Recent advances in THM CZT for Nuclear Radiation Detection
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1164-L10-04
Recent advances in THM CZT for Nuclear Radiation Detection J. MacKenzie1, H. Chen1, S. A. Awadalla1, P. Marthandam1, R. Redden1, G. Bindley1, Z. He2, D. R. Black3, M. Duff4, M. Amman5, J. S. Lee5, P. N. Luke5, M Groza6, and A. Burger6 1
Redlen Technologies, Sidney, BC V8L 5Y8 Canada University of Michigan, Ann Arbor, MI 48109 USA 3 National Institute of Standards and Technology, Gaithersburg, MD 20899 USA 4 Savannah River National Laboratory, Aiken, SC 29808 USA 5 Lawrence Berkeley National Laboratory, Livermore, CA 94720 USA 6 Fisk University, Nashville, TN 37208 USA 2
Abstract: Greater than 500 cm3 single crystal CdZnTe (CZT) has been grown using the travelling heater method providing thick (> 5 mm) detectors required for high energy gamma ray detection. Detectors greater than 5 mm thickness have achieved superior energy resolution or < 1 %FWHM for 662 keV gammas from a
137
Cs source while maintaining
this level of resolution for 1.17 and 1.33 MeV gammas from a60Co source. Standard, 5 mm thickness detectors also show increases in mobility-lifetime products for both electrons and holes in crystals grown over 3 years. The improvement in these measurable is attributable to improvements in quality of the grown CZT and post growth heat treatments.
Introduction: Currently, nuclear radiation detection and application still mainly employ scintillation detectors and solid state high purity Germanium (Ge) based detectors. These detectors, however, suffer from several drawbacks including the need for cryogenic cooling to reduce thermally generated leakage currents in Ge. The cooling requirement for Ge and photomultiplier tubes required for scintillator makes these detection systems bulky; requiring significant infrastructure costs for operation. Large scale deployment of gamma ray spectroscopy applied to areas of nuclear medical imaging, homeland security and astrophysics is hindered by the large size and infrastructure required for these detection systems. Cadmium Zinc Telluride (CZT) has been identified as a promising material for room temperature gamma and X-ray spectroscopy based on having a wide band-gap suitable for detecting such high energy photons. High resistivity CZT has been shown to have good electron collection properties and long term stability without suffering temperature polarization effects associated with room temperature operation [1]. Melt grown High and low pressure Bridgman (HPB, LPB respectively) are known to produce CZT suitable for high resolution gamma and X-ray spectroscopy and much effort has been devoted to commercialization of CZT using these growth techniques [2]. Unfortunately, the large cost and low yield associated with melt growth CZT techniques has impeded mass production. CZT grown using the solution growth, travelling heater method (THM) has been shown to produce CZT of equal or superior electrical properties suitable for gamma and X-ray spectroscopy [3]. Traditional prejudice held that the THM process was inappropriate for commercial production due to the slow grow
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