The DarkSide-20k experiment aims to the direct WIMP detection in extremely low background conditions, using a Time Projection Chamber (TPC) filled with 40 tons of Liquid Argon and equipped with more ...than 200000 Silicon Photomultipliers (SiPMs) operated at cryogenic temperature. Since many years, the Bruno Kessler Foundation has been involved in the development of different kind of SiPMs sensitive to different wavelengths with low dark count rate and correlated noise. After a long and successful R&D, excellent results have been obtained, fully matching the specifications required by a background-free liquid argon experiment. The TPC will be instrumented with 8280 Photo Detection Modules each made by a SiPM tile of 25 cm2 and a Front End Board, in an acrylic mechanical structure. A dedicated cryogenic electronics with an optical transmission of the signal has been developed to read out the large SiPM area and reduce the mass of the cables in the cryostat due to the wide number of independent channels guaranteeing at the same time a high level of radiopurity. Moreover, the assembly of such a huge number of photodetectors demands a dedicated facility: the DarkSide strategy and working plan will be also reported.
Muography is an imaging technique based on the measurement of absorption profiles for muons as they pass through rocks and earth. Muons are produced in the interactions of high-energy cosmic rays in ...the Earth's atmosphere. The technique is conceptually similar to usual X-ray radiography, but with extended capabilities of investigating over much larger thicknesses of matter thanks to the penetrating power of high-energy muons. Over the centuries a complex system of cavities has been excavated in the yellow tuff of Mt. Echia, the site of the earliest settlement of the city of Naples in the 8th century BC. A new generation muon detector designed by us, was installed under a total rock overburden of about 40 metres. A 26 days pilot run provided about 14 millions of muon events. A comparison of the measured and expected muon fluxes improved the knowledge of the average rock density. The observation of known cavities proved the validity of the muographic technique. Hints on the existence of a so far unknown cavity was obtained. The success of the investigation reported here demonstrates the substantial progress of muography in underground imaging and is likely to open new avenues for its widespread utilisation.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A large number of particle detectors employ liquid argon as their target material owing to its high scintillation yield and its ability to drift ionization charge over large distances. Scintillation ...light from argon is peaked at 128 nm and a wavelength shifter is required for its efficient detection. In this work, we directly compare the light yield achieved in two identical liquid argon chambers, one of which is equipped with polyethylene naphthalate (PEN) and the other with tetraphenyl butadiene (TPB) wavelength shifter. Both chambers are lined with enhanced specular reflectors and instrumented with SiPMs with a coverage fraction of approximately 1%, which represents a geometry comparable to the future large scale detectors. We measured the light yield of the PEN chamber to be 39.4
±
0.4(stat)
±
1.9(syst)% of the yield of the TPB chamber. Using a Monte Carlo simulation this result is used to extract the wavelength shifting efficiency of PEN relative to TPB equal to 47.2
±
5.7%. This result paves the way for the use of easily available PEN foils as a wavelength shifter, which can substantially simplify the construction of future liquid argon detectors.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A Time of Flight (ToF) scintillator system has been developed for the PAMELA satellite-borne cosmic ray experiment. The main scientific goal of the experiment is the measurement of the antiproton and ...positron fluxes in the cosmic radiation over large energy ranges. The ToF system provides the fast trigger to the experiment, the rejection of albedo particles and the possibility to distinguish electrons from antiprotons up to about 1.5
GeV.
In this paper we describe the performances of the ToF system measured on flight data.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Yarrowia lipolytica is an oleaginous yeast that can be genetically engineered to produce lipid and non-lipid biochemicals from a variety of feedstocks. Metabolic engineering of this organism usually ...requires genetic markers in order to select for modified cells. The potential to combine multiple genetic manipulations depends on the availability of multiple or recyclable selectable markers.
We found that Y. lipolytica has the ability to utilize acetamide as the sole nitrogen source suggesting that the genome contains an acetamidase gene. Two potential Y. lipolytica acetamidase gene candidates were identified by homology to the A. nidulans acetamidase amdS. These genes were deleted in the wild-type Y. lipolytica strain YB-392, and deletion strains were evaluated for acetamide utilization. One deletion strain was unable to grow on acetamide and a putative acetamidase gene YlAMD1 was identified. Transformation of YlAMD1 followed by selection on acetamide media and counterselection on fluoroacetamide media showed that YlAMD1 can be used as a recyclable genetic marker in Saccharomyces cerevisiae and Ylamd1Δ Y. lipolytica.
