STM-D-0507Paper2001Published and peer-reviewed

Effect of discrete wires on the implosion dynamics of wire array Z pinches

S. V. Lebedev · F. N. Beg · S. N. Bland · J. P. Chittenden · A. E. Dangor · M. G. Haines · K. H. Kwek · S. A. Pikuz · T. A. Shelkovenko

Summary and citation · read the original at the source · none found

In one page

A Z-pinch is the most direct fusion machine there is: send an enormous current down a column of matter and the column’s own magnetic field crushes it inward. At Imperial College the column is a cage of hair-fine wires, and Sergey Lebedev and his colleagues use the MAGPIE generator — about a million amps in a quarter of a microsecond — to establish what actually happens inside one. Their answer replaces the picture of a shell collapsing all at once. For roughly the first eighty per cent of the implosion the wires do not move: each stays put as a solid core, boiling off plasma that jets continuously inward and fills the interior of the array with a precursor cloud. Only when the boiling opens gaps through the cores does the implosion proper start, and it then sweeps up that pre-filled cloud in a rapid snowplough. Lebedev argues the cloud’s density, peaked on the axis, is a key reason these implosions stay stable, and sets out how to scale the picture to larger machines.

Why it matters hereChapter 9 is about plasma that builds its own structure, and this is the cleanest laboratory case of it: cores, coronas and inward jets arrange themselves, and the machine’s output follows from that arrangement rather than from the drive alone. Chapter 12 takes the practical lesson — what a pinch does at stagnation is decided by how the mass got there, which is why array geometry is a design variable on the same footing as stored energy.

What it claims

01For about the first eighty per cent of the implosion the wire cores remain stationary in their initial positions, while coronal plasma jets continuously from those cores to the axis of the array. The array is redistributing its own mass long before anything that looks like an implosion begins.Abstract
Published and peer-reviewed
02That stationary phase ends with the formation of gaps in the wire cores, and the gaps open because the ablation rate is not uniform along the length of each wire.Abstract
Published and peer-reviewed
03The final phase, starting at that moment, is a rapid snowplough-like implosion of the radially distributed precursor plasma that was injected into the interior of the array during the stationary phase — so the imploding sheath runs into material that is already there rather than into vacuum.Abstract
Published and peer-reviewed
04The density distribution of that precursor plasma is peaked on the array axis, and the authors propose it as a key factor providing the stability of wire array implosions operating in the regime of discrete wires — stability supplied by the plasma’s own arrangement rather than imposed from outside.Abstract
Published and peer-reviewed
05The model is phenomenological and built directly on measurement: it is derived from experimental data taken on the MAGPIE generator, and its purpose is to supply modified initial conditions for one-dimensional and two-dimensional radiation-magnetohydrodynamic simulations in the r and z plane, which had been started from the wrong picture of the early implosion.Abstract; title and affiliation
Published and peer-reviewed
06The paper closes on a scaling question it hands to the larger machines: whether this discrete-wire behaviour, and the axially peaked precursor it produces, carries over to a substantially larger drive current.Abstract, closing sentence on scaling to a larger drive current
What to watch

The way in

https://doi.org/10.1063/1.1385373Published as Physics of Plasmas volume 8, issue 8, pages 3734 to 3747, August 2001. LICENCE AND TEXT. The Crossref deposit carries no licence of any kind, Unpaywall and OpenAlex both report the article closed with no repository copy, the Imperial College repository holds only theses on this subject rather than the paper, and the publisher’s servers decline automated retrieval, so this page carries no reproduced text and does not reprint the abstract. SOURCE FOR THE CLAIMS. The authors’ own published abstract was recovered in full from the publisher’s deposit as indexed and read on 2026-09-08; the summary and every claim below are written from it and from the bibliographic record, and each locator names the abstract rather than a section of the full text. REGISTRY CORRECTION. The record reached the library with eight of the nine authors and with only two of them credited on the front of the sheet; the ninth, T. A. Shelkovenko, is restored here from the publisher’s by-line, and the by-line is given in the published order. THE MACHINE. The experiments are on MAGPIE, the Mega Ampere Generator for Plasma Implosion Experiments in the Plasma Physics Group at Imperial College London, which drives about one mega-amp in about 250 nanoseconds.

How to cite it

S. V. Lebedev, F. N. Beg, S. N. Bland, J. P. Chittenden, A. E. Dangor, M. G. Haines, K. H. Kwek, S. A. Pikuz, T. A. Shelkovenko (2001) Effect of discrete wires on the implosion dynamics of wire array Z pinches. doi:10.1063/1.1385373

Where it sits in the curriculum

Plasmoids, charge clusters and the orbs Lattice confinement fusion