D.F. Rankin

A fast and compact θ-pinch electromagnetic flux-compression generator

Ultrahigh magnetic fields up to 300 T (3 MG) have been generated by electromagnetic flux compression using only 63 kJ from a fast capacitor bank to implode aluminium liners, with 14.7 kJ from a slow capacitor bank needed to provide an initial magnetic field. With no initial field present, pulses of magnetic flux density having a time rate-of-change exceeding 3 × 108 T s−1 have been produced and measured, opening the way for a range of dynamic transformer applications. The outcome of the work suggests that, when using fast multi-MA banks, flux compression can be viewed as an alternative to the single-turn coil technique that will move the boundary of the magnetic fields well beyond 300 T without the need for significant additional investments.

An insulator-metallic phase transition cascade for improved electromagnetic flux-compression in /spl theta/-pinch geometry

During an initial phase of an ongoing research program at Loughborough University, ultrahigh magnetic fields of up to 300 T (3 MG) have been generated. These have been produced using only 63 kJ from a fast capacitor bank to implode an aluminum liner in a /spl theta/-pinch geometry, and 14.7 kJ from a slow capacitor bank to provide an initial magnetic field. The paper analyzes various ways of improving both the /spl theta/-pinch magnetic flux-compression efficiency and its reproducibility. As a practical illustration, experimental evidence is presented to demonstrate the benefits obtained from the use of an insulator-metallic phase transition cascade made from powder aluminum.

Electromagnetic flux-compression: experimentation

Electromagnetic flux-compression experiments performed at Loughborough University have produced magnetic flux densities in excess of 300 T with a high degree of reproducibility, using two condenser banks with a total energy of about 80 kJ. In an ongoing research programme, a time rate-of-change of 3.5 10/sup 8/ T/s is being generated, which is more than adequate to move onto the second phase of the research that aims to produce fast high voltage pulses.

Use of the Aluminum Powder Cascade Technique to Stabilize Liner Implosions

Electromagnetic flux compression requires high-quality liners, with copper being a much more effective material than the aluminum used in previous experiments at Loughborough for producing fields of 300 T. Unfortunately, similar small-size copper liners cannot be economically manufactured with sufficiently precise tolerances to prevent the development of liner instabilities during an implosion, leading to a much lower magnetic flux density than anticipated. The paper describes how the performance can however be dramatically improved by the use of an aluminum powder cascade, and presents results showing that the use of this technique has enabled flux densities up to 350 T to be generated using only a 70-kJ capacitor bank

Advances in Electromagnetic Flux Compression at Loughborough University

This paper presents the most recent results obtained from an ongoing research programme at Loughborough University related to the generation and measurement of ultrahigh magnetic fields. Initially, results obtained from detailed 2D modelling of thetas-pinch electromagnetic flux compression are presented and discussed, and suggestions are made for the improvement of the technique. Secondly, results obtained when using an imploding copper liner and a novel insulator-metallic phase transition cascading technique are presented. Magnetic flux densities in excess of 350 T were produced and reliably measured, even when major liner instabilities existed during the implosion. Finally, interesting characteristics are demonstrated of a further novel phase transition technique, implemented into an exploding single-turn discharge. Most importantly, ultrahigh magnetic flux densities are sustained over much longer periods of time than in conventional single-turn discharge experiments.

Finite Element Analysis of Magnetic Field Single-Turn Systems

Modelling of pulsed magnetic systems has extensive application in the optimisation of electromagnetic metal forming as well as in pulsed ultrahigh field generation systems. This paper presents a detailed three-dimensional finite element analysis model to be used in such power systems and compares simulated solutions with accurate experimental data.

Flux-compression dynamic transformers as pulsed-voltage sources

During recent years, the pulsed power group at Loughborough University has developed various electromagnetically driven flux-compression generators. Using thetas-pinch geometry and injecting an initial magnetic field of 2.5 T, ultrahigh magnetic fields in excess of 300 T have been generated in aluminum liner implosions. The fields have a time rate-of-change of up to 350 MT/s. Z-pinch imploding geometry was also investigated, using a cylindrical electric gun with a 50 micron thick aluminum fuse. Helical dynamic transformers were implemented and tested for both geometries, and recordings are presented of the fast-rising high-voltage pulses that were obtained. Potential techniques are suggested and ways to modulate the voltage pulses are demonstrated

A two dimensional electromagnetic-electroplastic modelling technique

The use of two dimensional filamentary modelling techniques has proven to be an accurate approach to modelling the complex electro-magnetic interactions that occur in high magnetic field generation experiments. Due however to the nature of this modelling, limitations arise when considering two dimensional, and three dimensional deformation of the geometry. Accurate modelling leads to a fundamental understanding, and consequently enables the generation system to be optimised. This paper outlines the preliminary steps in investigating into the potential and suitability of finite element analysis for the modelling of two high magnetic field generation experiments; single-turn coil technique, and /spl theta/-pinch flux compression, using a commercially available software package, ANSYS.