Fast Simulation

This example is a simulation chain optimized for speed. A setup like this is well suited for unirradiated standard planar silicon detectors, where a linear electric field is a good approximation.

The setup consists of six Timepix-type detectors with a sensor thickness of 300um arranged in a telescope-like structure. The charge deposition is performed by Geant4 using a standard physics list (with the EmStandard_opt3 option) suited for tracking detectors. The Geant4 stepping length is chosen rather coarse with 10um.

The detector setup contains the position and orientation of the telescope planes, which are divided into an upstream and downstream arm and are inclined in both X and Y to increase charge sharing. In addition, the alignment precision in position and orientation is specified in order to randomly misalign the setup and allow reconstruction without tracking artifacts from pixel-perfect alignment.

The main speedup compared to other setups comes from the usage of the ProjectionPropagation module to simulate the charge carrier propagation. A setting of charge_per_step = 100 is chosen over the default of 10 charge carriers to further reduce the CPU load. With a sensor thickness of 300um and an most probable energy deposition of more than 20'000 charge carriers, no impact on the precision is to be expected.

Also the exclusion of DepositedCharge and PropagatedCharge objects from the output trees help in speeding up the simulation and in keeping the output file size low.