152 research outputs found
Positron timing and detection in the MEG experiment
No full textHere the high timing resolution positron detector designed to be used in the MEG experiment is described. Several technical challenges have been faced to obtain the unprecedented goal resolution of 100 ps FWHM for positrons to be detected in the MEG experiment. Also an overview on past experiments is proposed. The key role of the MEG experiment in unveiling New Physics phenomena is briefly stressed. © owned by the author
Fabrication and Test of Large Area Spider-Web Bolometers for CMB Measurements
No full textDetecting the primordial âB-modeâ polarization of the cosmic microwave background is one of the major challenges of modern observational cosmology. Microwave telescopes need sensitive cryogenic bolometers with an overall equivalent noise temperature in the nK range. In this paper, we present the development status of large area (about 1 cm2) spider-web bolometer, which imply additional fabrication challenges. The spider-web is a suspended Si3N41 Î1⁄4 m-thick and 8-mm diameter with mesh size of 250 Î1⁄4 m. The thermal sensitive element is a superconducting transition edge sensor (TES) at the center of the bolometer. The first prototype is a TiâAu TES with transition temperature tuned around 350 mK, new devices will be a MoâAu bilayer tuned to have a transition temperature of 500 mK. We present the fabrication process with micro-machining techniques from silicon wafer covered with SiO2- Si3N4CVD films, 0.3 and 1 Î1⁄4 m- thick, respectively, and preliminary tests
A simulation tool for scintillating fibers coupled to SiPM for MIP and heavy ionizing particle identification
No full textThe MEG experiment searches for the μ+e+γ decay by stopping on a thin passive target the most intense continuous muon beam in the world. We are studying the possibility to have an active target, which should continuously monitor the muon beam and provide a precise measurement of the decay vertex, complementing the new spectrometer. The detector is based on thin scintillating fibers coupled to silicon photomultipliers (SiPMs), exploiting their insensitivity to the magnetic field, competitive PDE with respect to nominal PMT QE and low HV supply.This device can be used as a stand alone tool. In this paper we present a Monte Carlo simulation for a single fiber coupled to SiPM in order to study the propagation of the photons through the fiber and the response of the SiPM
Properties of single crystal para-terphenyl as medium for high resolution TOF detector
No full textIn the last years organic scintillators have been largely investigated in order to achieve high light yield together with good time response. Pure organic compound with high quality crystalline structure can achieve both this goals. Among a large type of organic compound, para-terphenyl (C18H14) have proven to have practical applications as detector medium for particle physics. In this work, the characterization of different sizes high quality mono-crystal p-terphenyl samples is presented. The optical and scintillation properties (emission spectrum, light yield, attenuation length, and decay time) are investigated. Coupling a Silicon PhotoMultiplier-based readout system to the crystal, a small prototype for a high resolution TOF detector was built; the preliminary results, obtained on a 20Ã30Ã3 mm3sample, with dual-side read-out (Hamamatsu S10931-050P SiPMs) and irradiated with90Sr source, show a time resolution of 35 ps
The Timing Counter of the MEG experiment: calibration and performance
No full textThe MEG detector is designed to test Lepton Flavor Violation in the μ+→e+γ decay down to a Branching Ratio of a few 10-13. The decay topology consists in the coincident emission of a monochromatic photon in direction opposite to a monochromatic positron. A precise measurement of the relative time te+γ is crucial to suppress the background. The Timing Counter (TC) is designed to precisely measure the time of arrival of the e+ and to provide information to the trigger system. It consists of two sectors up and down stream the decay target, each consisting of two layers: the outer one made of scintillating bars and the inner one of scintillating fibers. Their design criteria and performances are described. © 2011 Elsevier B.V
Timing resolution measurements of a 3 in. lanthanum bromide detector
No full textCerium-doped lanthanum bromide (LaBr3:Ce) is a scintillator that presents very good energy and timing resolutions and it is a perfect candidate for photon detector in future experiments to search for lepton flavor violation as in μ → e γ or μ → e conversion. While energy resolution was thoroughly investigated, timing resolution at several MeV presents some experimental challenge. We measured the timing resolution of a 3 in.×3 in. cylindrical LaBr3(Ce) crystal versus few reference detectors by means of a nuclear reaction from a Cockcroft-Walton accelerator that produces coincident γ-rays in the 4.4-11.6 MeV range. Preliminary results allow us to extrapolate the properties of a segmented γ-ray detector in the 50-100 MeV range
Feasibility study of a high-performance LaBr3(Ce) calorimeter for future lepton flavor violation experiments
No full textLaBr3(Ce) is a very attractive material due to its ultra high light output and its fast response, resulting in a good candidate as a crystal for a calorimeter able to provide simultaneously very high energy and timing performances. We report here a first test with a cylindrical 3′′×3′′ LaBr3(Ce) crystal coupled to PMT (Photonics XP53A2B), where we explore the detector performances at relative high energies, on the region of interest for future charged Lepton Flavor Violation (cLFV) experiments, using photons in the interval of 55 83 MeV from π0 decays up to 129 MeV from the radiative capture of negative pions on protons. © 2014 Elsevier B.V
APPORTO DELL'ECOGRAFIA NELL'ITER DIAGNOSTICO DELLE MASSE SURRENALICHE DELL'ETA' PEDIATRICA.
No full textDesign and test of an extremely high resolution Timing Counter for the MEG II experiment: preliminary results
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