11 Dec 2019



Ultra-Fast Silicon Detectors




Co-supervisors: PPD - S. McMahon, University of Oxford - D. Bortoletto

Both ATLAS and CMS are planning precision timing layers outside their trackers for the HL-LHC upgrades. These will be instrumented with Low Gain Avalanche Detectors (LGADs) with timing resolution of ~30 ps to connect charged tracks to the correct production vertices and reduce the effect of the large pile up at the HL-LHC. ​Many other experiments nuclear and medical physics would also benefit from precision timing information.

LGADs use charge multiplication due to the avalanche initiated by a charge moving in large electrical fields to reach the picosecond regime. Unfortunately, the performance of these devices is limited by radiation damage when exposed to particle fluences higher than about 1014 particles/cm2.
​Recently RAL and Oxford have started a collaboration with Te2V and Birmingham University to develop radiation tolerant LGADs, which has obtained STFC funding.  Giulio Villani, who will start soon a Ph. D in Oxford, is providing TCAD simulations. Te2V has already started the work needed to fabricate a variety of test structures which could be deployed in a large-scale timing detector, like the ATLAS High Granularity Timing Detector. A shared studentship between RAL and Oxford would considerably strengthen the small team dedicated to this project. Specifically, the student will provide prompt characterization of the structures fabricated by Te2V before and after exposure to radiation, and study the performance degradation (loss of signal, loss of gain, inhomogeneous spatial response, etc.) as a function of radiation fluence. These studies will require carefully laboratory measurements and test beam campaigns. The measurements will validate the TCAD simulations, improve our understanding of these devices, and lead to new optimised rad-hard designs.

Contact: McMahon, Steve (STFC,RAL,PPD)