Z-pinch discharges in aluminum and tungsten wires
J. Ruiz-Camacho · F. N. Beg · A. E. Dangor · M. G. Haines · E. L. Clark · I. Ross
Abstract and summary · read the original at the source · none found
In one page
A Z-pinch turns a hair-thin wire into plasma by pushing an enormous current through it, and the current’s own magnetic field then crushes that plasma inward. What the wire is made of turns out to matter a great deal. Ruiz-Camacho, Beg, Dangor, Haines, Clark and Ross at Imperial College fire 160,000 amps into single wires, rising to peak in 65 billionths of a second, and compare tungsten wires of several thicknesses against a fine aluminium wire. Tungsten’s vapour cloud expands at about 9,400 metres a second; aluminium’s goes at least twice as fast. Aluminium also loses its shape sooner — the sausage-like necking of the column starts at about 8 nanoseconds against 20 for tungsten — and the bright spots, the intensely radiating knots strung along the pinch, appear earlier and, on the thicker tungsten wires, last far longer. Only tungsten radiates hard X-rays above 6 kiloelectronvolts from the plasma itself, while both metals drive an electron beam that lights up the anode.
Why it matters hereChapter 9 is about plasma that organises itself into structures which hold together and carry current, and this paper is a direct measurement of how much that self-organisation depends on the material it is made from: the same current, the same machine, and two metals give different expansion speeds, different instability clocks, different bright spots and different radiation. Anyone designing a pinch — as a radiation source or as a fusion driver — is choosing that behaviour when they choose the wire.
What it claims
01The same driver gives materially different pinches. Driven by a pulsed-power generator delivering 160 kiloamps with a 10 to 90 percent rise time of 65 nanoseconds, tungsten wires of various diameters and a 15 micrometre aluminium wire behave differently enough that wire material and wire diameter are treated as the experiment’s variables.Abstract, opening sentences
Published and peer-reviewed02Schlieren imaging measures the expansion of the coronal plasma around the wire: for tungsten wires of various diameters it is 9.4 plus or minus 1.0 times 10 to the 3 metres per second, and the aluminium pinch expands at least a factor of 2 faster.Abstract
Published and peer-reviewed03The instability clock runs on the material. The m equals zero sausage perturbations appear at about 8 nanoseconds for aluminium against about 20 nanoseconds for the tungsten pinch, and for both wires the wavelength and the diameter of the perturbations grow with time, relatively faster for aluminium.Abstract
Published and peer-reviewed04Wire thickness controls how long fine structure survives: short wavelength perturbations of about 200 micrometres persist for a longer time on larger diameter tungsten wires.Abstract
Published and peer-reviewed05Bright spots — the intensely radiating knots that form along the column — appear after 60 nanoseconds from the start of the current for tungsten and after 40 nanoseconds for aluminium, and they decay in 40 nanoseconds on the smallest diameter tungsten wire against only a few nanoseconds on the larger diameters.Abstract
Published and peer-reviewed06Hard X-ray emission above 6 kiloelectronvolts is observed from tungsten wire pinches but from neither the bright spots nor the plasma column of the aluminium pinch; separately, hard X-ray emission from the anode, produced by an electron beam, is observed for wires of both materials.Abstract, closing sentences
Published and peer-reviewed
Read it · abstract
Abstract
A series of experiments on Z-pinch plasmas, driven by a pulsed power generator that delivers 160 kA with a rise time (10%–90%) of 65 ns are reported. Tungsten wires of various diameters were used and results are compared with 15 μm diameter aluminum wire. The expansion of the pinch is studied as a function of wire diameter and material. Schlieren observations show that the coronal plasma of various diameters of tungsten wires expands with the velocity of (9.4±1.0)×10³ m/s. The aluminum pinch expands at least a factor of 2 faster. The m=0 perturbations appear at about 8 ns for the aluminum compared with 20 ns for the tungsten pinch. The wavelength and diameter of the perturbations increase with time for both types of wires, and relatively faster for the aluminum pinch. The short wavelength perturbations (∼200 μm) persist for a longer time for larger diameter tungsten wires. Bright spots are seen to appear after 60 ns from the current start for tungsten wires, whereas for aluminum wires, bright spots appear after 40 ns. The decay time of bright spots is 40 ns for the smallest diameter tungsten wire compared with only a few nanoseconds for larger diameter wires. Hard x-ray emission above 6 keV was observed from tungsten wire pinches, but it was not observed from either bright spots or the plasma column for the aluminum pinch. However, hard x-ray emission from the anode due to an electron beam was observed for wires of both materials.
J. Ruiz-Camacho, F. N. Beg, A. E. Dangor, M. G. Haines, E. L. Clark and I. Ross, Z-pinch discharges in aluminum and tungsten wires, Physics of Plasmas 6, 2579 (1999), from the Plasma Physics Group of the Blackett Laboratory, Imperial College London.
(Abstract only, and the full text was not reachable — see the rights note above. On this site, the same group’s two-wire Z-pinch is at /library/stm-704d7be815, their prepulse experiment on a fibre pinch at /library/stm-06c1a40035, their wire-array implosion experiments at /library/stm-33d8266a67, and what the discreteness of the wires does to an implosion at /library/stm-bb03ac17ef. The steady-state ablation that feeds the corona measured here is at /library/stm-a2345abd6a, the analytic model of how an array of such columns implodes at /library/stm-fbf26262c6, the fibre-ablation question in a solid-deuterium pinch at /library/stm-69ab32821f, and Sandia’s microfabricated arrays built to control the geometry at /library/stm-98d874080d.)
The way in
https://doi.org/10.1063/1.873529SOURCE NOT REACHED IN FULL. The article is held by AIP Publishing as Physics of Plasmas volume 6, issue 6, pages 2579 to 2587, and Crossref carries no licence statement for it at all. On 2026-09-08 the paper was looked for and not found as an open copy: OpenAlex and Unpaywall both report open access status closed with no repository location, Semantic Scholar reports the same and returns no open PDF, the Imperial College Spiral repository search returns other pinch papers from the group but not this one, OSTI holds no record of it, and the authors posted no preprint. The status was raised from summary-only to abstract-only because the authors’ own complete abstract is carried by Crossref and by OpenAlex, and it is that abstract which is reproduced below and which the summary and every claim are written from; the locators therefore all say Abstract, because the abstract is what was read. AUTHORS. Initials are left unexpanded because no publisher record consulted gives the authors’ given names. The work is from the Plasma Physics Group of the Blackett Laboratory, Imperial College London, with the Central Laser Facility at the Rutherford Appleton Laboratory.
How to cite it
J. Ruiz-Camacho, F. N. Beg, A. E. Dangor, M. G. Haines, E. L. Clark, I. Ross (1999) Z-pinch discharges in aluminum and tungsten wires. doi:10.1063/1.873529
Where it sits in the curriculum