57 research outputs found
High brightness laser-plasma X-ray source at IFAM : Characterization and applications
A high brightness laser-plasma X-ray source has
been set-up and is presently available at IFAM. A wide
range of diagnostics has been set up to monitor the properties
of the X-ray radiation and to control the main parameters
including photon energy, flux intensity, and pulse duration.
A beam extractor enables access to the X-ray radiation
at atmospheric pressure. A simple, easy-to-use projection
microscope has been built which is capable of single-shot
micron resolution imaging with digital acquisition. Preliminary
biomedical experiments show that the X-ray doses available
on a single laser shot exposure of our source fully meet
the conditions required for an important class of biological
experiments based on X-ray induced DNA damage providing
an ideal alternative to the long time exposures needed
with X-ray tubes
The laser-matter interaction meets the high energy physics: Laser-plasma accelerators and bright X/gamma-ray sources
Laser matter interaction in the regime of super-intense and ultra-short laser pulses is discovering common interests and goals for plasma and elementary particles physics. Among them, the electron laser wakefield acceleration and the X/γ tunable sources, based on the Thomson scattering (TS) of optical photons on accelerated electrons, represent the most challenging applications. The activity of the Intense Laser Irradiation Laboratory in this field will be presented
Line spectroscopy with spatial resolution of laser-plasma X-ray emission
High dynamic range, space-resolved X-ray spectra of an
aluminum laser–plasma in the 5.5–8 Å
range were obtained using a TlAP crystal and a cooled CCD
camera as a detector. This technique was used to investigate
the emission region in the longitudinal direction over
a distance of approximately 350 μm from the solid target
surface. These data show that the electron density profile
varies by two orders of magnitude with the temperature
ranging from about 180 eV in the overdense region to about
650 eV in the underdense region. Accordingly, different
equilibria take place across the explored region which
can be identified with this experimental technique. Detailed
studies on highly ionized atomic species in different plasma
conditions can therefore be performed simultaneously under
controlled conditions
Ray-tracing simulations of a bent crystal X-ray optics for imaging using laser-plasma X-ray sources
Ray-tracing simulations of an optical X-ray system based on a spherically bent crystal operating in Bragg configuration for monochromatic projection imaging of thin samples are presented, obtained using a code developed for that purpose. The code is particularly suited for characterizing experimental arrangements routinely used with laser-produced plasma X-ray sources. In particular, the spatial resolution of the imaging system was investigated and a careful study of the complex pattern of the X-ray backlighting beam was performed
Soft laser-plasma X-ray source for differential absorption imaging of tracing elements in thin samples
The differential imaging technique is particularly suitable for the
detection of small concentrations of contrasts agents for biological
and medical applications in samples using X-ray radiography. In this
paper, we present an application of this technique using a laser-plasma
soft X-ray source combined with a bent crystal. Using a Fresnel plate
as a test object, we were able to obtain spatial resolutions of the
order of a few tens of microns. The use of our configuration to perform
differential imaging of a test-sample at the L2 edge of Br
at 1,596 eV is finally demonstrated
Flora da Bahia: Oleaceae
A taxonomic treatment of the Oleaceae from Bahia, Brazil, is present as a contribution to the knowledge of the flora of the state. Four species of the genus Chionanthus are recognized: C. crassifolius, C. filiformis, C. micranthus and C. parviflorus. The taxonomic treatment consists of an identification key, descriptions, comments, illustrations and distribution maps of the species in Bahia.É apresentado o tratamento taxonômico das Oleaceae da Bahia, Brasil, como contribuição ao conhecimento da flora do estado. São reconhecidas quatro espécies do gênero Chionanthus: C. crassifolius, C. filiformis, C. micranthus e C. parviflorus. O tratamento consiste de uma chave de identificação, descrições, comentários, ilustrações e mapas de distribuição das espécies na Bahia
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Right fronto-parietal white matter disruption contributes to speech impairments in amyotrophic lateral sclerosis
INTRODUCTION
Non-linguistic properties of speech are widely heterogeneous and require complex neurological integration. The association between white matter integrity and the severity of dysarthria was investigated in a group of patients diagnosed with amyotrophic lateral sclerosis (ALS).
METHODS
Thirty-six patients diagnosed with amyotrophic lateral sclerosis completed a magnetic resonance imaging protocol inclusive of diffusion-weighted images. A clinical assessment of pneumo-phono-articulatory abilities was conducted for each patient, and a composite score of residual speech capacity was calculated. Tract-Based Spatial Statistics was carried out to model the potential association between residual speech capacity and microstructural properties of white matter (fractional anisotropy, mean and radial diffusivity).
RESULTS
A significant negative association was found between residual speech capacity and mean diffusivity in a large white matter cluster located in frontal, parietal and right temporal regions. These subcortical areas were characterised by pathological microstructural disruption, as revealed bypost hoc analyses.
CONCLUSIONS
Non-linguistic aspects of speech are associated with microstructural integrity of frontal, parietal and right temporal white matter in amyotrophic lateral sclerosis. Such mapping is consistent with the centres responsible of volitional control of speech and sensory feedback during non-linguistic speech production
Non-adiabatic cluster expansion after ultrashort laser interaction
AbstractWe used X-ray spectroscopy as a diagnostic tool for investigating the properties of laser-cluster interactions at the stage in which non-adiabatic cluster expansion takes place and a quasi-homogeneous plasma is produced. The experiment was carried out with a 10 TW, 65 fs Ti:Sa laser focused on CO2 cluster jets. The effect of different laser-pulse contrast ratios and cluster concentrations was investigated. The X-ray emission associated to the Rydberg transitions allowed us to retrieve, through the density and temperature of the emitting plasma, the time after the beginning of the interaction at which the emission occurred. The comparison of this value with the estimated time for the "homogeneous" plasma formation shows that the degree of adiabaticity depends on both the cluster concentration and the pulse contrast. Interferometric measurements support the X-ray data concerning the plasma electron density
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