S. Billotta

Features of Silicon Photo Multipliers: Precision Measurements of Noise, Cross-Talk, Afterpulsing, Detection Efficiency

Solid state single photon detectors are an emerging issue, with applications in the wide field of sensors and transducers. A new kind of device named Silicon Photomultiplier (SiPM) shows timing and charge resolution features that in some respect could even replace traditional photomultiplier tubes. In this paper we illustrate a complete method for the evaluation of gain, dark noise, afterpulsing, cross-talk and detection efficiency of SiPM detectors. We show the application of the method by comparing the performance of our newly developed SiPM (produced by ST Microelectronics) with another sensor present on the market (produced by Hamamatsu), and proving that our device is indeed already outstanding.

Silicon Photomultiplier Technology at STMicroelectronics

In this paper we present the results of the first electrical and optical characterization performed on 1 mm2 total area Silicon Photomultipliers (SiPM) fabricated in standard silicon planar technology at the STMicroelectronics Catania R&D clean room facility. The device consists of 289 microcells and has a geometrical fill factor of 48%. Breakdown voltage, gain, dark noise rate, crosstalk, photon detection efficiency and linearity have been measured in our laboratories. The optical characterization has been performed by varying the temperature applied to the device. The results shown in the manuscript demonstrate that the device already exhibits relevant features in terms of low dark noise rate and inter-pixel crosstalk probability, high photon detection efficiency, good linearity and single photoelectron resolution. These characteristics can be considered really promising in view of the final application of the photodetector in the Positron Emission Tomography (PET).

Characterization of a Novel 100-Channel Silicon Photomultiplier—Part I: Noise

In this paper, we present the results of the first noise characterization performed on our novel 100-channel silicon photomultiplier. We have improved our previous single-photon avalanche photodiode technology in order to set up a working device with outstanding features in terms of single-photon resolving power up to R = 45, timing resolution down to 100 ps, and photon-detection efficiency of 14% at 420 nm. Tests were performed, and features were measured, as a function of the bias voltage and of the incident photon flux. A dedicated data-analysis procedure was developed that allows one to extract at once the relevant parameters and quantify the noise.

Characterization of a Novel 100-Channel Silicon Photomultiplier—Part II: Charge and Time

In this paper, we present the results of the charge and time characterization performed on our novel 100-channel silicon photomultiplier. We have improved our previous single-photon-avalanche-diode technology in order to set up a working device with outstanding features in terms of single-photon resolving power up to R = 45, a timing resolution down to 100 ps, and photon-detection efficiency of 14% at 420 nm. Tests were performed, and features were measured as a function of the bias voltage and of the incident photon flux. A dedicated data analysis procedure was developed that allows to extract at once the relevant parameters from the amplitude spectra and to determine the timing features.

Iqueye, a single photon-counting photometer applied to the ESO new technology telescope

Context. A new extremely high speed photon-counting photometer, Iqueye, has been installed and tested at the New Technology Telescope, in La Silla. Aims. This instrument is the second prototype of a “quantum” photometer being developed for future Extremely Large Telescopes of 30–50 m aperture. Methods. Iqueye divides the telescope aperture into four portions, each feeding a single photon avalanche diode. The counts from the four channels are collected by a time-to-digital converter board, where each photon is appropriately time-tagged. Owing to a rubidium oscillator and a GPS receiver, an absolute rms timing accuracy better than 0.5 ns during one-hour observations is achieved. The system can sustain a count rate of up to 8 MHz uninterruptedly for an entire night of observation. Results. During five nights of observations, the system performed smoothly, and the observations of optical pulsar calibration targets provided excellent results.

