Correlation between the parameters of ion and X-ray emissions from the plasma of a micropinch discharge

Ion emission from the plasma of a micropinch discharge is studied by analyzing the plasma flow from the discharge region with the help of time-of-flight technique and probe diagnostics. Concurrently, soft Xray emission from the micropinch is recorded. The experimental data are interpreted using the radiative contraction model.     

Generation of superthermal electrons in a micropinch discharge

Results are presented from experimental studies of the formation of the superthermal electron component in a micropinch discharge plasma. Radiative collapse in a Z-pinch is found to affect the energy of the accelerated electrons. That the radiative collapse has been reached may be inferred from the energy of the emitted hard X-ray photons.     

Study of the contributions of the electrode materials to the plasma of a high-current vacuum spark

The contribution of the electrode material to the formation of the plasma of a low-inductive high-current vacuum spark and its influence on the process of discharge micropinching were studied using X-ray spectroscopy and laser diagnostics. Electrode system configurations are determined in which the contributions of the materials of both electrodes to the plasma emitting X-rays are comparable and in which the contribution of one electrode is dominating. It is found that discharge pinching occurs primarily in the vapor of the pointed electrode independently of its polarity. The experimental results indicate the formation of a suprathermal electron beam in the micropinch region.     

Study of the hard component of pulsed X-ray emission of micropinch discharge plasma

A set of spectrometers that allow simultaneous measurements of the spectra of pulsed X-ray and electron emission from a micropinch discharge in a wide energy range (1.5?C500 keV) is described. The experimental results of the study of electron and X-ray spectra of micropinch discharge plasma are discussed. The mechanism for the formation of hard X-rays is caused by acceleration processes in micropinch discharge plasma.     

Current scaling for the radiative characteristics of a micropinch discharge

The absolute VUV and soft X-ray (hν > 100 eV) yield from a micropinch discharge is measured for a fixed current of 150 kA. The current scaling in the range of 30–250 kA is found for a number of the discharge parameters: the VUV and soft X-ray yield, the electron temperature, the effective temperature of suprathermal electrons, and the energy of bremsstrahlung emission from thermal electrons. The experimental data are in good agreement with the simulations performed by using the model of radiative collapse in fast Z-pinches in plasmas of high-Zelements.     

Formation of an anisotropic electron velocity distribution function and production of multicharged ions in the micropinch discharge plasma

Analysis of the results of polarimetric measurements of X-ray line radiation of multicharged ions in a Z-pinch discharge indicates that the formation of an anisotropic electron velocity distribution in the neck of the current channel and the generation of highly charged ions are separated in time. The generation of a fast electron beam in the longitudinal ohmic electric field in the stage of plasma compression in the neck results in the polarization of X-ray bremsstrahlung continuum. In the stage of expansion of the hot dense micropinch plasma, the radial electric field prevails, due to which X-ray line radiation of multicharged ions becomes linearly polarized.     

Study of the Spectral Composition of X-ray Emission from Different Regions of Micropinch Discharge Plasma

Plasma Physics Reports - The measurement technique and results are presented from studies of the spectral composition of X-ray emission from different regions of micropinch discharge plasma in a...     

Studies of the structure and dynamics of the radiating plasma of a micropinch discharge

Space-resolved X-ray spectra and electron emission spectra from a micropinch discharge are measured with the help of tracking detectors. Results from measurements of the discharge optical emission with a high temporal and spatial resolution are also presented.     

X-ray spatial distribution of a low-inductance vacuum spark discharge

The paper presents the results of X-ray source spatial distribution measurements of a low-inductance vacuum spark discharge based on the analysis of helium-like ions spectral lines structure. The intensities of spectral lines of FeXXV ions and dielectronic satellites with spatial resolution were measured. The polarization of satellite line 1s2p ^{2 2} D _5/2-1s ²2p ² P _3/2 was found. The obtained dependence of maximum plasma parameters during micropinch events from initial plasma line density in discharge corresponds to the radiative collapse model.     

Characteristics of X-ray Emission from a Micropinch Discharge at Different Polarities of the Discharge Electrodes

Plasma Physics Reports - The measurement technique and results are presented from studies of the X-ray spectra and X-ray yield from micropinch discharge plasma in a low-inductive vacuum spark...     

Comparative study of the spatial structure of the X-ray and ion emission sources in the micropinch discharge plasma

Images of ion emission sources in the micropinch discharge plasma are obtained by the pinhole camera technique. A region that is the source of the most intense ion emission has a length of about 3 mm along the discharge axis and a width of ≤1 mm. It seems that the image of the emitting region recorded in the axial direction reflects the action of the discharge current magnetic field on the directional pattern of the ion flow.     

