5,503 research outputs found
A Monte-Carlo simulation of the equilibrium beam polarization in ultra-high energy electron (positron) storage rings
With the recently emerging global interest in building a next generation of
circular electron-positron colliders to study the properties of the Higgs
boson, and other important topics in particle physics at ultra-high beam
energies, it is also important to pursue the possibility of implementing
polarized beams at this energy scale. It is therefore necessary to set up
simulation tools to evaluate the beam polarization at these ultra-high beam
energies. In this paper, a Monte-Carlo simulation of the equilibrium beam
polarization based on the Polymorphic Tracking Code(PTC) (Schmidt et al., 2002
[1]) is described. The simulations are for a model storage ring with parameters
similar to those of proposed circular colliders in this energy range, and they
are compared with the suggestion (Derbenev et al., 1978 [2]) that there are
different regimes for the spin dynamics underlying the polarization of a beam
in the presence of synchrotron radiation at ultra-high beam energies. In
particular, it has been suggested that the so-called "correlated" crossing of
spin resonances during synchrotron oscillations at current energies, evolves
into "uncorrelated" crossing of spin resonances at ultra-high energies.Comment: submitted to and accepted by Nucl. Instrum. Meth.
Anisotropic intrinsic lattice thermal conductivity of phosphorene from first principles
Phosphorene, the single layer counterpart of black phosphorus, is a novel
two-dimensional semiconductor with high carrier mobility and a large
fundamental direct band gap, which has attracted tremendous interest recently.
Its potential applications in nano-electronics and thermoelectrics call for a
fundamental study of the phonon transport. Here, we calculate the intrinsic
lattice thermal conductivity of phosphorene by solving the phonon Boltzmann
transport equation (BTE) based on first-principles calculations. The thermal
conductivity of phosphorene at is
(zigzag) and
(armchair), showing an obvious anisotropy along different directions. The
calculated thermal conductivity fits perfectly to the inverse relation with
temperature when the temperature is higher than Debye temperature (). In comparison to graphene, the minor contribution around
of the ZA mode is responsible for the low thermal conductivity of
phosphorene. In addition, the representative mean free path (MFP), a critical
size for phonon transport, is also obtained.Comment: 5 pages and 6 figures, Supplemental Material available as
http://www.rsc.org/suppdata/cp/c4/c4cp04858j/c4cp04858j1.pd
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