@article{ZiemonsHeinrichsStreunetal.2004,
  author    = {Ziemons, Karl and Heinrichs, U. and Streun, M. and Pietrzyk, U.},
  title     = {Validation of GEANT3 simulation studies with a dual-head PMT ClearPET™ prototype},
  series = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 5},
  journal   = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 5},
  issn      = {1082-3654},
  pages     = {3053 -- 3056},
  year      = {2004},
  abstract  = {The ClearPET™ project is proposed by working groups of the Crystal Clear Collaboration (CCC) to develop a 2nd generation high performance small animal positron emission tomograph (PET). High sensitivity and high spatial resolution is foreseen for the ClearPET™ camera by using a phoswich arrangement combining mixed lutetium yttrium aluminum perovskite (LuYAP:Ce) and lutetium oxyorthosilicate (LSO) scintillating crystals. Design optimizations for the first photomultiplier tube (PMT) based ClearPET camera are done with a Monte-Carlo simulation package implemented on GEANT3 (CERN, Geneva, Switzerland). A dual-head prototype has been built to test the frontend electronics and was used to validate the implementation of the GEANT3 simulation tool. Multiple simulations were performed following the experimental protocols to measure the intrinsic resolution and the sensitivity profile in axial and radial direction. Including a mean energy resolution of about 27.0\% the simulated intrinsic resolution is about (1.41±0.11)mm compared to the measured of (1.48±0.06)mm. The simulated sensitivity profiles show a mean square deviation of 12.6\% in axial direction and 3.6\% in radial direction. Satisfactorily these results are representative for all designs and confirm the scanner geometry.},
  language  = {en}
}
@article{StreunChristHellendungetal.2005,
  author    = {Streun, M. and Christ, D. and Hellendung, A. and Larue, H. and Ziemons, Karl and Halling, H.},
  title     = {Effects of crosstalk and gain nonuniformity using multichannel PMTs in the Clearpet® scanner},
  series = {Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
  volume    = {537},
  journal   = {Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
  number    = {1-2},
  isbn      = {0168-9002},
  pages     = {402 -- 405},
  year      = {2005},
  abstract  = {The ClearPET® scanners developed by the Crystal Clear Collaboration use multichannel PMTs as photodetectors with scintillator pixels coupled individually to each channel. In order to localize an event each channel anode is connected to a comparator that triggers when the anode signal exceeds a common predefined threshold. Two major difficulties here are crosstalk of light and the gain nonuniformity of the PMT channels. Crosstalk can generate false triggering in channels adjacent to the actual event. On the one hand this can be suppressed by sufficiently increasing the threshold, but on the other hand a threshold too high can already prevent valid events on the lower gain channels from being detected. Finally, both effects restrict the dynamic range of pulse heights that can be processed. The requirements to the dynamic range are not low as the ClearPET® scanners detect the depth of interaction by phoswich pixels consisting of LSO and Lu0.7Y0.3AP, two scintillators with different light yields. We will present a model to estimate the achievable dynamic range and show solutions to increase it.},
  language  = {en}
}