Polarization properties of bremsstrahlung continuum and line emission of multicharged ions in a micropinch

The polarization properties of X-ray emission from micropinch discharge plasma in the spectral range corresponding to the K-lines of iron were studied experimentally. It is shown that emissions of different nature differ in the preferred orientation of polarization. The mechanisms responsible for the emission polarization are discussed.     

Experimental study of the spatial structure of high-energy ion sources in micropinch

Images of ion sources in the plasma of a micropinch discharge were recorded. The most intense ion source was found to be a ⩾1-mm-diameter 3-mm-long anode region. The main contribution to the images is made by single-charged ions of the plasma-forming element with energies of 10–50 keV.     

Peculiarities of the spatial structure and dynamics of the plasma of a fast Z-pinch produced in the high-Z medium of a high-current vacuum spark

The spatial structure and dynamics of the plasma of a high-current vacuum spark is investigated using pulsed shadowgraphy. Anisotropy of the plasma outflow from a micropinch region has been revealed. The existence of cavities in the sausage-type instability in the final stage of pinching has been recorded. The formation of a filamentary plasma structure at the discharge periphery is revealed.     

Effect of the anode material on the X-ray spectrum of micropinch discharge plasma

The effect of the elemental composition of the anode material on the parameters and X-ray spectrum of micropinch discharge plasma have been studied using a low-inductance vacuum spark device. It is shown that the plasma electron temperature T _e and intensity of hard X-ray emission increase with increasing nuclear charge number Z of the anode material of the discharge system.     

Measurements of the gas-kinetic pressure in plasma flows emerging from a micropinch discharge by means of laser interferometry

A new method for measuring the gas-kinetic pressure in pulsed plasma flows is developed in which an acoustic line in the form of a thin rod built in the optical scheme of a laser interferometer is used as a detector. The time evolution of the gas-kinetic pressure in particle flows emerging from a micropinch discharge (a low-inductance vacuum spark) was studied. Due to the wide dynamic range of the method (～10⁵), it can be applied in various plasma devices with a wide range of parameters.     

Multichannel vacuum arc discharge used for Z-pinch formation

Results are presented from experimental studies of the implosion dynamics and radiative characteristics of an aluminum Z-pinch formed from a plasma shell (PS). The PS with an initial diameter of 4 cm was produced with the help of a multichannel vacuum arc discharge and formed due to the evaporation of the electrode material in ten parallel arc discharges. The PS composition depended on the electrode material in the arc discharge. The described experiments were performed with aluminum electrodes. The total arc current was 80 kA. The PS implosion was provided by an IMRI-5 high-current generator with a current amplitude of 450 kA and rise time of 500 ns. The PS implosion resulted in the formation of a 0.2-cm-diameter plasma column with an electron temperature of 700?C900 eV and average ion density of (5?C8) × 10¹⁷ cm^?3. The maximum radiation power per unit length in aluminum K-lines reached 300 MW/cm, the duration of the radiation pulse being 20 ns.     

Spectroscopic measurements and numerical simulations of the electrode plasma of an electrode microwave discharge in hydrogen

The structure of an electrode microwave discharge in hydrogen at pressures of 1–8 torr and incident powers of 20–100 W is studied using optical spectroscopy. A two-dimensional computer code is developed for self-consistently simulating a self-sustained steady-sate electrode microwave discharge ignited at the end of the inner conductor of a coaxial line. The model is based on simultaneously solving time-dependent Maxwell’s equations, the balance equations for charged particles, and a homogeneous Boltzmann equation. The numerical results referring to the electrode region of the discharge are in fair agreement with the experimental data. This confirms the early suggestion (inferred from experimental data) of the combined “self-sustained-non-self-sustained” character of the electrode discharge. It is shown that the self-sustained discharge domain is located in the electrode region of the discharge.     

Study of low-temperature plasma between rotating electrodes

Results are presented from experimental studies of the electrophysical and spatiotemporal characteristics of a dielectric barrier discharge operating in atmospheric-pressure air in a discharge cell with a dielectric barrier in the form of a rotating disc. One of the electrodes of the discharge cell was stationary and placed at a certain distance from the dielectric surface, and the following two versions of the second electrode were used: (i) a metal disc electrode was attached to the surface of the rotating dielectric disc, while on the opposite surface of the disc, there was a rectangular strip electrode that was at the same potential as a metal disc electrode and had a sliding contact with the dielectric; (ii) only the strip electrode with the sliding contact was connected to the high-voltage source, while the metal disc electrode was disconnected. Due to barrier rotation, the discharge operated in a pulse mode, although it was supplied from a dc voltage source. The current-voltage characteristic of such a dielectric barrier discharge was measured and analyzed. The number of microdischarge channels arising at the stationary electrode, the geometrical parameters of the microdischarge channels, and the discharge current were studied as functions of the supplied voltage, the distance between the stationary electrode and the dielectric surface, and the rotation velocity of the barrier disc.