Introduction

Initially, the photomultiuplier 7980 was identified as a photomultiplier with a good performance, i.e. a good separation between the SER and the pedestal. We then proceeded to measure the photon yield of a few of the scintillators with this photomultiplier.

Later, one of the UV sensitive photomultipliers was made available (PMT 6094) which had a significantly better performance, as expected, so the final results were obtained with this photomultiplier.

The scintillators were set up in the middle of a coincidence of another two scintilators. In this way, once there was a coincidence we could be sure that there was a cosmic muon going between the two coincidence scintillators and consequently, nearly certain it would be going through the scintillator under measurement. The charge produced by the PMT is then proportional to the number of photons that the PMT receives. This number of photons is effectively convoluted by the single electron response (previously measured: PhotomultiplierSER). By operating the PMT at the same voltage as when the SER was measured, the two effects can be decorrelated and an estimate of the number of photons received by the photomultiplier is obtained.

Consequently, the charge produced by the PMT when a cosmic muon triggers the coincidence is registered. These values are accumulated and produce a histogram which is subsequently fitted with a generic gaussian (to allow for the non-zero skewness). The mean/median/mode of the gaussian are then compared to the mean of the single electron response, resulting in the average number of photons received by the PMT.

All the code performing the analysis can be found on the daquser account. The code was written in jupyter under SWAN (swan.cern.ch) using cernbox as the storage. All files were placed under the swan directory: ~/labdata/2018/lab11/PMTs/, in particular note the jupyter notebook called AnalyzeScints.ipynb. The cernbox space corresponds to an eos mounted space which can easily be accessed from lxplus. The cernbox/swan home directory corresponds to the path: /eos/user/d/daquser. Consequently, the directory above can be accessed through: /eos/user/d/daquser/labdata/2018/lab11/PMTs/ and the jupyter notebook at /eos/user/d/daquser/labdata/2018/lab11/PMTs/AnalyzeScints.ipynb. However, it is best to access the jupyter notebooks through SWAN or CERNBOX in order to adequately see the contents.

Notes

Below SC1 corresponds to SCL1 and SC2 corresponds to SCL3.


PMT 7980

Single electron response @ 2200V

PM7980_2200.png

  • SER mean: $-5.49\times10^{-11}$
  • Pedestal mean: $1.10\times10^{-11}$

Single electron response @ 2250V

PM7980_2250.png

  • SER mean: $-8.34\times10^{-11}$
  • Pedestal mean: $1.09\times10^{-12}$

Number of photons

Scintillator Comment Voltage Histogram Mean Median Mode
SC1 Bad alignment 2200 SC1_PM7980_2200.png $-9.24\times10^{-9}$ ($168.5 \gamma$) $-8.63\times10^{-9}$ ($157.2 \gamma$) $-7.60\times10^{-9}$ ($138.4 \gamma$)
SC1 Fixed alignment 2200 SC1_2_PM7980_2200.png $-9.76\times10^{-9}$ ($177.8 \gamma$) $-8.88\times10^{-9}$ ($161.8 \gamma$) $-7.52\times10^{-9}$ ($137.1 \gamma$)
SC2   2200 SC2_PM7980_2200.png $-5.04\times10^{-9}$ ($91.8 \gamma$) $-4.61\times10^{-9}$ ($84.1 \gamma$) $-3.92\times10^{-9}$ ($71.4 \gamma$)
SC1   2250 SC1_PM7980_2250.png $-1.40\times10^{-8}$ ($168.3 \gamma$) $-1.27\times10^{-8}$ ($152.6 \gamma$) $-1.07\times10^{-8}$ ($128.8 \gamma$)

PMT 6094

Single electron response @ 1625V

PM6094_1625.png

  • SER mean: $-4.73\times10^{-11}$
  • Pedestal mean: $-1.21\times10^{-12}$

Single electron response @ 1650V

PM6094_1650.png

  • SER mean: $-5.42\times10^{-11}$
  • Pedestal mean: $1.44\times10^{-12}$

Number of photons

Scintillator Comment Voltage Histogram Mean Median Mode
SC1   1625 SC1_PM6094_1625.png $-1.12\times10^{-8}$ ($238.6 \gamma$) $-1.04\times10^{-8}$ ($220.1 \gamma$) $-9.07\times10^{-9}$ ($191.8 \gamma$)
SC2   1625 SC2_PM6094_1625.png $-3.93\times10^{-9}$ ($83.2 \gamma$) $-3.66\times10^{-9}$ ($77.4 \gamma$) $-3.21\times10^{-9}$ ($67.8 \gamma$)
isoTDAQ There is no visible pedestal because of geometry. Also had to use a different fit function, therefore no median. 1625 isoTDAQ_PM6094_1625.png $-1.23\times10^{-9}$ ($26.0 \gamma$) NA $-1.13\times10^{-9}$ ($23.8 \gamma$)


-- CristovaoDaCruzESilva - 2018-07-31

Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng PM6094_1625.png r1 manage 24.4 K 2018-06-22 - 15:04 CristovaoDaCruzESilva Response of PMT 6094 @ 1625 V, fitted
PNGpng PM6094_1650.png r1 manage 24.8 K 2018-06-22 - 15:04 CristovaoDaCruzESilva Response of PMT 6094 @ 1650 V, fitted
PNGpng PM7980_2200.png r1 manage 26.8 K 2018-06-22 - 14:36 CristovaoDaCruzESilva Response of PMT 7980 @ 2200 V, fitted
PNGpng PM7980_2250.png r1 manage 26.9 K 2018-06-22 - 14:44 CristovaoDaCruzESilva Response of PMT 7980 @ 2250 V, fitted
PNGpng SC1_2_PM7980_2200.png r1 manage 32.6 K 2018-06-22 - 15:52 CristovaoDaCruzESilva Response of SC1 with PM7980 @ 2200 (fixed alignment)
PNGpng SC1_PM6094_1625.png r1 manage 30.8 K 2018-07-31 - 11:31 CristovaoDaCruzESilva Response of SC1 with PM6094 @ 1625
PNGpng SC1_PM7980_2200.png r1 manage 26.8 K 2018-06-22 - 15:51 CristovaoDaCruzESilva Response of SC1 with PM7980 @ 2200
PNGpng SC1_PM7980_2250.png r1 manage 32.6 K 2018-06-22 - 16:00 CristovaoDaCruzESilva Response of SC1 with PM7980 @ 2250
PNGpng SC2_PM6094_1625.png r1 manage 28.1 K 2018-07-31 - 12:58 CristovaoDaCruzESilva Response of SC2 with PM6094 @ 1625
PNGpng SC2_PM7980_2200.png r1 manage 27.3 K 2018-06-22 - 15:52 CristovaoDaCruzESilva Response of SC2 with PM7980 @ 2200
PNGpng isoTDAQ_PM6094_1625.png r1 manage 23.7 K 2018-07-31 - 11:40 CristovaoDaCruzESilva Response of isoTDAQ with PM6094 @ 1625
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