The performances of an optical readout of Time Projection Chambers (TPCs) with multiple Gas Electron Multipliers (GEMs) amplification stages are presented. The detector is characterized by using 55Fe ...photons converting inside a 7 litre sensitive volume detector in different electric field configurations. This prototype is developed as part of the R&D for the CYGNO project for an application to direct Dark Matter search by detection of tracks of nuclear recoils in the gas within the keV energy range.
The goal of the Cryogenic wide-Area Light Detectors with Excellent Resolution project is the development of light detectors with large active area and noise energy resolution smaller than 20 eV RMS ...using phonon-mediated kinetic inductance detectors. The detectors are developed to improve the background suppression in large-mass bolometric experiments such as CUORE, via the double read-out of the light and the heat released by particles interacting in the bolometers. In this work, we present the design and the fabrication process, starting from the silicon wafer arriving to the single chip. The Al thin films (40 nm) are evaporated on high-quality, high-resistivity (>
10
k
Ω
cm) Si(100) substrates using an electron beam evaporator in a high-vacuum chamber. Detectors are patterned in direct-write mode, using electron beam lithography , positive tone resist poly-methyl methacrylate and lift-off process. Finally the wafer is diced into 20
×
20 mm
2
chips and assembled in a holder OFHC copper (oxygen-free high conductivity) using PTFE supports.
► TeO2 crystals are good bolometer for neutrinoless double beta decay search. ► Up to now alpha background cannot be distinguished in TeO2 bolometers. ► We detected light from TeO2 crystals which ...allows alpha background rejection. ► The light can be explained as due to Cerenkov emission.
TeO2 crystals have proven to be superb bolometers for the search of neutrinoless double beta decay in many respects. However, if used alone, they do not exhibit any feature that allows to discriminate an α energy deposit from a β/γ one. This fact limits their ability to reject the background due to natural radioactivity and eventually affects the sensitivity of the search. In this paper we show the results of a TeO2 crystal where, in coincidence with its bolometric heat signal, also the luminescence light escaping the crystal is recorded. The results show that we are able to measure the light produced by β/γ particles, which can be explained as due to Cerenkov emission. No light is detected from α particles, allowing the rejection of this background source.
TeO2 crystals are currently used as bolometric detectors in experiments searching for the neutrinoless double beta decay of 130Te. The extreme rarity of the studied signal forces the experiments to ...reach an ultra low background level. The main background source is represented by α particles emitted by radioactive contaminants placed in the materials that compose and surround the detector. Recent measurements show that a particle discrimination in TeO2 bolometers detecting the light emitted by β/γ particles is possible, opening the possibility to make large improvements in the performance of experiments based on this kind of materials. In order to understand the nature of this light emission a measurement at room temperature with TeO2 crystals was performed. According to these results, the detected light was compatible with the Cherenkov emission, even though the scintillation hypothesis could not be discarded. In this work a Monte Carlo (MC) simulation of the Cherenkov radiation emitted by TeO2 crystal when crossed by cosmic muons was performed. The data from MC and the room temperature measurement are perfectly compatible and prove that the Cherenkov light is the only component of the light yield of TeO2 crystals.
The goal of the CYGNO project is to deploy at Laboratori Nazionali del Gran Sasso (LNGS) an high resolution Time Projection Chamber (TPC) with Gas Electron Multipliers (GEMs) amplification and ...optical 3D readout of an Helium/Fluorine based gas mixture for directional Dark Matter (DM) searches at low 1-10 GeV WIMP masses. The determination of the incoming direction of WIMP particles can in fact offer not only additional handles for discrimination of the annoying backgrounds, but especially an unique key for a positive, unambiguous identification of a DM signal.
First results and perspectives of CALDER Vignati, M.; Bellini, F.; Cardani, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2016, Letnik:
824
Journal Article
Recenzirano
Large-mass arrays of bolometers proved to be good detectors for Neutrinoless Double Beta Decay (0νββ) and Dark Matter searches. CUORE and LUCIFER are bolometric 0νββ experiments which will start to ...take data in 2016 at Laboratori Nazionali del Gran Sasso in Italy. The sensitivity of CUORE could be increased by removing the background due to α particles, by detecting the small amount of Cherenkov light (100eV) emitted by the βs׳ signal and not by αs. LUCIFER could be extended to detect also Dark Matter, provided that the background from β/γ particles (100eV of scintillation light) is discriminated from nuclear recoils of about 10keV energy (no light). CALDER is a project to develop light detectors for CUORE, LUCIFER and similar bolometric experiments. The goal is to obtain detectors with an active area of 5×5cm2 (the face of bolometric crystals), operating at 10mK, and with a baseline resolution better than 20eV. We have chosen to develop phonon-mediated devices using Kinetic Inductance Detectors (KIDs). We present the first results and the perspectives of the project.
