1,198 research outputs found
Particle Tracking Studies Using Dynamical Map Created from Finite Element Solution of the EMMA Cell
The unconventional size and the possibility of transverse displacement of the magnets in the EMMA non-scaling FFAG motivates a careful study of particle behavior within the EMMA ring. The magnetic field map of the doublet cell is computed using a Finite Element Method solver; particle motion through the field can then be found by numerical integration, using (for example) OPERA, or ZGOUBI. However, by obtaining an analytical description of the magnetic field (by fitting a Fourier-Bessel series to the numerical data) and using a differential algebra code, such as COSY, to integrate the equations of motion, it is possible to produce a dynamical map in Taylor form. This has the advantage that, after once computing the dynamical map, multi-turn tracking is far more efficient than repeatedly performing numerical integrations. Also, the dynamical map is smaller (in terms of computer memory) than the full magnetic field map; this allows different configurations of the lattice, in terms of magnet positions, to be represented very easily using a set of dynamical maps, with interpolation between the coefficients in different maps*
Electron Cloud in Linear Collider Damping Rings
No abstract prepared
Beam dynamics in NF-FFAG EMMA with dynamical maps
Copyright @ 2010 by IPAC'10/ACFAThe Non-Scaling Fixed Field Alternating Gradient accelerator EMMA has a compact linear lattice, in which the effects of magnet fringe fields need to be modelled carefully. A numerical magnetic field map can be generated frommagnetmeasurements ormagnet design software. We have developed a technique that produces from the numerical field map, a dynamical map for a particle travelling in a full EMMA cell, for a given reference energy, without acceleration. Since the beam dynamics change with energy, a set of maps have been produced with various reference energies between 10MeV and 20MeV. For each reference energy, the simulated tune and time of flight have been compared with results in Zgoubi - tracking directly through numerical field map. The range of validity of a single map has been investigated by tracking particles with large energy deviation: the results can be used to implement a model of acceleration based on dynamical mapsThis work was supported by the Engineering and Physical Sciences Research Council (EPSRC), UK
Analytical expressions for fringe fields in multipole magnets
Fringe fields in multipole magnets can have a variety of effects on the
linear and nonlinear dynamics of particles moving along an accelerator
beamline. An accurate model of an accelerator must include realistic models of
the magnet fringe fields. Fringe fields for dipoles are well understood and can
be modelled at an early stage of accelerator design in such codes as MAD8, MADX
or ELEGANT. However, usually it is not until the final stages of a design
project that it is possible to model fringe fields for quadrupoles or higher
order multipoles. Even then, existing techniques rely on the use of a numerical
field map, which will usually not be available until the magnet design is well
developed. Substitutes for the full field map exist but these are typically
based on expansions about the origin and rely heavily on the assumption that
the beam travels more or less on axis throughout the beam line. In some types
of machine (for example, a non-scaling FFAG such as EMMA) this is not a good
assumption.
In this paper, a method for calculating fringe fields based on analytical
expressions is presented, which allows fringe field effects to be included at
the start of an accelerator design project. The magnetostatic Maxwell equations
are solved analytically and a solution that fits all orders of multipoles
derived. Quadrupole fringe fields are considered in detail as these are the
ones that give the strongest effects. Two examples of quadrupole fringe fields
are presented. The first example is a magnet in the LHC inner triplet, which
consists of a set of four quadrupoles providing the final focus to the beam,
just before the interaction point. Quadrupoles in EMMA provide the second
example. In both examples, the analytical expressions derived in this paper for
quadrupole fringe fields provide a good approximation to the field maps
obtained from a numerical magnet modelling code.Comment: 27 pages, 39 figures. The figures are new with respect to the
previous version, Several mistakes also correcte
Units on the local history of Chelsea to supplement a course in American history.
Thesis (Ed.M.)--Boston Universit
Multidecadal variability in hydro-climate of Okavango river system, southwest Africa, in the past and under future climate
The focus of this paper is to understand the multi-decadal oscillatory component of variability in the Okavango River system, in southwestern Africa, and its potential evolution through the 21st century under climate change scenarios. Statistical analyses and hydrological modelling are used to show that the observed multi-decadal wet and dry phases in the Okavango River and Delta result from multi-decadal oscillations in rainfall, which are likely to be related to processes of internal variability in the climate system, rather than external natural or anthropogenic forcing. Analyses of changes in this aspect of variability under projected climate change scenarios are based on data from a multi-model ensemble of 19 General Circulation Models, which are used to drive hydrological models of the Okavango River and Delta. Projections for the 21st century indicate a progressive shift towards drier conditions attributed to the influence of increasing temperatures on water balance. It is, however, highly likely that multi-decadal oscillations, possibly of similar magnitude to that of 20th century, will be superimposed on the overall trend. These may periodically offset or amplify the mean drying trend. This effect should be accounted for in water and catchment management and climate change adaptation strategies
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