Disc Cherenkov Counter

-- KlausFoehl - 25 Apr 2006

Detector thickness in the active angular range: 10mm (or similar), fused silica with specific weight 2.2g/cm3, about 9% radiation length. The Li_F material in the solenoid shadow requires moderate precautions against radiation, a Japanese supplier website states.

In the latest PANDA drawing (2006-4-24) there seems to be too little space foreseen to accomodate the focussing lightguide plus photon detectors part of this PID device.

  • 3.5sigma boundaries for pi-K-separation:
    3.5sigma boundaries for pi-K-separation
  • kfpanda12l.eps: eps separation calculation

This calculation is based on an early 2005 design where the disc radius is 50% larger than the 22 degrees limit. No finished calculation yet for the current lightguide, but on the 25 degrees side I expect the black line to drop to 4GeV/c because of the disc edge being closer to the 22/25degrees radius.

Line starting at 5 degrees shows the effect of a circular hole. Green line the entire focal plane is covered with photon detector pixels, black line only part of it, and also using two different pixel sizes, alltogether 3072 pixel. Red line is lower limit for kaon ID, onset of total reflection for kaon Cherenkov light.

Fused silica (blue) disc, LiF (magenta) plate and fused silica lightguide typically 100mm thick. Side view, numbers given in mm. This version using a 4th-order polynomial focusses to better than 1mm (max distance) in the plane shown and certainly can still be optimised a wee bit further.

One surface has cylindrical (1-dim) curvature, this should be feasible to machine with CNC, all other surfaces are flat. All light reflections are total internal reflections.

There are three optical joints, two are fused silica-LiF, the third is fused silica-PMT glass. If the disc is cooled to the temperature of the surrounding detectors (EMC in particular), the expansion coefficents do not differ too much and the glue can take the strain without affecting the optical properties, transmission in particular.

The magnetic field in this area is in the order of 0.2Tesla, one has a few options in orienting the phototubes, but then magnetic shielding might be required nevertheless.

Topic attachments
I Attachment Action Size Date Who Comment
curvedx3m05x4m01c.epseps curvedx3m05x4m01c.eps manage 10.0 K 25 Apr 2006 - 13:59 KlausFoehl eps figure lightguide
curvedx3m05x4m01c.gifgif curvedx3m05x4m01c.gif manage 8.2 K 25 Apr 2006 - 13:38 KlausFoehl design suggestion for a curved lightguide
curvedx3m05x4m01c_.gifgif curvedx3m05x4m01c_.gif manage 4.6 K 25 Apr 2006 - 14:07 KlausFoehl design suggestion for a curved lightguide
kfpanda12l.epseps kfpanda12l.eps manage 25.3 K 25 Apr 2006 - 14:00 KlausFoehl eps separation calculation
kfpanda12l.gifgif kfpanda12l.gif manage 5.6 K 25 Apr 2006 - 13:11 KlausFoehl 3.5sigma boundaries for pi-K-separation
kfpanda12l_.gifgif kfpanda12l_.gif manage 3.8 K 25 Apr 2006 - 14:07 KlausFoehl 3.5sigma boundaries for pi-K-separation
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Topic revision: r1 - 25 Apr 2006, KlausFoehl
 
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