The single-mirror small-size telescope (SST-1M) is one of the three proposed designs for the small-size telescopes (SSTs) of the Cherenkov Telescope Array (CTA) project. The SST-1M will be equipped ...with a 4 m-diameter segmented reflector dish and an innovative fully digital camera based on silicon photo-multipliers. Since the SST sub-array will consist of up to 70 telescopes, the challenge is not only to build telescopes with excellent performance, but also to design them so that their components can be commissioned, assembled and tested by industry. In this paper we review the basic steps that led to the design concepts for the SST-1M camera and the ongoing realization of the first prototype, with focus on the innovative solutions adopted for the photodetector plane and the readout and trigger parts of the camera. In addition, we report on results of laboratory measurements on real scale elements that validate the camera design and show that it is capable of matching the CTA requirements of operating up to high moonlight background conditions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A mini-imaging air Cherenkov Telescope Ekoume, S.N.; Alispach, C.; Cadoux, F. ...
Journal of instrumentation,
04/2020, Letnik:
15, Številka:
4
Journal Article
Recenzirano
In this paper we describe the different software and hardware elements of a mini-telescope for the detection of cosmic rays and gamma-rays using the Cherenkov light emitted by their induced particle ...showers in the atmosphere. We estimate the physics reach of the standalone mini-telescope and present some results of the measurements done at the Sauverny Observatory of the University of Geneva and at the Saint-Luc Observatory. These measurements demonstrate the ability of the telescope to observe cosmic rays with energy above about 100 TeV. Such a mini-telescope can constitute a cost-effective out-trigger array that can surround other gamma-ray telescopes or extended air showers detector arrays. Its development was born out of the desire to illustrate to students and amateurs the cosmic ray and gamma-ray detection from ground, as an example of what is done in experiments using larger telescopes. As a matter of fact, a mini-telescope can be used in outreach night events. While outreach is becoming more and more important in the scientific community to raise interest in the general public, the realisation of the mini-telescope is also a powerful way to train students on instrumentation such as photosensors, their associated electronics, acquisition software and data taking. In particular, this mini-telescope uses silicon photomultipliers (SiPM) and the dedicated ASIC, CITIROC.
Characterization of a large area silicon photomultiplier Nagai, A.; Alispach, C.; Barbano, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2019, Letnik:
948
Journal Article
Recenzirano
This work illustrates and compares some methods to measure the most relevant parameters of silicon photo-multipliers (SiPMs), such as photon detection efficiency as a function of over-voltage and ...wavelength, dark count rate, optical cross-talk, afterpulse probability. For the measurement of the breakdown voltage, VBD, several methods using the current–voltage IV curve are compared, such as the “IV Model”, the “relative logarithmic derivative”, the “inverse logarithmic derivative”, the “second logarithmic derivative”, and the “third derivative” models. We also show how some of these characteristics can be quite well described by few parameters and allow, for example, to build a function of the wavelength and over-voltage describing the photodetection efficiency. This is fundamental to determine the working point of SiPMs in applications where external factors can affect it.
These methods are applied to the large area monolithic hexagonal SiPM S10943-2832(X), developed in collaboration with Hamamatsu and adopted for a camera for a gamma-ray telescope, called the SST-1M. We describe the measurements of the performance at room temperature of this device. The methods used here can be applied to any other device and the physics background discussed here are quite general and valid for a large phase-space of the parameters.
The single mirror Small Size Telescope (SST-1M) is one of the proposed designs for the smallest type of telescopes, SSTs that will compose the Cherenkov Telescope Array (CTA).
The SST-1M camera will ...use Silicon PhotoMultipliers (SiPM) which are nowadays commonly used in High Energy Physics experiments and many imaging applications. However the unique pixel shape and size have required a dedicated development by the University of Geneva and Hamamatsu. The resulting sensor has a surface of ∼94mm2 and a total capacitance of ∼3.4nF. These unique characteristics, combined with the stringent requirements of the CTA project on timing and charge resolution have led the University of Geneva to develop custom front-end electronics.
The preamplifier stage has been tailored in order to optimize the signal shape using measurement campaigns and electronic simulation of the sensor. A dedicated trans-impedance pre-amplifier topology is used resulting in a power consumption of 400mW per pixel and a pulse width <30ns. The measurements that have led to the choice of the different components and the resulting performance are detailed in this paper.
The slow control electronics was designed to provide the bias voltage with 6.7mV precision and to correct for temperature variation with a forward feedback compensation with 0.17°C resolution. It is fully configurable and can be monitored using CANbus interface. The architecture and the characterization of the various elements are presented.
A prototype camera for one of the Cherenkov Telescope Array (CTA) projects for the small size telescopes, the single mirror Small Size Telescope (SST-1M), has been designed and is under construction. ...The camera is a hexagonal matrix of 1296 large area (95 mm super(2)) hexagonal silicon photomultipliers. The sensors are grouped into 108 modules of 12 pixels each, hosting a preamplifier board and a slow-control board. Among its various functions, this latter implements a compensation logic that adjusts the bias voltage of each sensor as a function of temperature. The fully digital readout and trigger system, DigiCam, is based on the latest generation of FPGAs, featuring a high number of high speed I/O interfaces, allowing high data transfer rates in an extremely compact design.
