TY - JOUR
T1 - Radiation damage in the diamond based beam condition monitors of the CMS experiment at the Large Hadron Collider (LHC) at CERN
AU - Guthoff, Moritz
AU - Afanaciev, Konstantin
AU - Dabrowski, Anne
AU - De Boer, Wim
AU - Lange, Wolfgang
AU - Lohmann, Wolfgang
AU - Stickland, David
PY - 2013
Y1 - 2013
N2 - The Beam Condition Monitor (BCM) of the CMS detector at the LHC is a protection device similar to the LHC Beam Loss Monitor system. While the electronics used is the same, poly-crystalline Chemical Vapor Deposition (pCVD) diamonds are used instead of ionization chambers as the BCM sensor material. The main purpose of the system is the protection of the silicon Pixel and Strip tracking detectors by inducing a beam dump, if the beam losses are too high in the CMS detector. By comparing the detector current with the instantaneous luminosity, the BCM detector efficiency can be monitored. The number of radiation-induced defects in the diamond, reduces the charge collection distance, and hence lowers the signal. The number of these induced defects can be simulated using the FLUKA Monte Carlo simulation. The cross-section for creating defects increases with decreasing energies of the impinging particles. This explains, why diamond sensors mounted close to heavy calorimeters experience more radiation damage, because of the high number of low energy neutrons in these regions. The signal decrease was stronger than expected from the number of simulated defects. Here polarization from trapped charge carriers in the defects is a likely candidate for explaining the difference, as suggested by Transient Current Technique (TCT) measurements. A single-crystalline (sCVD) diamond sensor shows a faster relative signal decrease than a pCVD sensor mounted at the same location. This is expected, since the relative increase in the number of defects is larger in sCVD than in pCVD sensors.
AB - The Beam Condition Monitor (BCM) of the CMS detector at the LHC is a protection device similar to the LHC Beam Loss Monitor system. While the electronics used is the same, poly-crystalline Chemical Vapor Deposition (pCVD) diamonds are used instead of ionization chambers as the BCM sensor material. The main purpose of the system is the protection of the silicon Pixel and Strip tracking detectors by inducing a beam dump, if the beam losses are too high in the CMS detector. By comparing the detector current with the instantaneous luminosity, the BCM detector efficiency can be monitored. The number of radiation-induced defects in the diamond, reduces the charge collection distance, and hence lowers the signal. The number of these induced defects can be simulated using the FLUKA Monte Carlo simulation. The cross-section for creating defects increases with decreasing energies of the impinging particles. This explains, why diamond sensors mounted close to heavy calorimeters experience more radiation damage, because of the high number of low energy neutrons in these regions. The signal decrease was stronger than expected from the number of simulated defects. Here polarization from trapped charge carriers in the defects is a likely candidate for explaining the difference, as suggested by Transient Current Technique (TCT) measurements. A single-crystalline (sCVD) diamond sensor shows a faster relative signal decrease than a pCVD sensor mounted at the same location. This is expected, since the relative increase in the number of defects is larger in sCVD than in pCVD sensors.
KW - Beam condition monitor
KW - CMS
KW - Diamond detector
KW - Polarization
KW - Radiation damage
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U2 - 10.1016/j.nima.2013.05.041
DO - 10.1016/j.nima.2013.05.041
M3 - Article
AN - SCOPUS:84888346933
SN - 0168-9002
VL - 730
SP - 168
EP - 173
JO - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
JF - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
ER -