2,259 research outputs found
Full Phase-Space Analysis of Particle Beam Transport in the Thermal Wave Model
Within the Thermal Wave Model framework a comparison among Wigner function,
Husimi function, and the phase-space distribution given by a particle tracking
code is made for a particle beam travelling through a linear lens with small
aberrations. The results show that the quantum-like approach seems to be very
promising.Comment: 15 pages, plain LaTeX, + 3 uuencoded figures, to be published in
Phys. Lett.
Classical and Quantum-like approaches to Charged-Particle Fluids in a Quadrupole
A classical description of the dynamics of a dissipative charged-particle
fluid in a quadrupole-like device is developed. It is shown that the set of the
classical fluid equations contains the same information as a complex function
satisfying a Schrodinger-like equation in which Planck's constant is replaced
by the time-varying emittance, which is related to the time-varying temperature
of the fluid. The squared modulus and the gradient of the phase of this complex
function are proportional to the fluid density and to the current velocity,
respectively. Within this framework, the dynamics of an electron bunch in a
storage ring in the presence of radiation damping and quantum-excitation is
recovered. Furthermore, both standard and generalized (including dissipation)
coherent states that may be associated with the classical particle fluids are
fully described in terms of the above formalism.Comment: LaTex, to appear in Physica Script
Effective cosmological constant induced by stochastic fluctuations of Newton's constant
We consider implications of the microscopic dynamics of spacetime for the
evolution of cosmological models. We argue that quantum geometry effects may
lead to stochastic fluctuations of the gravitational constant, which is thus
considered as a macroscopic effective dynamical quantity. Consistency with
Riemannian geometry entails the presence of a time-dependent dark energy term
in the modified field equations, which can be expressed in terms of the
dynamical gravitational constant. We suggest that the late-time accelerated
expansion of the Universe may be ascribed to quantum fluctuations in the
geometry of spacetime rather than the vacuum energy from the matter sector.Comment: 10 pages, 1 figure, v2: added legend in Fig.1 and a referenc
The slingshot effect: a possible new laser-driven high energy acceleration mechanism for electrons
We show that under appropriate conditions the impact of a very short and
intense laser pulse onto a plasma causes the expulsion of surface electrons
with high energy in the direction opposite to the one of propagation of the
pulse. This is due to the combined effects of the ponderomotive force and the
huge longitudinal field arising from charge separation ("slingshot effect").
The effect should also be present with other states of matter, provided the
pulse is sufficiently intense to locally cause complete ionization. An
experimental test seems to be feasible and, if confirmed, would provide a new
extraction and acceleration mechanism for electrons, alternative to traditional
radio-frequency-based or Laser-Wake-Field ones.Comment: File RevTex, 12 pages, 8 figure
Propagation of ultrastrong femtosecond laser pulses in PLASMON-X
The derivation is presented of the nonlinear equations that describe the
propagation of ultrashort laser pulses in a plasma, in the Plasmon-X device. It
is shown that the Plasmon-X scheme used for the electron acceleration uses a
sufficiently broad beam () that justifies the use
of the standard stationary 1-D approximation in the electron hydrodynamic
equations, since the pulse width is sufficiently bigger than the pulse length
(). Furthermore, with the laser power of TW
and the spot size, the dimensionless laser vector potential
is sufficiently small , the nonlinearity is sufficiently weak to allow the power
expansion in the nonlinear Poissons's equation. Such approximation yields a
nonlinear Schr\" odinger equation with a reactive nonlocal nonlinear term. The
nonlocality contains a cosine function under the integral, indicating the
oscillating wake. For a smaller spot size that is used for the Thomson
scattering, m, the length and the width of the pulse are
comparable, and it is not possible to use the 1-D approximation in the
hydrodynamic equations. With such small spot size, the laser intensity is very
large, and most likely some sort of chanelling in the plasma would take place
(the plasma gets locally depleted so much that the electromagnetic wave
practically propagates in vacuum).Comment: Oral contribution O3.205 delivered at the 38th EPS Conference on
Plasma Physics, Strasbourg, France, 26 June - 1 July, 201
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