386 research outputs found
5.5-7.5 MeV Proton generation by a moderate intensity ultra-short laser interaction with H2O nano-wire targets
We report on the first generation of 5.5-7.5 MeV protons by a moderate
intensity short-pulse laser (4.5 \times 1017 W/cm^2, 50 fsec) interacting with
H2O nano-wires (snow) deposited on a Sapphire substrate. In this setup, the
laser intensity is locally enhanced by the tip of the snow nano-wire, leading
to high spatial gradients. Accordingly, the plasma near the tip is subject to
enhanced ponderomotive potential, and confined charge separation is obtained.
Electrostatic fields of extremely high intensities are produced over the short
scale length, and protons are accelerated to MeV-level energies.Comment: submitted to PRL, under press embargo. 6 figure
Spallative ablation of dielectrics by X-ray laser
Short laser pulse in wide range of wavelengths, from infrared to X-ray,
disturbs electron-ion equilibrium and rises pressure in a heated layer. The
case where pulse duration is shorter than acoustic relaxation time
is considered in the paper. It is shown that this short pulse may cause
thermomechanical phenomena such as spallative ablation regardless to
wavelength. While the physics of electron-ion relaxation on wavelength and
various electron spectra of substances: there are spectra with an energy gap in
semiconductors and dielectrics opposed to gapless continuous spectra in metals.
The paper describes entire sequence of thermomechanical processes from
expansion, nucleation, foaming, and nanostructuring to spallation with
particular attention to spallation by X-ray pulse
On the characterisation of a Bragg spectrometer with X-rays from an ECR source
Narrow X-ray lines from helium-like argon emitted from a dedicated ECR source
have been used to determine the response function of a Bragg crystal
spectrometer equipped with large area spherically bent silicon (111) or quartz
(10) crystals. The measured spectra are compared with simulated ones
created by a ray-tracing code based on the expected theoretical crystal's
rocking curve and the geometry of the experimental set-up.Comment: Version acceptee (NIM
High resolution X-ray emission spectra from picosecond laser irradiated Ge targets
Investigations of a high resolution X-ray emission spectrum in the range 0.66–0.75 nm obtained by irradiating a Germanium target with high-power p-polarized, 40 picosecond laser radiation at 532 nm wavelength was done. Spectra in the wavelength region of 2l-4l′ and 2l-5l′ L-shell transitions in F-like, Ne-like and Na-like germanium ions were recorded using the FSSR-2D spectrometer equipped with a spherically bent quartz crystal with a spectral resolution λ/Δλ better than 5000. Spectral lines were compared with theoretical values obtained using the LANL plasma kinetic code ATOMIC. Fair agreement between experimental and theoretical spectral lines has been observed, which allowed to measure enough high bulk electron temperature values of 560 eV and electron density of ∼1021 cm−3 in Ge plasma irradiated by rather small commercial high repetition rate Nd:YAG laser system
Formation of the X-ray line emission spectrum of excimer laser-produced plasmas
Time- and space-integrated emission spectra measurements have been performed in plasma produced by 308 nm wavelength XeCl laser radiation (IL = (4–10)·1012 W/cm2, τ = 10 ns) and by 248 nm wavelength KrF laser pulse train radiation (IL = 5·1015 W/cm2, τ = 7 ps, 16 pulses in train) on CF2 plane target. Theoretical modelling of Lyman series and He-like ion resonance series of fluorine and its fit of experimental data show considerable differences in the absorption of laser radiation in the two plasmas
Contact X-ray microscopy of living cells by using LiF crystal as imaging detector
In this paper, the use of lithium fluoride (LiF) as imaging
radiation detector to analyse living cells by single-shot soft
X-ray contact microscopy is presented. High resolved X-ray
images on LiF of cyanobacterium Leptolyngbya VRUC135,
two unicellular microalgae of the genus Chlamydomonas
and mouse macrophage cells (line RAW 264.7) have been
obtained utilizingX-ray radiation in the water window energy
range from a laser plasma source. The used method is based on
loading of the samples, the cell suspension, in a special holder
where they are in close contactwith a LiF crystal solid-state Xray
imaging detector. After exposure and sample removal, the
images stored in LiF by the softX-ray contactmicroscopy technique
are read by an optical microscope in fluorescence mode.
The clear image of the mucilaginous sheath the structure
of the filamentous Leptolyngbya and the visible nucleolus in
the macrophage cells image, are noteworthiness results. The
peculiarities of the used X-ray radiation and of the LiF imaging
detector allow obtaining images in absorption contrast revealing
the internal structures of the investigated samples at high
spatial resolution. Moreover, thewidedynamicrangeof theLiF
imaging detector contributes to obtain high-quality images. In
particular, we demonstrate that this peculiar characteristic of
LiF detector allows enhancing the contrast and reveal details
even when they were obscured by a nonuniform stray light
High resolution and high efficiency coloration of lithium fluoride by soft X-rays irradiation
The efficient coloration of LiF material, in the form of bulk and films, by EUV and soft X-rays emitted by a laser-plasma source is demonstrated. The short penetration depth of soft-X-rays is exploited to obtain high spatial resolution luminescent patterns while the high dynamic range of proportionality between X-ray dose and coloration is exploited for using LiF as image detector in micro-radiography and soft X-ray microscopy applications
Hydrodynamic instabilities in a highly radiative environment
In this paper, we present the effects of a radiative shock (RS) on the morphology of jet-like objects subjected to hydrodynamic instabilities. To this end, we used an experimental platform developed to create RSs on high energy laser facilities such as LULI2000 and GEKKO XII. Here, we employed modulated targets to initiate Richtmyer–Meshkov and Rayleigh–Taylor instability (RTI) growth in the presence of an RS. The RS is obtained by generating a strong shock in a dense pusher that expands into a low-density xenon gas. With our design, only a limited RTI growth occurs in the absence of radiative effects. A strongly radiative shock has opposite effects on RTI growth. While its deceleration enhances the instability growth, the produced radiations tend to stabilize the interfaces. Our indirect experimental observations suggest a lower instability growth despite the interface deceleration. In addition, the jets, produced during the experiment, are relevant to astrophysical structures such as Herbig–Haro objects or other radiatively cooling jets
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