Documentation

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, https://doi.org/10.1016/j.nima.2021.165167

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

urn:nbn:de:hbz:294-35269

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

Specifications

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