AFS dynamic evolution during the emergence of an active region

Using data acquired during an observational campaign carried out at the THEMIS telescope in IPM mode, coordi- nated with other ground- and space-based instruments (IOACT, TRACE, EIT/SOHO, MDI/SOHO), we have analyzed the first evolutionary phases of a recurrent active region (NOAA 10050), in order to study the morphology and dynamics of its magnetic structures during their emergence and early development. The main result obtained from this analysis concerns the dynamic evolution of the arch filament system (AFS) crossing the polarity inversion line: the line of sight velocities determined from Doppler measurements confirm that the loops forming the AFS show an upward motion at their tops and a downward motion at their extremities, but also indicate that the upward motion decreases while the active region develops. Moreover, it has been found that, within the limits of the temporal cadence and spatial resolution of the instruments used, the first evidence of the active region formation is initially observed in the transition region and lower corona, and later on (i.e. after about 6 h) in the inner layers (chromosphere and photosphere). Another interesting result concerns the analysis of the magnetograms, indicating that the initial increase in the magnetic flux seems to be synchronous with the appearance od the active region appearance in the transition region and lower corona, and that the rate of increase of the magnetic flux during the formation of the active region is not constant, but is steeper at the beginning (i.e. during the first 150 h) than in the following period. All these results may indicate the presence of some mechanism that decelerates the magnetic flux emergence as more and more flux tubes rise towards higher atmospheric layers. Finally, we would like to stress the observed asymmetries between the preceding and the following sides of NOAA 10050: the p-side is more extented than the f-side, the p-side moves forward from the initial outbreak position much faster than the f-side recedes; the AFS f-side exhibits higher downflows than the p-side.

Quantum Detection Efficiency in Geiger Mode Avalanche Photodiodes

The fabrication of silicon shallow junction photodiodes is a relevant topic for the detection of blue and near ultraviolet weak photon fluxes. In this paper we present a simple model to calculate the quantum detection efficiency (QDE) of a Geiger mode avalanche photodiode (GMAP) as a function of the dead layer thickness above the junction depletion layer. A comparison between calculated and experimental data is also presented. Moreover, by using the same model, an analysis of the QDE at 420 nm wavelength of conventional GMAPs based on shallow N+-P and P+-N junctions is given.

Characterization and performance of the ASIC (CITIROC) front-end of the ASTRI camera

Abstract The Cherenkov Imaging Telescope Integrated Read Out Chip, CITIROC, is a chip adopted as the front-end of the camera at the focal plane of the imaging Cherenkov ASTRI dual-mirror small size telescope (ASTRI SST-2M) prototype. This paper presents the results of the measurements performed to characterize CITIROC tailored for the ASTRI SST-2M focal plane requirements. In particular, we investigated the trigger linearity and efficiency, as a function of the pulse amplitude. Moreover, we tested its response by performing a set of measurements using a silicon photomultiplier (SiPM) in dark conditions and under light pulse illumination. The CITIROC output signal is found to vary linearly as a function of the input pulse amplitude. Our results show that it is suitable for the ASTRI SST-2M camera.

Silicon Photomultipliers Electrical Model Extensive Analytical Analysis

The present work aims to address a comprehensive analytical analysis of a new accurate equivalent electrical model of silicon photomultiplier (SiPM) detectors. The proposed circuit model allows to truthfully reproduce the output signal waveform generated by the light sensors apart from the specific technology adopted for the fabrication process, and can also be profitably exploited to perform reliable circuit-level simulations. A detailed and in-depth investigation of the functional parameters involved in the output pulse signals is here developed, and the most significant physical relationships are analytically derived as well. Experimental measurements are finally carried out on real devices, in order to validate the accuracy of the attained expressions, and good fittings are achieved between the analytical curve plots and the associated measurements results. The adopted analysis turns out to be particularly helpful when designing an optimum front-end architecture for SiPM detectors, since the performance of the entire detection system, especially in terms of dynamic range and timing resolution, can be accurately predicted as a function of the SiPM model parameters and the foremost features of the coupled front-end electronics.

UVSiPM: A light detector instrument based on a SiPM sensor working in single photon counting

Abstract UVSiPM is a light detector designed to measure the intensity of electromagnetic radiation in the 320–900 nm wavelength range. It has been developed in the framework of the ASTRI project whose main goal is the design and construction of an end-to-end Small Size class Telescope prototype for the Cherenkov Telescope Array. The UVSiPM instrument is composed by a multipixel Silicon Photo-Multiplier detector unit coupled to an electronic chain working in single photon counting mode with 10 nanosecond double pulse resolution, and by a disk emulator interface card for computer connection. The detector unit of UVSiPM is of the same kind as the ones forming the camera at the focal plane of the ASTRI prototype. Eventually, the UVSiPM instrument can be equipped with a collimator to regulate its angular aperture. UVSiPM, with its peculiar characteristics, will permit to perform several measurements both in lab and on field, allowing the absolute calibration of the ASTRI prototype.