High precision measurements of accelerated liner velocities (by optical velocimetry VISAR, PDV) produce high-resolution isentropes of test materials - pressure-density curves in the whole range of pressures reached in a single shot [1]. Their interpretation requires solving an inverse mathematical problem by Iterative Lagrangian Analysis (ILA) methods. But in case of magnetic implosion of liners, when the highest isentropic pressures are generated by cumulation, application of such methods presents difficulties. In this paper, we use a similar method of inverse solution with optimization: a small number of parameters are varied to reach the best match between the experimental velocity of the inner liner boundary and the velocity obtained by 1D magnetohydrodynamic calculations. As an example we consider the implosion of aluminum liners having a radius of 4cm and thickness of 2-3mm driven by currents up to 30-75MA (azimuthal magnetic field up to 2-10MG) delivered by ALT-1-3 devices [2-3], when liner velocities and isentropic pressures in aluminum reach 12-40km/s and 0.2-8Mbar. Inner liner surface velocities measured by VISAR in the ALT-1,2 experiments reached 12 km/s. The resulting isentrope of aluminum is close to the experimental data available. Accuracy specifications for liner velocity measurements up to 40 km/s in the developed ALT-3 driver were discussed.

Warm Dense Matter (WDM) is the state of matter in the range between condensed matter and ideal plasma, which has higher temperature than condensed matter, but lower temperature and higher density than the traditional ideal plasma. In this range, which is often characterized by temperatures of 1<; T<; 50 eV and densities of 0.01ρ 0 <; ρ <; 2ρ 0 (ρ 0 is solid density), matter cannot be described by theories applicable to ideal plasma or condensed (solid) matter. Understanding WDM properties is a challenging physical problem, because this state of matter is hard to simulate theoretically or produce/measure experimentally under laboratory conditions. WDM occurs in the core of gas-giant planets and in engineering and physical applications it forms in systems with fast solid-to-plasma transition, such as exploding wires or quickly heated (by laser or high magnetic fields) materials. This paper investigates a WDM generation system by electric explosion of a thin cylindrical metal foil enclosed in an insulator. This experimental setup provides the homogeneity of the WDM and present availability of WDM for the diagnostics. The electric explosion of the metal foil can be realized by currents of such current sources as the helical explosive magnetic flux compression generator (EMG) with an opening switch and stationary facility PHELIX of LANL. A diameter 200 mm EMG with an explosive opening switch can deliver a current of ~5 MA with a characteristic rise time of 0.3 μs. It is shown that in such the WDM generation system driven by the EMG with the opening switch one can obtain a large volume of matter with density on the order of (0.01-1) of solid density and temperature about 2-3 eV. The PHELIX facility is a small-size capacitor bank coupled to the current transformer; it allows to reach load currents 3-5 MA with characteristic times ~10 μs. The paper shows that in a system with using of this facility significant volumes of uniform WDM with the density of ~ 0.1-1 g/cm 3 and temperature of 3-4 eV can be obtained with good accessibility for measurements. A way to recover the WDM parameters based on electrotechnical measurements and exploded foil boundary velocimetry is described.

High-current circuit breakers based on vacuum interrupter (VI) represent an alternative type of switching equipment suitable for operation under severe climatic conditions. Such devices can offer a number of other technological or environmental benefits compared to the currently used ones. Bringing the performance of the VI-based circuit breakers to the level of ~3 kA nominal currents, ~40 kA rate breaking currents and ~100...200 kV operational voltages requires improved physical models and advanced computational capabilities for the description of their operation. According to contemporary concepts, to ensure working efficiency of a device, in addition to addressing the issues of electrical strength, it is important to account for the system of magnetic field generation between electrodes, which influences the flow of current in the electrode gap and formation of a uniform diffusive discharge. In this paper we present the results of preliminary calculations of electric and magnetic fields for the case of a simplified VI design accounting for the shape of magnetic field generation electrodes and conducting material between them. We explore the effects of magnetic materials used in the chamber design and calculate the force acting on the electrodes and electrode heating by the flowing current. The simulation results can be used to find critical parameters and design regions, and represent the first stage in the modeling of VI operation, which at the next stage should take into account plasma generation at the electrodes.