These findings add to our understanding of Y. lipolytica nitrogen utilization and expand the set of genetic tools available for engineering this organism, as well as S. cerevisiae.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Recent developments of the nuclear emulsion technology led to the production of films with nanometric silver halide grains suitable to track low energy nuclear recoils with submicrometric length. ...This improvement opens the way to a directional Dark Matter detection, thus providing an innovative and complementary approach to the on-going WIMP searches. An important background source for these searches is represented by neutron-induced nuclear recoils that can mimic the WIMP signal. In this paper we provide an estimation of the contribution to this background from the intrinsic radioactive contamination of nuclear emulsions. We also report the neutron-induced background as a function of the read-out threshold, by using a GEANT4 simulation of the nuclear emulsion, showing that it amounts to about 0.06 per year per kilogram, fully compatible with the design of a 10 kg × year exposure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Abstract
In this work we will document the design and the performances of a SiPM-based photo-detector with a surface area of 100 cm
2
conceived to operate as a replacement for PMTs. The signals from ...94 SiPMs are summed up to produce an aggregated output that exhibits in liquid nitrogen a dark count rate (DCR) lower than 100 cps over the entire surface, a signal to noise ratio better than 13, and a timing resolution better than 5.5 ns. The module feeds about 360 mW at 5 V with a dynamic range in excess of 500 photo-electrons on a 100 Ω differential line. The unit can also operate at room temperature, at the cost of an increase of DCR to 10
8
cps.
The Schwarzschild Couder Medium Size Telescope prototype (pSCT) is going to test the Schwarzschild Couder solution proposed for Medium Size telescopes for the Cherenkov Telescope Array. The camera ...consists of 177 photodetection modules grouped into sectors of maximum 25 modules each. The sensitive elements of the modules, located in the focal plane of the telescope, are matrices of 64 6 mm × 6 mm pixels of Silicon Photomultipliers (SiPMs). The front-end electronics is designed for signal sampling technique using the TARGET-7 ASIC. The prototype under construction and test at the Fred Lawrence Whipple Observatory site will be equipped with the inner central sector fully operational. Sensors from Fondazione Bruno Kessler will be used for 9 of the 25 modules. A complete characterization of these very recent, highly sensitive Near UV sensors, the assembly procedure and metrology results on several focal plane elements has been conducted. Performances of the 16-sensors matrices and measurements with the TARGET-7 ASIC front-end coupled to FBK sensors will be shown and deeply discussed.
•A camera for the prototype Schwarzschild Couder Telescope for CTA is being tested.•A 16-FBK SiPM matrix was studied and its homogeneity was verified.•The TARGET 7 readout module was coupled and optimized to the FBK SiPMs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The development of automatic scanning systems was a fundamental issue for large scale neutrino detectors exploiting nuclear emulsions as particle trackers. Such systems speed up significantly the ...event analysis in emulsion, allowing the feasibility of experiments with unprecedented statistics. In the early 1990s, R&D programs were carried out by Japanese and European laboratories leading to automatic scanning systems more and more efficient. The recent progress in the technology of digital signal processing and of image acquisition allows the fulfillment of new systems with higher performances. In this paper we report the description and the performance of a new generation scanning system able to operate at the record speed of 84 cm super(2)/hour and based on the Large Angle Scanning System for OPERA (LASSO) software infrastructure developed by the Naples scanning group. Such improvement, reduces the scanning time by a factor 4 with respect to the available systems, allowing the readout of huge amount of nuclear emulsions in reasonable time. This opens new perspectives for the employment of such detectors in a wider variety of applications.
We report about a study of the light response of a solid polystyrene-based scintillator with an arch shaped geometry, directly coupled to Silicon Photo Multiplier sensors for the light readout. This ...geometry is relevant for the design of a novel borehole detector for “muography” applications in Civil Engineering, Geology or Archaeology. The scintillator response has been investigated using a dedicated experimental set-up based on the detection of cosmic ray muons. Configurations that use reflecting and diffusive materials have been tested, as well as configurations with a cover specifically designed to enclose and protect the scintillator. The results found a good compromise between the light response and an easy solution for the detector assembly.
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