1,721,125 research outputs found
Overview on the main parameters and technology of modern Silicon Photomultipliers
No full textIn this paper, we give an overview of the main properties and technological implementation of densely packed
Single-photon Avalanche Diode arrays, which are commonly known as Silicon Photomultipliers, or SiPMs. These
detectors feature high internal gain, single-photon sensitivity, a high Photon Detection Efficiency, proportional
response to weak and fast light flashes, excellent timing resolution, low bias voltage, ruggedness and insensitivity
to magnetic field. They compare favorably to the traditional Photomultiplier Tube in several applications. In this
overview paper, we go through the SPAD/SiPM theory of operation, the modern SiPM implementations and the
typical technological options to build the sensor. This is done in conjunction with the description of the main
SiPM parameters, such as the Photon Detection Efficiency, the electrical properties, the primary and correlated
noise sources and the Single Photon Time Resolution
"The readout electronics and the DAQ system of the DRAGO Anger Camera"
No full textThe aim of the DRAGO project is the development of a compact, high resolution gamma ray imager, based on the Anger Camera principle, with sub-millimeter spatial resolution. The imager is composed by a monolithic array of 77 silicon drift detectors, with an active area of 26 times 29 mm, coupled to a CsI(Tl) scintillator. The position of interaction of the photon, inside the crystal is obtained by a digital centroid identification algorithm. In this work we describe the electronic readout system of the camera, which is composed by an analog front end and an acquisition board. The analog front end is composed of 80 readout channels divided in 10 CMOS chips, built in 0.35 um CMOS technology, each one processing 8 channels. Each analog channel of the circuit includes a low-noise preamplifier, a 6th order semi Gaussian shaping amplifier with four selectable peaking times from 1.8 us up to 6 us, a peak stretcher and a baseline holder. The acquisition board converts all the data coming from the 77 detectors, with a resolution of 13 bits, and sends them to the host PC via a USB interface. The two system have been experimentally characterized alone and working together, also during Anger Camera operation
A Passive-Quenching Active-Recharge Analog Silicon Photomultiplier
No full textIn this work, we propose a new analog SiPM structure, characterized by the Passive Quenching Active Recharge operation of the microcells. The structure is obtained by including a MOSFET transistor close to each cell. The transistor is built without any changes to the standard SiPM micro-fabrication process and it does not significantly reduce the fill-factor of the device. We operated this detector in a periodic pulsed reset mode. Potential advantages of this approach are: reduction of the effective Dark Count Rate, strong suppression of the afterpulsing, very short pulse duration, lower fabrication cost. In this paper, we provide a preliminary characterization of the first 1x1 mm2 prototype of the structure, with 50x50 μm2 cells, fabricated at FBK. The measured duration of he single-cell response is 3.4 ns FWHM. Using a pulsed LED source, we were able to measure a very good photon counting resolution at a level of 18 detected photons and more, thanks to the absence of after pulses
The DLED Algorithm for Timing Measurements on Large Area SiPMs Coupled to Scintillators
No full textOne of the main factors limiting the precision of timing measurements with silicon photomultipliers coupled to scintillators is the dark noise, especially in the case of large devices. In order to cope with it, a suitable signal processing should be employed. The method we propose is called differential leading edge discriminator (DLED) and allows an effective compensation of the baseline fluctuations due to the dark counts of the detector.
In this paper we show a comparison between the measurements
obtained using the traditional Leading Edge Discriminator technique
and the DLED. The improvement we observe is remarkable.
