Scintillator pad detector: Very front end electronics. Design and pre-series

S. Luengo, J. Riera, S. Tortella, X. Vilasis-Cardona, D. Gascón, A. Comerma, L. Garrido

Research output: Book chapterConference contributionpeer-review


The SPD (Scintillator Pad Detector) is a part of LHCb calorimeter which is designed to distinguish electrons and photons for this first level trigger. This detector is a plastic scintillator layer, divided in about 6000 cells of different size to obtain better granularity near the beam. Charged particles will produce, and photons will not, ionisation on the scintillator. This ionisation generates a light pulse that is collected by a Wavelength Shifting (WLS) fibre that is twisted inside the scintillator cell. The light is transmitted through a clear fibre to the readout system. For cost reduction, these 6000 cells are divided in groups using a MAPMT of 64 channels for receiving information in the readout system. The signal outing the SPD PMTs is rather unpredictable as a result of the low photostatistics, 20-30 photoelectrons per MIP, and the response of the WLS fibre, which has low decay time. Then, the signal processing must be performed by first integrating the total charge and later subtracting to avoid pile-up. The SPD Readout system is performed by an ASIC which integrates the signal, makes the pile-up compensation, and compares the level obtained to a programmable threshold (distinguishing electrons and photons), an FPGA which programmes the ASIC thresholds and pile-up subtraction and finally LVDS serializers, in order to send information to the first level trigger system. The design of the VFE unit takes into account not only mechanical constraints, as a result of the little space for the readout electronics but also the radiation quote expected in the environment and the distance between the VFE electronics and the racks were information is sent.

Original languageEnglish
Subtitle of host publicationXII International Conference
Number of pages8
Publication statusPublished - 2006
EventCALORIMETRY IN HIGH ENERGY PHYSICS: XII International Conference - Chicago, IL, United States
Duration: 5 Jun 20069 Jun 2006

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


ConferenceCALORIMETRY IN HIGH ENERGY PHYSICS: XII International Conference
Country/TerritoryUnited States
CityChicago, IL


  • Electronics
  • LHCb
  • Photomultiplier
  • Readout
  • Scintillator pad detector


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