Abstract
Since 1984 INFN and University of Pisa scientists performing experiments at Fermilab have been running a two-month summer training program for Italian students at the lab. In 1984 the ...program involved only a few physics students from the University of Pisa, but it was later extended to other INFN groups and to engineering students. Since 2004 the program has been supported in part by the US Department of Energy (DOE) in the frame of an exchange agreement with INFN and has been run by the Cultural Association of Italians at Fermilab (CAIF). In 2007 the Sant’Anna School of Advanced Studies (Pisa) established an agreement with Fermilab to share the cost of four engineering students each year. In the almost 40 years of its history, the program has hosted at Fermilab approximately 550 Italian students from more than 20 Italian universities and from some non-Italian universities. In addition, in the years 2010-2019, with the support of the Italian National Institute of Astrophyics (INAF), the Italian Space Agency (ASI), and CAIF, 30 students were hosted in other US laboratories and universities. The Fermilab training programs spanned from data analysis to design and construction of particle detectors and accelerator components, R/D on superconductive elements, theory of accelerators, and analysis of astrophysical data. At the other US laboratories the offered training was on Space Science. In 2015 the University of Pisa endorsed the program as one of its own Summer Schools. The interns are enrolled as Pisa students for the duration of the internship. They are required to write summary reports published in the Fermilab and University of Pisa web pages. Upon positive evaluation by a University board, students are acknowledged 6 ECTS credits. The entire program is expected to expand further under CAIF management. An agreement has been signed between ASI and CAIF, for ASI to support yearly three two-months fellowships in US space science. In the following we inform on student recruiting, training programs, and final evaluation
We consider a class of nonconvex functionals of the gradient in one dimension, which we regularize with a second order derivative term. After a proper rescaling, suggested by the associated dynamical ...problems, we show that the sequence \{F_\nu \} of regularized functionals \Gamma -converges, as \nu \to 0^+, to a particular class of free-discontinuity functionals \mathcal {F}, concentrated on SBV functions with finite energy and having only the jump part in the derivative. We study the singular dynamic associated with \mathcal {F}, using the minimizing movements method. We show that the minimizing movement starting from an initial datum with a finite number of discontinuities has jump positions fixed in space and whose number is nonincreasing with time. Moreover, there are a finite number of singular times at which there is a dropping of the number of discontinuities. In the interval between two subsequent singular times, the vector of the survived jumps is determined by the system of ODEs which expresses the L^2-gradient of the \Gamma -limit. Furthermore the minimizing movement turns out to be continuous with respect to the initial datum. Some properties of a minimizing movement starting from a function with an infinite number of discontinuities are also derived.
Properties of the Ukraine polystyrene-based plastic scintillator UPS 923A Artikov, A.; Budagov, J.; Chirikov-Zorin, I. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2005, Letnik:
555, Številka:
1
Journal Article
Recenzirano
The polystyrene-based scintillator UPS 923A was chosen for upgrading of the muon system for the CDF detector at the Fermilab Tevatron. Properties of this scintillator such as light output, light ...attenuation, long-term stability and also timing characteristics of scintillators and wavelength-shifting fibers were investigated. The method for the Bulk Attenuation Length measurements of the scintillator to its own light emitted was proposed.
Comparison measurements of the characteristics of the UPS 923A and the polyvinyltoluene-based scintillator NE 114 are done. It was found that natural aging of the NE 114 was two times faster than that of the UPS 923A.
