Vladimir Borodin, Alexander Charukchev, Victor Chernov, Oleg Gilev, Anatoly Zapysov, Vladimir Il'in, Vladimir Komarov, Vladimir Malinov, Vaycheslav Migel, Nikolai Nikitin, V. Saprikin
The interaction of a 1053 nm picosecond laser pulse with a solid target for focused intensities of up to 1019 W/cm2 are studied by measurements of the absorption of the laser light in the plasma and by measurements of the production of hard x-rays. Absorption measurements are made by collecting the scattered light in set of calorimeters. Light scattered in backward and specular directions is collected separately. Measurements are presented for both high and low Z targets. Hard x-ray spectrum in range 15-1000 keV and hot electron production in range 1-22 MeV are measured using a multichannel filter/scintillator and filter/semiconductor spectrometers. Spatial parameters of fast ions are studied.
Oleg Gilev, Victor Asadchikov, Angela Duparre, Nikolai Havronin, Igor Kozhevnikov, Yury Krivonosov, Sergey Kuznetsov, Vitaly Mikerov, Vladimir Ostashev, Vladimir Tukarev
It is demonstrated that the simplest model of a surface, assuming step-like variation of the dielectric permeability at a vacuum-matter interface, does not permit the quantitative description of all the features of x-rays reflection and scattering observed in experiment, even though the effects of the surface roughness are taken into consideration accurately. These features are much more pronounced for metals having a large number of the conductivity electrons which are bound slightly with individual atoms. Evidently, the wave function of the electron gas of a metal cannot abrupt sharply at a surface but decreases gradually into vacuum at a distance of several angstroms. To validate or disprove the hypothesis for the presence of a near surface transition layer of the electron density in metals, a set of experiments is performed. Reflection and scattering of hard and soft x-rays, and cold neutrons (which are sensitive to nuclear density distribution and insensitive to the electron one) from metal samples are measured. The independent measurements of the surface micro-topography are performed with the use of atomic force microscopy. The results obtained demonstrate the presence of a near surface layer, which is caused by gradual change of electron density, with a thickness of several angstroms.
The surface roughness of polished glass substrates as well as metal an dielectric coatings is studied using atomic force microscopy, hard and soft x-ray scattering at the wavelength (lambda) equals 0.154 nm and 4.47 nm, and light scattering (LS) at (lambda) equals 325 nm. It is demonstrated that all the methods, permitting the determination of PSD functions in partly overlapping, partly different ranges of spatial frequency, are in a good agreement in spite of different physical principles underlying the methods. The possible reasons for some differences in the PSD functions determined form different measurements are discussed. The main of them are a more difficult interpretation of LS data when dielectric coatings are present and a limitation on the angular range of hard x-ray scattering measurements imposed by the applicability of the perturbation theory used for experimental data processing.
We propose to extend x-ray scattering method to the investigation of concave surface roughness. Our approach is based on the use of the whispering gallery effect, which consists in that an x-ray beam falling tangentially on to a concave surface slides along a surface due to successive total external reflections. During its propagation the beam gradually broadens because the scattering transfers some part of radiation to the range of larger glancing angles. Fitting of a simulated angular distribution of outgoing beam to a measure done enables the determination of statistical parameters of concave surface roughness. Possible experimental schemes are analyzed by using ray-tracing technique, radiation scattering by surface roughness being modeled by the Monte Carlo method. Results of experiments in x-ray spectral region are discussed. Carbon-coated cylindrical surfaces with the radius of curvature of 6 cm and the arc angle of 45 and 60 degrees are studied with soft x-rays. The measured angular distributions of outgoing radiation are shown to agree quantitatively with the theoretical calculations when the scattering of x-rays by the surface roughness are taken into account. The rms roughness and the correlation length of the studied surface are found to be about 1.2 nm and 0.3 micrometers , respectively. The possibility of the study of concave surface roughness with the use of hard x-rays is also discussed.
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