219 research outputs found
Analytical model for the uncorrelated emittance evolution of externally injected beams in plasma-based accelerators
This article introduces an analytical formalism for the calculation of the
evolution of beam moments and the transverse emittance for beams which are
externally injected into plasma wakefield accelerators. This formalism is then
applied to two scenarios with increasing complexity - a single beam slice
without energy gain and a single beam slice with energy gain, both propagating
at a fixed co-moving position behind the driver. The obtained results are then
compared to particle-in-cell (PIC) simulations as well as results obtained
using an semi-analytic numerical approach (SANA). We find excellent agreement
between results from the analytical model and from SANA and PIC
Ponderomotive Injection in Plasma Wakefield Accelerators
A new electron injection scheme is proposed in sub-relativistic plasma
wakefield accelerators. A transverse laser ionizes a dopant gas and
ponderomotively accelerates the released electrons in the direction of wake
propagation. This process enables electron trapping in the wakefield even for a
wakefield potential below the trapping threshold. We study the scheme
theoretically and by means of particle-in-cell simulations to demonstrate
high-quality beam formation and acceleration with sub-micrometer normalized
emittances and sub-percent uncorrelated energy spreads
Plasma Lenses for Relativistic Laser Beams in Laser Wakefield Accelerators
Focusing petawatt-level laser beams to a variety of spot sizes for different
applications is expensive in cost, labor and space. In this paper, we propose a
plasma lens to flexibly resize the laser beam by utilizing the laser
self-focusing effect. Using a fixed conventional focusing system to focus the
laser a short distance in front of the plasma, we can adjust the effective
laser beam waist within a certain range, as if a variety of focusing systems
were used with the plasma lens acting as an adjustable eyepiece in a telescope.
Such a setup is a powerful tool for laser wakefield accelerator experiments in
state-of-art petawatt laser projects and allows for scanning focal spot
parameters.Comment: 12 pages, 11 figure
Plasma Lens Prototype Progress: Plasma Diagnostics And Particle Tracking For ILC e+ Source
In recent years, the concept of high-gradient, symmetric focusing using
active plasma lenses has regained notable attention owing to its potential
benefits in terms of compactness and beam dynamics when juxtaposed with
traditional focusing elements. An enticing application lies in the optical
matching of extensively divergent positrons originating from the
undulator-based ILC positron source, thereby enhancing the positron yield in
subsequent accelerating structures. Through a collaboration between the
University of Hamburg and DESY Hamburg, a scaled-down prototype for this
purpose has been conceptualized and fabricated. In this presentation, we
provide an overview of the ongoing progress in the development of this
prototype. Furthermore, first insights into the development of a particle
tracking code especially designed for plasma lenses with implemented Bayes
optimization, are given.Comment: TALK PRESENTED AT THE INTERNATIONAL WORKSHOP ON FUTURE LINEAR
COLLIDERS (LCWS2023), 15-19 MAY 2023. C23-05-15.3., LCWS23, SLAC, Plasma
lens, ILC, 3 page
Emittance-preserving acceleration of high-quality positron beams using warm plasma filaments
Preserving the quality of positron beams in plasma-based accelerators, where
wakefields are generated in electron filaments, is challenging. These
wakefields are characterized by transversely non-linear focusing fields and
non-uniform accelerating fields. However, a nonzero plasma temperature
linearizes the transverse wakefield within the central region of the electron
filament. In this study, we employ 3D particle-in-cell simulations with mesh
refinement to demonstrate that beams with emittances on the order of tens of
nanometers are contained within the linearized region of the transverse
wakefield. This enables emittance preservation to one percent, while positron
beams with the same charge and micrometer emittances, which sample the
non-linear part of the transverse wakefield, experience a relative emittance
growth of ten percent. Additionally, we observe a significant reduction in the
growth rate of the slice energy spread for the tens of nanometers emittance
beams in comparison to the micrometer emittance beams. The utilization of warm
plasmas in conjunction with low-emittance beams opens up new avenues for
enhancing the beam quality across various plasma-based positron acceleration
approaches.Comment: To be submitted as a proceedings for the 6th European Advanced
Accelerator Concepts worksho
Generation of quasi continuous-wave electron beams in an L-band normal conducting pulsed RF injector for laboratory astrophysics experiments
We report on an approach to produce quasi continuous-wave (cw) electron beams
with an average beam current of milliamperes and a mean beam energy of a few
MeV in a pulsed RF injector. Potential applications are in the planned
laboratory astrophysics programs at DESY. The beam generation is based on field
emission from a specially designed metallic field emitter. A quasi cw beam
profile is formed over subsequent RF cycles at the resonance frequency of the
gun cavity. This is realized by debunching in a cut disk structure accelerating
cavity (booster) downstream of the gun. The peak and average beam currents can
be tuned in beam dynamics simulations by adjusting operation conditions of the
booster cavity. Optimization of the transverse beam size at specific positions
(e.g., entrance of the plasma experiment) is performed by applying magnetic
focusing fields provided by solenoids along the beam line. In this paper, the
design of a microtip field emitter is introduced and characterized in
electromagnetic field simulations in the gun cavity. A series of particle
tracking simulations are conducted for multi-parametric optimization of the
parameters of the produced quasi cw electron beams. The obtained results will
be presented and discussed. In addition, measurements of the parasitic field
emission (PFE) current (dark current) in the PITZ gun will be exemplarily shown
to distinguish its order of magnitude from the produced beam current by the
designed field emitter.Comment: 23 pages, 17 figure
Controlled density-downramp injection in a beam-driven plasma wakefield accelerator
This paper describes the utilization of beam-driven plasma wakefield
acceleration to implement a high-quality plasma cathode via density-downramp
injection in a short injector stage at the FLASHForward facility at DESY.
Electron beams with charge of up to 105 pC and energy spread of a few percent
were accelerated by a tunable effective accelerating field of up to 2.7 GV/m.
The plasma cathode was operated drift-free with very high injection efficiency.
Sources of jitter, the emittance and divergence of the resulting beam were
investigated and modeled, as were strategies for performance improvements that
would further increase the wide-ranging applications for a plasma cathode with
the demonstrated operational stabilityComment: 11 pages, 9 figure
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