X-ray 2-D position-sensing with multilinear silicon drift detectors

To be position sensitive, silicon drift detectors (SDDs) require a trigger signal synchronous with the interaction time (i.e., the start of the electrons´ motion) since the interaction position along the drift coordinate is obtained from the measurement of the electrons´ drift time. In the case of a photon interaction, the trigger must be provided by the detector itself. One way to obtain a fast trigger signal exploits the induction signal given by the holes collected by the p⁺ strips close to the interaction point. We have designed and instrumented a multilinear SDD especially intended to study the self-triggering technique and its application to two-dimensional (2-D) X-ray position sensing. The measured position resolution along the drift coordinate is of the order of 10 ns with 10 keV photons, leading to a position resolution of 30 μm rms at typical drift velocities. A comparable position resolution can be obtained on the lateral coordinate. By engineering the electron trajectory in the collection region, the anode capacitance can be minimized (<0.1 pF) leading to excellent energy resolution even at room temperature.