V. Mintsev

Pressure-produced ionization of nonideal plasma in a megabar range of dynamic pressures

The low-frequency electrical conductivity of strongly nonideal hydrogen, helium, and xenon plasmas was measured in the megabar range of pressures. The plasmas in question were generated by the method of multiple shock compression in planar and cylindrical geometries, whereby it was possible to reduce effects of irreversible heating and to implement a quasi-isentropic regime. As a result, plasma states at pressures in the megabar range were realized, where the electron concentration could be as high as ne≈2×023 cm−3, which may correspond to either a degenerate or a Boltzmann plasma characterized by a strong Coulomb ΓD=1–10) and a strong interatomic Γa=rana1/3∼1) interaction. A sharp increase (by three to five orders of magnitude) in the electrical conductivity of a strongly nonideal plasma due to pressure-produced ionization was recorded, and theoretical models were invoked to describe this increase. Experimental data available in this region and theoretical models proposed by various authors are analyzed. The possibility of a first-order “phase transition” in a strongly nonideal plasma is indicated.

Unique capabilities of an intense heavy ion beam as a tool for equation-of-state studies

Intense heavy ion beams open new possibilities in high-energy-density matter research. Due to the unique feature of the energy deposition process of heavy ions in dense matter (volume character of heating) it is possible to generate high entropy states in matter without the necessity of shock compression. Previously, such high entropy states could only be achieved by using the most powerful shock wave generators, like nuclear explosions or powerful lasers. In this paper this novel technique of heavy ion heating and expansion is proposed to explore new fascinating regions of the phase diagram, including the liquid phase, the evaporation region with the critical point, and strongly coupled plasmas.

Electrical conductivity of nonideal hydrogen plasma at megabar dynamic pressures

The electrical conductivity of a nonideal hydrogen plasma is measured under shock-wave compression to pressures ∼1.5 Mbar. It is found that the conductivity increases sharply (by five orders of magnitude) at a density ρ∼0.3−0.4 g/cm3, reaching close to liquid-metal values ∼103 S/cm. The data obtained can be described by a nonideal-plasma model taking into account the increase in the number of conduction electrons as a result of “ionization by pressure.”

Experimental measurements of the compressibility, temperature, and light absorption in dense shock-compressed gaseous deuterium

Experimental data on the shock compression, temperature, and absorptivity of gaseous deuterium with an initial density close to its value in the liquid state were obtained on a spherical explosion shock-wave generator in a pressure range of 80–90 GPa. The obtained results are compared with the existing experimental and theoretical data.

Reflectivity of shock compressed xenon plasma

Experimental results [1] for the reflection coefficient of shock-compressed dense xenon plasmas at pressures of 1.6 – 17 GPa and temperatures around 30 000 K using a laser beam with λ = 1.06 μm are compared with calculations based on different theoretical approaches to the dynamical collision frequency. It is found that a reasonable description can be given assuming a spatial electron density profile corresponding to a finite width of the shock wave front of about 2 · 10–6 m.

Diagnostics of fast processes by charged particle beams at TWAC-ITEP accelerator-accumulator facility

A new setup for the experimental investigation of rapid dynamic processes using proton radiography techniques has been created at the TWAC-ITEP terawatt accelerator-accumulator facility. A set of equipment for conducting shock-wave experiments has been designed, constructed, and tested, and an instrumentation-software complex has been developed for the automation of experiments. The first series of experiments with dynamic targets representing high explosives have been carried out, in which the density distribution in detonation waves initiated in these explosives has been measured.

Coulomb contribution to the direct current electrical conductivity of dense partially ionized plasmas

The Coulomb contribution to the electrical conductivity of partially ionized plasmas is discussed and its general behavior is investigated. Recent experiments on the direct current conductivity in shock wave induced argon and xenon plasmas are analyzed in this context. Within the relaxation time approach, the Coulomb contribution is extracted by eliminating the contribution of scattering from neutrals. Alternatively, the Coulomb contribution can be calculated directly within linear-response theory. In particular, from the latter approach a generalized Spitzer factor is derived for taking into account electron-electron interactions within the relaxation time approximation. Experimental results for the Coulomb contribution to the electrical conductivity are in reasonable agreement with an interpolation formula derived from linear-response theory.

Frontiers of dense plasma physics with intense ion and laser beams and accelerator technology

Interaction phenomena of intense ion and laser radiation with matter have a large range of application in different fields of science, from basic research of plasma properties to application in energy science. The hot dense plasma of our neighbouring star the Sun provides a deep insight into the physics of fusion, the properties of matter at high energy density, and is moreover an excellent laboratory for astroparticle physics. As such the Suns interior plasma can even be used to probe the existence of novel particles and dark matter candidates. We present an overview on recent results and developments of dense plasma physics addressed with heavy ion and laser beams combined with accelerator and nuclear physics technology.

Reflectivity in shock wave fronts of xenon

New results for the reflection coefficient of shock-compressed dense xenon plasmas at pressures of 1.6–20 GPa and temperatures around 30 000 K are interpreted. Reflectivities typical of metallic systems are found at high densities. A consistent description of the measured reflectivities is achieved if a finite width of the shock wave front is considered. Several mechanisms to give a microscopic explanation for a finite extension of the shock front are discussed.

Measurements of the electron concentration and conductivity of a partially ionized inert gas plasma

The results are presented of experiments performed to measure the electron concentration and conductivity of a partially ionized inert gas plasma in a magnetic field. The plasma was generated behind the front of incident and reflected shock waves excited by explosively driven linear generators. A magnetic field of about 5 T was formed inside a solenoid wound on the generator channel. Measurements were taken at P=30−650 MPa, T=6000−17000 K, and a Coulomb nonideality parameter of 0.01–2.8. Electron concentrations calculated from measured Hall voltages reached 1.6×1021 cm−3. The recorded conductivities were in the range 0.1–200 Ω −1 cm−1. The experimental results were compared with various models of the thermodynamic and transport properties of a nonideal plasma.