9,757 research outputs found
High-quality ion beams by irradiating a nano-structured target with a petawatt laser pulse
We present a novel laser based ion acceleration scheme, where a petawatt
circularly polarized laser pulse is shot on an ultra-thin (nano-scale)
double-layer target. Our scheme allows the production of high-quality light ion
beams with both energy and angular dispersion controllable by the target
properties. We show that extraction of all electrons from the target by
radiation pressure can lead to a very effective two step acceleration process
for light ions if the target is designed correctly. Relativistic protons should
be obtainable with pulse powers of a few petawatt. Careful analytical modeling
yields estimates for characteristic beam parameters and requirements on the
laser pulse quality, in excellent agreement with one and two-dimensional
Particle-in Cell simulations.Comment: 18 pages, 7 figures, accepted in New. J. Phy
Laser acceleration of monoenergetic protons via a double layer emerging from an ultra-thin foil
We present theoretical and numerical studies of the acceleration of monoenergetic protons in a double layer formed by the laser irradiation of an ultra-thin film. The ponderomotive force of the laser light pushes the electrons forward, and the induced space charge electric field pulls the ions and makes the thin foil accelerate as a whole. The ions trapped by the combined electric field and inertial force in the accelerated frame, together with the electrons trapped in the well of the ponderomotive and ion electric field, form a stable double layer. The trapped ions are accelerated to monoenergetic energies up to 100 MeV and beyond, making them suitable for cancer treatment. We present an analytic theory for the laser-accelerated ion energy and for the amount of trapped ions as functions of the laser intensity, foil thickness and the plasma number density. We also discuss the underlying physics of the trapped and untrapped ions in a double layer. The analytical results are compared with those obtained from direct Vlasov simulations of the fully nonlinear electron and ion dynamics that is controlled by the laser light
Laser-Generated Proton Beams for High-Precision Ultra-Fast Crystal Synthesis
We present a method for the synthesis of micro-crystals and micro-structured surfaces using laseraccelerated
protons. In this method, a solid surface material having a low melting temperature is
irradiated with very-short laser-generated protons, provoking in the ablation process thermodynamic
conditions that are between the boiling and the critical point. The intense and very quick proton energy
deposition (in the ns range) induces an explosive boiling and produces microcrystals that nucleate in a
plasma plume composed by ions and atoms detached from the laser-irradiated surface. The synthesized
particles in the plasma plume are then deposited onto a cold neighboring, non-irradiated, solid
secondary surface. We experimentally verify the synthesizing methods by depositing low-meltingmaterial
microcrystals - such as gold - onto nearby silver surfaces and modeling the proton/matter
interaction via a Monte Carlo code, confrming that we are in the above described thermodynamic
conditions. Morphological and crystallinity measurements indicate the formation of gold octahedral
crystals with dimensions around 1.2 μm, uniformly distributed onto a silver surface with dimensions
in the tens of mm2. This laser-accelerated particle based synthesis method paves the way for the
development of new material synthesis using ultrashort laser-accelerated particle beams
Multi-Cascade Proton Acceleration by Superintense Laser Pulse in the Regime of Relativistically Induced Slab Transparency
A regime of multi-cascade proton acceleration in the interaction of
W/cm laser pulse with a structured target is proposed.
The regime is based on the electron charge displacement under the action of
laser ponderomotive force and on the effect of relativistically induced slab
transparency which allows to realize idea of multi-cascade acceleration. It is
shown that a target comprising several properly spaced apart thin foils can
optimize the acceleration process and give at the output quasi-monoenergetic
beams of protons with energies up to hundreds of MeV with energy spread of just
few percent.Comment: 5 pages with 4 figure
Vlasov simulation of laser-driven shock acceleration and ion turbulence
We present a Vlasov, i.e. a kinetic Eulerian simulation study of nonlinear
collisionless ion-acoustic shocks and solitons excited by an intense laser
interacting with an overdense plasma. The use of the Vlasov code avoids
problems with low particle statistics and allows a validation of
particle-in-cell results. A simple original correction to the splitting method
for the numerical integration of the Vlasov equation has been implemented in
order to ensure the charge conservation in the relativistic regime. We show
that the ion distribution is affected by the development of a turbulence driven
by the relativistic "fast" electron bunches generated at the laser-plasma
interaction surface. This leads to the onset of ion reflection at the shock
front in an initially cold plasma where only soliton solutions without ion
reflection are expected to propagate. We give a simple analytic model to
describe the onset of the turbulence as a nonlinear coupling of the ion density
with the fast electron currents, taking the pulsed nature of the relativistic
electron bunches into account
Laser beam coupling with capillary discharge plasma for laser wakefield acceleration applications
One of the most robust methods, demonstrated up to date, of accelerating
electron beams by laser-plasma sources is the utilization of plasma channels
generated by the capillary discharges. These channels, i.e., plasma columns
with a minimum density along the laser pulse propagation axis, may optically
guide short laser pulses, thereby increasing the acceleration length, leading
to a more efficient electron acceleration. Although the spatial structure of
the installation is simple in principle, there may be some important effects
caused by the open ends of the capillary, by the supplying channels etc., which
require a detailed 3D modeling of the processes taking place in order to get a
detailed understanding and improve the operation. However, the discharge
plasma, being one of the most crucial components of the laser-plasma
accelerator, is not simulated with the accuracy and resolution required to
advance this promising technology. In the present work, such simulations are
performed using the code MARPLE. First, the process of the capillary filling
with a cold hydrogen before the discharge is fired, through the side supply
channels is simulated. The main goal of this simulation is to get a spatial
distribution of the filling gas in the region near the open ends of the
capillary. A realistic geometry is used for this and the next stage
simulations, including the insulators, the supplying channels as well as the
electrodes. Second, the simulation of the capillary discharge is performed with
the goal to obtain a time-dependent spatial distribution of the electron
density near the open ends of the capillary as well as inside the capillary.
Finally, to evaluate effectiveness of the beam coupling with the channeling
plasma wave guide and electron acceleration, modeling of laser-plasma
interaction was performed with the code INF&RNOComment: 11 pages, 9 figure
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