T. Held, M. Albrecht, T. Erlen, M. Fink, F.H. Heinsius, C. Motzko, P. Musiol, C. Schnier, M. Steinke, H.-C. Wenzel, U. Wiedner, An LED/LCD-based monitoring system for the PANDA Electromagnetic Calorimeter, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 997, 2021, 165167, ISSN 0168-9002,

The light pulser monitoring system is described in the thesis of Christof Motzko, Ruhr-Universität Bochum, April 2012 (in German)


More up to date information can be found in the thesis of Patrick Musiol, Ruhr-Universität Bochum, June 2018 (in German) urn:nbn:de:hbz:294-57322'

Optical fibers

The optical fibers will be Silica / Silica fibers with a Polyimid jacket and a numerical aperture of 0.28. For every crystal 4 optical fibers with a core diameter of 200 µm will be mounted close to each over.

Producer Name Core diameter Cladding diameter Buffer diameter Jacket diameter Datasheet
Ceram Optec UV 200/220 P 28 200 µm 220 µm   245 µm Datasheet


The light pulser monitoring system has to provide the following functions
  • Monitoring of the photodetector-electronics gain at a precision of 0.1% repeated at the order of minutes. The absolute stability has to be at least 0.1 % at the order of days.
  • Monitoring of the radiation damage of the crystals by comparing the output of the red/green LEDs with the blue LED. Repeated at the order of minutes, possibly within the cycle.
  • Monitoring of the linearity of the electronics: Repeated about every hour during cycle break. Precision about 10% of the resolution.

Energy resolution and corresponding number of pulses:

Energy Energy resolution Required precision Width of LP pulse Required number of pulses
10 GeV 1% 0.1% 0.3% 10
1 GeV 2.5% 0.25%    
100 MeV 7% 0.7% 4.3% 40
20 MeV 14% 1.4%    

Beam structure and time for light pulses
  • Every 1.8 µs a 400ns break (bucket barrier cavity) -> time for gain checks (not at maximum energy to avoid pileup!)
  • Per cycle o(hour) about 1000s accumulation -> time for linearity checks

Number of light pulser = 44
  • 2 backward EMC
  • 32 barrel EMC
  • 10 forward EMC

Light pulser properties
  • repetition rate 30 Hz

-- ChristofMotzko - 23 Oct 2009

-- FritzHerbertHeinsius - 11 Mar 2021
Topic revision: r4 - 2021-03-11, FritzHerbertHeinsius
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