Application of avalanche detectors in scientific and industrial measurement systems
Creators: name: Ficorella, Andrea
Publisher: name: Universit� degli studi di Trento
Year: 2019

description: Geiger-Mode avalanche photodiodes (GM-APDs) are diodes designed to operate at a reverse voltage that exceeds the breakdown voltage. Their ability to detect single photons combined with their excellent timing resolution make them ideal for applications in which low amplitude signals need to be detected with sub-ns timing resolution. In the research activity reported in this dissertation two different applications of Geiger-Mode Avalanche Photo Diode arrays have been analysed: a two-tier GM-APD array with in-pixel coincidence for particle tracking and a direct Time-of-Flight range meter with a SiPM-based receiver. The increasing complexity of particle tracking systems at collider experiments demands for high performance detectors with high granularity and position accuracy, low material budget and power consumption. Both Hybrid and monolithic detectors have been proposed as particle trackers. Hybrid detectors have the advantage of allowing an independent customization of sensors and readout electronics, but they exhibit a higher input capacitance that increases readout noise, thus limiting their minimum thickness (100 �m). Monolithic detectors have lower input capacitance, thus a better minimum detectable charge, with a charge time collection of few tens of ns. Thanks to their high gain, particle detectors based on GM-APDs have the potential for combining low material budget, low power consumption and an excellent timing resolution in the range of 100 ps. However, their use as particle tracking detectors has been prevented by their Dark Count Rate, since it is not possible to discriminate a particle-generated event from a dark event. To overcome this issue, the use of GM-APDs in coincidence has been proposed. The activity reported in this dissertation has been conducted in the framework of APiX2 and ASAP projects funded by Istituto Nazionale di Fisica Nucleare (INFN). A two-tier sensor based on avalanche detectors in coincidence has been designed and fabricated in standard 150 nm CMOS technology. A charged particle crossing both GM-APDs integrated in a pixel triggers an avalanche in both devices. The output signal from each detector reaches the coincidence electronics, that allows the device to discriminate the particle detection from dark events. The performance of the proposed detector has been evaluated in a complete electrical and functional characterization campaign. The feasibility to reduce the substrate thickness has been studied in some devices thinned down to 50 �m and 25 �m. The electronics for coincidence detection was also used to directly measure optical crosstalk, a phenomenon that is getting greater importance as stacked optical and image sensors are becoming common. The functional characterization of the APiX prototype was performed with a beta-source and an evaluation of the radiation hardness of the devices was carried out in an irradiation campaign with neutrons at the INFN Laboratori Nazionali di Legnaro (LNL). SiPMs take advantage of the characteristics of GM-APDs such as high sensitivity, high efficiency and very low time jitter, and overcome the problem related to the dead time connecting several sensitive elements in parallel, making them suitable for the simultaneous detection of more than one photon. The evaluation of a SiPM-based direct Time-of-Flight range meter has been performed at two different wavelengths: 405 nm and 810 nm. The set of measurement at 405 nm has been performed using a TCSPC module as acquisition system, while in the 810 nm measurements a low-cost FPGA-based TDC was used. The replacement of the TCSPC module with an FPGA-based TDC represents an important step towards the integration of a low-cost prototype thanks also to the low power consumption of the device. In order to evaluate the feasibility of a SiPM-based range meter in the NIR region, a collaboration with the Circuits and Systems Research Unit of the ITEE Faculty of the University of Oulu was established to set up a system with a GaAs/AlGaAs multiple quantum well laser diode with a spectral emission of 0.808 �m as transmitter and a NIR-HD SiPM with an enhanced efficiency for NIR photons recently developed at FBK as receiver. The evaluation was performed at high repetition rate (MHz range), for the perspective purpose to upgrade the system including a 2-axis scanning mirror to perform real-time 3D imaging.