Electronic Noise in Semiconductor-Based Radiation Detection Systems: A Comprehensive Analysis With a Unified Approach

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.