115 research outputs found

### Cooling force on ions in a magnetized electron plasma

Electron cooling is a well-established method to improve the phase space
quality of ion beams in storage rings. In the common rest frame of the ion and
the electron beam the ion is subjected to a drag force and it experiences a
loss or a gain of energy which eventually reduces the energy spread of the ion
beam. A calculation of this process is complicated as the electron velocity
distribution is anisotropic and the cooling process takes place in a magnetic
field which guides the electrons. In this paper the cooling force is calculated
in a model of binary collisions (BC) between ions and magnetized electrons, in
which the Coulomb interaction is treated up to second-order as a perturbation
to the helical motion of the electrons. The calculations are done with the help
of an improved BC theory which is uniformly valid for any strength of the
magnetic field and where the second-order two-body forces are treated in the
interaction in Fourier space without specifying the interaction potential. The
cooling force is explicitly calculated for a regularized and screened potential
which is both of finite range and less singular than the Coulomb interaction at
the origin. Closed expressions are derived for monochromatic electron beams,
which are folded with the velocity distributions of the electrons and ions. The
resulting cooling force is evaluated for anisotropic Maxwell velocity
distributions of the electrons and ions.Comment: 22 pages, 10 figure

### Excitation of nonlinear one-dimensional wake waves in underdense and overdense magnetized plasma by a relativistic electron bunch

The excitation of wake waves by a relativistic homogeneous electron bunch
passing through cold magnetized plasma at equilibrium is studied for arbitrary
values of the ratio of bunch density to plasma density. The analysis is based
on the assumption that the magnetic field is sufficiently strong ($\omega_B\gg
\omega_p$, where $\omega_p$ and $\omega_B$ are the electron plasma and
cyclotron frequences respectively). The periodic and nonperiodic solutions for
the momentum of plasma electrons inside and outside the bunch are analyzed. It
was shown that the presence of strong external magnetic field may increase the
amplitude of wake waves and the maximum transformer ratio, the latter being
reached at densities of bunch lower than that in the absence of magnetic field.
The optimum conditions for obtaining the maximum values of the wake field
amplitude and of the transformer ratio are found.Comment: 23 pages, 10 figures, LaTe

### Energy transfer in binary collisions of two gyrating charged particles in a magnetic field

Binary collisions of the gyrating charged particles in an external magnetic
field are considered within a classical second-order perturbation theory, i.e.,
up to contributions which are quadratic in the binary interaction, starting
from the unperturbed helical motion of the particles. The calculations are done
with the help of a binary collisions treatment which is valid for any strength
of the magnetic field and involves all harmonics of the particles cyclotron
motion. The energy transfer is explicitly calculated for a regularized and
screened potential which is both of finite range and nonsingular at the origin.
The validity of the perturbation treatment is evaluated by comparing with
classical trajectory Monte Carlo (CTMC) calculations which also allow to
investigate the strong collisions with large energy and velocity transfer at
low velocities. For large initial velocities on the other hand, only small
velocity transfers occur. There the nonperturbative numerical CTMC results
agree excellently with the predictions of the perturbative treatment.Comment: 12 pages, 4 figure

### The Dynamics of Charges Induced by a Charged Particle Traversing a Dielectric Slab

We studied the dynamics of surfacea and wake charges induced by a charged
particle traversing a dielectric slab. It is shown that after the crossing of
the slab first boundary, the induced on the slab surface charge (image charge)
is transformed into the wake charge, which overflows to the second boundary
when the particle crosses it. It is also shown, that the polarization of the
slab is of an oscillatory nature, and the net induced charge in a slab remains
zero at all stages of the motion.Comment: 12 pages, 1 figur

### An exact solution of the moving boundary problem for the relativistic plasma expansion in a dipole magnetic field

An exact analytic solution is obtained for a uniformly expanding, neutral,
highly conducting plasma sphere in an ambient dipole magnetic field with an
arbitrary orientation of the dipole moment in the space. Based on this solution
the electrodynamical aspects related to the emission and transformation of
energy have been considered. In order to highlight the effect of the
orientation of the dipole moment in the space we compare our results obtained
for parallel orientation with those for transversal orientation. The results
obtained can be used to treat qualitatively experimental and simulation data,
and several phenomena of astrophysical and laboratory significance.Comment: 7 pages, 2 figures. arXiv admin note: substantial text overlap with
arXiv:physics/060323

### Spectrum of surface-mode contributions to the excitation probability for electron beam interacting with sharp-edged dielectric wedges

The interaction of a nonrelativistic charged particle beam, travelling
parallel to the surface of a sharp-edged dielectric wedge is analyzed. The
general expressions for excitation probability are obtained for a beam moving
along the direction of a symmetry axis, either outside or inside the dielectric
wedge. The dielectric function of the medium is assumed to be isotropic, and
numerical results are given for the materials of experimental interest.Comment: LaTeX 2.09, 15 pages, 10 figure

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