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====== TileCal LED tests ======

Here  is a data library with PMT signals with different attenuators. 
The dynamic rage is from 1 pC to 2000 pC. The data are collected using R5900 PMT with active dividers and 676 V, and a WLS fibre, Patrick's driver 
with 4 ns pulse width and David's LED setup.

The talk that describes this study is [[https://indico.cern.ch/event/441970/contribution/16/attachments/1162896/1675431/LEDResults.pdf| Studies of PMT block signal shapes using passive and active dividers, Tile upgrade week, Sep 30, 2015]]
 
Download the signal files from  [[https://atlaswww.hep.anl.gov/asc/phase2/data/]], and then gunzip  it. To make a plot for 1 trace, use

<code bash>
wget --no-check-certificate https://atlaswww.hep.anl.gov/asc/phase2/data/pmt_signals_phase2.tgz -O - | tar -xz;
cd pmt_signals_phase2/
python show_trace.py data/D1_traces_full.txt.gz 1 # show 1st trace out of 1000
</code>

We used several 50% (0.3) neutral density filters (NDF50), and 1 neutral density filter x16 (NDF16).
Data files with traces are  in "data/*". There are 1000 traces in each file.
The file names has a letter "D" that indicates attenuation strength for the light.

  - D1 NDF16 + 6xNDF50. Reduction of light by 6*2*16. About 0.3 pc -> x1024
  - D2 NDF16 + 5xNDF50 -> x512
  - D3 NDF16 + 4xNDF50 -> x256
  - D4 NDF16 + 3xNDF50 -> x128
  - D5 NDF16 + 2xNDF50 -> x64
  - D6 NDF16 + 1xNDF50 -> x32
  - D7 NDF16  (light reduction by a factor 16) -> x16
  - D8 3xNDF50 -> x8
  - D9  2xNDF50 -> x4
  - D10 1xNDF50  (light reduction by a factor 2) -> x2
  - D11  - no NDF. About 2000 pC ->0

Figures for 1000 traces are in "figures".  Each trace was centralized at time=0. We use a numeric noise suppression for all traces as shown in this image.

{{:noise.png}}

Blue lines show traces before the noise removal, and small grey dots after the noise suppression. The green dots show the noise in the LED driver.

 --- //[[chekanov@anl.gov|Sergei Chekanov]] 2015/07/17 14:00//
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