Three-dimensional position sensing and field shaping in orthogonal-strip germanium gamma-ray detectors

We have fabricated a prototype orthogonal-strip germanium detector for gamm a-ray imaging studies. With this detector we demonstrate that a gamma-ray i nteraction event in the detector can be located in three dimensions. In par ticular, we determine the interaction depth from the difference in time in the arrival of the holes at an electrode on one side of the detector and th e arrival of the electrons at an electrode on the opposing detector surface . This depth of interaction sensing should lead to improved image resolutio n. A separate issue with such a detector is the loss of energy resolution a nd efficiency resulting from incomplete charge collection for interaction e vents taking place in the gap regions between the detector electrodes. We a lso demonstrate with our prototype detector that this problem can be substa ntially reduced by using field-shaping electrodes. A bias applied between t he charge-sensing electrodes and the held-shaping electrodes improves the c harge collection to the charge-sensing electrodes and consequently the dete ctor performance. (C) 2000 Elsevier Science B.V. All rights reserved.