Low-cost predicted beam loss counting
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Low-cost predicted beam loss counting


The charged particle crosses both PIN diodes, causing a coincidence.

Synchrotron radiation photons, if stopped by either PIN-diode, do not cause a coincidence.

K. Wittenburg was awarded the Faraday Cup in 2000 for the design of the PIN photodiode Beam Loss Monitor and its implementation at HERA.

Bergoz Instrumentation was granted a license by DESY to use Wittenburg's original development.

Main features

  • Single particle detection efficiency > 30 %
  • Spurious count rate < 0.1 Hz
  • Maximum count rate > 10 MHz


  • Very small size and low unit cost make it possible to monitor all locations where beam loss is predicted.
  • Vacuum quality around the storage ring can be measured based on BLM count rate.
  • Two PIN-photodiodes mounted face-to-face detect charges particles. Coincidence counting makes it insensitive to synchrotron radiation photons.
  • Spurious count very low: < 1 count in 10 seconds. • Up to 10MHz counting: dynamic range >10E8
  • Recovers 100ns after a hit
  • Choice of detector solid angle: Large PIN-diodes can be user installed
  • Output is a TTL compatible pulse: easy counting
  • Tested up to 10E8 Rads for hardness

See also