
> https://www.jlab.org/physics/dsg/technical_documentation/hall_b/rich/mirror_data
> 
> 
>  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).
> 
>  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.
> 
>  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.
> 
>  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.
> 
>  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).
> 
>  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.
> 
>  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.
> 
>  Thanks,
>  -Tyler
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