3 research outputs found
Shadow monochromatic backlighting: Large-field high resolution X-ray shadowgraphy with improved spectral tunability
The shadow monochromatic backlighting (SMB) scheme, a modification
of the well-known soft X-ray monochromatic backlighting scheme,
is proposed. It is based on a spherical crystal as the dispersive
element and extends the traditional scheme by allowing one to
work with a wide range of Bragg angles and thus in a wide spectral
range. The advantages of the new scheme are demonstrated
experimentally and supported numerically by ray-tracing
simulations. In the experiments, the X-ray backlighter source
is a laser-produced plasma, created by the interaction of an
ultrashort pulse, Ti:Sapphire laser (120 fs, 3–5 mJ,
1016 W/cm2 on target) or a short wavelength
XeCl laser (10 ns, 1–2 J, 1013 W/cm2 on
target) with various solid targets (Dy, Ni + Cr, BaF2).
In both experiments, the X-ray sources are well localized spatially
(∼20 μm) and are spectrally tunable in a relatively wide
wavelength range (λ = 8–15 Å). High quality monochromatic
(δλ/λ ∼ 10−5–10−3)
images with high spatial resolution (up to ∼4 μm) over a large field
of view (a few square millimeters) were obtained. Utilization
of spherically bent crystals to obtain high-resolution, large
field, monochromatic images in a wide range of Bragg angles
(35° < Θ < 90°) is demonstrated for the first
time
X-ray radiation from ions with K-shell vacancies
Abstract New types of space resolved X-ray spectra produced in light matter experiments with high intensity lasers have been investigated experimentally and theoretically. This type of spectra is characterised by the disappearance of distinct resonance line emission and the appearance of very broad emission structures due to the dielectronic satellite transitions associated to the resonance lines. Atomic data calculations have shown, that rather exotic states with K-shell vacancies are involved. For quantitative spectra interpretation we developed a model for dielectronic satellite accumulation (DSA-model) in cold dense optically thick plasmas which are tested by rigorous comparison with space resolved spectra from ns-lasers. In experiments with laser intensities up to 10 19 W/cm 2 focused into nitrogen gas targets, hollow ion configurations are observed by means of soft X-ray spectroscopy. It is shown that transitions in hollow ions can be used for plasma diagnostic. The determination of the electron temperature in the long lasting recombining regime is demonstrated. In Light-matter interaction experiments with extremely high contrast (up to 10 10 ) short pulse (400 fs) lasers electron densities of n e ≈3×10 23 cm −3 at temperatures between kT e =200–300 eV have been determined by means of spectral simulations developed previously for ns-laser produced plasmas. Expansion velocities are determined analysing asymmetric optically thick line emission. Further, the results are checked by observing the spectral windows involving the region about the He α -line and the region from the He β -line to the He-like continuum. Finally, plasmas of solid density are characteristic in experiments with heavy ion beams heating massive targets. We report the first spectroscopic investigations in plasmas of this type with results on solid neon heated by Ar-ions. A spectroscopic method for the determination of the electron temperature in extreme optically thick plasmas is developed