Very High Dose Rate Detector for the LHC BLM system

by Daniel Kramer (CERN/EN)

Thursday 29 Jan 2009, 14:15 → 15:15 Europe/Zurich

AB Auditorium Prevessin (CERN)

The LHC BLM system uses ionization chambers as standard detectors, and in the areas with very high dose rates Secondary Emission Monitor (SEM) chambers are employed to increase the dynamic range. The SEM is characterized by a high linearity and accuracy, low sensitivity, fast response and a good radiation tolerance. The sensitivity of the SEM was modeled in GEANT4 via the Photo-Absorption Ionization module together with a custom parameterization for the very low energy secondary electron production using the modified Sternglass formula. The simulations were validated by comparative measurements of several prototypes with proton beams of the CERN PS Booster dump line, the SPS transfer line, the PSI Optis line and by a muon beam in the COMPASS beam line. Tests of the complete acquisition chain were performed in the LHC test collimation area of the SPS and compared to the combined Fluka and GEANT4 simulations. The linearity and long term stability was also tested in the high energy beam dump area of the SPS. A dedicated fixed target experiment was designed in the CERN H4 secondary beam line for testing all the 400 detectors produced in IHEP Protvino. The simulations were also used for the prediction of the signal levels expected in the LHC and for an absolute dose calibration. The simulation and measurement result will be discussed and the determined accuracy of this new radiation detector will be presented.

Information