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Search Results: 1 - 10 of 167661 matches for " E. Vallazza "
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Photoproduction of electron-positron pairs in bent single crystals
Yu. A. Chesnokov,V. A. Maisheev,D. Bolognini,S. Hasan,M. Prest,E. Vallazza
Physics , 2010, DOI: 10.1103/PhysRevSTAB.13.070706
Abstract: The process of photoproduction of electron-positron pairs in bent single crystals is considered in this paper. In particular, it is shown that the probability of the process for gamma-quanta with energies from 100 GeV on is significantly higher than the one in an amorphous medium. A possible scenario for the experimental validation of the process is discussed and the positive features of the photoproduction in bent crystals compared to straight ones are underlined from the point of view of possible applications.
Channeling Radiation of Positrons with Energy in the Region of 100 GeV in Single Crystals
V. A. Maisheev,Y. A. Chesnokov,P. N. Chirkov,I. A. Yazynin,D. Bolognini,S. Hasan,M. Prest,E. Vallazza
Physics , 2011,
Abstract: The process of radiation of 120-GeV positrons moving in a channeling regime in (011) plane of a single crystal was considered. At the beginning on the basis of the theory of nonlinear oscillations the trajectory of moving positrons at different initial conditions were derived. Then taking into account the nonlinearity of motion the distribution function over oscillation amplitudes of channeling particles was found. After this the intensity of radiation at different initial conditions was calculated with the help of two various methods. These results may be useful for comparison with experimental data at positron energies from 100 and more GeV.
SuperAGILE: the X-ray Monitor of the AGILE gamma-ray Mission
M. Feroci,E. Costa,E. Del Monte,I. Lapshov,M. Mastropietro,E. Morelli,M. Rapisarda,A. Rubini,P. Soffitta,G. Barbiellini,F. Longo,M. Prest,E. Vallazza,A. Argan,S. Mereghetti,M. Tavani,S. Vercellone,A. Morselli
Physics , 2001,
Abstract: SuperAGILE is the X-ray stage of the AGILE gamma-ray mission. It is devoted to monitor X-ray (10-40 keV) sources with a sensitivity better than 10 mCrabs in 50 ks and to detect X-ray transients in a field of view of 1.8 sr, well matched to that of the gamma-ray tracker, with few arc-minutes position resolution and better than 5 us timing resolution. SuperAGILE is designed to exploit one additional layer of four Si microstrip detectors placed on top of the AGILE tracker, and a system of four mutually orthogonal one-dimensional coded masks to encode the X-ray sky. The total geometric area is 1444 cm^2. Low noise electronics based on ASIC technology composes the front-end read out. We present here the instrumental and astrophysical performances of SuperAGILE as derived by analytical calculations, Monte Carlo simulations and experimental tests on a prototype of the silicon microstrip detector and front-end electronics.
Experimental evidence of planar channeling in a periodically bent crystal
E. Bagli,L. Bandiera,V. Bellucci,A. Berra,R. Camattari,D. De Salvador,G. Germogli,V. Guidi,L. Lanzoni,D. Lietti,A. Mazzolari,M. Prest,V. V. Tikhomirov,E. Vallazza
Physics , 2014, DOI: 10.1140/epjc/s10052-014-3114-x
Abstract: The usage of a Crystalline Undulator (CU) has been identified as a promising solution for generating powerful and monochromatic $\gamma$-rays. A CU was fabricated at SSL through the grooving method, i.e., by the manufacturing of a series of periodical grooves on the major surfaces of a crystal. The CU was extensively characterized both morphologically via optical interferometry at SSL and structurally via X-ray diffraction at ESRF. Then, it was finally tested for channeling with a 400 GeV/c proton beam at CERN. The experimental results were compared to Monte Carlo simulations. Evidence of planar channeling in the CU was firmly observed. Finally, the emission spectrum of the positron beam interacting with the CU was simulated for possible usage in currently existing facilities.
Relaxation of axially confined 400 GeV/c protons to planar channeling in a bent crystal
L. Bandiera,A. Mazzolari,E. Bagli,G. Germogli,V. Guidi,A. Sytov,I. V. Kirillin,N. F. Shul'ga,A. Berra,D. Lietti,M. Prest,D. De Salvador,E. Vallazza
Physics , 2015,
Abstract: An investigation on the mechanism of relaxation of axially confined 400 GeV/c protons to planar channeling in a bent crystal was carried out at the extracted line H8 from CERN Super Proton Synchrotron. The experimental results were critically compared to computer simulations, showing a good agreement. We firmly individuated a necessary condition for the exploitation of axial confinement or its relaxation for particle beam manipulation in high-energy accelerators. We demonstrated that with a short bent crystal, aligned with one of its main axis to the beam direction, it is possible to realize either a total beam steerer or a beam splitter with adjustable intensity. In particular, in the latter case, a complete relaxation from axial confinement to planar channeling takes place, resulting in beam splitting into the two strongest skew planar channels.
A non-conventional neutrino beamline for the measurement of the electron neutrino cross section
A. Berra,S. Cecchini,F. Cindolo,C. Jollet,A. Longhin,L. Ludovici,G. Mandrioli,N. Mauri,A. Meregaglia,A. Paoloni,L. Pasqualini,L. Patrizii,F. Pupilli,M. Pozzato,M. Prest,G. Sirri,F. Terranova,E. Vallazza,L. Votano
Physics , 2015,
Abstract: Absolute neutrino cross section measurements at the GeV scale are ultimately limited by the knowledge of the initial $\nu$ flux. In order to evade such limitation and reach the accuracy that is needed for precision oscillation physics ($\sim 1$%), substantial advances in flux measurement techniques are requested. We discuss here the possibility of instrumenting the decay tunnel to identify large-angle positrons and monitor $\nu_e$ production from $K^+ \rightarrow e^+ \nu_e \pi^0$ decays. This non conventional technique opens up opportunities to measure the $\nu_e$ CC cross section at the per cent level in the energy range of interest for DUNE/HK. We discuss the progress in the simulation of the facility (beamline and instrumentation) and the ongoing R&D.
