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Search Results: 1 - 10 of 167650 matches for " E. Segreto "
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An analytic technique for the estimation of the light yield of a scintillation detector
Ettore Segreto
Physics , 2011, DOI: 10.1088/1748-0221/7/05/P05008
Abstract: A simple model for the estimation of the light yield of a scintillation detector is developed under general assumptions and relying exclusively on the knowledge of its optical properties. The model allows to easily incorporate effects related to Rayleigh scattering and absorption of the photons.The predictions of the model are benchmarked with the outcomes of Monte Carlo simulations of specific scintillation detectors. An accuracy at the level of few percent is achieved. The case of a real liquid argon based detector is explicitly treated and the predicted light yield is compared with the measured value.
Evidence of delayed light emission of TetraPhenyl Butadiene excited by liquid Argon scintillation light
Ettore Segreto
Physics , 2014, DOI: 10.1103/PhysRevC.91.035503
Abstract: TetraPhenyl Butadiene is the wavelength shifter most widely used in combination with liquid Argon. The latter emits scintillation photons with a wavelength of 127 nm that need to be downshifted to be detected by photomultipliers with glass or quartz windows. TetraPhenyl Butadiene has been demonstrated to have an extremely high conversion efficiency, possibly higher than 100 % for 127 nm photons, while there is no precise information about the time dependence of its emission. It is usually assumed to be exponentially decaying with a characteristic time of the order of one ns, as an extrapolation from measurements with exciting radiation in the near UV. This work shows that TetraPhenyl Butadiene, when excited by 127 nm photons, reemits photons not only with a very short decay time, but also with slower ones due to triplet states de-excitations. This fact can strongly contribute to clarify the anomalies in liquid Argon scintillation light reported in literature since seventies, namely the inconsistency in the measured values of the long decay time constant and the appearance of an intermediate component. Similar effects should be also expected when the TPB is used in combination with Helium and Neon, that emit scintillation photons with wavelengths shorter than 127 nm.
The populations of hard X- and γ-ray sources: a correlation study and new possible identifications
A. Maselli,G. Cusumano,E. Massaro,A. Segreto,V. La Parola,A. Tramacere,I. Donnarumma
Physics , 2011, DOI: 10.1051/0004-6361/201116916
Abstract: We present the results of our analysis devoted to the research of sources emitting in the energy bands surveyed by both the Swift-BAT and the Fermi-LAT telescopes. We cross-correlate the Fermi-LAT 1-year point source catalogue (1FGL) of {\gamma}-ray sources and the second Palermo BAT catalogue (2PBC) of hard X-ray sources, establishing a correspondence between sources when their error boxes overlap. We also extract the significance value in the BAT 15-150 keV map, obtained using a dedicated software for the reduction of BAT data, in the direction of the 1FGL sources and take into account those above the significance threshold {\sigma} = 3. We obtain a sample of common sources emitting in both the hard X- and the {\gamma}-ray energy bands and evaluate its content in galactic and extragalactic objects. We assess the fraction of unidentified sources and describe in greater detail the properties of two of them, 1FGL J0137.8+5814 and 1FGL J2056.7+4938, supporting their classification as blazars after the analysis of their broad-band spectral energy distribution. We discuss the blazar content of the collected 1FGL-2PBC sources: we build its redshift distibution and compare it with that of the whole blazar population as reported in the second edition of the BZCAT blazar catalogue.
Optical Characterization of Organic Light-Emitting Thin Films in the Ultraviolet and Visible Spectral Ranges
R. M. Montereali,M. A. Vincenti,E. Nichelatti,F. Di Pompeo,E. Segreto,N. Canci,F. Cavanna
Physics , 2012,
Abstract: The spectrophotometric characterization of high efficiency, optically-active samples such as light-emitting organic bulks and thin films can be problematic because their broad-band luminescence is detected together with the monochromatic transmitted and reflected signals, hence perturbing measurements of optical transmittance and reflectance at wavelengths within the photoexcitation band. As a matter of fact, most commercial spectrophotometers apply spectral filtering before the light beam reaches the sample, not after it. In this Report, we introduce and discuss the method we have developed to correct photometric spectra that are perturbed by photoluminescence.
Swift/BAT detection of hard X-rays from Tycho's Supernova Remnant: Evidence for Titanium-44
E. Troja,A. Segreto,V. La Parola,D. Hartmann,W. Baumgartner,C. Markwardt,S. Barthelmy,G. Cusumano,N. Gehrels
Physics , 2014, DOI: 10.1088/2041-8205/797/1/L6
Abstract: We report Swift/BAT survey observations of the Tycho's supernova remnant, performed over a period of 104 months since the mission's launch. The remnant is detected with high significance (>10 sigma) below 50 keV. We detect significant hard X-ray emission in the 60-85 keV band, above the continuum level predicted by a simple synchrotron model. The location of the observed excess is consistent with line emission from radioactive Titanium-44, so far reported only for Type II supernova explosions. We discuss the implications of these results in the context of the galactic supernova rate, and nucleosynthesis in Type Ia supernova.
