A NOVEL SILICON DRIFT DETECTOR WITH 2-DIMENSIONAL DRIFT TIME MEASUREMENT

Until now silicon drift detectors with two dimensional position resolu tion made use of drift time measurement in one dimension only. The res olution in the other dimension was obtained by dividing the collecting anode into small pixels. In this paper we present a new type of drift detector that uses drift time measurements for both dimensions. The d esign consists of concentric quadrilateral closed strips with a small collecting anode in the centre. At first electrons will travel perpend icular to the strips until they reach a diagonal. Then they will proce ed along this diagonal until they are collected at the centre. Positio n resolution in two dimensions can be obtained when both the time the electrons need to reach the diagonal and the time they need to reach t he centre are measured. The latter is obtained from the collecting ano de, the former from a diagonal strip present at the back side of the d etector. Compared to common 2D drift detectors this detector offers th e advantage of a small amount of readout electronics. It also has the advantage of having just one small collecting anode with a very low ca pacitance, resulting in low noise and therefore in a good energy resol ution.