0 Helical MFCG for Driving a High Inductance Load

Title	:	Helical MFCG for Driving a High Inductance Load
Authors	:	Andreas A. Neuber, Juan-Carlos Hernandez, James C. Dickens, Magne Kristiansen
		Electromagnetic Phenomena, V. 3, No.3 (11), 2003

Abstract

Even at small dimensions of less than 0.5 meter in length end-initiated helical magnetic flux compression generators (MFCG) have at least one order of magnitude higher energy density (by weight or volume) than capacitive energy storage with similar discharge time characteristics. However, simple MFCGs with a single helix produce high output energy only into low inductance loads, thus producing several 100 kA of current at a voltage level of less than 10 kV. Many pulsed power devices require less current but a considerably higher voltage level. For effectively driving a high inductance load of several μH, a multistage MFCG design has been suggested. We successfully tested a dual stage MFCG with a total length of 250 mm, a helix inner diameter of 51 mm, which is wound with Teflon insulated stranded wire of different sizes in the range from AWG 12 to AWG 22. We have presently achieved an energy gain of ~13 into a 3 μH load and will discuss the generator performance based on experimental current/voltage waveforms and specify the observed losses.

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0 Explosive Shocks and Impedance Mismatch in Armatures

Title	:	Explosive Shocks and Impedance Mismatch in Armatures
Authors	:	Jason Baird
		Electromagnetic Phenomena, V. 3, No.3 (11), 2003

Abstract

This investigation presents and discusses the influence of impedance mismatch on the explosive expansion of multilayer armature tubes, as an adjunct to helical flux-compression generator research at the University of Missouri-Rolla, directly affecting the understanding of flux cut-off and high strain-rate changes in generator armatures.
A previous investigation, reported elsewhere, studied longitudinal fractures that characteristically developed in single-layer armatures at smaller expansion ratios than predicted by classical analysis. The current study examines shock-produced tensile stresses in the armature skin, and the effects on those tensile stresses caused by density variations within layers of multi-layer armatures. In the original investigation, these tensile stresses produced cracks that occurred within two diameters of the detonator end of the armature, but did not extend when the tubing expanded under explosive pressurization. Such cracks appear to cause magnetic flux cut-off, and flux losses seriously affect energy conversion efficiency. The current study utilizes a two-dimensional Lagrangian finitedifference numerical model, classical impedance-matching calculations, and explosives-loaded multi-layer armature testing to analyze the effect of detonation waves on multi-layer armatures of different compositions. As an extension of the original work, this study further isolates shock wave effects during armature expansion.

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0 Evaluating the Limits of Shock Wave Magnetic Flux Compression in Solids

Title	:	Evaluating the Limits of Shock Wave Magnetic Flux Compression in Solids
Authors	:	S.V. Kolosenok, V.S. Soukhomlinov, Yu.A. Tolmachev, L.L. Altgilbers, D.J. Hemmert
		Electromagnetic Phenomena, V. 8, No.1 (19), 2008

Abstract

In this paper we present the results of an investigation of the interaction of ionizing shock waves in solids with strong magnetic fields in the Shock Wave Magnetic Flux Compression (SWMFC) generator. Deceleration of the ionizing shock waves by magnetic pressure is calculated for cesium iodide (CsI). It will be shown that it is possible to evaluate the limiting magnetic pressure for the SWMFC by a relatively simple and clearly understandable method.

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0 Dynamical Process of Liner Implosion in the Electromagnetic Flux Compression for Ultra-high Magnetic Fields

Title	:	Dynamical Process of Liner Implosion in the Electromagnetic Flux Compression for Ultra-high Magnetic Fields
Authors	:	D Nakamura, H Sawabe, Y H Matsuda and S Takeyama

Abstract

The spatial distribution of magnetic fields that are generated by the electromagnetic flux compression technique is investigated, with emphasis on the dynamical processes of an imploding liner. By comparing with the results of computer simulations, we found that the non-uniform implosion of a liner is important in order to explain the magnetic field’s distribution during the liner’s implosion. In addition, our results suggest that the initial inwards compressing spool-like motion of the liner subsequently turns out to be outwards stretching barrel-like motion along the magnetic field axis.

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0 Development of Small, Tapered Stator Helical Magnetic Flux Compression Generators

Title	:	Development of Small, Tapered Stator Helical Magnetic Flux Compression Generators
Authors	:	Bruce L. Freeman, Larry L. Altgilbers, Alvin D. Luginbill, James C. Rock
		"Electromagnetic Phenomena", V.3, 3 (11), 2003

Abstract

For some applications of magnetic flux compression generators, shorter pulse widths, with associated higher voltages and power levels, are required.We have developed a family of small, tapered stator generators that begin to address these requirements. Specifically, the three versions of these FCGs developed use stator angles of 100, 120, and 130 with respect to the generator axis. These three respective angles resulted in increasingly larger phased closure velocities. The armature diameter is 2.54 cm, and the armature expansion ratio is about 2:1. The shortest dI/dt pulse, in terms of Full-Width-Half-Maximum (FWHM), produced is 398 ns in the current derivative. The peak value for dI/dt is about 3.5 × 10¹⁰ amps/sec.

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