Jason Baird

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).

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.

Compact autonomous explosive-driven pulsed power system based on a capacitive energy storage charged by a high-voltage shock-wave ferromagnetic generator

A new concept for constructing compact autonomous pulsed power systems is presented. This concept utilizes a high-voltage explosive-driven shock-wave ferromagnetic generator (FMG) as a charging source for capacitive energy storage. It has been experimentally demonstrated that miniature FMGs (22–25cm3 in size and 84–95g in mass) developed for these experiments can be successfully used to charge capacitor banks. The FMGs, containing Nd2Fe14B energy-carrying elements, provided pulsed powers of 35–45kW in times ranging from 10to15μs. A methodology was developed for digital simulation of the operation of the transverse FMG. Experimental results that were obtained are in a good agreement with the results of digital simulations.

Note: Autonomous Pulsed Power Generator Based on Transverse Shock Wave Depolarization of Ferroelectric Ceramics

Autonomous pulsed generators utilizing transverse shock wave depolarization (shock front propagates across the polarization vector P(0)) of Pb(Zr(0.52)Ti(0.48))O(3) poled piezoelectric ceramics were designed, constructed, and experimentally tested. It was demonstrated that generators having total volume of 50 cm(3) were capable of producing the output voltage pulses with amplitude up to 43 kV with pulse duration 4 μs. A comparison of high-voltage operation of transverse and longitudinal shock wave ferroelectric generators is given.

Note: Miniature 120-kV autonomous generator based on transverse shock-wave depolarization of Pb(Zr0.52Ti0.48)O3 ferroelectrics

The design of autonomous ultrahigh-voltage generators with no moving metallic parts based on transverse explosive shock wave depolarization of Pb(Zr(0.52)Ti(0.48))O(3) (PZT 52∕48) poled ferroelectrics was explored and studied. It follows from experimental results that the output voltage produced by the shock-wave ferroelectric generators (FEGs) is directly proportional to the number of PZT 52/48 elements connected in series. It was demonstrated that miniature FEGs (volume less than 180 cm(3)) were capable of reliably producing output voltage pulses with amplitudes exceeding 120 kV which is the record reported in open literature.

The depolarization of Pb(Zr0.52Ti0.48)O3 ferroelectrics by cylindrical radially expanding shock waves and its utilization for miniature pulsed power

The effects of depolarization of Pb(Zr(0.52)Ti(0.48))O(3) (PZT 52∕48) poled ferroelectrics by cylindrical radially expanding shock waves propagated along and across the polarization vector P(0) were experimentally detected. Miniature (total volume 100 cm(3)) autonomous generators based on these effects were capable of producing output voltage pulses with amplitudes up to 25 kV and output energies exceeding 1 J.

Pulsed Charging of Capacitor Bank by Compact Explosive-Driven High-Voltage Primary Power Source Based on Longitudinal Shock Wave Depolarization of Ferroelectric Ceramics

Results of the investigation of the operation of autonomous ultracompact explosive-driven high-voltage primary power sources based on longitudinal (when the shock wave propagates along the polarization vector P0) shock wave depolarization of ferroelectric materials in the open circuit and charging modes are presented. The energy-carrying elements of shock wave ferroelectric generators (FEGs) were poled lead zirconate titanate (PZT) Pb(Zr52Ti48)O3 polycrystalline piezoelectric ceramic disks with volume 0.35 cm3. The PZT modules were shock compressed in the stress range from 1.5 to 3.8 GPa by a longitudinal shock wave generated by high explosives. In the charging mode, the FEGs provided pulsed power with peak amplitudes up to 0.29 MW. The maximum efficiency of the electric charge transfer from the energy-carrying PZT elements to the capacitor bank was 46%.

Completely Explosive Ultracompact High-Voltage Pulse Generating System

A conventional pulsed power technology has been combined with an explosive pulsed power technology to produce an autonomous high voltage power supply. The power supply contained an explosive-driven high-voltage primary power source and a power-conditioning stage. Two types of ultracompact explosive primary power sources were used, one of which was based on the physical effect of shock wave demagnetization of high- energy ferromagnets, and the other one was based on shock wave depolarization of high-energy ferroelectric materials. The volumes of the energy-carrying ferroelectric elements in the shock wave ferroelectric generators (FEGs) varied from 1.2 to 2.6 cm3. The volume of the energy-carrying ferromagnetic elements in the shock wave ferromagnetic generators (FMGs) was 8.75 cm3 for all tests performed. The power-conditioning stage was based on the spiral vector inversion generator (VIG). The combined FEG-VIG and FMG-VIG systems demonstrated successful operation and good performance. The output voltage pulse amplitude of the combined FEG-VIG system exceeded 90 kV, with risetime of 6.8 ns.

The effects of the flyer plate's radius of curvature on the performance of an explosively formed projectile

An explosively formed projectile (EFP) is known for its ability to penetrate vehicle armor effectively. Understanding how an EFPs physical parameters affect its performance is crucial to development of armor capable of defeating such devices. The present study uses two flyer plate radii of curvature to identify the experimental effects of the flyer plates radius of curvature on the measured projectile velocity, depth of penetration, and projectile shape. The Gurney equation is an algebraic relationship for estimating the velocity imparted to a metal plate in contact with detonating explosives [1]. The authors of this research used a form of the Gurney equation to calculate the theoretical flyer plate velocity. Two EFP designs that have different flyer plate radii of curvature, but the same physical parameters and the same flyer-weight to charge-weight ratio should theoretically have the same velocity. Tests indicated that the flyer plates radius of curvature does not affect the projectiles velocity an...

Maximizing resolution of the high-speed photography of explosive-driven power generator (EDPG) armatures in operation

An integral part of the Explosive-Driven Power Generation Program is to enhance the quality and resolution of photography of the surface of EDPG armatures during explosive expansion. The quality and resolution of photography are affected by the amount of illumination, its wavelength, pulse duration, shock effects from the explosive event, explosive plasmas, and surrounding atmospheric characteristics (shock generation of light, blurring, refraction, etc.). Current methods of providing illumination for very high speed photography (/spl sim/1/spl times/10/sup 6/ frames per second) involve the utilization of intense light generated by explosive events such as so-called argon bombs; however, such devices reduce the maximum explosive weight in the experimental device and also generate light of a less desirable wavelength. A new system was developed in-house using inexpensive equipment that allows flash photography at 1/spl times/10/sup 6/ frames per second utilizing 100 ISO film. This equipment is described along with the techniques used to mitigate the deleterious effects of the explosive event on its surrounding environment. The resultant imaging maximizes resolution of phenomena at the armature surface, far surpassing any previously achieved at this facility.