Evgueni F. Talantsev

Longitudinal-shock-wave compression of Nd2Fe14B high-energy hard ferromagnet: The pressure-induced magnetic phase transition

A study of a magnetic phase state of Nd2Fe14B high-energy hard ferromagnets subjected to longitudinal-shock-wave compression (where the shock wave propagates along magnetization vector M) has been performed. The results of the investigation show that longitudinal-shock-wave compression of Nd2Fe14B at 28–38 GPa causes a magnetic phase transition terminated by practically complete demagnetization of Nd2Fe14B. Due to this phase transition all electromagnetic energy stored in Nd2Fe14B is released and can be transformed into pulsed power. Explosive-driven autonomous sources of primary power utilizing this effect are capable of producing high-current pulses [current amplitude of 1.0 kA, full width at half maximum (FWHM) of 165 μs] and high-voltage pulses (peak voltage of 13.4 kV, FWHM of 8.2 μs).

Ultracompact explosive-driven high-current source of primary power based on shock wave demagnetization of Nd2Fe14B hard ferromagnetics

A new type of explosive driven high-current pulsed source utilizing a shock wave demagnetization of a Nd2Fe14B hard ferromagnetic energy carrier was developed. The design of the ferromagnetic energy carrier, which was made a hollow cylinder, has made it possible to reduce dramatically to 1 g the amount of the explosive providing a complete demagnetization of Nd2Fe14B energy carrier of weight 64 g. The developed generator is capable of producing high-current [up to 1.9 kA, 100 μs full width at half maximum (FWHM)] and high-power pulses (up to 42 kW, 2.8 μs FWHM).

Transverse shock wave demagnetization of Nd2Fe14B high-energy hard ferromagnetics

The action of transverse shock waves (the shock wave propagates across the magnetization vector M) on the magnetic phase state of a Nd2Fe14B high-energy hard ferromagnetic was investigated experimentally. The design of the ferromagnetic sample, which was made as a hollow cylinder, has made it possible to dramatically reduce the amount of the explosive that initiates a transverse shock wave in Nd2Fe14B to 1.0 g (for Nd2Fe14B samples weighing 67.5 g). The results of the experiment have shown that the transverse shock wave propagating through Nd2Fe14B causes “hard ferromagnetic-to-paramagnetic” phase transformation terminating by practically complete demagnetization of Nd2Fe14B. Pulse generators based on the transverse shock wave demagnetization of hollow cylindrical Nd2Fe14B samples with diameter of 25.4 mm and length of 19.1 mm are capable of producing high-voltage pulses [peak voltage of 11.3 kV, full width at half maximum (FWHM) of 4.5 μs] and high-current pulses (peak current of 1.93 kA, FWHM of 100 μs,...

Currents produced by explosive driven transverse shock wave ferromagnetic source of primary power in a coaxial single-turn seeding coil of a magnetocumulative generator

Experimental and digital simulation studies of the generation of seed currents by an ultracompact (8.66–8.75 cm3 in volume) ferromagnetic explosive-driven generator of primary power (FMG) loaded on the coaxial single-turn seeding coil of a magnetocumulative generator (MCG) have been performed. The operation of the FMG is based on transverse shock wave demagnetization of Nd2Fe14B high-energy hard ferromagnets. The FMG is capable of producing in the coaxial seeding coil of MCG a seed current with peak amplitude I(t)max=3.0 kA and full width at half maximum of 60 μs. The methodology was developed for digital simulation of the seeding processes in the combined FMG/MCG system.