VUV-Vis optical characterization of Tetraphenyl-butadiene films on glass and specular reflector substrates from room to liquid Argon temperature
R. Francini,R. M. Montereali,E. Nichelatti,M. A. Vincenti,N. Canci,E. Segreto,F. Cavanna,F. Di Pompeo,F. Carbonara,G. Fiorillo,F. Perfetto
Physics , 2013, DOI: 10.1088/1748-0221/8/09/P09006
Abstract: The use of efficient wavelength-shifters from the vacuum-ultraviolet to the photosensor's range of sensitivity is a key feature in detectors for Dark Matter search and neutrino physics based on liquid argon scintillation detection. Thin film of Tetraphenyl-butadiene (TPB) deposited onto the surface delimiting the active volume of the detector and/or onto the photosensor optical window is the most common solution in current and planned experiments. Detector design and response can be evaluated and correctly simulated only when the properties of the optical system in use (TPB film + substrate) are fully understood. Characterization of the optical system requires specific, sometimes sophisticated optical methodologies. In this paper the main features of TPB coatings on different, commonly used substrates is reported, as a result of two independent campaigns of measurements at the specialized optical metrology labs of ENEA and University of Tor Vergata. Measured features include TPB emission spectra with lineshape and relative intensity variation recorded as a function of the film thickness and for the first time down to LAr temperature, as well as optical reflectance and transmittance spectra of the TPB coated substrates in the wavelength range of the TPB emission.
BeppoSAX monitoring of the ``anomalous'' X-ray pulsar 4U 0142+61
G. L. Israel,T. Oosterbroek,L. Angelini,S. Campana,S. Mereghetti,A. N. Parmar,A. Segreto,L. Stella,J. van Paradijs,N. E. White
Physics , 1999,
Abstract: The 8.7s X-ray pulsar 4U 0142+61 was monitored by BeppoSAX between January 1997 and February 1998. This source belongs to the rapidly growing class of "anomalous" X-ray pulsars (AXPs) which have pulse periods in the 6-12s range and no plausible optical, infrared or radio counterparts. The BeppoSAX periods measurements show that 4U 0142+61 continues its spin-down at a nearly constant rate of about 2 times 10^{-12}s s^{-1}. The 0.5-10 keV pulse shape is double peaked. The phase-averaged spectrum can be described by a steep absorbed power-law (Gamma about 4) plus a blackbody with kT = 0.4 keV. 4U 0142+61 was also detected serendipitously in a March 1996 RossiXTE observation pointed towards the nearby 1455s X-ray pulsar RX J0146.9+6121. The timing analysis results are reported for this observation and the spin history of 4U 0142+61 since 1979 is discussed.
Tests of PMT Signal Read-out of Liquid Argon Scintillation with a New Fast Waveform Digitizer
R. Acciarri,N. Canci,F. Cavanna,A. Cortopassi,M. D'Incecco,G. Mini,F. Pietropaolo,A. Romboli,E. Segreto,A. M. Szelc
Physics , 2012, DOI: 10.1088/1748-0221/7/07/P07003
Abstract: The CAEN V1751 is a new generation of Waveform Digitizer recently introduced by CAEN SpA. It features 8 Channels per board, 10 bit, 1 GS/s using Flash ADCs Waveform Digitizers (or 4 channels at 2 GS/s in Dual Edge Sampling mode) with threshold and Auto-Trigger capabilities. This provides a good basis for data acquisition in Dark Matter searches using PMTs to detect scintillation light in liquid argon, as it matches the requirements for measuring the fast scintillation component. The board was tested by operating it in real experimental conditions and by comparing it with a state of the art digital oscilloscope. We find that the sampling at 1 or 2 GS/s is appropriate for the reconstruction of the fast component of the scintillation light in argon (characteristic time of about 6-7 ns) and the extended dynamic range, after a small customization, allows for the detection of signals in the range of energy needed. The bandwidth is found to be adequate and the intrinsic noise is very low.
The pulsed light curves of Her X-1 as observed by BeppoSAX
D. Dal Fiume,M. Orlandini,G. Cusumano,S. Del Sordo,M. Feroci,F. Frontera,T. Oosterbroek,E. Palazzi,A. N. Parmar,A. Santangelo,A. Segreto
Physics , 1997, DOI: 10.1063/1.54148
Abstract: We report on the timing analysis of the observation of the X-ray binary pulsar Her X-1 performed during the BeppoSAX Science Verification Phase. The observation covered more that two full orbital cycles near the maximum of the main-on in the 35 day cycle of Her X-1. We present the pulse profiles from 0.1 to 100 keV. Major changes are present below 1 keV, where the appearance of a broad peak is interpreted as re-processing from the inner part of the accretion disk, and above 10 keV, where the pulse profile is less structured and the main peak is appreciably harder. The hardness ratios show complex changes with pulse phase at different energies.
The broad-band (0.1-200 keV) spectrum of Her X-1 observed with BeppoSAX
D. Dal Fiume,M. Orlandini,G. Cusumano,S. Del Sordo,M. Feroci,F. Frontera,T. Oosterbroek,E. Palazzi,A. N. Parmar,A. Santangelo,A. Segreto
Physics , 1997,
Abstract: The X-ray pulsar Her X-1 was observed for more than two orbital cycles near the maximum of the 35 day X-ray intensity cycle by the Narrow Field Instruments on-board the BeppoSAX satellite. We present the first simultaneous measurement of the 0.1-200 keV spectrum. Three distinct continuum components are evident in the phase averaged spectrum: a low energy excess, modeled as a 0.1 keV blackbody; a power-law and a high energy cut-off. Superposed on this continuum are Fe L and K emission features at 1.0 and 6.5 keV, respectively, and a ~40 keV cyclotron absorption feature. The cyclotron feature can be clearly seen in raw count spectra. We present the properties of the cyclotron feature with unprecedented precision and discuss the indications given by this measurement on the physical properties of the emitting region.
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