Georgiy V. Ivanenkov

High-performance x-ray spectroscopic devices for plasma microsources investigations

X-ray spectroscopy with high spectral (up to Δλ/λ = 10−4) and spatial resolution (up to 1 μm) is discussed. Devices based on crystals, diffraction and Bragg-Fresnel elements and their applications in Z- and X-pinches and laser plasma experiments are described.

Radiative properties of hot dense X-pinch

Abstract A high luminosity spectrometer with a spherically bent mica crystal has been used to obtain H- and He-like spectra of Al and Si ions in X-pinch plasma with high spectral (λ/Δλ ∼ 3000) and spatial (∼ 30 μm) resolution. The electron density (up to 2.1024 cm-3) and the temperature (up to 950 eV) in the “hot point” were measured by means of X-ray spectroscopy methods. The estimates show, that the emission of K-line radiation can be up to 1 J, the power being 109 W). The total energy emitted in the spectral region 5–100 A is about 1 kJ.

Investigations of Exploding Wires and Dielectric Fibres Dynamics

Here are discussed the experiments with high‐current nanosecond discharges through metal wires and dielectric fibres on NIKE‐3 device (100 kA, 50 ns) and BIN one (250 kA, 100 ns). Discharge regime is investigated as a function of load linear density μ by way of example of glass fibres. While mass is increasing discharge through diode changes from regime mismatched regime with electron beam generation (μ   30 μg/cm). Strong influence of surface condition on metal wires explosion character was found. The explosion of the metal wires heated up to 300–500°C for cleaning the surface was the most stable. The experimental results of the wire explosion were explained by the metal‐plasma transition model. The results of optical measurements of the plasma movement and column instability development during the discharge process are presented. In several experiments simultaneous development of kink and saus...

Different mechanisms of shock wave generation and scenarios of second breakdown development upon electrical explosion of wires

The structure of the discharge channel upon nanosecond wire explosion has been studied using laser Schlieren probing. Wires of 25 μm diameter and 12 mm length were exploded in air and vacuum by 10 kA current pulse having a 50 A/ns rise time. The development of shock waves in the air was observed. The propagation of shock waves was analyzed using a simple model of flat piston. It became possible to draw conclusions the dislocation of the flow of the main part of the current in the volume of the discharge channel. This permitted to distinguish two scenarios of development of secondary breakdown of the interelectrode gap. The scenario (shunting or internal) in accordance with which secondary breakdown develops in each concrete case depends to a large extent on the properties of the material of the exploding conductor.

Modeling a dense Z-pinch plasma with a cold, dense core using a 2D 2-temperature MHD code

A 2D (r-z) and 2-temperature (Te,i) nonideal MHD numerical model of dense Z-pinch dynamics and its applications to exploded wire plasmas with a cold dense core are presented. The numerical simulation algorithm is based on an Eulerian-Lagrangian method that is related to one suggested by D’yachenko for hydrodynamic calculations. As expected, a high density core that appears in the initial stage of the electrical explosion of a metal wire is found to be colder than the surrounding plasma. Model results are in good agreement with experimental data for exploded wires in a high current nanosecond diode.

High-performance x-ray spectroscopy of plasma microsources

X-ray spectroscopy with high spectral (up to (Delta) (lambda) /(lambda) equals 10-4) and spatial resolution (up to microns) is discussed. Devices based on crystals, diffraction, and Bragg-Fresnel elements and their application in Z- and X-pinches and laser plasma experiments are observed.

X‐Pinch in High‐Current Diode

The review of X‐pinch investigations in high current diode of BIN facility (250 kA, 100 ns) is presented. The main purposes were to investigate pinch forming processes and hot dense plasma properties. X‐pinch is also considered as a source for multiple charged ions spectroscopy and for X‐ray optics testing. The set of diagnostics applied in these experiments allowed us to investigate the pinch forming processes in different configurations of crossed wires loads. High spectral and space resolved measurements of plasma radiation in 1–200 A range, absolute energy measurements and electron beam registration were provided. Plasma parameters were obtained from relative intensities and shapes of multiple charged ions spectral lines. Electron density of plasma with the temperature Te = 0.2–1 keV variated from 1023 cm−3 in hot spot to 1018 cm−3 during plasma expansion. In recombining plasma, an inversion of Al He‐like ions levels population was registrated. Total radiation output of 0.5 mm pinch reached hundreds Joules in 2–100 A range during 100 ns.The review of X‐pinch investigations in high current diode of BIN facility (250 kA, 100 ns) is presented. The main purposes were to investigate pinch forming processes and hot dense plasma properties. X‐pinch is also considered as a source for multiple charged ions spectroscopy and for X‐ray optics testing. The set of diagnostics applied in these experiments allowed us to investigate the pinch forming processes in different configurations of crossed wires loads. High spectral and space resolved measurements of plasma radiation in 1–200 A range, absolute energy measurements and electron beam registration were provided. Plasma parameters were obtained from relative intensities and shapes of multiple charged ions spectral lines. Electron density of plasma with the temperature Te = 0.2–1 keV variated from 1023 cm−3 in hot spot to 1018 cm−3 during plasma expansion. In recombining plasma, an inversion of Al He‐like ions levels population was registrated. Total radiation output of 0.5 mm pinch reached hundreds J...

Study of the hybrid X-pinch with an external axial magnetic field

Summary form only given. The hot spot that develops in the gap between the electrodes of a hybrid X-pinch (HXP) [1] is a unique source of X-rays. The hot spot location is within 100-1000 μm of the center of symmetry of the X-pinch, and uncertainty depends on the gap size. Investigation of the X-pinch neck cascade process [2] showed that the hot spot tended to develop on one side of the minidiode that constitutes the z-pinch electrode structure in an X-pinch. The addition of an axial magnetic field component as a means to shift the hot spot in a specific direction and to stabilize its location has been tested in HXP experiments on 250 kA-1.2 MA pulsers [3]. It was shown that a configuration with twisted return current rods can generate too strong an axial magnetic, seriously disturbing the neck cascade process and hot spot development. In this work we have been continuing to study magnetized HXBs using a large set of available diagnostics: laser probing, X-ray, XUV and optical imaging, tiny magnetic probes and X-ray spectroscopy. The magnetic field profile around an HXP with twisted return current rods was measured on BIN (270 kA current, 100 ns risetime) and COBRA (1.2 MA current, 100 ns risetime) pulsers and optimal for x-ray production axial/azimuthal magnetic field ratio was determined.

Microsecond Gas‐Puff Plasma Implosion at GPX Device

There are presented hollow cylindrical gas‐puff plasmas of electrical discharges at GPX device (200 kA, 40 kV, 1μs, Ne/Ar‐mixture) experimental results. Investigation of plasma with time and spatial resolution in wide spectral range was enabled by the set of diagnostics. Plasma processes were investigated in visible and IR light by frame and streak cameras, in XUV by transmission grating spectrograph and XRD, in sort X‐rays by convex and spherically bent crystal spectrograph, X‐ray crystal microscope, pin‐holes, pin‐diodes. Plasma parameters (ne = 1019–1022 cm−3, Te = 0.2–1.3 keV) were controlled by spectroscopic methods using H‐ and He‐like Ne and Ar spectra. Kink instability and hot spots were observed simultaneously in maximum X‐ray emission regimes. Also argon Kα line emission from plasma was observed. Plasma stabilization methods are discussed.