Induced signals in X-ray detectors with steering grid geometry

Oncoming pixelated X-ray detectors with semiconductor sensor layers made of CdTe or GaAs can be operated in single photon counting mode. Each charge cloud generated by an interacting photon induces a signal in the electronics which is amplified, shaped and compared to a threshold. This process needs to be very fast for high flux applications, which leads to the necessity of understanding the signal induction process. The adjoint simulation of the shape and timing of the signals can be done with the finite element software COMSOL using the convection and diffusion package. For a given sensor material, the signals depend on the geometry of the electrodes and this offers ways to optimise the size and shape of the electrodes. Even additional steering electrodes can be implemented which will be the main part of this contribution. Fully 3D simulations have been carried out to study the possible effects of steering electrodes on the signal shape.