Filamentation in the pinched column of the dense plasma focus
P. Kubeš · M. Paduch · J. Cikhardt · B. Cikhardtová · D. Klír · J. Kravárik · K. Řezáč · E. Zielińska · M. J. Sadowski · A. Szymaszek · K. Tomaszewski · D. Zaloga
Abstract and summary · read the original at the source · none found
In one page
A dense plasma focus dumps a bank of capacitors into a gas, drives a sheet of current down a pair of coaxial electrodes and lets it collapse onto the axis into a pencil of plasma dense and hot enough to fuse deuterium. Kubeš and eleven colleagues in Prague and Warsaw photographed that pencil in high-energy ultraviolet light on a mega-ampere machine, and found it is not a smooth column at all. Thin filaments run inward from the surface of the pinch, and they last longer than fifty billionths of a second — for a plasma this hot, long enough to count as structures rather than flickers. The filaments end on small plasma balls about a millimetre across which sit still inside the column and live as long as the filaments do. Every deuterium shot produced fusion neutrons. The authors read the picture as the current itself being discrete: flowing in separate channels through and around the column, and carrying plasma inward from the outer layers.
Why it matters hereChapter 9 is about plasma that organises itself — the pinch, the plasmoid, the ball that holds together far longer than it has any right to. This is a photograph of exactly that, taken inside a fusion machine: millimetre-scale plasmoids standing still in the middle of a mega-ampere discharge, wired to the outside of the column by current-carrying filaments, with fusion neutrons coming off every shot.
What it claims
01The pinched column of a mega-ampere dense plasma focus is not smooth. A filamentary structure is observed in the high-energy ultraviolet radiation, in discharges filled with hydrogen or deuterium and puffed with hydrogen, deuterium or helium, and the lifetime of that structure exceeds 50 nanoseconds.Abstract, sentences 1 and 2
Published and peer-reviewed02The filaments connect the surface of the pinched column with plasmoids formed inside it, across different combinations of filling and puffing gases, and they should transport some current and some plasma between the two.Abstract, sentence 3
Published and peer-reviewed03Fusion-produced neutrons were recorded during all the investigated deuterium shots. Deuterons must therefore be present in the region where they are accelerated, and this holds independently of which gas was puffed.Abstract, sentences 4 and 5
Published and peer-reviewed04Small plasma balls of millimetre dimensions were observed inside the dense plasma column at the same time as the filaments. They had a similar lifetime — longer than the relaxation time — and quasi-stationary positions in the discharge volume.Abstract, sentence 6
Published and peer-reviewed05The authors’ reading of the images is that the filaments and the balls may be a manifestation of two things at once: a discrete spatial structure of the current flowing through and around the dense plasma column, and transport of plasma from the external layers into the central region. Discrete current channels rather than a smooth sheath is the load-bearing part of that.Abstract, sentence 7, points i and ii
What to watch06The structures were made easier to form and easier to see by adding air to the puffed gas — a diagnostic and experimental handle on a phenomenon that is otherwise hard to catch.Abstract, final sentence
On the bench now
Read it · abstract
Abstract
The paper describes the filamentary structure observed in the high-energy ultraviolet radiation for discharges performed at the hydrogen- or deuterium-filling and at the puffing of hydrogen, deuterium or helium, in a mega-ampere dense plasma-focus facility. The lifetime of this structure overcomes 50 ns. These filaments connect the surface of a pinched column with internal plasmoids formed at different combinations of filling and puffing gases and they should transport some current and plasma. During all the investigated deuterium shots, the fusion-produced neutrons were recorded. Therefore, deuterons should be present in the region of their acceleration, independent of the applied puffing of the gas. Simultaneously with the observed filaments, inside the dense plasma column small plasma-balls of mm-dimensions were observed, which had a similar lifetime (longer than the relaxation time) and quasi-stationary positions in the discharge volume. The observed filaments and balls might be a manifestation of the (i) discrete spatial structure of the current flowing through and around the dense plasma column and (ii) transport of the plasma from external layers to the central region. Their formation and visualization were easier due to the application of air admixtures in the puffed gas.
P. Kubeš, M. Paduch, J. Cikhardt, B. Cikhardtová, D. Klír, J. Kravárik, K. Řezáč, E. Zielińska, M. J. Sadowski, A. Szymaszek, K. Tomaszewski and D. Zaloga, Filamentation in the pinched column of the dense plasma focus, Physics of Plasmas volume 24, article 032706, 1 March 2017.
(Abstract only — no full text of this article was reachable; see the rights note above for what was and was not read. On this site, the same Warsaw machine driving a foam liner is at /library/stm-77cc1c549c, the Lee model code that reproduces plasma-focus discharges shot by shot is at /library/stm-a9cc428c6d, the PF-24 neutron campaign that varies the gas the same way is at /library/stm-ef8e9744ca, the filamentary breakup of a two-wire Z-pinch is at /library/stm-704d7be815, Eric Lerner’s plasma-focus route to proton-boron fusion is at /library/stm-05100e66da, and the free-force magnetic knot proposed for ball lightning — the same shape of object, outside a machine — is at /library/stm-14147817fb.)
The way in
https://doi.org/10.1063/1.4978558PUBLICATION. Physics of Plasmas, volume 24, issue 3, article number 032706, dated 1 March 2017, published by AIP Publishing. LICENCE AND TEXT. Crossref registers no licence of any kind for this DOI and Unpaywall reports the article closed with no open location anywhere; INSPIRE-HEP holds no record of it, and the publisher’s own article page refuses automated retrieval — all checked 2026-09-08. Nothing beyond the article’s own abstract is reproduced here. WHAT WAS READ. The abstract below is the one AIP Publishing deposited with Crossref, read from the Crossref record for this DOI on 2026-09-08 and cross-checked word for word against the identical text carried by OpenAlex. Every claim is located to a sentence of it. AUTHORS. The publisher prints the authors by initial and no record consulted expands them, so the initials are left as they stand; the diacritics dropped by the Crossref deposit are restored from the OpenAlex record — Kubeš, Cikhardtová, Klír, Kravárik, Řezáč, Zielińska. THE MACHINE. The abstract itself says only mega-ampere dense plasma-focus facility. The author affiliations recorded by OpenAlex place the experiment between the Czech Technical University in Prague — Kubeš, Cikhardt, Cikhardtová, Klír, Kravárik, Řezáč — and the Institute of Plasma Physics and Laser Microfusion in Warsaw, where Paduch, Zielińska, Szymaszek and Sadowski work and where the mega-ampere machine PF-1000 stands; Sadowski and Zaloga are also at the National Centre for Nuclear Research. The identification of the facility as PF-1000 comes from those affiliations and from the group’s long series of PF-1000 papers, not from the abstract. FUNDING as recorded in the Crossref deposit: CTU SGS grant 16/266/OHK3/3T/13; the Czech Ministry of Education, Youth and Sports, grant LG 15013; and Polish national resources for the support of international collaborative projects, 2016. CHAPTERS. The skeleton carried none; this is self-organised plasma structure inside a pinch, so it is filed to chapter 9.
How to cite it
P. Kubeš, M. Paduch, J. Cikhardt, B. Cikhardtová, D. Klír, J. Kravárik, K. Řezáč, E. Zielińska, M. J. Sadowski, A. Szymaszek, K. Tomaszewski, D. Zaloga (2017) Filamentation in the pinched column of the dense plasma focus. doi:10.1063/1.4978558
Where it sits in the curriculum