Hard X- and γ-ray measurements with a large volume coplanar grid CdZnTe detector

Abstract

The recent introduction of coplanar grid techniques has led to resurgence in interest in developing large volume compound semiconductor detectors that have a reasonable g-ray response but also good spectroscopic resolution. We report the results of a series of hard X-and g-ray measurements on a large 15 Â 15 mm 2 , 10 mm thick CdZnTe coplanar grid detector. The measurements were carried out at the HASYLAB and ESRF synchrotron radiation facilities using highly monochromatic pencil beams across the energy range 20-800 keV. Additional full-area measurements were carried out using radioactive sources. All measurements were carried out at room temperature. The measured energy resolution under full-area illumination was 8 and 12 keV FWHM at 59.95 and 662 keV, respectively. Under pencil beam illumination, the measured resolutions were essentially the same. The detector energy response function was found to be linear over the energy range 20-1400 keV with an average rms nonlinearity of 1.4%, consistent with statistics. The spatial uniformity of the detector was evaluated at 30, 60 and 180 keV by raster scanning a 20 Â 20 mm 2 monoenergetic X-ray beam across the active area. Apart from a few localized areas, the detector response was found to uniform at the few percent level, consistent with statistics. At 180 keV, the nonuniformity in the energy response due to the grids was estimated to be at the 0.7% level.

Semiconductor materials and radiation detection

“…In fact, operating the grids as a simple planar detector results in no spectroscopic signal, but when operated in the co-planar geometry, the results are quite dramatic and are illustrated in fig. 3 (from Owens et al, 2005b). (Owens et al, 2005b).…”

Non‐uniformity effects in CdZnTe coplanar‐grid detectors

“…These detectors, now available from several vendors, offer high efficiency in detection, and good energy resolution, typically ~2% FWHM at 662 keV, depending on the detector's size and geometry. The best energy resolution measured with large-volume (>2 cm 3 ) devices was 1.8% at 662 keV [2], still far from the statistical limit predictable based on the Fano-factor. Despite a great deal of work, the potentials of CPG devices have not been fully realized.…”

Synchrotron light sources and radiation detector metrology

“…Owens / Nuclear Instruments and Methods in Physics Research A 695 (2012) [1][2][3][4][5][6][7][8][9][10][11][12] electrons resulting in a narrow cone of very intense high energy radiation. The synchrotron light produced at the bending magnets is extracted by a suitable beamport and directed to an experimental station by a vacuum beampipe.…”