Response of Silicon photo-multipliers to a constant light flux

The response of a Silicon Photomultiplier to a constant illumination has been interpreted in term of Geiger- Mueller avalanche frequency, actually correlated to the photon flux via the photon detection efficiency. The hypothesis has been verified in laboratory tests and applied throughout the development of a device for real-time dosimetry in mammography

Silicon photomultiplier readout of a scintillating noble gas detector for homeland security

Detectors based on scintillation by high pressure 4He are a viable technology for instruments against the illicit trafficking of nuclear material. A design based on the use of solid state photodetectors is presented in this paper and the preliminary qualification discussed

Recent results on GaAs detectors - 137

The present understanding of the charge collection in GaAs detectors with respect to the materials used and its processing are discussed. The radiation induced degradation of the charge collection efficiency and the leakage current of the detectors are summarised. The status of strip and pixel detectors for the ATLAS experiment are reported along with the latest results from GaAs X-ray detectors for non-high energy physics applications.Comment: 7 pages. 4 postscript figures + 1 postscript preprint logo + 1 LaTeX file + 1 style file. Also available at http://ppewww.ph.gla.ac.uk/preprints/97/05

SiPM technology applied to radiation sensor development

The Silicon Photo-Multiplier (SiPM) being yet in its infancy, a full protocol for the sensor characterization has been developed and implemented at the Physics Department of Universita\u2019 dell\u2019Insubria. Sensors from different producers have been analyzed and compared, in view of the integration in the instruments for radiation detection. Exemplary illustrations are reported here, together with the first results on real-time dosimetry in mammography

Mammodos – In-Vivo Dosimetry in Mammography

In the scope of the RAPSODI EU research project, a prototype detector for in-vivo dose measurements in Mammography was developed. We present and discuss first results on the system qualification, in particular on the linear dynamic range, the energy response and the radiological as well as optical transparency of the detector

Commissioning and Field Tests of a Van-Mounted System for the Detection of Radioactive Sources and Special Nuclear Material

MODES-SNM project aimed at developing a mobile/portable modular detection system for radioactive sources and Special Nuclear Material (SNM). Its main goal was to deliver a tested prototype capable of passively detecting weak or shielded radioactive sources with accuracy higher than that of currently available systems. By the end of the project all the objectives have been successfully achieved. Results from the laboratory commissioning and the field tests are presented in this publication

Imaging of biological samples with silicon pixel detectors

Beta autoradiography is a well-established technique to measure the distribution of macromolecule concentration in biological samples. The potential of silicon pixel detectors for imaging tritium radio-labeled samples has already been demonstrated. In the following, a direct comparison between two general purpose sensors, MIMOSA5 and MEDIPIX2, characterized by complementary technologies and architectures is reported. The MIMOSA5 is a high-granularity monolithic CMOS active pixel detector with full analog output, while the MEDIPIX2 is a hybrid device with moderate granularity and a counting architecture. The comparison is based on two main figures: the effective activity and the dark counting rate. Tests were performed relying on tritium standards for autoradiography, with specific activities comparable to radio-labeled proteins in daily use. Different algorithms were developed and tested to discriminate against stochastic noise and cosmic rays. The results do confirm the advantage of real time granular sensors against films and phosphor imaging screens and set the basis for an optimized, customized development

Analysis of the response of silicon photomultipliers to optical light fields

Silicon Photo-Multipliers (SiPMs) consist of a high density array of p-n junctions with a common output (∼ 103 cells per mm2), operated beyond the breakdown voltage in a Geiger-Müller regime. With a typical gain of the order of 106, time resolution at the 100 ps level, a dead time per diode limited to 100 ns, enhanced blue sensitivity, photon detection efficiency in excess of 30% and, notably, a photon number resolving capability up to a few tens of photons even at room temperatures, their performances are comparable with the common use Photo-Multiplier Tubes, with the advantage of operability in magnetic fields. However, SiPMs present a significant Dark Count Rate (DCR), ranging from a few 100 kHZ to the MHz level at room temperature, and a relevant optical cross-talk between the cells, with values depending on the detector design and the biasing condition, so that their use is far from being trivial. The performance of SiPMs have been tested in the context of the characterization of the photon number distribution in a light field. Infact, while the Geiger-Müller avalanche triggering by impinging photons can be modelized as a pure bernoullian process that preserves the photon number distribution of measured light field, relevant values of DCR and cross-talk can cause sizeable deviations from this statistics. Taking into account the DCR and cross-talk effects in the Geiger-Müller avalanche distribution, we demonstrate that photon number distributions in a poissonian and thermal-like light field can be properly reconstructed