676 research outputs found
Conceptual design of elliptical cavities for intensity and position sensitive beam measurements in storage rings
Position sensitive beam monitors are indispensable for the beam diagnostics
in storage rings. Apart from their applications in the measurements of beam
parameters, they can be used in non-destructive in-ring decay studies of
radioactive ion beams as well as enhancing precision in the isochronous mass
measurement technique. In this work, we introduce a novel approach based on
cavities with elliptical cross-section, in order to compensate for existing
limitations in ion storage rings. The design is aimed primarily for future
heavy ion storage rings of the FAIR project. The conceptual design is discussed
together with simulation results.Comment: Added definition of Uv and Pdiss in the introduction section. Added
Mode numbering in table 1 and figure 1 for more clarity. Corrected one wrong
figure reference. Other minor typo correction
Temperature Dependence of Facet Ridges in Crystal Surfaces
The equilibrium crystal shape of a body-centered solid-on-solid (BCSOS) model
on a honeycomb lattice is studied numerically. We focus on the facet ridge
endpoints (FRE). These points are equivalent to one dimensional KPZ-type growth
in the exactly soluble square lattice BCSOS model. In our more general context
the transfer matrix is not stochastic at the FRE points, and a more complex
structure develops. We observe ridge lines sticking into the rough phase where
thesurface orientation jumps inside the rounded part of the crystal. Moreover,
the rough-to-faceted edges become first-order with a jump in surface
orientation, between the FRE point and Pokrovsky-Talapov (PT) type critical
endpoints. The latter display anisotropic scaling with exponent instead
of familiar PT value .Comment: 12 pages, 19 figure
Investigation of Planar Pick-up and Kicker Electrodes for Stochastic Cooling
The success of stochastic cooling crucially depends on the interaction between the beam and high frequency devices for detection (pick-up electrodes) and deflection (kicker electrodes). This contribution shows the theoretical investigation of a planar electrode to be used for stochastic cooling of secondary particles with a beta of 0.83. The coupling to the beam is realised by a slot line. Transition networks are added to extract the signal. The detailed investigation is performed via a numerical electromagnetic field analysis. The longitudinal kick of the deflectors is calculated as a function of the beam position and scaled to the applied voltage. According to the Panofsky-Wenzel theorem the transverse kick is obtained simultaneously. The electromagnetic properties of the discussed electrode are compared to existing ones as currently in use in the ESR storage ring (GSI, Darmstadt)
Crossover Scaling Functions in One Dimensional Dynamic Growth Models
The crossover from Edwards-Wilkinson () to KPZ () type growth is
studied for the BCSOS model. We calculate the exact numerical values for the
and massgap for using the master equation. We predict
the structure of the crossover scaling function and confirm numerically that
and , with . KPZ type growth is
equivalent to a phase transition in meso-scopic metallic rings where attractive
interactions destroy the persistent current; and to endpoints of facet-ridges
in equilibrium crystal shapes.Comment: 11 pages, TeX, figures upon reques
West Nile Virus Antibody Prevalence in Wild Mammals, Southern Wisconsin
Twenty percent prevalence of West Nile virus antibody was found in free-ranging medium-sized Wisconsin mammals. No significant differences were noted in antibody prevalence with regard to sex, age, month of collection, or species. Our results suggest a similar route of infection in these mammals
Asymmetric XXZ chain at the antiferromagnetic transition: Spectra and partition functions
The Bethe ansatz equation is solved to obtain analytically the leading
finite-size correction of the spectra of the asymmetric XXZ chain and the
accompanying isotropic 6-vertex model near the antiferromagnetic phase boundary
at zero vertical field. The energy gaps scale with size as and
its amplitudes are obtained in terms of level-dependent scaling functions.
Exactly on the phase boundary, the amplitudes are proportional to a sum of
square-root of integers and an anomaly term. By summing over all low-lying
levels, the partition functions are obtained explicitly. Similar analysis is
performed also at the phase boundary of zero horizontal field in which case the
energy gaps scale as . The partition functions for this case are found
to be that of a nonrelativistic free fermion system. From symmetry of the
lattice model under rotation, several identities between the partition
functions are found. The scaling at zero vertical field is
interpreted as a feature arising from viewing the Pokrovsky-Talapov transition
with the space and time coordinates interchanged.Comment: Minor corrections only. 18 pages in RevTex, 2 PS figure
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