Development of portable CdZnTe spectrometers for remote sensing of signatures from nuclear materials
|Arnold Burger , U. N. Roy , Michael Groza , M. Guo|
Fisk University, Department of Physics, Materials Science and Applications Group, 1000 17th Ave. N., Nashville, TN 37208-305, United States
Room temperature cadmium zinc telluride (CZT) gamma-ray spectrometers are being developed for a number of years for medical, space and national security applications where high sensitivity, low operating power and compactness are indispensable. The technology has matured now to the point where large volume (several cubic centimeters) and high energy resolution (approximately 1% at 660 eV) gamma photons, are becoming available for their incorporation into portable systems for remote sensing of signatures from nuclear materials. The straightforward approach of utilizing a planar CZT device has been excluded due to the incomplete collection arising from the trapping of holes and causing broadening of spectral lines at energies above 80 keV, to unacceptable levels of performance. Solutions are being pursued by developing devices aimed at processing the signal produced primarily by electrons and practically insensitive to the contribution of holes, and recent progress has been made in two areas, material growth and signal processing. Present materials challenges are in the growth of CZT boules from which large, oriented single crystal pieces can be cut to fabricate such sizable detectors. Since virtually all the detector grade CZT boules consist of several grains, the availability and costs of a large, single crystal section is still high. Co-planar detectors, capacitive Frisch-grid detectors and devices taking advantage of the small pixel effect, are configurations with a range of requirements in crystallinity and defect content and, involve variable degrees of complexity in the fabrication, surface passivation and signal processing. These devices have been demonstrated by several research groups and will be discussed in terms of their sensitivity and availability.
Presentation: invited oral at NATO Advanced Research Workshop, by Arnold Burger
See On-line Journal of NATO Advanced Research Workshop
Submitted: 2004-08-04 21:23 Revised: 2009-06-08 12:55