81,125 research outputs found
Helical channel design and technology for cooling of muon beams
Novel magnetic helical channel designs for capture and cooling of bright muon
beams are being developed using numerical simulations based on new inventions
such as helical solenoid (HS) magnets and hydrogen-pressurized RF (HPRF)
cavities. We are close to the factor of a million six-dimensional phase space
(6D) reduction needed for muon colliders. Recent experimental and simulation
results are presented.Comment: 6 pp. 14th Advanced Accelerator Concepts Workshop 13-19 Jun 2010:
Annapolis, Marylan
Convergence of the Poincare Constant
The Poincare constant R(Y) of a random variable Y relates the L2 norm of a
function g and its derivative g'. Since R(Y) - Var(Y) is positive, with
equality if and only if Y is normal, it can be seen as a distance from the
normal distribution. In this paper we establish a best possible rate of
convergence of this distance in the Central Limit Theorem. Furthermore, we show
that R(Y) is finite for discrete mixtures of normals, allowing us to add rates
to the proof of the Central Limit Theorem in the sense of relative entropy.Comment: 11 page
SATMC: Spectral Energy Distribution Analysis Through Markov Chains
We present the general purpose spectral energy distribution (SED) fitting
tool SED Analysis Through Markov Chains (SATMC). Utilizing Monte Carlo Markov
Chain (MCMC) algorithms, SATMC fits an observed SED to SED templates or models
of the user's choice to infer intrinsic parameters, generate confidence levels
and produce the posterior parameter distribution. Here we describe the key
features of SATMC from the underlying MCMC engine to specific features for
handling SED fitting. We detail several test cases of SATMC, comparing results
obtained to traditional least-squares methods, which highlight its accuracy,
robustness and wide range of possible applications. We also present a sample of
submillimetre galaxies that have been fitted using the SED synthesis routine
GRASIL as input. In general, these SMGs are shown to occupy a large volume of
parameter space, particularly in regards to their star formation rates which
range from ~30-3000 M_sun yr^-1 and stellar masses which range from
~10^10-10^12 M_sun. Taking advantage of the Bayesian formalism inherent to
SATMC, we also show how the fitting results may change under different
parametrizations (i.e., different initial mass functions) and through
additional or improved photometry, the latter being crucial to the study of
high-redshift galaxies.Comment: 17 pages, 11 figures, MNRAS accepte
Mapping the optical properties of slab-type two-dimensional photonic crystal waveguides
We report on systematic experimental mapping of the transmission properties
of two-dimensional silicon-on-insulator photonic crystal waveguides for a broad
range of hole radii, slab thicknesses and waveguide lengths for both TE and TM
polarizations. Detailed analysis of numerous spectral features allows a direct
comparison of experimental data with 3D plane wave and finite-difference
time-domain calculations. We find, counter-intuitively, that the bandwidth for
low-loss propagation completely vanishes for structural parameters where the
photonic band gap is maximized. Our results demonstrate that, in order to
maximize the bandwidth of low-loss waveguiding, the hole radius must be
significantly reduced. While the photonic band gap considerably narrows, the
bandwidth of low-loss propagation in PhC waveguides is increased up to 125nm
with losses as low as 82dB/cm.Comment: 10 pages, 8 figure
Parametric Representation for the Multisoliton Solution of the Camassa-Holm Equation
The parametric representation is given to the multisoliton solution of the
Camassa-Holm equation. It has a simple structure expressed in terms of
determinants. The proof of the solution is carried out by an elementary theory
of determinanats. The large time asymptotic of the solution is derived with the
fomula for the phase shift. The latter reveals a new feature when compared with
the one for the typical soliton solutions. The peakon limit of the phase shift
ia also considered, showing that it reproduces the known result.Comment: 14 page
Symmetric achromatic low-beta collider interaction region design concept
We present a new symmetry-based concept for an achromatic low-beta collider
interaction region design. A specially-designed symmetric Chromaticity
Compensation Block (CCB) induces an angle spread in the passing beam such that
it cancels the chromatic kick of the final focusing quadrupoles. Two such CCBs
placed symmetrically around an interaction point allow simultaneous
compensation of the 1st-order chromaticities and chromatic beam smear at the IP
without inducing significant 2nd-order aberrations to the particle trajectory.
We first develop an analytic description of this approach and explicitly
formulate 2nd-order aberration compensation conditions at the interaction
point. The concept is next applied to develop an interaction region design for
the ion collider ring of an electron-ion collider. We numerically evaluate
performance of the design in terms of momentum acceptance and dynamic aperture.
The advantages of the new concept are illustrated by comparing it to the
conventional distributed-sextupole chromaticity compensation scheme.Comment: 12 pages, 17 figures, to be submitted to Phys. Rev. ST Accel. Beam
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