Advances in High-Energy-Resolution CdZnTe Linear Array Pixel Detectors with Fast and Low Noise Readout Electronics

Abstract

Radiation detectors based on Cadmium Zinc Telluride (CZT) compounds are becoming popular solutions thanks to their high detection efficiency, room temperature operation, and to their reliability in compact detection systems for medical, astrophysical, or industrial applications. However, despite a huge effort to improve the technological process, CZT detectors’ full potential has not been completely exploited when both high spatial and energy resolution are required by the application, especially at low energies (<10 keV), limiting their application in energy-resolved photon counting (ERPC) systems. This gap can also be attributed to the lack of dedicated front-end electronics which can bring out the best in terms of detector spectroscopic performances. In this work, we present the latest results achieved in terms of energy resolution using SIRIO, a fast low-noise charge sensitive amplifier, and a linear-array pixel detector, based on boron oxide encapsulated vertical Bridgman-grown B-VB CZT crystals. The detector features a 0.25-mm pitch, a 1-mm thickness and is operated at a −700-V bias voltage. An equivalent noise charge of 39.2 el. r.m.s. (corresponding to 412 eV FWHM) was measured on the test pulser at 32 ns peaking time, leading to a raw resolution of 1.3% (782 eV FWHM) on the 59 keV line at room temperature (+20 °C) using an uncollimated 241Am, largely improving the current state of the art for CZT-based detection systems at such short peaking times, and achieving an optimum resolution of 0.97% (576 eV FWHM) at 1 µs peaking time. The measured energy resolution at the 122 keV line and with 1 µs peaking time of a 57Co raw uncollimated spectrum is 0.96% (1.17 keV). These activities are in the framework of an Italian collaboration on the development of energy-resolved X-ray scanners for material recycling, medical applications, and non-destructive testing in the food industry.

Window-Based Energy Selecting X-ray Imaging and Charge Sharing in Cadmium Zinc Telluride Linear Array Detectors for Contaminant Detection

“…However, this allowed us to demonstrate that charge sharing between adjacent pixels produces moderate distortions in X-ray images and, therefore, the ERPC prototype (equipped with a slit collimator) can operate at high rates without charge sharing detection. Moreover, we foresee it working at high rates by coupling the detectors to new front-end electronics, recently developed by our group [ 18 ], allowing excellent energy resolution (<1 keV) even with very fast peaking times (<50 ns); this would allow us to work with very short-shaped pulses ( ballistic deficit pulse processing approach [ 42 ]), ensuring excellent energy resolution and high throughput at high-rate measurements.…”

“…(Reggio Emilia, Italy; , accessed on 14 March 2023). The detector was based on a CZT crystal (3.0 × 10.4 × 1.1 mm 3 ) grown by the boron oxide encapsulated vertical Bridgman (B-VB) growth technique [ 13 , 14 , 15 , 16 , 17 , 18 ]. Recently, B-VB CZT detectors with pixel and planar electrode geometries have been successfully realized at IMEM-CNR of Parma, Italy [ 13 , 14 , 15 , 16 , 17 , 18 ].…”

“…The detector was based on a CZT crystal (3.0 × 10.4 × 1.1 mm 3 ) grown by the boron oxide encapsulated vertical Bridgman (B-VB) growth technique [ 13 , 14 , 15 , 16 , 17 , 18 ]. Recently, B-VB CZT detectors with pixel and planar electrode geometries have been successfully realized at IMEM-CNR of Parma, Italy [ 13 , 14 , 15 , 16 , 17 , 18 ]. Generally, the detectors, equipped with quasi-ohmic gold electroless contacts, are characterized by very low leakage current (<100 pA at high bias voltage of 1000 V) and no bias-induced polarization effects [ 19 , 20 , 21 , 22 ].…”

“…Generally, the detectors, equipped with quasi-ohmic gold electroless contacts, are characterized by very low leakage current (<100 pA at high bias voltage of 1000 V) and no bias-induced polarization effects [ 19 , 20 , 21 , 22 ]. Interesting room temperature energy resolutions were obtained, ranging from 0.6 keV [ 18 ] to 2.4 keV [ 15 ] FWHM at 59.5 keV, depending on the noise-characteristics of the front-end electronics used. The good charge transport properties (mobility-lifetime products of electrons µτ e > 10 −3 cm 2 /V) beside the high-bias voltage operation (>7000 V/cm) allowed the minimization of the effects of high-flux radiation induced polarization in the detectors, with no spectral degradations up to 1 Mcps at 60 keV [ 15 ].…”

Development of travelling heater method for growth of detector grade CdZnTe single crystals

“…Cadmium zinc telluride (CdZnTe) is one of the most promising room-temperature semiconductor gamma radiation detector material due to its wide energy band gap and high atomic number [1][2][3][4]. The research activities carried out on detector technology over the past few decades have showcased that CdZnTe is an excellent substitute for scintillation detectors in terms of high sensitivity, better energy resolution and high spatial resolution at room temperature [4][5][6][7].…”