Optimized design topologies for position-sensitive Silicon Drift Detectors operating at high drift fields

We describe innovative topologies of Silicon Drift Detectors suitable for 2D position sensing applications with very fast readout (i.e. operating at high drift fields) and we report the experimental characterisation of two prototypes. The specific design issues taken into account in order to operate at high drift fields (e.g. able to achieve drift speeds of the order of 1 cm/μs) will be discussed. The designed detectors feature the possibility to independently bias the field-plates covering the inter-strip oxide in order to investigate the impact of the field-plate voltage on the transport properties and on the surface generated leakage current. In order to test the effectiveness of the proposed designs, a fast (100 ps) infrared pulsed laser, generating the desired signal charge, has been focused to a small spot (10 μm FWHM) on the front side of the detector and displaced along the drift and lateral directions to study the detector response. The experimental characterization, carried out close to room temperature, includes the assessment of the maximum drift field, of the achievable spatial resolution and of the lateral charge confinement.