563 research outputs found
Control of laser-driven ion acceleration
In laser-driven ion acceleration, there are issues,
including repetitive ion source, ion beam
quality, energy efficiency from laser to ion beam,
the total number of ions accelerated, laser efficiency,
particle energy, etc..
Control of laser-driven ion acceleration
In laser-driven ion acceleration, there are issues,
including repetitive ion source, ion beam
quality, energy efficiency from laser to ion beam,
the total number of ions accelerated, laser efficiency,
particle energy, etc..
Bacterial cells enhance laser driven ion acceleration
Intense laser produced plasmas generate hot electrons which in turn leads to ion acceleration. Ability to generate faster ions or hotter electrons using the same laser parameters is one of the main outstanding paradigms in the intense laser-plasma physics. Here, we present a simple, albeit, unconventional target that succeeds in generating 700 keV carbon ions where conventional targets for the same laser parameters generate at most 40 keV. A few layers of micron sized bacteria coating on a polished surface increases the laser energy coupling and generates a hotter plasma which is more effective for the ion acceleration compared to the conventional polished targets. Particle-in-cell simulations show that micro-particle coated target are much more effective in ion acceleration as seen in the experiment. We envisage that the accelerated, high-energy carbon ions can be used as a source for multiple applications
Enhancement of laser-driven ion acceleration in non-periodic nanostructured targets
Using particle-in-cell simulations, we demonstrate an improvement of the
target normal sheath acceleration (TNSA) of protons in non-periodically
nanostructured targets with micron-scale thickness. Compared to standard flat
foils, an increase in the proton cutoff energy by up to a factor of two is
observed in foils coated with nanocones or perforated with nanoholes. The
latter nano-perforated foils yield the highest enhancement, which we show to be
robust over a broad range of foil thicknesses and hole diameters. The
improvement of TNSA performance results from more efficient hot-electron
generation, caused by a more complex laser-electron interaction geometry and
increased effective interaction area and duration. We show that TNSA is
optimized for a nanohole distribution of relatively low areal density and that
is not required to be periodic, thus relaxing the manufacturing constraints.Comment: 11 pages, 8 figure
Electron heating in subpicosecond laser interaction with overdense and near-critical plasmas
n this work we investigate electron heating induced by intense laser interaction with micrometric flat solid
foils in the context of laser-driven ion acceleration. We propose a simple law to predict the electron temperature in
a wider range of laser parameters with respect to commonly used existing models. An extensive two-dimensional
(2D) and 3D numerical campaign shows that electron heating is due to the combined actions of j×B
and Brunel effect. Electron temperature can be well described with a simple function of pulse intensity and angle of incidence,
with parameters dependent on pulse polarization. We then combine our model for the electron temperature with
an existing model for laser-ion acceleration, using recent experimental results as a benchmark. We also discuss
an exploratory attempt to model electron temperature for multilayered foam-attached targets, which have been
proven recently to be an attractive target concept for laser-driven ion acceleration
Advanced Approaches to High Intensity Laser-Driven Ion Acceleration
Since the pioneering work that was carried out 10 years ago, the generation of highly energetic ion beams from laser-plasma interactions has been investigated in much detail in the regime of target normal sheath acceleration (TNSA). Creation of ion beams with small longitudinal and transverse emittance and energies extending up to tens of MeV fueled visions of compact, laser-driven ion sources for applications such as ion beam therapy of tumors or fast ignition inertial confinement fusion. However, new pathways are of crucial importance to push the current limits of laser-generated ion beams further towards parameters necessary for those applications.
The presented PhD work was intended to develop and explore advanced approaches to high intensity laser-driven ion acceleration that reach beyond TNSA. In this spirit, ion acceleration from two novel target systems was investigated, namely mass-limited microspheres and nm-thin, free-standing diamond-like carbon (DLC) foils. Using such ultrathin foils, a new regime of ion acceleration was found where the laser transfers energy to all electrons located within the focal volume. While for TNSA the accelerating electric field is stationary and ion acceleration is spatially separated from laser absorption into electrons, now a localized longitudinal field enhancement is present that co-propagates with the ions as the accompanying laser pulse pushes the electrons forward. Unprecedented maximum ion energies were obtained, reaching beyond 0.5 GeV for carbon C and thus exceeding previous TNSA results by about one order of magnitude. When changing the laser polarization to circular, electron heating and expansion were shown to be efficiently suppressed, resulting for the first time in a phase-stable acceleration that is dominated by the laser radiation pressure which led to the observation of a peaked C spectrum. Compared to quasi-monoenergetic ion beam generation within the TNSA regime, a more than 40 times increase in conversion efficiency was achieved. The possibility to manipulate the shape of the ion acceleration front was successfully demonstrated by use of a spherically curved target surface. Finally, the last part of the presented work is devoted to accomplishments in laser development
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