Development of timing detectors for future experiments in particle physicsHoward, Alissa Shirley-Ann (Avtor) Kramberger, Gregor (Mentor) ATLAS HGTDLHCsilicon detectorsradiation damageradiation hard detectorstiming detectorslow gain avalanche detectoracceptor removalimpact ionizationThis thesis presents an investigation into the design and operation of LGAD detectors within the HGTD framework in preparation for the upgrade of the LHC to HL-LHC. Samples from various manufacturers were measured and characterised using CV/IV, timing and collected charge measurements both before and after irradiation with reactor neutrons. In terms of design, it is clear that a high doping concentration of boron results in a lower removal constant, as does the addition of carbon up to a certain point. The affect of annealing and neutron flux was investigated in order to determine an operating plan for HGTD. It was found that the performance was not largely affected by either. The affect of floating pads on the remaining connected pads was studied using 2x2 arrays with varying inter-pad gaps. As expected, a smaller inter-pad gap leads to early breakdown and punch-through occurring at a lower bias. A new setup was designed to test the long term stability of sensors under high biases. Overall the samples proved to be very robust in laboratory tests. However, destructive breakdown of irradiated sensors has been observed when operated at high biases in a high energy particle beam. Samples were sent to two test beam campaigns. It was determined that these destructive breakdowns occur when the average electric field in the sensor goes beyond 12 V/$\mu$m. In order to simulate LGADs, the impact ionization parameters for silicon needed to be determined. The dependence of the parameters on temperature was also determined. Their validity was then tested using measurements from irradiated sensors up to $2.5\cdot10^{15}$ cm$^{-2}$ and it was found that they were acceptable at low biases.20262026-09-30 08:15:07Doktorsko delo/naloga188892sl