Specification for pair spectrometer hodoscopes

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The following paragraphs describe the pair spectrometer hodoscope in Hall B (Primex spectrometer). Electrons and positrons produced in a thin converter foil and deflected in the 1.5Tm dipole magnet are momentum analyzed using a symmetric set of 32 scintillators on each side. The scintillators are positioned in two layers of 16 counters each allowing for front-back coincidences.

  • scintillator size:
   front: 2.4 cm wide, 7.5 cm long, 0.5 cm thick 
   back: 3.9 cm wide, 9.3 cm long, 2.0 cm thick
  • PMTs: front: Hamamatsu R6427, back:

Hamamatsu R580-17 (with <mu>-metal shielding).

  • Scintillator, light guides, and PMT are glued with optical cement.

Counter arrangement for Primex spectrometer (by Mike Zarecky) Pair-counters.gif