378 research outputs found
Short-range wakefields generated in the blowout regime of plasma-wakefield acceleration
In the past, calculation of wakefields generated by an electron bunch
propagating in a plasma has been carried out in linear approximation, where the
plasma perturbation can be assumed small and plasma equations of motion
linearized. This approximation breaks down in the blowout regime where a
high-density electron driver expels plasma electrons from its path and creates
a cavity void of electrons in its wake. In this paper, we develop a technique
that allows to calculate short-range longitudinal and transverse wakes
generated by a witness bunch being accelerated inside the cavity. Our results
can be used for studies of the beam loading and the hosing instability of the
witness bunch in PWFA and LWFA
Wake and Impedance
A systematic exposition of the basic concepts of wakes and impedances is
given for relativistic beams in accelerators.Comment: Lecture presented at JAS'2000 Accelerator School On Frontiers Of
Accelerator Technology: High Quality Beams, St. Petersburg - Moscow, Russia,
1-7 July 200
A novel fast simulation technique for axisymmetric PWFA configurations in the blowout regime
In the blowout regime of plasma wakefield acceleration (PWFA), which is the
most relevant configuration for current and future applications and
experiments, the plasma flow that is excited by the ultra-relativistic drive
beam is highly nonlinear. Thus, fast and accurate simulations codes are
indispensable tools in the study of this extremely important problem. We have
developed a novel algorithm that deals with the propagation of axisymmetric
bunches of otherwise arbitrary profile through a cold plasma of uniform
density. In contrast to the existing PWFA simulation tools, our code PLEBS
(PLasma-Electron Beam Simulations) uses a new computational scheme which
ensures that the transverse and longitudinal directions are completely
decoupled---a feature which significantly enhances the speed and robustness of
the new method. Our numerical results are benchmarked against the QuickPic code
and excellent agreement is established between the two approaches. Moreover,
our new technique provides a very convenient framework for studying issues such
as beam loading and short-range wakefields within the plasma cavity
Microbunched Electron Cooling with Amplification Cascades
The Microbunched Electron Cooling (MBEC) is a promising cooling technique
that can find applications in future hadron and electron-ion colliders to
counteract intrabeam scattering that limits the maximum achievable luminosity
of the collider. To minimize the cooling time, one would use amplification
cascades consisting of a drift section followed by a magnetic chicane. In this
paper, we first derive and optimize the gain factor in an amplification section
for a simplified one-dimensional model of the beam. We then deduce the cooling
rate of a system with one and two amplification cascades. We also analyze the
noise effects that counteract the cooling process through the energy diffusion
in the hadron beam. Our analytical formulas are confirmed by numerical
simulations for a set of model parameters.Comment: arXiv admin note: text overlap with arXiv:1806.0278
Wake excited in plasma by an ultrarelativistic pointlike bunch
We study propagation of a relativistic electron bunch through a cold plasma assuming that the transverse and longitudinal dimensions of the bunch are much smaller than the plasma collisionless skin depth. Treating the bunch as a point charge and assuming that its charge is small, we derive a simplified system of equations for the plasma electrons and show that, through a simple rescaling of variables, the bunch charge can be eliminated from the equations. The equations demonstrate an ion cavity formed behind the driver. They are solved numerically and the scaling of the cavity parameters with the driver charge is obtained. A numerical solution for the case of a positively charged driver is also found.Department of Energy DE-AC03-76SF00515U.S. Department of Energy DEFG02-04ER54742 DE-SC0007889 DE-SC0010622Air Force Office of Scientific Research (AFOSR) FA9550-14-1-0045Physic
Calculation of wakefields in 2D rectangular structures
We consider the calculation of electromagnetic fields generated by an
electron bunch passing through a vacuum chamber structure that, in general,
consists of an entry pipe, followed by some kind of transition or cavity, and
ending in an exit pipe. We limit our study to structures having rectangular
cross-section, where the height can vary as function of longitudinal coordinate
but the width and side walls remain fixed. For such structures, we derive a
Fourier representation of the wake potentials through one-dimensional
functions. A new numerical approach for calculating the wakes in such
structures is proposed and implemented in the computer code ECHO(2D). The
computation resource requirements for this approach are moderate and comparable
to those for finding the wakes in 2D rotationally symmetric structures.
Numerical examples obtained with the new numerical code are presented.Comment: 31 pages, 10 figure
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