368 research outputs found
The Computational Complexity of Traditional Lattice-BoltzmannMethods for Incompressible Fluids
No full textIt is well-known that customary direct solution methods (based on the discretization of the fluid fields) for the fluid equations of incompressible fluids may be affected by a high computational complexity. This is due primarily to the numerical solution of the Poisson equation for the fluid pressure and occurs when the scale-length of turbulent fluctuations becomes comparable to the discretization scale which characterizes the numerical solution method. An alternative, which can reduce significantly the complexity caused by the numerical solution of the fluid equations for incompressible fluids, may be achieved by so-called particle simulation methods. In such a case the dynamics of fluids is approximated in terms of a set of test particles which advance in time in terms of suitable evolution equations defined in such a way to satisfy identically the Poisson equation. Particle simulation methods rely typically on appropriate kinetic models for the fluid equations which permit the evaluation of the fluid fields in terms of suitable expectation values (or momenta) of the kinetic distribution function f(r,v,t), being respectively r and v the position an velocity of a test particle with probability density f(r,v,t). These kinetic models can be continuous or discrete in phase space, yielding respectively continuous or discrete kinetic models for the fluids. However, also particle simulation methods may be biased by an undesirable computational complexity. In particular, a fundamental issue is to estimate the algorithmic complexity of numerical simulations based on traditional LBM's (Lattice-Boltzmann methods; for review see Succi, 2001 Succi). These methods, based on a discrete kinetic approach, represent currently an interesting alternative to direct solution methods. Here we intend to prove that for incompressible fluids fluids LBM's may present a high complexity. The goal of the investigation is to present a detailed account of the origin of the various complexity sources appearing in customary LBM's. The result is relevant to establish possible strategies for improving the numerical efficiency of existing numerical methods
Summary of Section “New Accelerators, Detectors, Calculus and New Technologies”
No full textDeployment and development of advanced technologies for accelerators, detectors, electronics and computing is inherent in everyday activity of all research projects and experiments funded by INFN. However, when a part of the
research work can be clearly identified as an R&D activity aimed at the development of a new technology or procedure for specific, or a more general, application it is
worthwhile to cut it off and manage it as an independent self-consistent experiment. For many of them it is also easy to find applications in other research discipline or industry. In this case it is important to verify the potentiality of the technology, customize it and improve it, in collaboration with the end user, for the specific
application
Ring imaging Cherenkov detectors. Proceedings, 6th International Workshop, RICH 2007, Trieste, Italy, October 15-20, 2007.
No full text
The COMPASS Experiment and the measurement of the gluon polarisation
No full textCOMPASS, a new fixed target experiment at CERN, aimed at the study of nucleon spin structure and hadron spectroscopy, has started to collect physics data in Autumn 2001. This paper describes the COMPASS apparatus and the measurement of the gluon polarisation . The apparatus consists in a solid state polarised target and a two stage spectro-meter with high resolution tracking, particle identification and calorimetry, capable of standing high event rates. COMPASS measures the longitudinal spin asymmetry of open charm production in polarised deep inelastic muon nucleon scattering: this asymmetry is directly related to since at COMPASS energies open charm is essentially produced by photon gluon fusion only. A second channel, used to access with higher statistics, is the production of correlated high hadron pairs
Status of COMPASS RICH-1 Upgrade with MPGD-based Photon Detectors
No full textA Set of new MPGD-based Photon Detectors is being built for the upgrade of COMPASS RICH-1. The detectors cover a total active area of 1.4 m2 and are based on a hybrid architecture consisting of two THGEM layers and a Micromegas. A CsI film on one THGEM acts as a reflective photocathode. The characteristics of the detector, the production of the components and their validation tests are described in detail.A Set of new MPGD-based Photon Detectors is being built for the upgrade of COMPASS RICH-1. The detectors cover a total active area of 1.4 m and are based on a hybrid architecture consisting of two THGEM layers and a Micromegas. A CsI film on one THGEM acts as a reflective photocathode. The characteristics of the detector, the production of the components and their validation tests are described in detail
Monte Carlo studies of the COMPASS RICH 1 optical properties
No full textBaum G, Birsa R, Bradamante F, et al. Monte Carlo studies of the COMPASS RICH 1 optical properties. In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. Nucl.Instrum.Meth. A. Vol 433. ELSEVIER SCIENCE BV; 1999: 401-405.A dedicated Monte Carlo has been built to study the optical properties of the RICH 1 detector presently under construction for the COMPASS experiment at CERN. In this paper we focus on the optimization of the position of the photon detector with respect to the RICH mirror and on the alignment of the mirror elements forming the mirror surface. (C) 1999 Elsevier Science B.V. All rights reserved
Status of the COMPASS experiment
No full textThe COMPASS Experiment at CERN has a broad physics program aimed at the study of nucleon spin structure and hadron spectroscopy. It has an outstanding fixed-target apparatus, mostly commissioned in 2001, presently consisting of a solid /sup 6/LiD polarised target and a two stage spectrometer with high resolution tracking, particle identification and calorimetry, capable of standing high event rates. This paper describes the apparatus and its performances during the run of 2002, when 260 TB of polarised muon nucleon scattering data have been collected. First physics signals from the analysis and projections for the expected accuracy of the measurement of the gluon polarisation Delta G/G from photon gluon fusion are presented too. (15 refs)
The COMPASS RICH1 detector
No full textBaum G, Birsa R, Bradamante F, et al. The COMPASS RICH1 detector. In: Nuclear Physics B - Proceedings Supplements. Nucl.Phys.Proc.Suppl. Vol 78. ELSEVIER SCIENCE BV; 1999: 354-359.A large acceptance gas RICH detector is presently under construction for the spectrometer of the COMPASS Experiment. Tts design parameters are presented and the main characteristics of the vessel, the mirrors system, the photon detectors and the front-end electronics are-discussed together with some results from prototyping activities
- …
