Fixed array: design

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Scintillators for broadband hodoscope

material: EJ-228

height: 33mm (3mm slotted into bottom face of LG)
thickness: 6mm
width: 22x 21mm, 18x 16mm, 24x 10mm, 17x 8mm, 58x 5mm, max. 36x 4mm, max. 67x 3mm
(the max. numbers account for positioning of the microscope with coh.edge at 9.1 to 7.9 GeV).

Light guides for broadband hodoscope

(update 4/22/2013)

material: UVT acrylic

cylinder (diameter: 22.2mm, length: 100 mm)
(6mm wide and 3mm deep slot on bottom face)


  • The counters are positioned vertically, hanging from top with 30mm high scintillators (SC) centered at the focal plane.
  • NEW: 10cm long light guides (LG) are fixed by a nylon collar bolted to a horizontal 1/2" aluminum plate. The screw holes in the al. plate are drilled at positions that ensure that the SCs face in the direction of the electron trajectory. The bottom face of the LG is slotted (width 6mm) to fit the thickness of the SC (ensuring that the SC are accurately glued to the LG).
  • The top face of the LG will be connected to the photocathode of the 1" PMT (Hamamatsu R9800) via a silicone cookie (or air gap). PMT and top part of the LG will be covered by a mu-metal cylinder (separated from the PMT by one layer of felt).
  • The back face of the PMT should be covered by a light tight paint such that voltage divider and preamplifier do not have to be tightly covered.

Pmt.gif     LG+collar.gif

Example: 1m long module containing the counters at 6.73 < Eel < 8.0 GeV