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 mu m 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.