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

[Marco Mirazita]

Hi Tyler,
I attached plots for the two sets of measurements 01 and 02.
Both show a problem in the bkg subtraction, the 02 less than the 01. 
This could hopefully be because 02 has a shorter exposition time.
I suggest to try a measurement with exposition time 0.5 ms, increasing 
the light source intensity if it is necessary and possible.
Then, few questions
- which background did you subtract in these two sets of measurements?
- what are you showing exactly in your photo5?
- can you post in your web page the code to do the analysis of the data 
(subtract the bkg, make the root files, etc)?
- do you know if it is possible to access the location of your web page 
from ifarm or jlabl1? Today it took hours for me to download all the 
data from the web page (and then I had to copy back everything to the 
farm!).
Marco




Il 2021-10-12 12:52 Marco Mirazita ha scritto:
> 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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