Intelligent gamma-ray spectroscopy using 3-D position-sensitive detectors

The performance of gamma-ray spectrometers at high energies (several MeV) can be greatly improved through intelligent spectroscopic analysis if spatial information is obtained for each energy deposition. In position-sensitive detectors, the energy and three-dimensional (3-D) position of each interaction in the detector are determined. Recognizing the signatures of multiple interactions in the detector can help to reconstruct the energies of the initial gamma-rays even when the full energies are not deposited. Experimental work by our research group has demonstrated the feasibility of carrying out spatially resolved measurements of individual gamma-ray interactions throughout the volume of a CdZnTe spectrometer. We present the results of a simulation study for gamma-rays incident upon a 6-cm/sup 3/ CdZnTe detector using two reconstruction methods: highefficiency intelligent spectroscopy (HEIS) in which the peak-to-total ratio is greatly improved relative to traditional spectroscopy while maintaining almost the same intrinsic peak efficiency; and peak-only intelligent spectroscopy (POIS) in which the peak-to-total ratio can approach 0.9, assuming realistic values for energy resolution. Although POIS reduces the intrinsic peak efficiency, it will significantly improve the signal-to-noise ratio for many measurements. The predicted performance is unprecedented for a detector of such small volume and illustrates the gains that can be expected by exploiting 3-D information.