A method for reducing the characteristic time of action of the pulse produced by explosive magnetic generators is proposed. An experiment was performed whose results confirm that this method can be used in practice.

In recent years, the method of driving the liner with a magnetic field in a classical Z-pinch scheme has been intensively developed by the world research laboratories. The application of this method with the use of a liner as a cylindrical impactor opens up wide possibilities for studying the dynamic properties of materials under conditions of shock-wave axisymmetric loading. The paper presents the studies of the dynamic properties of various materials in the liner experiments using a helical EMG equipped with an explosive switch as a source of pulsed power. The setup and results of a series of experiments investigating the shear strength of beryllium in the strain rate range of 10(3)-10(4) s(-1) are described. A comparative analysis of applicability of various computational models for a description of the deformation process in axisymmetric geometry has been performed. The results of experiments studying the lead "ejecta" process under conditions of shock-wave loading are presented. The numerical simulation has determined the influence of the ejecta-forming surface profile on the velocity and distribution of particles in a dust cloud by varying the amplitude of the shock wave in the range of 15-40 GPa.

The paper presents the results of model experiments to test a new field liner driver based on the disk explosive magnetic flux compression generator, results of driver development, and revised two-dimensional magnetohydrodynamic simulations of liner implosion.

This paper presents the results of laboratory and explosive experiments with a plasma focus discharge Mather-type chamber at a discharge current amplitude of 1.3–1.4 MA. It has been found that in laboratory experiments, the yield of a deuterium-deuterium neutrons reached 1011, and in an explosive experiment using the chamber filled with a deuterium-tritium gas mixture, the integral yield of a deuterium-tritium neutrons with an energy of 14 MeV was more than 1012 neutrons.

Damage initiation and evolution, failure, and recollection processes under axisymmetric convergence were studied in the Russian-Damage experimental series, a joint effort between the Los Alamos National Laboratory and the All-Russian Institute of Experimental Physics. A helical explosive magnetic generator was used to drive a cylindrical liner shell to produce shock wave loading of a concentric cylindrical target shell. Shock wave amplitude was controlled by the liner-to-target spacing and by the magnetic field amplitude. Variation of the current pulse duration produced either a single impact, to study damage initiation through failure, or a double impact, to study failure with recollection. Both full and partial recollection of the main crack was obtained. By fielding high-precision diagnostics to measure the dynamic drive conditions and material response and by employing post-shot metallographic analysis, this project produced well-characterized experimental data across a range of damage and recollection levels for the chosen material, aluminum. We present selected experimental results to illustrate the methodology and utility of this experimental technique.

To study the peculiarities of initiation, evolution and recollection of spall-type damage under axis-symmetric convergence using the impact method, the test bench with an explosive magnetic pulsed power source (EPPS) on the basis of a helical generator with an explosive opening switch and a current interrupter has been created. The EPPS allows shaping the trapezoidal current pulses with the amplitude from 4 MA to 12 MA, full base duration from 10 to 250 μs and front rise duration ~ 2 μs in the load (liner). The magnetic field produced by the EMG current ensures the isentropic drive of a cylindrical liner used to create a shock wave of the required characteristics in the targets. In experiments “R-Damage-8,9” representing the completion stage of the experimental series “R-Damage-0-9” realized jointly by the VNIIEF and LANL teams we used the isentropically driven liners to realize a set of processes of shock-wave compression, evolution of damage and recollection of a damaged matter under axis-symmetric convergence in the extruded aluminum. The features of these processes were recorded with the use of PDV technique due to the time dependencies of the hollow targets' inner surface velocity. The presented method allowed apparently for the first time realizing the full and incomplete recollection of the main crack as the results of metallographic analysis have showed. This result made it possible to verify the numerical models of the damaged medium recollection being developed at the present time.

To study the peculiarities of initiation, evolution and recollection of spall-type damage under axis-symmetric convergence using the impact method, the test bench with an explosive magnetic pulsed power source (EPPS) on the basis of a helical generator with an explosive opening switch and a current interrupter has been created. The EPPS allows shaping the trapezoidal current pulses with the amplitude from 4 MA to 12 MA, full base duration from 10 to 250 mu s and front rise duration similar to 2 mu s in the load (liner). The magnetic field produced by the EMG current ensures the isentropic drive of a cylindrical liner used to create a shock wave of the required characteristics in the targets. In experiments "R-Damage-8,9" representing the completion stage of the experimental series "R-Damage-0-9" realized jointly by the VNIIEF and LANL teams we used the isentropically driven liners to realize a set of processes of shock-wave compression, evolution of damage and recollection of a damaged matter under axis-symmetric convergence in the extruded aluminum. The features of these processes were recorded with the use of PDV technique due to the time dependencies of the hollow targets' inner surface velocity. The presented method allowed apparently for the first time realizing the full and incomplete recollection of the main crack as the results of metallographic analysis have showed. This result made it possible to verify the numerical models of the damaged medium recollection being developed at the present time.

Electromagnetic implosion of the cylindrical condensed liners is of great interest for the studies of high energy density physics, and in particular for getting pressures of terapascal range and for measuring the Hugoniots of materials under such pressures. The pulsed power systems on the basis of disk explosive magnetic generators (DEMG) provide the highest currents in the liner loads. A device on the basis of a 15-element DEMG Ø 0.4 m with a foil current opening switch and an explosive closing switch connecting the load is being developed to explore a possibility of driving the aluminum liner to a velocity of ~ 20 km/s and using it as an impactor. It is planned to check the operability of this device in the joint VNIIEF-LANL experiment ALT-3. To test the key systems of the ALT-3 assembly, a series of model experiments has been conducted. The model units will be described, the setup of the experiments testing the operability of the explosive current closing switch able to commute the currents of 60 - 70 MA and the system of high-voltage insulation of the line delivering the energy to the liner and able to withstand high voltages will be discussed. The experiment with the system modeling the ALT-3 device to check the scheme of operation of the pulsed power source' elements and the operability of disk elements under the explosive magnetic regime at the initial feeding current of 7.0 - 7.5 MA will be considered.

