2,603 research outputs found
Halo Formation in Spheroidal Bunches with Self-Consistent Stationary Distributions
A new class of self-consistent 6-D phase space stationary distributions is
constructed both analytically and numerically. The beam is then mismatched
longitudinally and/or transversely, and we explore the beam stability and halo
formation for the case of 3-D axisymmetric beam bunches using particle-in-cell
simulations. We concentrate on beams with bunch length-to-width ratios varying
from 1 to 5, which covers the typical range of the APT linac parameters. We
find that the longitudinal halo forms first for comparable longitudinal and
transverse mismatches. An interesting coupling phenomenon - a longitudinal or
transverse halo is observed even for very small mismatches if the mismatch in
the other plane is large - is discovered.Comment: 3 pages, 3 figures; presented at European Particle Accelerator
Conference, Stockholm, Sweden (June 22-26, 1998
Phenomenological analysis of the CLAS data on double charged pion photo and electro- production
First comprehensive data on the evolution of nucleon resonance photocouplings
with photon virtuality Q^2 are presented for excited proton states in the mass
range from 1.4 to 2.0 GeV. N^* photocouplings were determined in
phenomenological analysis of CLAS data on 2 pi photo and electroproduction
within the framework of the JLAB-MSU phenomenological model.Comment: 10 pages, 7 figures (encapsulated postscript
Model Analysis of the Electroproduction Reaction on the Proton
Recent CLAS data on the electroproduction off protons at
1.3W1.57 GeV and 0.250.6 GeV have been analyzed using
a meson-baryon phenomenological model. By fitting nine 1-fold differential
cross section data for each and bin, the charged double pion
electroproduction mechanisms are identified from their manifestations in the
observables. We have extracted the cross sections from amplitudes of each of
the considered isobar channels as well as from their coherent sum. We also
obtained non-resonant partial wave amplitudes of all contributing isobar
channels which could be useful for advancing a complete coupled-channel
analysis of all meson electroproduction data.Comment: Experiment Numbers: E93-006, E94-005 Group: Hall
Helical Undulator Based on Partial Redistribution of Uniform Magnetic Field
A new type of helical undulator based on redistribution of magnetic field of
a solenoid by ferromagnetic helix has been proposed and studied both in theory
and experiment. Such undulators are very simple and efficient for promising
sources of coherent spontaneous THz undulator radiation from dense electron
bunches formed in laser-driven photo-injectors
Asymmetric transmission of light through a planar chiral metamaterial
We report that normal incidence transmission of circularly polarized light through lossy anisotropic planar chiral meta-material is asymmetric for opposite directions. The new effect is fundamentally distinct from conventional gyrotropy of bulk chiral media and the Faraday Effect
Metamaterial with polarization and direction insensitive resonant transmission response mimicking electromagnetically induced transparency
We report on a planar metamaterial, the resonant transmission frequency of which does not depend on the polarization and angle of incidence of electromagnetic waves. The resonance results from the excitation of high-Q antisymmetric trapped current mode and shows sharp phase dispersion characteristic to Fano-type resonances of the electromagnetically induced transparency phenomenon
Affine algebraic groups with periodic components
A connected component of an affine algebraic group is called periodic if all
its elements have finite order. We give a characterization of periodic
components in terms of automorphisms with finite number of fixed points. It is
also discussed which connected groups have finite extensions with periodic
components. The results are applied to the study of the normalizer of a maximal
torus in a simple algebraic group.Comment: 20 page
Cooperative resonance linewidth narrowing in a planar metamaterial
We theoretically analyze the experimental observations of a spectral line
collapse in a metamaterial array of asymmetric split ring resonators [Fedotov
et al., Phys. Rev. Lett. 104, 223901 (2010)]. We show that the ensemble of
closely-spaced resonators exhibits cooperative response, explaining the
observed system-size dependent narrowing of the transmission resonance
linewidth. We further show that this cooperative narrowing depends sensitively
on the lattice spacing and that significantly stronger narrowing could be
achieved in media with suppressed ohmic losses.Comment: 19 pages, 6 figures, to appear in New Journal of Physic
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