Silicon photomultipliers: characterization and application to fluorescence flucturation spectroscopy.

This thesis originates from and develops around Silicon Photomultipliers (SiPMs): starting from a description of the working principles of these devices, this work presents a review on this technology and on some of its possible applications. The great part of this work took place within the framework of an international scientific and industrial collaboration (RAPSODI1, a project funded by the European Commetee), with the aim of developing three radiation detectors using the SiPM technology; in order to find the optimal sensor for each application, an exhaustive protocol to provide a characterization of the performances of the main SiPM parameters (gain, photo-detection efficiency, dark count rate, optical cross-talk, breakdown voltage dependence from temperature) has been provided. In order to further improve the knowledge on Silicon PhotoMultipliers, a phenomenological model describing the statistics of Geiger-Müller avalanches for impinging photons with known probability distribution has been elaborated: this model takes into account the contribution given by the thermally generated avalanches and by the cross-talk, thus providing a model for the SiPM deviations from the ideal bernoullian detection. Last, a feasibility study on the possibility of using this sensors as detecting technology in Fluorescence Fluctuation Spectroscopy (FFS) biophysical experiments had been conducted. In FFS experiments the parameters describing the system under study (proteins ligated with fluorophores in a solution) are measured from the deviations of the fluorescence intensity around its mean value: the use of fast (with a sub-nanosecond temporal resolution) detectors with an large photon number resolution can costitute an improvement of the experimental conditions. Thus a dedicated setup had been commissioned and SiPMs demonstrated to be able to perform an effective Photon Counting Histogram (one of the FFS techniques) measurement. 1RAdiation Protection with Silicon Optoelectronic Devices and Instruments – COOP 3299