4,793 research outputs found
Nanostructured target fabrication with metal and semiconductor nanoparticles
The development of ultra-intense high-energy (≫1 J) short (<1 ps) laser pulses in the last decade hasenabled the acceleration of high-energy short-pulse proton beams. A key parameter for enhancing theacceleration regime is the laser-to-target absorption, which heavily depends on the target structureand material. In this work, we present the realization of a nanostructured target with a sub-laserwavelength nano-layer in the front surface as a possible candidate for improving the absorption. Thenanostructuredfilm was realized by a simpler and cheaper method than using conventionallithographic techniques: A colloidal solution of metallic or semiconductor nanoparticles (NPs) wasproduced by laser ablation and, after a heating and sonication process, was spray-dried on the frontsurface of an aluminum target. The obtained nanostructuredfilm with a thickness of 1μm appears, atmorphological and chemical analysis, uniformly nanostructured and distributed on the target surfacewithout the presence of oxides or external contaminants. Finally, the size of the NPs can be tuned fromtens to hundreds of nanometers simply by varying the growth parameters (i.e., irradiation time,fluence, and laser beam energy
Laser-Plasma driven synthesis of carbon-based nanomaterials
In this paper we introduce a laser-plasma driven method for the production of carbon based nanomaterials and in particular bi- and few-layers of Graphene. This is obtained by using laser-plasma exfoliation of amorphous Graphite in a liquid solution, employing a laser with energy in the order of 0.5 J/mm2. Raman and XPS analysis of a carbon colloidal performed at different irradiation stages indicate the formation of Graphene multilayers with an increasing number of layers: the amount of layers varies from a monolayer obtained in the first few seconds of the laser irradiation, up to two layers obtained after 10 s, and finally to Graphite and amorphous carbon obtained after 40 s of irradiation. The obtained colloidals are pure, without any presence of impurities or Graphene oxides, and can easily be deposited onto large surfaces (in the order of cm2) for being characterized or for being used in diverse applications
In situ study of nucleation and aggregation phases for nanoparticles grown by laser-driven methods
In the last decades, nanomaterials and nanotechnologies have become fundamental and irreplaceable in many fields of science and technology. When used in applications, their properties depend on many factors such as size, shape, internal structure and composition. For this, exact knowledge of their structural features is essential when developing fabrication technologies and searching for new types of nanostructures or nanoparticles with specific properties. For the latter, the knowledge of the precise temporal evolution of the growth processes is fundamental when it comes to industrial production and applications. Here we present a method to control, with very high precision, the starting of the aggregation phase during the Laser Ablation in solution growth process. This is obtained by monitoring the optical absorption of the colloidal solution. We apply this control method on the most popular metallic nanoparticle materials (Ag, Al, Co, and Ti) and verify the technique using morphological analysis conducted by AFM and SEM microscopy. The experimental results are explained in terms of Mie extinction theory and Thermal Model for Laser Ablatio
Inelastic Dark Matter and the SABRE Experiment
We present here the sensitivity of the SABRE (Sodium iodide with Active
Background REjection) experiment to benchmark proto-philic, spin dependent,
Inelastic Dark Matter models previously proposed due to their lowered tension
with existing experimental results. We perform fits to cross section, mass, and
mass splitting values to find the best fit to DAMA/LIBRA data for these models.
In this analysis, we consider the Standard Halo Model (SHM), as well as an
interesting extension upon it, the SHM+Stream distribution, to investigate the
influence of the Dark Matter velocity distribution upon experimental
sensitivity and whether or not its consideration may be able to help relieve
the present experimental tension. Based on our analysis, SABRE should be
sensitive to all the three benchmark models within 3-5 years of data taking.Comment: Adjusted for full DAMA run 1+2 efficiency. Updated to match published
versio
Laser-Accelerated proton beams as diagnostics for cultural heritage
This paper introduces the first use of laser-generated proton beams as diagnostic for materials of interest in the domain of Cultural Heritage. Using laser-accelerated protons, as generated by interaction of a high-power short-pulse laser with a solid target, we can produce proton-induced X-ray emission spectroscopies (PIXE). By correctly tuning the proton flux on the sample, we are able to perform the PIXE in a single shot without provoking more damage to the sample than conventional methodologies. We verify this by experimentally irradiating materials of interest in the Cultural Heritage with laser-accelerated protons and measuring the PIXE emission. The morphological and chemical analysis of the sample before and after irradiation are compared in order to assess the damage provoked to the artifact. Montecarlo simulations confirm that the temperature in the sample stays safely below the melting point. Compared to conventional diagnostic methodologies, laser-driven PIXE has the advantage of being potentially quicker and more efficien
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
CP asymmetries at D0
Using two independent measurements of the semileptonic CP asymmetry in the
system, we constrain the CP violating phase of the system to be
. The data sample corresponds to an integrated
luminosity of 1.1 fb accumulated with D0 detector at the Fermilab
Tevatron collider. We also measure the direct CP violating asymmetry in the
decay to be (stat)(syst). The data corresponds to an integrated
luminosity of 1.6 fb.Comment: contributed paper to EPS07, Manchester, UK, manuscript number
EPSHEPP17
Measuring the Higgs boson's parity using tau --> rho nu
We present a very promising method for a measurement of the Higgs boson
parity using the H/A -> tau^+ tau^- --> rho^+ nu rho^- nu --> pi^+ pi^0 nu pi^-
pi^0 nu decay chain. The method is both model independent and independent of
the Higgs production mechanism. Angular distributions of the tau decay products
which are sensitive to the Higgs boson parity are defined and are found to be
measurable using typical properties of a future detector for an e^+ e^- linear
collider. The prospects for the measurement of the parity of a Higgs boson with
a mass of 120 GeV are quantified for the case of e^+ e^- collisons of 500 GeV
center of mass energy with an integrated luminosity of 500 fb^-1. The Standard
Model Higgsstrahlung production process is used as an example.Comment: 10 pages, 4 figures, LaTeX, version of Phys. Lett.
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