Numerical Modelling of a Flyer Plate Electromagnetic Accelerator

Abstract

A joint program involving the study and practical performance of a foil-flyer electromagnetic accelerator has recently been initiated by Atomic Weapons Establishment, Aldermaston, and Loughborough University. As an initial phase of the work, both 0-D and 2-D numerical models for the foil-flyer accelerator have been developed. The 0-D model, although very crude, is capable of providing an insight into the accelerator phenomena and is currently used for parametric design studies. The 2-D model is based on the well-proven Loughborough filamentary modeling technique and is capable of accurately calculating the 2-D distribution of current, velocity, acceleration, and temperature of the flyer, together with the complete distribution of the magnetic and electric fields generated during a shot. The paper presents the two models and compares typical theoretical predictions with the corresponding experimental results.

MIDOT: A novel probe for monitoring high-current flat transmission lines

“…3 Because the strip-line is represented by a collection of parallel imaginary filaments the idea is, as shown in Figure 2, to install similar but real filaments parallel to but outside the line, with the same type of procedure used to calculate the mutual inductances between those filaments and the transmission line. Each external filament effectively is an open circuit and, during a test, the time variation of the strip-line current induces an emf that can be expressed as follows:…”

“…As described in our previous work, 3 when filamentary modelling of a stripline is undertaken, the available computer memory limits the number of filaments to a rather low figure. Because of the thin and wide geometry of the flyer plate, the filaments have a rectangular cross section with one side many tens of times longer than the other, very much like a very thin strip.…”

“…Such an array was later used for detecting the current dynamics of an accelerated flyer. 3 The array could withstand the impact of the flyer, without the risk of a galvanic connection between the flyer high-voltage circuit and the MIDOT circuits attached to sensitive oscilloscope outputs. Flyer related results will be presented later.…”

“…As the mutual inductance between the probe and a strip line can be calculated as a collection of mutual inductances with a large number of parallel bifilar lines (see the work on filamentary modelling 3 ), in what follows only the technique used to calculate the mutual inductance between the MIDOT and a bifilar line is presented. The exact formula for the mutual inductance between a pair of very thin wires separated by distance d and having length l is…”

“…(i) high-velocity electromagnetic launchers such as the railgun, 1 (ii) the "slapper" flyer plate impact shock-wave systems 2 such as the recently developed AMPERE foil-flyer accelerator, 3 (iii) isentropic compression experimentation. 4 Many other examples can be found in a number of worldwide facilities that employ large high-current capacitor banks coupled to a load via strip-lines, with an extreme example being SHIVA STAR.…”