SYNCHROTRON-RADIATION MICROTOMOGRAPHY FOR THE NON-DESTRUCTIVE STRUCTURAL EVALUATION OF BOWED STRINGED INSTRUMENTS
Luigi Rigon,Erik Vallazza,Fulvia Arfelli,Renata Longo
E-Preservation Science , 2010,
Abstract: Feasibility studies have been car ried out at the SYRMEPbeamline of the Elettra synchrotron laborator y in Triestewith the aim of demonstrating the advantages and evaluatingthe ef fectiveness of synchrotron radiation X-raymicrotomography as a suitable technique for nondestructiveanalysis of bowed stringed instr uments. T heparticular geometr y of the X-ray beam and the use of anovel detector allow structural evaluation of the maindetails of the instruments with unprecedented richnessof details. This, in turn, will allow precise dendrochronologicalinvestigation of historical violins, as well as thecharacterization of their structure, defects, wood thicknessand density.
The AGILE Gamma-ray Astronomy Mission
S. Mereghetti,G. Barbiellini,G. Budini,P. Caraveo,E. Costa,V. Cocco,G. Di Cocco,M. Feroci,C. Labanti,F. Longo,E. Morelli,A. Morselli,A. Pellizzoni,F. Perotti,P. Picozza,M. Prest,P. Soffitta,L. Soli,M. Tavani,E. Vallazza,S. Vercellone
Physics , 1999, DOI: 10.1063/1.1291412
Abstract: We describe the AGILE gamma-ray astronomy satellite which has recently been selected as the first Small Scientific Mission of the Italian Space Agency. With a launch in 2002, AGILE will provide a unique tool for high-energy astrophysics in the 30 MeV - 50 GeV range before GLAST. Despite the much smaller weight and dimensions, the scientific performances of AGILE are comparable to those of EGRET.
Rivermouth Alteration of Agricultural Impacts on Consumer Tissue δ15N
James H. Larson, William B. Richardson, Jon M. Vallazza, John C. Nelson
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0069313
Abstract: Terrestrial agricultural activities strongly influence riverine nitrogen (N) dynamics, which is reflected in the δ15N of riverine consumer tissues. However, processes within aquatic ecosystems also influence consumer tissue δ15N. As aquatic processes become more important terrestrial inputs may become a weaker predictor of consumer tissue δ15N. In a previous study, this terrestrial-consumer tissue δ15N connection was very strong at river sites, but was disrupted by processes occurring in rivermouths (the ‘rivermouth effect’). This suggested that watershed indicators of N loading might be accurate in riverine settings, but could be inaccurate when considering N loading to the nearshore of large lakes and oceans. In this study, the rivermouth effect was examined on twenty-five sites spread across the Laurentian Great Lakes. Relationships between agriculture and consumer tissue δ15N occurred in both upstream rivers and at the outlets where rivermouths connect to the nearshore zone, but agriculture explained less variation and had a weaker effect at the outlet. These results suggest that rivermouths may sometimes be significant sources or sinks of N, which would cause N loading estimates to the nearshore zone that are typically made at discharge gages further upstream to be inaccurate. Identifying definitively the controls over the rivermouth effect on N loading (and other nutrients) will require integration of biogeochemical and hydrologic models.
The AGILE observations of the hard and bright GRB 100724B
E. Del Monte,G. Barbiellini,I. Donnarumma,F. Fuschino,A. Giuliani,F. Longo,M. Marisaldi,G. Pucella,M. Tavani,M. Trifoglio,A. Trois,A. Argan,A. Bulgarelli,P. Caraveo,P. W. Cattaneo,A. Chen,E. Costa,F. D'Ammando,G. Di Cocco,Y. Evangelista,M. Feroci,M. Galli,F. Gianotti,C. Labanti,I. Lapshov,F. Lazzarotto,P. Lipari,S. Mereghetti,E. Moretti,A. Morselli,L. Pacciani,A. Pellizzoni,F. Perotti,G. Piano,P. Picozza,M. Pilia,M. Prest,M. Rapisarda,A. Rappoldi,S. Sabatini,P. Soffitta,E. Striani,E. Vallazza,S. Vercellone,V. Vittorini,L. A. Antonelli,S. Cutini,C. Pittori,P. Santolamazza,F. Verrecchia,P. Giommi,L. Salotti
Physics , 2011, DOI: 10.1051/0004-6361/201117053
Abstract: The observation of Gamma Ray Bursts (GRBs) in the gamma-ray band has been advanced by the AGILE and Fermi satellites after the era of the Compton Gamma-Ray Observatory. AGILE and Fermi are showing that the GeV-bright GRBs share a set of common features, particularly the high fluence from the keV up to the GeV energy bands, the high value of the minimum Lorentz factor, the presence of an extended emission of gamma-rays, often delayed with respect to lower energies, and finally the possible presence of multiple spectral components. GRB 100724B, localised in a joint effort by Fermi and the InterPlanetary Newtork, is the brightest burst detected in gamma-rays so far by AGILE. Characteristic features of GRB 100724B are the simultaneous emissions at MeV and GeV, without delayed onset nor time lag as shown by the analysis of the cross correlation function, and the significant spectral evolution in hard X-rays over the event duration. In this paper we show the analysis of the AGILE data of GRB 100724B and we discuss its features in the context of the bursts observed so far in gamma-rays and the recently proposed models.
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