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.

A fully integrated pulsed reset charge-sensitive amplifier (CSA) optimized for low-capacitance (<; 100 fF) radiation detectors was developed on a 0.35-μm low-noise CMOS technology. The CSA was successfully tested with a collimated 10-mm ² silicon drift detector (SDD) and extensively characterized. The experimental setup and the achieved spectrometry results with SDD are described for triangular and trapezoidal shaping filters with peaking times ranging from t _peak =0.1-12.8 μs at an operating temperature of -35 °C. With a minimum equivalent noise charge (ENC) of 3.4 electrons rms measured at tpeak

The electronic noise is a key-issue during the phases of design, integration and characterization of a detection system for ionizing radiation, as it determines both its ultimate and actual performances. The precise identification and quantification of all noise sources and associated components allow to implement specific strategies for their control and minimization during the system design and manufacturing phases, to disentangle all noise contributions, and to verify their correspondence with the expectations during the system characterization. An effective approach to the electronic noise problem requires to consider in detail all the parts of the detection system but it is not so rare to still observe that the electronic noise is erroneously confused or interpreted as the noise of the electronics or as the quadratic sum of the electronics’ and detector’s noise, usually reducing the latter to that one associated to its dark current only. In this paper, a detailed analysis of the noise model of a radiation detection system employing a semiconductor detector is presented using a unified approach which takes into account all sources and causes of electronic noise and their reciprocal interaction. The noise related to the generation, transport and loss of the signal charge in the detector are analyzed in detail and, in particular, the charge trapping and detrapping processes, showing how their contributions could be not negligible even in detectors based on high purity semiconductors. The unified approach allows to disclose the interplay between the detector, the interconnection and the front-end electronics showing that some noise contributions cannot be attributed exclusively to a single part, but it is correct to refer to them as system noises. Several examples taken from experimental data are presented and discussed and a method to determine the dielectric noise introduced by the interconnection and the detector is described. The concept of Equivalent Noise Energy is formalized revealing how it is useful to compare systems employing detectors made with different semiconductors and eventually affected by charge trapping. The analysis is developed assuming semiconductor detectors but can be easily applied to system using other types of radiation detectors.