In view of application in upgraded particles detectors at the LHC accelerator, CERN has developed a radiation and magnetic field tolerant 10W Point-Of-Load (POL) buck DC/DC converter. The DCDC is ...based on FEAST2, an ASIC designed using 'Hardness-By- Design' (HBD) techniques in a selected commercial high voltage CMOS technology. The main features of the circuit, together with electrical characterization as well as radiation data for TID, Displacement Damage (DD) and SEEs are presented. FEAST2 meets all the requirements of the LHC experiments and is also a possible good candidate for applications in Space.
The Cherenkov Telescope Array (CTA), the next generation very high energy gamma-rays observatory, will consist of three types of telescopes: large (LST), medium (MST) and small (SST) size telescopes. ...The SSTs are dedicated to the observation of gamma-rays with energy between a few TeV and a few hundreds of TeV. The SST array is expected to have 70 telescopes of different designs.
The single-mirror small size telescope (SST-1M) is one of the proposed telescope designs under consideration for the SST array. It will be equipped with a 4m diameter segmented mirror dish and with an innovative camera based on silicon photomultipliers (SiPMs).
The challenge is not only to build a telescope with exceptional performance but to do it foreseeing its mass production. To address both of these challenges, the camera adopts innovative solutions both for the optical system and readout.
The Photo-Detection Plane (PDP) of the camera is composed of 1296pixels, each made of a hollow, hexagonal light guide coupled to a hexagonal SiPM designed by the University of Geneva and Hamamatsu. As no commercial ASIC would satisfy the CTA requirements when coupled to such a large sensor, dedicated preamplifier electronics have been designed. The readout electronics also use an innovative approach in gamma-ray astronomy by adopting a fully digital approach. All signals coming from the PDP are digitized in a 250MHz Fast ADC and stored in ring buffers waiting for a trigger decision to send them to the pre-processing server where calibration and higher level triggers will decide whether the data are stored. The latest generation of FPGAs is used to achieve high data rates and also to exploit all the flexibility of the system. As an example each event can be flagged according to its trigger pattern. All of these features have been demonstrated in laboratory measurements on realistic elements and the results of these measurements will be presented in this contribution.
SiPM behaviour under continuous light Nagai, A.; Alispach, C.; Volpe, D. della ...
Journal of instrumentation,
12/2019, Letnik:
14, Številka:
12
Journal Article
Recenzirano
This paper reports on the behaviour of Silicon Photomultiplier (SiPM) detectors under continuous light. Usually, the bias circuit of a SiPM has a resistor connected in series to it, which protects ...the sensor from drawing too high current. This resistor introduces a voltage drop when a SiPM draws a steady current, when illuminated by constant light. This reduces the actual SiPM bias and then its sensitivity to light. As a matter of fact, this effect changes all relevant SiPM features, both electrical (i.e. breakdown voltage, gain, pulse amplitude, dark count rate and optical crosstalk) and optical (i.e. photon detection efficiency). To correctly operate such devices, it is then fundamental to calibrate them under various illumination levels. In this work, we focus on the large area (∼1 cm2) hexagonal SiPM S10943-2832(X) produced by Hamamatsu HPK for the camera of a gamma-ray telescope with 4 m-diameter mirror, called the SST-1M. We characterize this device under light rates raging from 3 MHz up to 5 GHz of photons per sensor at room temperature (T=25ˆC). From these studies, a model is developed in order to derive the parameters needed to correct for the voltage drop effect. This model can be applied for instance in the analysis of the data acquired by the camera to correct for the effect. The experimental results are also compared with a toy Monte Carlo simulation and finally, a solution is proposed to compensate for the voltage drop.
3D silicon pixel sensors: Recent test beam results Hansson, P.; Balbuena, J.; Barrera, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2011, Letnik:
628, Številka:
1
Journal Article
Recenzirano
The 3D silicon sensors aimed for the ATLAS pixel detector upgrade have been tested with a high energy pion beam at the CERN SPS in 2009. Two types of sensor layouts were tested: full-3D assemblies ...fabricated in Stanford, where the electrodes penetrate the entire silicon wafer thickness, and modified-3D assemblies fabricated at FBK-irst with partially overlapping electrodes. In both cases three read-out electrodes are ganged together to form pixels of dimension
50
×
400
μ
m
2
. Data on the pulse height distribution, tracking efficiency and resolution were collected for various particle incident angles, with and without a 1.6
T magnetic field. Data from a planar sensor of the type presently used in the ATLAS detector were used at the same time to give comparison.
This paper describes a comparison of photon detection efficiency and optical crosstalk measurements performed by three partners: Geneva University, Catania Observatory and Nagoya University. The ...measurements were compared for three different SiPM devices with different active areas: from 9mm2 up to 93.6mm2 produced by Hamamatsu. The objective of this work is to establish the measurements and analysis procedures for calculating the main SiPM parameters and their precision. This work was done in the scope of SENSE project which aims to build roadmap for the last developments in field of sensors for low light level detection.
•Hamamatsu MPPC: LVR-3050CS, LVR-6050CS and Hexagonal MPPC for CTA.•PDE vs Overvoltage, PDE vs Wavelength measurements.•Optical crosstalk measurements.•Comparison of measurements between three labs.
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