The comparative analysis of positive and negative features of systems with the magnetic compression of the thermonuclear fusion target (MAGO/MTF) aimed at solution of the controlled thermonuclear fusion (CTF) problem is presented. The niche of the MAGO/MTF system among the other CTF systems in the parameter space of the energy delivered to the target and the time of its input into the target is shown. This approach was investigated at RFNC-VNIIEF for more than 15 years by means of the unique technique applying explosive magnetic generators (EMG) as the energy source to preheat fusion plasma and accelerate a liner for compression of the preheated fusion plasma to the parameters required for ignition. EMG based systems produce the fusion neutrons already and their relatively low cost and record energy yield enable the full scale experiments to study possibility of ignition threshold achievement without construction of expensive stationary installations. Short review of the milestone results on the way of CTF problem solution in the MAGO/MTF system is made.

Summary form only given. MAGO/MTF concept suggests a two-stage achievement of a thermonuclear reaction ignition:- generation of hot magnetized plasma; compression of the generated plasma and achievement of a thermonuclear reaction. The calculations show that it is possible to separate the processes of formation and compression of hot plasma in MAGO chamber not only in time but also in space by means of plasma transportation to a special compression section.

Instability of anisotropic ion distribution function in the velocity space and its quasilinear relaxation to saturation of parallel energy growth due to coupling with the ion cyclotron mode with the wave vector parallel to the magnetic field art investigated. The initial ion velocity is assumed to be perpendicular to the magnetic field to model plasma state downstream the shock wave front. A numerical method to solve the integral dispersion equation for growing and decaying modes in a wide range of increments is proposed and tested for some analytic distribution functions. Quasilinear relaxation results in isotropisation of the ion distribution function. It is shown that times exceeding one hundred ion gyrotimes are required to achieve substantial isotropy via ion cyclotron mode coupling for plasmas with beta similar to 1.

Magnetized plasma with characteristic density 8/spl middot/10/sup 17/ cm/sup -3/ and average temperature 250 eV has been obtained in a MAGO plasma chamber. One and two dimensional magneto-hydrodynamic computations are performed in which a solid density aluminum liner is imploded on the MAGO target plasma. An influence of a liner compressibility, 2-dimensional effects and various heat losses on the compressed plasma parameters are studied. The computations demonstrate that for a liner energy that has already been achieved experimentally the compressed plasma parameters can meet the Lawson criterion and this plasma can provide a large amount of neutrons and X-ray radiation.

Relatively soft X-rays (quantum energy about 0.3 keV) may be produced by acceleration of a plasma liner up to a velocity of /spl sim/300 km/s followed by stagnation in a pinch. This means that if the plasma acceleration distance is several cm, the time of plasma motion must be about 0.1 of a microsecond. This results in a difficulty, associated with the problem of plasma stability and the liner having very small thickness and very small tolerance on initial thickness and density. Besides, quick energy input into the load requires complicated fast opening switches, which need to be experimentally tested. For experiments with explosive magnetic generators (EMG) it is reasonable to develop simpler systems to reach mass velocities about 300 km/sec. The work by A.M Buyko et al. (1995) theoretically considers one of these systems, where a liner mass during its magnetic deceleration significantly decreases and the velocity increases, i.e., a variable mass liner (VML). The same work suggests two experimental designs to test a new concept: full-scale experiment, including X-rays generation and a model experiment, including testing of the initial stage of VML formation (v

Powerful pulse installations are usually used to produce large yields of X-ray radiation. With an increase of the stored energy up to 100 MJ, the costof a single experiment on these installations becomes comparable to the cost of a shot with explosive magnetic generators (EMG), according to expert estimates. The physical scheme of a device with a changeable mass liner forlarge soft X-ray (in the range of 0.3 to 0.5 keV) yields eneration is investigated. The scheme investigated is substantially free from difficulties connected with high precision liners and fast switches for current pulse sharpening.