Validation of synthetic diamond for a beam condition monitor for the compact muon solenoid experiment

The CERN Large Hadron Collider (LHC) will collide two counter rotating proton beams. The energy stored in each beam is about 350 MJ. If there is a failure in an element of the accelerator, the resulting beam losses could cause damage not only to the machine but also to the experiments. Within the Compact Muon Solenoid experiment (CMS), a beam condition monitor (BCM) is foreseen to monitor fast increments of the flux near the interaction point, to flag the onset of adverse beam conditions within the CMS experiment, and if necessary, to input into the beam abort system of the LHC. Strong constraints on BCM design from radiation hardness, a minimal material and services budget, and the need for fast signals from sensors with high sensitivity and a large dynamic range, have led to the investigation of synthetic chemical vapour deposited (CVD) diamond for the BCM sensor. In a 5 GeV hadron enriched secondary beam the response of CVD diamonds was tested in fluences ranging from single minimum ionizing particles (MIPs) to 10⁵ MIPs per cm delivered over a 40 ns beam spill. The signal response, linearity, orientation, and stability of both un-irradiated and irradiated sensors were tested over this range, and will be presented herein. The results corroborate the applicability of CVD diamond for this beam monitoring application.