Contaminant detection in non-destructive testing using a CZT photon-counting detector

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.

Section: Introductionmentioning

confidence: 99%

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

Mele

Quercia

Abbene

et al. 2023

“…The importance of energy-resolved photon counting (ERPC) systems for quality enhancements in X-ray images is now widely recognized [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Due to the energy-dependence of the X-ray attenuation processes, spectral X-ray imaging represents a key tool for high resolution material detection and quantitative analysis, especially for medical diagnosis [ 4 , 5 , 9 , 10 ] and non-destructive testing (NDT) in security and food industry [ 6 , 7 , 8 ]. Once the spectral images are acquired, different techniques and algorithms can be easily applied to combine and weight the energy-binned images.…”

Section: Introductionmentioning

confidence: 99%

“…While the advantages of the energy-resolved approach have been well demonstrated in several studies [ 9 , 10 , 11 , 12 ], the development of ERPC systems with high spatial and energy resolution is still currently under research and development. ERPC prototypes based on room temperature compound semiconductor detectors have given the best results, ensuring direct photon counting detection and good room temperature energy/spatial resolution [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Among these materials, cadmium zinc telluride (CdZnTe or CZT) has reached an excellent maturity level in room temperature X-ray and gamma-ray detection from photon energies of few keV up to 1 MeV [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ].…”

Section: Introductionmentioning

confidence: 99%

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

Buttacavoli

Principato

Gerardi

et al. 2023

The spectroscopic and imaging performance of energy-resolved photon counting detectors, based on new sub-millimetre boron oxide encapsulated vertical Bridgman cadmium zinc telluride linear arrays, are presented in this work. The activities are in the framework of the AVATAR X project, planning the development of X-ray scanners for contaminant detection in food industry. The detectors, characterized by high spatial (250 µm) and energy (<3 keV) resolution, allow spectral X-ray imaging with interesting image quality improvements. The effects of charge sharing and energy-resolved techniques on contrast-to-noise ratio (CNR) enhancements are investigated. The benefits of a new energy-resolved X-ray imaging approach, termed window-based energy selecting, in the detection of low- and high-density contaminants are also shown.

“…After the first CZT detector was presented by Butler in 1992 [12], intense research activities started with important progress made in both crystal growth and electrical contact technology. CZT detectors with pixel and strip electrodes were widely developed for X-ray and gamma-ray spectroscopic imaging, meeting the different requirements of many applications, including diagnostic-nuclear medicine [4][5][6][7], astrophysics [8][9][10][11], security [1], and non-destructive testing in the food industry [13,14]. Typically, the best-spectroscopic-grade CZT crystals are grown via Bridgman (B) [15][16][17][18] and traveling heater method (THM) growth [18][19][20][21][22] techniques.…”

Section: Introductionmentioning

confidence: 99%

Incomplete Charge Collection at Inter-Pixel Gap in Low- and High-Flux Cadmium Zinc Telluride Pixel Detectors

Buttacavoli

Principato

Gerardi

et al. 2022

The success of cadmium zinc telluride (CZT) detectors in room-temperature spectroscopic X-ray imaging is now widely accepted. The most common CZT detectors are characterized by enhanced-charge transport properties of electrons, with mobility-lifetime products μeτe > 10−2 cm2/V and μhτh > 10−5 cm2/V. These materials, typically termed low-flux LF-CZT, are successfully used for thick electron-sensing detectors and in low-flux conditions. Recently, new CZT materials with hole mobility-lifetime product enhancements (μhτh > 10−4 cm2/V and μeτe > 10−3 cm2/V) have been fabricated for high-flux measurements (high-flux HF-CZT detectors). In this work, we will present the performance and charge-sharing properties of sub-millimeter CZT pixel detectors based on LF-CZT and HF-CZT crystals. Experimental results from the measurement of energy spectra after charge-sharing addition (CSA) and from 2D X-ray mapping highlight the better charge-collection properties of HF-CZT detectors near the inter-pixel gaps. The successful mitigation of the effects of incomplete charge collection after CSA was also performed through original charge-sharing correction techniques. These activities exist in the framework of international collaboration on the development of energy-resolved X-ray scanners for medical applications and non-destructive testing in the food industry.