Mass Storage Management and the Grid

The University of Edinburgh has a significant interest in mass storage systems as it is one of the core groups tasked with the roll out of storage software for the UK's particle physics grid, GridPP. We present the results of a development project to provide software interfaces between the SDSC Storage Resource Broker, the EU DataGrid and the Storage Resource Manager. This project was undertaken in association with the eDikt group at the National eScience Centre, the Universities of Bristol and Glasgow, Rutherford Appleton Laboratory and the San Diego Supercomputing Center.Comment: 4 pages, 3 figures, Presented at Computing for High Energy and Nuclear Physics 2004 (CHEP '04), Interlaken, Switzerland, September 200

Numerical and analytic descriptions of cosmic-ray transport

It is not trivial to solve the equations that describe charged particle transport with the aid of computers, for instabilities, inaccuracies, and subtle artifacts are well known afflictions of numerical analysis. Two specific points are discussed. First to avoid inaccuracies, pitch angle scattering must be treated with great care. In particular, slightly inappropriate numerical formulations give rise to mean free paths that are in error by large factors. Secondly, A previously unrecognized artifact, numerical dispersion, is very similar to the physical phenomenon of dispersion. To avoid misinterpretations arising from this similarity, the spatial increment of the finite difference grid must be a small fraction of the mean free path. These points are illustrated by calculations based upon finite difference approximations to the transport equation

The diffusive idealization of charged particle transport in random magnetic fields

The transport of charged particles diffusing in a random magnetic field parallel to a relatively large guiding field is presented. The same coefficient of diffusion is obtained by three methods. Two corrections must be added to the expression in which the diffusive flux is proportional to the gradient of the density. Explicit expressions are given for a characteristic time and a characteristic length which describe the corrections. The well known divergence of the coefficient of diffusion, which is implied by the quasilinear analysis of pitch angle scattering, does not occur if the scattering rate is finite at 90 deg pitch angle. This effect is illustrated by formulas which give the coefficient of diffusion when the quasilinear expression is perturbed by a variable amount of isotropic scattering

Thermal structures: Four decades of progress

Since the first supersonic flight in October 1947, the United States has designed, developed and flown flight vehicles within increasingly severe aerothermal environments. Over this period, major advances in engineering capabilities have occurred that will enable the design of thermal structures for high speed flight vehicles in the twenty-first century. Progress in thermal-structures is surveyed for the last four decades to provide a historical perspective for future efforts

Modulation of cosmic ray electrons

The origin and variations of the steep spectrum of electrons observed below 20 MeV is explained by a simple model in which the spectrum of interplanetary cosmic rays is decomposed, at low energies, into two independently varying components

Stochastic simulation of charged particle transport on the massively parallel processor

Computations of cosmic-ray transport based upon finite-difference methods are afflicted by instabilities, inaccuracies, and artifacts. To avoid these problems, researchers developed a Monte Carlo formulation which is closely related not only to the finite-difference formulation, but also to the underlying physics of transport phenomena. Implementations of this approach are currently running on the Massively Parallel Processor at Goddard Space Flight Center, whose enormous computing power overcomes the poor statistical accuracy that usually limits the use of stochastic methods. These simulations have progressed to a stage where they provide a useful and realistic picture of solar energetic particle propagation in interplanetary space

The dispersive evolution of charged-particle bunches in random magnetic fields

Shortly after a strongly anisotropic beam of charged particles is injected along a guiding magnetic field on which is superimposed a small random conponent, the particle density can be represented by a Gaussian profile whose center moves with the coherent velocity and whose width increases with time at a rate controlled by the coefficient of dispersion. Both parameters depend upon the mean free path, which characterizes scattering by the random fields, and the focusing length, which characterizes spatial variations of the guiding field. These dependencies are known explicitly for the coherent velocity. Formulae for coefficient of dispersion are available only in the limits of very weak and very strong focusing. A new expression for coefficient of dispersion, which spans this gap, is presented

BdbServer++: A User Driven Data Location and Retrieval Tool

The adoption of Grid technology has the potential to greatly aid the BaBar experiment. BdbServer was originally designed to extract copies of data from the Objectivity/DB database at SLAC and IN2P3. With data now stored in multiple locations in a variety of data formats, we are enhancing this tool. This will enable users to extract selected deep copies of event collections and ship them to the requested site using the facilities offered by the existing Grid infrastructure. By building on the work done by various groups in BaBar, and the European DataGrid, we have successfully expanded the capabilities of the BdbServer software. This should provide a framework for future work in data distribution.Comment: Paper based on the poster from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 4 pages, LaTeX, 0 figures. PSN TUCP01