Ultrafast silicon detectors for 4D tracking in high energy physics and medicine

Abstract

The concept of fast-tracking detectors that can simultaneously measure the position and entry time of impinging charged particles (4D-tracking) has gained increasing popularity in recent years, largely due to the advent of Low Gain Avalanche Diodes (LGADs). Their fast timing performance in the range of tenths of picoseconds allows higher luminosities in accelerator experiments by reducing pile-up and enables precise energy calculations of charged particles with the time-of-flight method.In this thesis, we utilize a pair of trench-isolated silicon LGAD strip detectors, each with 30 strips and a total active area of 3 × 3 mm^2 , alongside two 16-channel readout boards and a 16+1 channel digitizer with a sampling rate of 5 GS/s, to explore the application of 4D-tracking. A range of experiments is performed, including characterization of signals using alpha and beta particle sources, temporal response analysis with a pulsed TCT infrared laser and time-of-flight measurements in a proton test beam at the MedAustron synchrotron. These experimental results are complemented by AllPix^2 simulations.The measured temporal resolution from measurements with the TCT-laser is 34 ps for minimum ionizing particles and drops as low as 20 ps for higher energy depositions. Time-of-flight measurements in the MedAustron proton beam yielded timing uncertainties between 4 % to 7 % (95% confidence level) for proton energies ranging from 30 MeV to 235 MeV at a time of flight distance in air of 46 cm. We also discuss potential limitations in the utilized readout chain and its role in increasing the uncertainty of the experimental timing performance compared to the simulations.