Inverted-conical light guide for crosstalk reduction in tightly-packed scintillator matrix and MAPMT assembly

Y.-Y. Chang, P. Chen, J.-J. Huang, J.W. Nam, M.-Z. Wang, M.A. Huang, T.-C. Liu, C.R. Chen, V. Bogomolov, M.I. Panasyuk, V. Petrov, S. Svertilov, I. Yashin, Søren Brandt, Carl Budtz-Jørgensen, A.J. Castro-Tirado, S. Jeong, H.S. Choi, P.H. Connell, C. EylesV. Reglero, J.M. Rodrigo, J.E. Kim, M.B. Kim, J. Lee, H. Lim, I.H. Park, S.-W. Kim, K.W. Min, J. Řípa

Research output: Contribution to journalJournal articleResearchpeer-review


In this paper we present the Inverted-Conical light guide designed for optical crosstalk reduction in the scintillator-MAPMT assemblies. The research was motivated by the 30% crosstalk observed in UFFO X-ray telescope, UBAT, during the preliminary calibration with MAPMTs of 64 2.88 × 2.88 mm2 pixels and identically gridded YSO crystal matrices. We began the study with the energy and crosstalk calibrations of the detector, then we constructed a GEANT4 simulation with the customized metallic film model as the MAPMT photocathode. The simulation reproduced more than 70% of the crosstalk and explained it as a consequence of the total reflection produced by the photocathode. The result indicated that the crosstalk mechanism could be a common case in most of the contact-assembled scintillation detectors. The concept of the Inverted-Conical light guide was to suppress the total reflection by contracting the incident angle of the scintillation. We optimized the design in the simulation and fabricated a test sample. The test sample reduced 52% crosstalk with a loss of 6% signal yield. The idea of the Inverted-Conical light guide can be adapted by scintillation detectors multi-pixel, imaging-purpose scintillation detectors such as the ultra-fast GRB observatory UFFO-UBAT, whose performances are sensitive to responding time, image resolution, and geometrical modifications.
Original languageEnglish
JournalNuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Pages (from-to)55-65
Number of pages11
Publication statusPublished - 2015


  • Crosstalk
  • GEANT4 simulation
  • Light guide
  • YSO
  • Calibration
  • Computer simulation
  • Electromagnetic wave reflection
  • Image resolution
  • Photocathodes
  • Pixels
  • Scintillation
  • Scintillation counters
  • Crosstalk reduction
  • Geometrical modification
  • Light guides
  • Optical cross-talk
  • Total reflection


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