Probing General Relativity and New Physics with Lunar Laser Ranging Dell'Agnello, S.; Maiello, M.; Currie, D.G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2012, Letnik:
692
Journal Article
Recenzirano
Odprti dostop
Over the past 40 years, Lunar Laser Ranging (LLR, developed by the Univ. of Maryland (PI) and INFN-LNF (Co-PI)) to the Apollo Cube Corner Retroreflector (CCR) arrays have supplied almost all the ...significant tests of General Relativity (Currie et al., 2009 12). LLR can evaluate the PPN (Post Newtonian Parameters), addressing this way both the possible changes in the gravitational constant and the self-energy properties of the gravitational field. In addition, the LLR has provided significant information on the composition and origin of the Moon. This is the only Apollo experiment that is still in operation. Initially the Apollo LLR arrays contributed a negligible fraction of the ranging error budget. Over the decades, the ranging capabilities of the ground stations have improved by more than two orders of magnitude. Now, because of the lunar librations, the existing Apollo retroreflector arrays contribute a significant fraction of the limiting errors in the range measurements. We built a new experimental apparatus (the ‘Satellite/Lunar Laser Ranging Characterization Facility’, SCF) and created a new test procedure (the SCF-Test) to characterize and model the detailed thermal behavior and the optical performance of cube corner laser retroreflectors in space for industrial and scientific applications (Dell'Agnello et al., 2011 13). Our key experimental innovation is the concurrent measurement and modeling of the optical Far Field Diffraction Pattern (FFDP) and the temperature distribution of the SLR retroreflector payload under thermal conditions produced with a close-match solar simulator. The apparatus includes infrared cameras for non-invasive thermometry, thermal control and real-time movement of the payload to experimentally simulate satellite orientation on orbit with respect to both solar illumination and laser interrogation beams. These unique capabilities provide experimental validation of the space segment for SLR and Lunar Laser Ranging (LLR). The primary goal of these innovative tools is to provide critical design and diagnostic capabilities for Satellite Laser Ranging (SLR) to Galileo and other GNSS (Global Navigation Satellite System) constellations. Implementation of new retroreflector designs being studied will help to improve GNSS orbits, which will then increase the accuracy, stability, and distribution of the International Terrestrial Reference Frame (ITRF) 4, to provide better definition of the geocenter (origin) and the scale (length unit). The SCF is also actively used to develop, validate and optimize the second generation LLR arrays for precision gravity and lunar science measurements to be performed with robotic missions of the International Lunar Network in which NASA and ASI participate (ILN). The capability will allow us to optimize the design of GNSS laser retroreflector payloads to maximize ranging efficiency, to improve signal-to-noise conditions in daylight and to provide pre-launch validation of retroreflector performance under laboratory-simulated space conditions. For the MAGIA lunar orbiter Phase A study funded by ASI (Dell'Agnello et al., 2010 14), we studied fundamental physics and absolute positioning metrology experiments, to improve test of the gravitational redshift in the Earth–Moon system predicted by General Relativity and a precursor test of our second generation LLR payload.
We characterize the lower semicontinuous envelope F― of the functional F(E):=∫∂E1+|κ∂E|p dH1, defined on boundaries of sets E⊂ℝ2, where κ∂E denotes the curvature of ∂E and p>1. Through a ...desingularization procedure, we find the domain of F― and its expression, by means of different representation formulas.
On caractérise l’enveloppe semi-continue inférieure F― de la fonctionnelle F(E):=∫∂E1+|κ∂E|p dH1, définie sur la classe des frontières des domaines E⊂ℝ2, où κ∂E dénote la courbure de ∂E et p>1. Grâce à une méthode de désingularisation, on trouve le domaine de F― et son expression, à l’aide de différentes formules de représentation.
We prove a result concerning the approximation of the elastica functional with a sequence of second order functionals, under radial symmetry assumptions. This theorem is strictly related to a ...conjecture of De Giorgi 8. PUBLICATION ABSTRACT
We study the mean curvature motion of a droplet flowing by mean curvature on a horizontal hyperplane with a possibly nonconstant prescribed contact angle. Using the solutions constructed as a limit ...of an approximation algorithm of Almgren–Taylor–Wang and Luckhaus–Sturzenhecker, we show the existence of a weak evolution, and its compatibility with a distributional solution. We also prove various comparison results.
Nous étudions le mouvement par courbure moyenne d'une goutte qui glisse par courbure moyenne sur un hyperplan horizontal avec un angle de contact prescrit éventuellement non constant. En utilisant les solutions construites comme limites d'un algorithme d'approximation dû à Almgren, Taylor et Wang et Luckhaus et Sturzenhecker, nous montrons l'existence d'une évolution faible, et sa compatibilité avec une solution au sens des distributions. Nous démontrons également plusieurs résultats de comparaison.
Let Φ:^sup n^arrow right 0,+Infinity be a given positively one-homogeneous convex function, and let ?^sub Φ^{Φ≤ 1 }. Pursuing our interest in motion by crystalline mean curvature in three dimensions, ...we introduce and study the class ?^sub Φ^ (^sup n^) of "smooth" boundaries in the relative geometry induced by the ambient Banach space (^sup n^, Φ). It can be seen that, even when ?^sub Φ^ is a polytope, ?^sub Φ^(^sup n^) cannot be reduced to the class of polyhedral boundaries (locally resembling partial differential?^sub Φ^). Curved portions must be necessarily included and this fact (as well as the nonsmoothness of partial differential?^sub Φ^) is the source of several technical difficulties related to the geometry of Lipschitz manifolds. Given a boundary deltaE in the class ?^sub Φ^(^sup n^), we rigorously compute the first variation of the corresponding anisotropic perimeter, which leads to a variational problem on vector fields defined on deltaE. It turns out that the minimizers have a uniquely determined (intrinsic) tangential divergence on deltaE. We define such a divergence to be the Φ-mean curvature κ^sub Φ^ of deltaE; the function κ^sub Φ^ is expected to be the initial velocity of deltaE, whenever deltaE is considered as the initial datum for the corresponding anisotropic mean curvature flow. We prove that κ^sub Φ^ is bounded on deltaE and that its sublevel sets are characterized through a variational inequality.PUBLICATION ABSTRACT
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