48 research outputs found
Imaging of biological samples with silicon pixel detectors
No full textBeta 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
No full textSilicon 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
Photon-number statistics with Silicon photomultipliers
No full textWe present a description of the operation of a multi-pixel detector in the presence of non-negligible dark-count and cross-talk effects. We apply the model to devise self-consistent calibration strategies to be performed on the very light under investigation
Response of Silicon photo-multipliers to a constant light flux
No full textThe 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
No full textDetectors 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
Neutron induced radiation damage of KETEK SiPMs
No full textSilicon photomultipliers (SiPMs), thanks to their excellent performance, are becoming the photodetectors of choice for many applications. One major limitation, in particular for their use at high-luminosity colliders, is the radiation damage by hadrons. In this work, SiPMs with 4384 pixels of 15 × 15 μm 2 size produced by KETEK have been irradiated by reactor neutrons to six fluences up to Φ eq = 10 12 cm -2 (1 MeV equivalent neutrons). Pulse-height, IV, and CV measurements with and without illumination by a LED for temperatures between -30 and 30° C have been performed. In this paper results from the IV, and CV measurements are shown. The fluence and the temperature dependence of the current and of the SiPM electrical parameters like pixel capacitance, quenching resistance and breakdown voltage allows to better understand the origin of the dark current and find ways to reduce the radiation-induced dark-count-rate
Development of a Silicon Photomultiplier toolkit for science and education
No full textSilicon Photomultipliers (SiPM) are a new class of photon sensors with single photon detection capability and high photon detection efficiency. They have been proved to be suitable for an increasing number of applications in science and industry. Nowadays, different companies are investing increasing efforts in SiPM detector performances and high quality mass production, such to make them a natural choice for an always wider field of applications.
In this scenario, a flexible and easy-to-use system that allows the measurement of the main SiPM characteristics has become an important platform to exploit SiPMs in different applications. This system can also be used to setup a series of experiments aimed to train physics and engineering undergraduate and master students in detector measurements and statistics analysis
Reconstruction of the statistics of photons by a pulsed LED using a Silicon Photomultiplier based set-up
No full textSilicon Photomultipliers are a new class of light sensitive detectors with single photon sensitivity and unprecedented photon number resolving capability. These properties open up the possibility to verify the statistics of the emitted light analysing the data collected by the sensor. In this paper, a procedure based on a Multi-Gaussian Fit of the spectrum and a model accounting for detector related effects is proposed and qualified using a LED illuminating a Silicon Photomultiplier