Compact explosive-driven generator of primary power based on a longitudinal shock wave demagnetization of hard ferri- and ferromagnets

A new type of compact explosive-driven generator of primary power, which utilizes phenomena of a shock wave demagnetization of hard ferri- and ferromagnets, was developed. The shock wave initiated by high explosive, as well as accelerated flyer plate, passes along the hard ferri- or ferromagnetic body, which serves as initial energy carrier. The shock wave demagnetizes the energy-carrying element, reducing the initial magnetic flux /spl Phi//sub 0/. In accordance with Faradays law, this change of magnetic flux /spl Delta//spl Phi//sub 0/ generates an electromotive force in a coil wound on the energy carrier. Several types of compact generators with energy-carrying element of 10 cm/sup 3/ in volume were explored. High-voltage generators that utilize energy of BaFe/sub 12/O/sub 19/ hard ferrimagnets are capable of producing pulses of amplitude 5.5 kV with full width at half maximum (FWHM) of 1 /spl mu/s. The generators that utilize energy of Nd/sub 2/Fe/sub 14/B high-energy hard ferromagnets are capable of producing pulses with amplitude more than 10 kV and FWHM about 4 /spl mu/s. The high-current generators based on Nd/sub 2/Fe/sub 14/B produced pulses yielded 826 A and FWHM of 180 /spl mu/s. The developed generator can be used as the most reliable and effective source of primary power capable of seeding magnetocumulative generators.

Shock wave demagnetization of BaFe12O19 hard ferrimagnetics

A study of the effect of shock waves on the phase state of a hard ferrimagnetic material has been performed. A plane shock wave was passed along the axis of a cylindrical BaFe12O19 hard ferrite magnet. The shock wave demagnetized the cylinder, reducing the magnetic flux. This change in magnetic flux generated an electromotive force (EMF) in a coil wound around the ferrite. The value of the EMF calculated on the assumption that the ferrite was completely demagnetized by the shock wave is in good agreement with the peak EMF value obtained experimentally.

Theoretical treatment of explosive-driven ferroelectric generators

As a part of the New World Vistas Program, a series of ultra-compact explosive-driven ferroelectric generators (EDFEGs) has been designed, constructed, and tested by Texas Tech University providing well-documented EDFEG output parameters that were used to benchmark a theoretical model of the EDFEG developed at the Institute of Electromagnetic Research. A description of the model for the EDFEG is presented along with a brief description of the EDFEG, the experimental setup, and test procedures that were used. A comparison of the experimental and calculated results shows them to be in good agreement.

Completely explosive pulsed power minisystem

It is demonstrated that it is feasible to produce pulsed power using an autonomous completely explosive system that harnesses two physical phenomena successively: the transverse shock wave demagnetization of Nd2Fe14B high-energy hard ferromagnets and magnetic cumulation.

Electric breakdown of longitudinally shocked Pb(Zr0.52Ti0.48)O3 ceramics

Electric breakdown of longitudinally-shock-compressed Pb(Zr0.52Ti0.48)O3 (PZT 52/48) ferroelectric ceramics was experimentally investigated. It was found that a dependence of breakdown field strength, Eg, of shocked ferroelectrics on the thickness of the element, d, ranging from 0.65 to 6.5 mm is described by the Eg(d)=γ·d-w law that describes the breakdown of dielectrics at ambient conditions. It follows from the experimental results that the tunnel effect is a dominant mechanism of injection of prime electrons in the shocked ferroelectric elements. It was demonstrated that electric breakdown causes significant energy losses in miniature autonomous generators based on shock depolarization of poled ferroelectric elements.

Depolarization mechanisms of PbZr0.52Ti0.48O3 and PbZr0.95Ti0.05O3 poled ferroelectrics under high strain rate loading

Stress-induced and thermal-induced depolarization studies along with X-ray diffraction were performed on lead zirconate titanate ferroelectrics of different compositions, PbZr0.52Ti0.48O3 (PZT 52/48) and PbZr0.95Ti0.05O3 (PZT 95/5). Specimens were shock loaded perpendicular to the polarization vector. It was found that the polarity of the stress-induced charge released by PZT 52/48 and 95/5 was opposite to the polarity of the charge generated due to the piezoelectric effect. PZT 52/48 was only partially (45%) depolarized under 1.5 ± 0.1 GPa mechanical compression, as opposed to PZT 95/5 which was fully depolarized. The experimental results indicate that the stress-induced depolarization mechanisms are different for these two compositions. PZT 52/48 is transformed to a state with lower polarization, while PZT 95/5 undergoes a phase transition to a non-polar antiferroelectric phase.