New results from testing an array of 6×6×15 mm 3 virtual Frisch-grid CdZnTe (CZT) detectors with common-cathode readout for charge signals correction and rejection of incomplete charge collection events (ICC) are presented. The array employs parallelepiped-shaped crystals of a large geometrical aspect ratio with two planar contacts on the top and bottom surfaces (anode and cathode) and an additional shielding electrode placed on the sides to create the virtual Frisch-grid effect. The detectors are arranged in 2×2 or 3×3 detector modules with the common cathode readout by a single electronic channel. Because of the common cathode, the length of the shielding electrode can be further reduced with no adverse effects on the device performance. By implementing a novel technique for rejecting ICC events caused by the extended defects, we can achieve good spectral responses from ordinary CZT crystals, which can be produced with higher yield and at lower cost. For such crystals, the resolution of individual detectors is expected to be in the range of 0.8-1.5% FWHM at 662 keV with an average value of 1.3%. Arrays of virtual Frisch-grid detectors offer a robust and low-cost approach for making large-area detection modules that can potentially substitute for more advanced, but also more expensive and less available, pixel detectors in applications with slightly relaxed requirements on position-and energy-resolution (e.g., for coded aperture telescopes). In addition, such virtual Frisch-grid arrays will require a comparably smaller number of readout channels, which allows for lower power consumption.
Bibliographical noteFunding Information:
Manuscript received December 02, 2011; revised January 12, 2012 and February 06, 2012; accepted February 07, 2012. Date of publication March 15, 2012; date of current version August 14, 2012. This work was supported in part by the U.S. Department of Energy, Office of Nonproliferation Research and Development, NA-22, and BNL’s Technology Maturation Award. The manuscript has been authored by Brookhaven Science Associates, LLC under Contract DE-AC02-98CH1-886 with the U.S. Department of Energy.
- crystal defects
- virtual Frisch-grid detectors
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Nuclear Energy and Engineering
- Electrical and Electronic Engineering