635 research outputs found
A Generalization of Abel Inversion to non axisymmetric density distribution
Abel Inversion is currently used in laser-plasma studies in order to estimate
the electronic density from the phase-shift map obtained
via interferometry. The main limitation of the Abel method is due to the
assumption of axial symmetry of the electronic density, which is often hardly
fulfilled. In this paper we present an improvement to the Abel inversion
technique in which the axial symmetry condition is relaxed by means of a
truncated Legendre Polinomial expansion in the azimutal angle. With the help of
simulated interferograms, we will show that the generalized Abel inversion
generates accurate densities maps when applied to non axisymmetric density
sources
Application of novel techniques for interferogram analysis to laser-plasma femtosecond probing
Recently, two novel techniques for the extraction of the phase-shift map
(Tomassini {\it et.~al.}, Applied Optics {\bf 40} 35 (2001)) and the electronic
density map estimation (Tomassini P. and Giulietti A., Optics Communication
{\bf 199}, pp 143-148 (2001)) have been proposed. In this paper we apply both
methods to a sample laser-plasma interferogram obtained with femtoseconds probe
pulse, in an experimental setup devoted to laser particle acceleration studies.Comment: Submitted to Laser and Particle Beam
Phase field modelling and simulation of damage occurring in human vertebra after screws fixation procedure
The present endeavour numerically exploits the use of a phase-field model to simulate and investigate fracture patterns, deformation mechanisms, damage, and mechanical responses in a human vertebra after the incision of pedicle screws under compressive regimes. Moreover, the proposed phase field framework can elucidate scenarios where different damage patterns, such as crack nucleation sites and crack trajectories, play a role after the spine fusion procedure, considering several simulated physiological movements of the vertebral body. Spatially heterogeneous elastic properties and phase field parameters have been computationally derived from bone density estimation. A convergence analysis has been conducted for the vertebra-screws model, considering several mesh refinements, which has demonstrated good agreement with the existing literature on this topic. Consequently, by assuming different angles for the insertion of the pedicle screws and taking into account a few vertebral motion loading regimes, a plethora of numerical results characterizing the damage occurring within the vertebral model has been derived. Overall, the phase field results confirm and enrich the current literature, shed light on the medical community, which will be useful in enhancing clinical interventions and reducing post-surgery bone failure and screw loosening. The proposed computational approach also investigates the effects in terms of fracture and mechanical behaviour of the vertebral-screws body within different metastatic lesions opening towards major life threatening scenarios
Acceleration with Self-Injection for an All-Optical Radiation Source at LNF
We discuss a new compact gamma-ray source aiming at high spectral density, up
to two orders of magnitude higher than currently available bremsstrahlung
sources, and conceptually similar to Compton Sources based on conventional
linear accelerators. This new source exploits electron bunches from
laser-driven electron acceleration in the so-called self-injection scheme and
uses a counter-propagating laser pulse to obtain X and gamma-ray emission via
Thomson/Compton scattering. The proposed experimental configuration inherently
provides a unique test-bed for studies of fundamental open issues of
electrodynamics. In view of this, a preliminary discussion of recent results on
self-injection with the FLAME laser is also given.Comment: 8 pages, 10 figures, 44 references - Channeling 2012 conferenc
Light Ion Accelerating Line (L3IA): Test Experiment at ILIL-PW
The construction of a novel Laser driven Light Ions Acceleration Line(L3IA)
is progressing rapidly towards the operation, following the recent upgrade of
the ILIL-PW laser facility. The Line was designed following the pilot
experimental activity carried out earlier at the same facility to define design
parameters and to identify main components including target control and
diagnostic equipment, also in combination with the numerical simulations for
the optimization of laser and target parameters. A preliminary set of data was
acquired following the successful commissioning of the laser system >100 TW
upgrade. Data include output from a range of different ion detectors and
optical diagnostics installed for qualification of the laser-target
interaction. An overview of the results is given along with a description of
the relevant upgraded laser facility and features.Comment: 6 pages, 7 figures, 18 references, presented at the EAAC 201
Experimental study of picosecond laser plasma formation in thin foils
A high performance, fully controlled picosecond
laser system has been designed and built with the aid of
a numerical code capable of simulating the temporal behavior
of the laser system, including each active and passive
component. The laser performance was characterized with
an optical streak camera, equivalent plane monitor, and
calorimeter measurements. The laser pulse was focused on
150-nm thick foils to investigate plasma formation and
the related transmittivity of the laser light. The experimental
data are in very good agreement with the predictions of
a simple, 2D analytical model that takes into account the
actual shot-to-shot features of the laser pulse. The temporal
profile of the pulse and the intensity distribution in
the focal spot were found to play a key role in determining
the transmission properties of the laser-irradiated foil.
This work may be relevant to a wide class of laser exploded
foil plasma experiments
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