Charge Cloud Simulation

When a highly intense and focused X-ray beam, for instance a Bragg diffraction from a nano-crystal, impinges on the detector, enough electron-hole pairs are created to form a so called electron-hole plasma. This electron-hole plasma will result in a shielding of the drift fields, and consequently a significant broadening of the charge cloud due to diffusion happens. By the same effect the signal formation is also decelerated. Both have impact on the interpretation of measurements as well as on the design of detectors and readout electronics.

The exact processes are however not known today, and therefore a charge-cloud study is launched. This study consists of numerical simulations using advanced techniques (performed by the Weierstrass Institute in Berlin) and experimental verifications using different techniques (lasers, X-rays, ions and alphas). The charge cloud studies are coordinated by the MPI-Semiconductor laboratory in Munich. Finally a 3d device simulator will be available which is able to handle the numerical problems involved with the large detector volume and the plasma effects.