This review is dedicated to the scientific research carried out by Academician V.E. Fortov at the Institute of Problems of Chemical Physics of the Russian Academy of Sciences (IPCP RAS) in ...Chernogolovka, where in 1971 he began his work after defending his candidate’s dissertation. Here, Fortov studies the generation, physical properties, and gas dynamics of nonideal low-temperature plasma. Intensive experimental and theoretical studies of the compressibility, electrical conductivity, and optical properties of such a medium are published in a number of central journals, such as
Physics—Uspekhi
,
Journal of Exper-imental and Theoretical Physics
,
Doklady Akademii Nauk
, and
High Temperature
. In 1977, Fortov defended his doctoral dissertation “Investigation of Nonideal Plasma by Dynamic Methods.” After the defense, his research on nonideal plasma and processes under the effect of powerful shock waves expanded significantly. Experiments were carried out on the explosive generation of neutrons and the reflective properties of powerful shock waves, and the processes of converting explosion energy into electromagnetic energy were studied by him. Particular attention was paid to the processes of metallization of hydrogen and inert gases, and a plasma phase transition in deuterium was discovered by him. This review attempts to briefly summarize Fortov’s studies on nonideal plasma generated by an explosion and demonstrate the logic of their occurrence.
Abstract
Vladimir Evgen’evich Fortov made an enormous contribution to the physics of extreme states of matter, high energy density physics, the physics of shock and detonation waves, thermal physics, ...chemical physics, energetics, and several other realms of physics and technology. Among this amazingly broad spectrum of V E Fortov’s scientific interests, special place is occupied by dynamic methods in the physics of nonideal plasmas. His scientific activity commenced in precisely this area, and it remained at the focus of his attention throughout his life. We have endeavored to briefly generalize V E Fortov’s investigations in the area of explosion-produced nonideal plasmas and reveal the logic of their origination.
A technique for measuring the spatial heterogeneity of the light yield of a proton radiography scintillator has been developed. It is based on the recording of digital images formed during the ...passage of a proton beam through a scintillator and the approximation of the intensity distribution in the beam cross section by a two-dimensional Gaussian-like function. The results of the spatial calibration of the light yield of a lutetium silicate scintillator obtained using a magneto-optical proton microscope PUMA are presented. It is shown that accounting of the spatial heterogeneity of the scintillator makes it possible to describe the transverse beam intensity at each point of the proton radiographic image with a mean accuracy of about 0.7%. Experimental data on fluctuations in the position of the beam center, its size, and shape in the scintillator plane of PUMA microscope were obtained. The proposed technique eliminates optical artifacts in the radiographic image caused by operation of the optical recording system and artifacts caused by the electron-optical shutter, provided that the signal is proportional to the intensity of the beam. It also eliminates or strongly suppresses optical artifacts in radiographic images due to changes in the efficiency of a charge-coupled digital camera.
Measurements of the brightness temperature and compressibility of a dense silicon plasma formed by powerful shock waves (SWs) passing through a single‐crystal sample have been carried out. Plane SWs ...were created using an explosive technique: the traditional plane acceleration of a steel driver plate made it possible to obtain pressures in silicon up to 133 GPa, and the use of “Mach” cumulative generators realized the pressures up to 510 GPa. The shock Hugoniot of silicon was determined by the impedance matching with α‐quartz as the reference. The intensity of emitted thermal radiation was measured in the infrared range λ ∼ 1.5 μm, where silicon is optically transparent, and in the visible range of the spectrum. A significant (up to five times) understatement of the measured values of the brightness temperature in comparison with the values calculated by the equation of state was found. Taking into account the reflective properties of the SW in silicon does not lead to an agreement with the experiment. The estimates of relaxation processes behind the shock front suggest the presence of a zone of the establishment of ionization equilibrium with a width of ∼10 μm.
New results of measurements of s- and p-polarized reflectivity of nonideal plasma at the frequency of the external electromagnetic field νlas = 2.83 × 1014 s−1, free-electron number density ne = 3.3 ...× 1021 cm−3 (Coulomb nonideal plasma parameter Γ = 1.2) and ne = 5.2 × 1021 cm−3 (Γ = 1.4) are presented. These data are the result of the next stage of study of optics of a warm dense matter. We present a microscopic approach to describe the entire set of experimental data on the optics of strongly correlated plasma.
String theory methods led to the hypothesis that the ratio of a shear viscosity coefficient to the volume density of entropy of any physical system has a lower bound. Systems with strong coupling ...have a small viscosity as compared to weakly coupled plasmas in which the viscosity is proportional to the mean free path. Here, we have estimated the fully ionized strongly coupled plasma viscosity based on the dynamic experimental data on electrical conductivity and have shown that the ratio of viscosity to entropy of the strongly coupled plasma is very close to that of the lower bound predicted by the string theory.
Experimental estimates of the process of the ejection of particles and the formation of plasma during the shock wave exits on the free surface of the cooper sample studied were carried out. The ...radiation intensity was recorded by a three-channel pulsed pyrometer in an experimental assembly with lateral observation. When the impactor speed was about 5 km/s, a stream of particles and plasma flew from the target surface, the front speed of which reached 12.5 km/s.
A high explosive shock tube of non-ideal gaseous plasma for proton radiography is described. The gas dynamic flow in the shock compressed xenon at initial pressure of 7 bar was investigated in the ...tube. The velocity of the shock wave in xenon and the associated particle velocity were measured by a high-speed rotating mirror streak camera. Experimental time-distance data was used for approximation of the velocities by exponential decay functions. The shock tube is intended for generation of non-ideal plasma of xenon at the pressure of 5-12 kbar, the density of 0.24-0.3 g/cm3 when the initial pressure is about 7 bar.
The shock compressibility of single-crystal silicon is experimentally studied in the pressure range of 280 to 510 GPa. Shock waves are created using Mach’s explosive cumulative generators. The ...parameters of shock waves are determined by the impedance matching method, and single-crystal quartz is used as a ref-erence substance. The results agree well with the
ab initio
calculation results and with the data obtained using laser shock waves.
An analysis of the response of a dense plasma to electromagnetic waves of moderate intensity can be used as a tool to study the validity of physical models describing the behavior of matter in ...extreme conditions. Within this work, the new experimental data are presented on oblique incidence of polarized electromagnetic wave. The study of polarized reflectivity properties of nonideal xenon plasma was accomplished using laser light at νlas = 2.83 × 1014 s−1. The measurements of polarized reflectivity coefficients of explosively driven dense plasmas have been carried out at incident angles up to θ = 70° for plasma density ρ = 1.8 g/cm3. The simple model of the ionization kinetics of the plasma transition region is considered.
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