The CUPID-0 detector hosted at the Laboratori Nazionali del Gran Sasso, Italy, is the first large array of enriched scintillating cryogenic detectors for the investigation of
Se neutrinoless ...double-beta decay (
). CUPID-0 aims at measuring a background index in the region of interest (RoI) for
at the level of 10
counts/(keV kg years), the lowest value ever measured using cryogenic detectors. CUPID-0 operates an array of Zn
Se scintillating bolometers coupled with bolometric light detectors, with a state of the art technology for background suppression and thorough protocols and procedures for the detector preparation and construction. In this paper, the different phases of the detector design and construction will be presented, from the material selection (for the absorber production) to the new and innovative detector structure. The successful construction of the detector lead to promising preliminary detector performance which is discussed here.
A convincing observation of neutrino-less double beta decay (0vDBD) relies on the possibility of operating high-energy resolution detectors in background-free conditions. Scintillating cryogenic ...calorimeters are one of the most promising tools to fulfill the requirements for a next-generation experiment. Several steps have been taken to demonstrate the maturity of this technique, starting form the successful experience of CUPID-0. The CUPID-0 experiment collected almost 10 kg y of exposure, running 26 Zn82Se crystals during two years of continuous detector operation. The complete rejection of the dominant α background was demonstrated, measuring the lowest counting rate in the region of interest for this technique. Furthermore, the most stringent limit on the 82Se 0vDBD was established. In this contribution we present the final results of CUPID-0 phase-I, including a detailed model of the background and the measurement of the 2vDBD half-life.
Oral food challenge (OFC) is still considered the gold standard for diagnosis of food allergy (FA). Skin prick test (SPT) and specific IgE (sIgE) tests are very useful but limited in their predictive ...accuracy. End point test (EPT) has been recently considered to determine the starting dose to induce oral desensitization. Allergometric tests combined may discriminate children at higher risk of reactions during OFC. We considered 94 children referred to our Allergy and Immunology Pediatric Department between January 2009 and December 2011 with CMA. Cutaneous allergometric skin tests (SPT and EPT) were periodically performed on all 94 children with CMA; sIgE levels against cow's milk proteins (CMP) α-lactalbumin, β-lactoglobulin and casein were periodically evaluated through blood samples every 6-12 months. During the period of the study, 26/94 (27.6%) children underwent more than once OFC. We collected 135 OFC compared with clinical presentation: 49/135 (36.2%) OFC were performed shortly after the onset of symptoms directly related to spontaneous intake of milk, to confirm suspicion of FA; 86/135 (63.7%) OFC were performed to evaluate the acquisition of tolerance. Of these, 52/86 (60.4%) OFC resulted positive, 34/86 (39.5%) were negative. The 3D EPT has the best ratio sensitivity (SE) / positive predictive value (PPV), SE 83%, specificity (SP) 58.3%, PPV 89.3%, negative predictive value (NPV) 45.1%. EPT 6D and 7D have the best PPV (100%) with a low NPV (respectively 22.2% and 21.2%). We obtained that a mean fresh milk wheal diameter ≥ 12 mm was predictive of 97% OFC, but only 32/101 (31.6%) allergic children presented this value. The tests with a wheal diameter ≤ 5 were performed on younger children, all of which were less than 9 months old; only 5 other tests performed on less than 9 months olds resulted in the others subgroups (1 in ≥ 12 mm wheal and 4 in the group between 6-11 mm). We also found that 95% of children with 4D EPT wheal diameter < 6 mm resulted tolerant. This cut off could be useful to decide which children have a lower risk of reactions during the OFC. EPT is more useful than SPT especially for children < 1 year of age being a less operator dependent test, and it could be helpful to discriminate between children with the highest risk to develop anaphylaxis following an OFC (≥ 5D positive EPT) and children with lowest risk (> 2D positive EPT), but it can't replace OFC, that currently remains the gold standard in the diagnosis of FA. We also underline that in allergic children younger than 9 months old, the values of SPT with fresh milk is much lower than in older children, so that it's better to separate this group of age when we try to predict the evolution of OFC through the evaluation with EPT. A validation of such results in a prospective study could maybe be useful to confirm the outcome of our data in the predictivity of OFC.
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