We consider an ALT-1,2-like [1,2] system to deliver up to 60-70 MA currents in the liner load and accelerate ~20 g/cm cylindrical liners to ~20 km/s (ALT-1,2: ~31 MA, ~13 g/cm, ~12 km/s). The system is intended for the ALT-3 experiment to test the efficiency of magnetic implosion of impacting liners and to verify the possibility of shock-wave measurements at up to 1 TPa pressures. We describe the physical configuration of the system and its diagnostic suite, which differ significantly from similar systems [3,4]. As compared with [4], changes are made to the physical configuration of individual system units and a number of system parameters: we increase load inductance by a factor of 1.5, use a We consider an ALT-1,2-like [1,2] system to deliver up to 60-70 MA currents in the liner load and accelerate ~20 g/cm cylindrical liners to ~20 km/s (ALT-1,2: ~31 MA, ~13 g/cm, ~12 km/s). The system is intended for the ALT-3 experiment to test the efficiency of magnetic implosion of impacting liners and to verify the possibility of shock-wave measurements at up to 1 TPa pressures. We describe the physical configuration of the system and its diagnostic suite, which differ significantly from similar systems [3,4]. As compared with [4], changes are made to the physical configuration of individual system units and a number of system parameters: we increase load inductance by a factor of 1.5, use a different transmission line and an AI liner (instead of envisaged two-layer liners) etc. Simulated characteristics of the system are presented.different transmission line and an AI liner (instead of envisaged two-layer liners) etc. Simulated characteristics of the system are presented.

The facilities for pulsed compression of materials are necessary to study the phase transformations and the dynamic parameters of substances. The acceleration of the solid liners with the help of magnetic field of the explosive magnetic generator (EMG) with subsequent deceleration on a specimen allows carrying out the pulsed compression. The paper describes a powerful pulsed source of current on the basis of helical EMG Oslash240 mm and explosive current opening switch Oslash 300 mm that makes it possible to shape the current pulse with the amplitude 15 MA with rise time adjustable from 3 mus to 10 mus in the liner load.

The design and the results of testing of an explosive device forming a current pulse of quasi-trapezoidal shape with the given amplitude and duration in the liner load are presented. A need for such devices was caused by a necessity to compare the experimental data obtained on the gas guns with the results of the experiments with a magnetic drive of the liners under the effect of current flowing through the liner. The results of the experiments in which the formed current pulse in the driven liner had the amplitude of 5 MA, the base duration of 10 ¿s, and the duration of the leading and trailing edges of 2 ¿s are presented.

The paper presents the results of application of the explosive magnetic pulsed power source (EMPPS), in the first experiments studying the spallation mechanisms of the solid substances damage under conditions of converging axisymmetric geometry of loading of samples by the impact of the cylindrical liner driven to a velocity of 0,2-1 km/s.

The source of high-voltage pulses. described in the paper. is a two-stage sharpening system that consists of a helical explosive magnetic generator and explosive and electroexplosive current opening switches separated by a current transformer. The helical explosive magnetic generator provides a stored energy of 1 MJ at a current of /spl sim/1.5 MA and a rise time of 40E10/sup -6/ s in an inductive load of 1E10/sup 6/ H. The cascade of the explosive current opening switch and the transformer reduce the pulse duration to 1E10/sup -6/ s. The electroexplosive opening switch is made from thin copper wires placed between layers of polyethylene insulation. The total length of the explosive magnetic pulsed power generator is about 3 m, its diameter being 300 mm. The voltage pulse, with 1.2 MV amplitude and 0.3E10/sup -6/ s duration, has been recorded on the output electrode at a connected load with an impedance of 15 Ohm.

Summary form only given, as follows. The source of high-voltage pulses, described in the paper, is a two-stage sharpening system that consists of a helical explosive magnetic generator, of explosive and electroexplosive current opening switches separated by a current transformer. The helical explosive magnetic generator provides the stored energy of 1 MJ at the current of /spl sim/1.5 MA and the rise time of 40 microsec in the inductive load of 1 microH. The cascade of the explosive current opening switch and the transformer reduces the pulse duration to 1 microsec. An electroexplosive opening switch is made from thin copper wires placed between the layers of polyethylene insulation. The total length of the explosive magnetic generator of pulses is about 3 m the diameter is 300 mm. The voltage pulse with 1.2 MV and 0.3 microsec duration has been recorded on the output electrode at a connected load with the impedance of 15 Ohm.

The source of high-voltage pulses. described in the paper. is a two-stage sharpening system [1] that consists of a helical explosive magnetic generator. of explosive [2] and electroexplosive [3] Current opening switches separated by a current transformer. The helical explosive magnetic generator provides the stored energy, of 1 MJ at the current of similar to1.5 MA and the rise time of 40(.)10(6) sec in the inductive load of 1(.)10(6) H. The cascade of the explosive current opening switch and the transformer reduce the pulse duration to 1(.)10(6) sec. Electroexplosive opening switch is made from thin copper wires placed between the layers of polyethylene insulation. The total length of the explosive magnetic generator of pulses is about 3 m. the diameter is 300 mm. The voltage pulse, with 1.2 MV amplitude and 0.3(.)10(6) sec duration has been recorded on the output electrode at a connected load with the impedance of 15 Ohm.