Fixed array: design

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Light guides for broadband hodoscope

material: UVT acrylic

length: 150 mm
thickness: 6mm
width: 22x 22mm, 18x 16mm, 24x 10mm, 185x 8mm

Concept:

  • The counters are positioned vertically, hanging from top with 30mm high scintillators (SC) centered at the focal plane.
  • The 15cm long light guides (LG) are fixed by two horizontal comb-like aluminum bars, i.e. two bars with comb-like slits of 8mm width separated vertically by 10cm, in which the wrapped LGs are (gently) pushed. The slits are cut away at such angles that the SCs face in the direction of the electron trajectory.
  • To ensure an accurate angular alignment of the SCs, the LGs have the same thickness (6mm) as the SCs. This also simplifies also the control of the gluing process because these 2 faces are visible while pressing the SC onto the LG. SCs of larger width (22, 16, 10, 8mm) will fit exactly onto the LG's face, the smaller SCs (5, 4, 3mm) will be centered onto the 8mm wide face of the LG by means of a mask.
  • LGs with larger cross section than the SC are more difficult to make light tight at the corners without using many layers of tape, which might obscure the upper part of the SC.
  • The upper 3cm of the LGs are cylindrical tops of 1" (2.54cm) diameter. The LG bars will be fixed in a 3mm deep slot in the center of the bottom face of the cylindrical top. The cylindrical top will lay (loosely) on the comb-like support, thus prevents the counters to sag.
  • The top face of the LG will be connected to the photocathode of the 1" PMT (Hamamatsu R9800) via a silicone cookie. PMT and cylindrical top of the LG will be covered by a 0.25mm thick mu-metal foil.
  • 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.


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