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
The Cherenkov Telescope Array (CTA) is a future gamma-ray observatory that is planned to significantly improve upon the sensitivity and precision of the current generation of Cherenkov telescopes. ...The observatory will consist of several dozens of telescopes with different sizes and equipped with different types of cameras. Of these, the FlashCam camera system is the first to implement a fully digital signal processing chain which allows for a traceable, configurable trigger scheme and flexible signal reconstruction. As of autumn 2016, a prototype FlashCam camera for the medium-sized telescopes of CTA nears completion. First results of the ongoing system tests demonstrate that the signal chain and the readout system surpass CTA requirements. The stability of the system is shown using long-term temperature cycling.
•A full-scale prototype of the FlashCam Cherenkov camera is in operation.•System level testing and characterisation in a dark room is ongoing.•The performances of the data acquisition and the signal chain have been verified.•The system is stable over long periods and robust against temperature variations.
With regard to automotive traffic, a tunnel-type semi enclosed atmosphere is characterized by a higher concentration of gaseous pollutants than on urban traffic roads and highlights the gaseous ...effluent species having an impact on material degradation. Therefore, a transverse approach between air quality and its consequences upon the longevity of materials is necessary, implying better knowledge of tunnel atmosphere and a better understanding of material degradation inside a tunnel for operating administration. Gaseous pollutant measurements carried out in a road tunnel in Rouen （Normandy） give the real world traffic concentrations of experimental exposure conditions. The sampling campaigns, achieved in summer and winter include SO2, NO2, BTEX and aldehyde analyses. Effluent profiles in the upward and downward tubes have been established. The current work shows that SO2, NO〉 formaldehyde, acetaldehyde, propanal and butanal must be considered in the degradation process of materials in a stuffy environment. As regards NO,, its concentration depends on the modification of the automotive fleet. The total aldehyde concentrations indicate no particular trend between the two bores. Formaldehyde, acetaldehyde, propanal, butanal and acrolein species are the most abundant species emitted by vehicles and represent 90% to 95% of the total aldehyde emissions.
A tunnel-type semi-enclosed atmosphere is characterized by a higher particulate pollution than urban zones and highlights the particulate species having an impact on material degradation. Therefore, ...a transverse approach between air composition and its consequences upon longevity of materials is necessary, requiring a better knowledge of tunnel atmosphere and a better understanding of material degradation inside a tunnel for operating administration. The characterization of particulate matter collected inside a road tunnel in Rouen (France) allows us to set up the features of the particle characteristics of the real conditions of field exposure. Two sampling campaigns include analyses of organic and water-soluble ionic fractions. The current work shows that organic species, grouped into two sets derived primarily from engine exhaust and debris with wear particles resuspended by the traffic, are divided into two groups: a majority comprising n-alkanes, alkanoic acids, phthalates, ketones, and benzothiazole and a minority one composed of BTEX (benzene, toluene, ethylbenzene, and xylenes), polycyclic aromatic hydrocarbons (PAHs), fatty acid methyl esters (FAMEs), furans, phenols, and alkenes. As regards the water-soluble ionic fraction, the ionic species such as Cl
−
, SO
4
2−
, CH
3
COO
−
, HCOO
−
, NO
3
−
, NH
4
+
, and Na
+
are involved in the degradation process. The inorganic particles (insoluble and slightly soluble), debris and wear particles, organic acids, and relative humidity play a key role and are important factors to consider in the degradation process.
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.
The runoff rates of copper, zinc, nickel and tin were studied in a French industrial area for 161 days. The mass variation of the metallic coupons and the adherent corrosion layers were analysed at ...different time intervals, using a multianalytical approach. Atmospheric corrosion of copper is associated with the formation of a corrosion layer which is partly soluble in water, mainly composed of cuprite and basic copper sulphate salts. The corrosion of zinc is accompanied by the formation of a corrosion layer, partly soluble, containing mainly basic zinc carbonate and basic zinc sulphate salts. The behaviour of nickel exposed in an unsheltered atmosphere is characterised by a pitting corrosion process. Soluble corrosion salts such as nickel sulphates, chlorides and nitrates, formed during relative dry periods, are totally dissolved during rainfall events. The corrosion product of tin has been identified as a poorly crystallised hydrated stannic oxide. Depending on the solubility of corrosion products, the runoff rates appear to be different for these metals in the following order: zinc>copper>nickel>tin. Tin runoff rate is insignificant because of the insoluble corrosion products formed on the surface. This paper sets out a comparison between metal ions and anionic species found in the runoff water at various collecting period. The results revealed the runoff amount of copper, zinc and nickel released mainly from the dissolution of soluble sulphate compounds present in the corrosion layers.
This study shows the effects of roughness on infrared spectra shapes of thin corrosion products on metallic substrates. The calculated spectra show that the baseline is mainly affected by increasing ...roughness and that such effects do not shift the position of the absorption bands. The model obtained has been used to extract data of artificial patina on a copper surface. Surface defects of copper substrates can be distinguished on the whole surface, from the morphological and chemical points of view, using optical profilometry and infrared microspectroscopy. An homogeneous layer of cuprite covers the surface except in the linear defects. Fourier transform infrared (FT-IR) analysis indicates that a mixture of atacamite and clinoatacamite is mainly located in these scratchs. The width of these particular areas is in good agreement with profilometric observations.
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.
FTIR reflectance spectroscopy has been used for the characterization of products formed by an accelerated wet ageing test on industrial hot-dip galvanized steel. Several aluminium contents are ...selected. Various products have been detected in this study. The kind and amount vary with the substrate, the type of ageing test used, the relative humidity level and the temperature. The galvanized coatings studied show a mixed zinc—aluminium compound, Zn
6Al
2(OH)
16CO
3·4H
2O. This phase is observed from the first exposure time on all coatings regardless of the amount of aluminium. Contrary to zinc, no basic aluminium compound has been detected.
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