Plastic scintillator studies for future bb experiments

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Plastic scintillator studies for future bb
experiments

• Ruben Saakyan
• University College London
• IDEA meeting
• Zaragoza
• 7-8 November 2005

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Motivation

• At least one of future bb experiments should be a
  tracking calorimeter
• SuperNEMO
• MOON
• A combination of the two?
• .
• Plastic scintillators is a good candidate
• Cheap (large quantities will be needed)
• Good timing resolution
• Surface contamination measurement
• Main task of RD to improve DE/E

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Plastic scintillator strips
Advantages

• Long strip ( 2m) read from both end removes
  PMTs from the sensitive part of the detector
  good background wise for bb and radioactivity
  measurements
• Especially for isotopes with long T1/22n
• 130Te, 136Xe, 82Se
• Fewer PMT channels

Standard readout method

• Continuation of successful studies of plastic
  scintillator blocks funded by PPARC (seed corn
  money)
• Standard method of WLS readout will not work
  for our needs (impossible to get more than 40-50
  p.e./MeV)

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ILIAS money spent for the project
Item Cost, euro
Plastic scintillator strips PVT, Bicron, BC404, BC408 2mx10cmx2cm (incl. cutting to size/machining) 4300
2 ETL, 5 photomultipliers PMT bases 2600
Other (light-tight housing,travel) 300
Total Overheads Total 7200 1500 8700
Total award 19200
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The Setup
Left PMT
Right PMT
20cm
40cm
60cm
80cm
100cm
-20cm
-40cm
-60cm
-80cm
-100cm
0
0
207Bi
AND/OR
Scintillator material polyvinyltoluene
(PVT) from Bicron
Existing DAQ electronics (CAMACNIM) and 207Bi
source used
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The Method
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The measurement
Subtracted electron spectra (sum from both ends)
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Single sided readout
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L/R ratio. Attenuation length.
Effective attenuation length 170 cm
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Energy resolution
400 p.e.
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Can we use timing from 2 pmts to reconstruct
Z-coordinate?
(Rpmt Lpmt) time difference as a function of
the source position
Can reconstruct the position of the source within
5cm (inclusive measurement)
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Time resolution
s 1ns
9 cm
The resolution is mainly determined by compton
electrons from gammas. If e-like events can be
identified the timing resolution should improve a
lot and 5-10 cm accuracy (3s) might be
reachable. An interesting possibility for
background rejection
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Summary

• At least DE/E 11 _at_ 1MeV (FWHM) is achievable
  with plastic scintillator strips of 2m.
• Further improvements are likely to be possible
  with modest RD
• Reflective coating
• Scintillator-PMT coupling
• Z-reconstruction can be used for background
  rejection
• Simulations are needed to determine requirements
  (DE/E, Dt/t etc)for a particular bb experiment
  or contamination measurement
• How to integrate this work into IDEA official
  activities