Gamma-Ray Imager Using Three-Dimensional Position-Sensitive CdZnTe Spectrometers

Conference · Sun Jun 17 04:00:00 EDT 2001

OSTI ID:785335

He, Z; Du, Y F; Wehe, D K

Portable gamma-ray spectrometers with imaging capability are of interest in radiation monitoring in nuclear facilities, radiation inspections, nuclear nonproliferation, medical imaging, gamma-ray astronomy, and high-energy physics. The incident direction of gamma-ray photons can be obtained based on Compton scattering if the energy depositions and their spatial coordinates in three dimensions can be recorded for each gamma-ray event. This paper reports our progress on developing the first Compton gamma-ray imaging device using three-dimensional (3-D) position-sensitive CdZnTe detectors. Each detector was built using a 1-cm cube of CdZnTe. Energy resolutions of {approx}1.7% full-width at half-maximum (FWHM) for single-pixel events and position resolutions of {approx}1 mm were obtained at the gamma-ray energy of 662 keV. Good angular resolution of a gamma-ray imager based on Compton scattering requires good position and energy resolution of gamma-ray detectors. The position resolution of {approx}1 mm in three dimensions and the measured energy resolution on our detectors provide unique advantages in constructing compact devices having good angular resolution ({approx}3 to 4 deg FWHM at 662 keV). In addition, the wide band-gap of the CdZnTe semiconductor allows room-temperature operation, in contrast to high-purity germanium detectors that must be cryogenically cooled. Over the last few decades, the use of wide band-gap semiconductors has been hindered primarily by problems of charge trapping and material nonuniformity, which resulted in energy resolution that was too poor to be useful. Introduced in 1994, single polarity charge sensing on semiconductor detectors has shown great promise in avoiding the hole trapping problem, and the newly demonstrated 3-D position-sensing technique can significantly mitigate the degradation of energy resolution due to the nonuniformity of detector material. As the result, it is now possible to construct portable gamma-ray imaging devices with good spectroscopic performance operating at room temperatures.

• Research Organization: University of Michigan, Ann Arbor, MI (US)
• Sponsoring Organization: US Department of Energy (US)
• OSTI ID: 785335
• Report Number(s): NONE; ISSN 0003-018X; CODEN TANSAO; ISSN 0003-018X; CODEN TANSAO
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
CDTE SEMICONDUCTOR DETECTORS
COMPTON EFFECT
DESIGN
ENERGY RESOLUTION
GAMMA SPECTROMETERS
IMAGES
PERFORMANCE
POSITION SENSITIVE DETECTORS
SEMICONDUCTOR DETECTORS