Combining this baseline correction algorithm with low temperatures,
we were able to reach a coincidence resolving time of 180 ps
FWHM, using 4mm x 4mm SiPMs produced at FBK coupled to
3.8mm x 3.8mm x 5 mm Teflon-wrapped LYSO crystals
Uso turistico del territorio
No full textIl contributo tratta del rapporto tra disciplina giuridica del mercato del turismo e disciplina giuridica del territorio, analizzandone i diversi livelli di criticità e di potenzialità
Analog Circuit for Timing Measurements With Large Area SiPMs Coupled to LYSO Crystals
No full textThe most common method for time pick-off from signals coming from SiPMs coupled to scintillator crystals in PET applications is the Leading Edge Triggering. In this work we propose a new filtering scheme to be applied before the discriminator. It implements a type of baseline compensation aimed at the reduction of the time jitter due to the dark counts of the detector and is based on a simple analog filter, which is well suited for an ASIC implementation. We describe a circuit, built with discrete components, that implements the filter. Finally we report on the Coincidence Resolving Time measurements performed coupling the circuit to the real detector, composed of a SiPM built at FBK and a LYSO crystal, for the detection of 511 keV photons. The results obtained are promising, showing that the method is quite effective in reducing the impact of the detector noise on the timing performance of the system
The electronics readout and the DAQ system of the DRAGO Anger Camera
No full textThe aim of the DRAGO project, supported by Italian INFN, is the development of a high-resolution, compact γ-ray imager, based on the Anger Camera principle. In this configuration, the light generated by a unique scintillator is read by an array of 77 Silicon Drift Detectors. In order to locate the position of interaction of the photon inside the scintillator, it is necessary to make an amplification and filtering of the detector signals followed by a processing of the acquired data. The electronics readout and processing system can be divided in two separate parts: the analog front end and the DAQ board. The analog front end is composed of 80 readout channels divided in 10 CMOS chips, produced in the 0.35 μm AMS technology, each one processing 8 channels. Each analog channel of the circuit includes a low-noise preamplifier, a sixth-order semigaussian shaping amplifier with four selectable peaking times from 1.8 μs up to 6 μs, a peak stretcher and a baseline holder. The energy resolution measured using a single channel of the chip with a Silicon Drift Detector Droplet (SD3) is of 128 eV FWHM at 6 keV with the detector cooled at −20 °C. The 8 analog channels of the chip are multiplexed to a single analog output and fed to the acquisition system. For each γ event, this system performs the A/D conversion of all the signals of the array and sends them to a host PC, where the position reconstruction algorithm is executed. The DAQ board contains 10 ADCs, each one dedicated to a single ASIC of the analog section and having a resolution of 13 bit (ENOB). The burst conversion rate of the 10 ADCs together is 50 Ms/s resulting in a dead time of about 2 μs/event. The converted data are stored in a FIFO memory, for buffering, and then are transferred to the host PC via a USB 2.0 interface, which allows an event rate of more than 40k events/s for the whole Anger Camera, compatible with the application
Il mercato turistico e il suo codice
No full textil contributo evidenzia l'impatto del nuovo codice del turismo, d.lgs. n. 79 del 2011 sull'ordinamento di settore e gli effetti della cancellzione di una parte rilevante delle nuove disposizioni da parte della sentenza della Corte costituzionale n. 80 del 2012, con effetti rilevanti sul mercato turistico, rimasto così privo di un riferimento normativo unitari
Timing Properties of Silicon Drift Detectors for Scintillation Detection
No full textIn this paper, we have evaluated the timing properties offered by silicon drift detectors to be used as scintillation photodetectors in systems for medical imaging. The peculiar drift mechanism of the charge created inside the SDD volume is responsible for a rise time of the signal at the output of the device when this is irradiated over its whole active area. Despite this effect, the rise time is in the order of 200 ns for a 5 mm2 device, therefore, still comparable with the shaping time used for timing measurements. In this paper, the effect on the timing performances of SDDs due to the drift mechanism is first theoretically evaluated.We have then carried out the experimental characterization of the timing properties of a 5-mm2 SDD coupled to a GSO crystal, in coincidence with a NaI-PMT detector, using a 22 Na source. Despite the low conversion gain of the system (2.5 e-/keV), due to the low light output of the crystal and the nonoptimized quantum efficiency of the SDD, a timing resolution of 22 ns was measured for 511 keV photons. This corresponds to a product resolution times number of collected electrons of about 13 9 103 ns e h which is comparable to the
one achieved with APDs of similar areas. By irradiating the SDD directly with laser pulses, a resolution better than 1 ns was achieved with more than 60.000 electrons, showing no relevant limitations due to possible jitters of the drift tim
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