2,652 research outputs found
Radiation Damping and Quantum Excitation for Longitudinal Charged Particle Dynamics in the Thermal Wave Model
On the basis of the recently proposed {\it Thermal Wave Model (TWM) for
particle beams}, we give a description of the longitudinal charge particle
dynamics in circular accelerating machines by taking into account both
radiation damping and quantum excitation (stochastic effect), in presence of a
RF potential well. The longitudinal dynamics is governed by a 1-D
Schr\"{o}dinger-like equation for a complex wave function whose squared modulus
gives the longitudinal bunch density profile. In this framework, the
appropriate {\it r.m.s. emittance} scaling law, due to the damping effect, is
naturally recovered, and the asymptotic equilibrium condition for the bunch
length, due to the competition between quantum excitation (QE) and radiation
damping (RD), is found. This result opens the possibility to apply the TWM,
already tested for protons, to electrons, for which QE and RD are very
important.Comment: 10 pages, plain LaTeX; published in Phys. Lett. A194 (1994) 113-11
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
Coherent instabilities of intense high-energy "white" charged-particle beams in the presence of nonlocal effects within the context of the Madelung fluid description
A hydrodynamical description of coherent instabilities that take place in the
longitudinal dynamics of a charged-particle coasting beam in a high-energy
accelerating machine is presented. This is done in the framework of the
Madelung fluid picture provided by the Thermal Wave Model. The well known
coherent instability charts in the complex plane of the longitudinal coupling
impedance for monochromatic beams are recovered. The results are also
interpreted in terms of the deterministic approach to modulational instability
analysis usually given for monochromatic large amplitude wave train propagation
governed by the nonlinear Schr\"odinger equation. The instability analysis is
then extended to a non-monochromatic coasting beam with a given thermal
equilibrium distribution, thought as a statistical ensemble of monochromatic
incoherent coasting beams ("white" beam). In this hydrodynamical framework, the
phenomenon of Landau damping is predicted without using any kinetic equation
governing the phase space evolution of the system.Comment: 14 pages, 1 figur
Dynamics of the wakefield of a multi-petawatt, femtosecond laser pulse in a configuration with ultrarelativistic electrons
The wake field excitation in an unmagnetized plasma by a multi-petawatt,
femtosecond, pancake-shaped laser pulse is described both analytically and
numerically in the regime with ultrarelativistic electron jitter velocities,
when the plasma electrons are almost expelled from the pulse region. This is
done, for the first time, in fluid theory. A novel mathematical model is
devised that does not break down for very intense pump strengths, in contrast
to the standard approach that uses the laser field envelope and the
ponderomotive guiding center averaging. This is accomplished by employing a
three-timescale description, with the intermediate scale associated with the
nonlinear phase of the electromagnetic wave and with the bending of its wave
front. The evolution of the pulse and of its electrostatic wake are studied by
the numerical solution in a two-dimensional geometry, with the spot diameter
\geq 100 microns. It reveals that the optimum initial pulse length needs to be
somewhat bigger than 1 micron (1-2 oscillations), as suggested by simple
analytical local estimates, because the nonlocal plasma response tends to
stretch very short pulses
Quantum corrected electron holes
The theory of electron holes is extended into the quantum regime. The
Wigner--Poisson system is solved perturbatively based in lowest order on a
weak, standing electron hole. Quantum corrections are shown to lower the
potential amplitude and to increase the number of deeply trapped electrons.
They, hence, tend to bring this extreme non--equilibrium state closer to
thermodynamic equilibrium, an effect which can be attributed to the tunneling
of particles in this mixed state system.Comment: 12 pages, 3 figure
Coherent States for Particle Beams in the Thermal Wave Model
In this paper, by using an analogy among {\it quantum mechanics}, {\it
electromagnetic beam optics in optical fibers}, and {\it charge particle beam
dynamics}, we introduce the concept of {\it coherent states} for charged
particle beams in the framework of the {\it Thermal Wave Model} (TWM). We give
a physical meaning of the Gaussian-like coherent structures of charged particle
distribution that are both naturally and artificially produced in an
accelerating machine in terms of the concept of coherent states widely used in
quantum mechanics and in quantum optics. According to TWM, this can be done by
using a Schr\"{o}dinger-like equation for a complex function, the so-called
{\it beam wave function} (BWF), whose squared modulus is proportional to the
transverse beam density profile, where Planck's constant and the time are
replaced by the transverse beam emittance and by the propagation coordinate,
respectively. The evolution of the particle beam, whose initial BWF is assumed
to be the simplest coherent state (ground-like state) associated with the beam,
in an infinite 1-D quadrupole-like device with small sextupole and octupole
aberrations, is analytically and numerically investigated.Comment: 21 pages, Late
Quantum computation by quantum-like systems
Using a quantumlike description for light propagation in nonhomogeneous
optical fibers, quantum information processing can be implemented by optical
means. Quantum-like bits (qulbits) are associated to light modes in the optical
fiber and quantum gates to segments of the fiber providing an unitary
transformation of the mode structure along a space direction. Simulation of
nonlinear quantum effects is also discussed.Comment: 12 pages, Late
Nonlocal effects in high energy charged particle beams
Within the framework of the thermal wave model, an investigation is made of
the longitudinal dynamics of high energy charged particle beams. The model
includes the self-consistent interaction between the beam and its surroundings
in terms of a nonlinear coupling impedance, and when resistive as well as
reactive parts are included, the evolution equation becomes a generalised
nonlinear Schroedinger equation including a nonlocal nonlinear term. The
consequences of the resistive part on the propagation of particle bunches are
examined using analytical as well as numerical methods.Comment: 6 pages, 6 figures, uses RevTeX
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