STM-D-0588Paper2015Published and peer-reviewed

Physical processes taking place in dense plasma focus devices at the interaction of hot plasma and fast ion streams with materials under test

V A Gribkov

Abstract and summary · read the original at the source

In one page

A dense plasma focus is a deceptively plain machine. A capacitor bank dumps its charge across two coaxial electrodes, a sheet of current sweeps down the gap, and when it collapses onto the axis a pinch of plasma sits there for a few billionths of a second behaving like a very small star. Vitaliy Gribkov, writing from the Institute of Plasma Physics and Laser Microfusion in Warsaw and the Baikov Institute in Moscow, sets out what happens inside that pinch and in the streams it throws off: hot plasma, fast electron and ion beams, X-rays and neutrons, all in nanosecond pulses and, in certain cases, at power flux densities reaching ten to the thirteenth watts per square centimetre. He draws on four machines whose stored energies run from a kilojoule to a megajoule, and names the mechanisms — how the jet forms, the current abruption event, how a super-Alfvén ion beam travels inside and outside the plasma, how secondary plasma and shock waves appear in the target.

Why it matters hereChapter 9 is about self-organised plasma structures that hold together and carry energy, and the dense plasma focus is the one such structure that hundreds of people have built on a laboratory bench and instrumented at nanosecond resolution, so it is where the vocabulary for the rest of the chapter comes from. Chapter 12 gets the practical end: the reason more than thirty laboratories run these devices is that the pulse they deliver to a target is the closest available stand-in for what a fusion reactor wall will have to survive. Read it beside the aneutronic programme at /library/stm-05100e66da, the numerical model of the same machine at /library/stm-fbd01b5713, and the tens-of-joules pinch at /library/stm-12f5d53acb.

What it claims

01A dense plasma focus device is a source of powerful streams of penetrating radiations — hot plasma, fast electron and ion beams, x-rays and neutrons — with pulse durations on the nanosecond scale, and the power flux densities of those radiation types may in certain cases reach values up to ten to the thirteenth watts per square centimetre.Abstract, opening two sentences
Settled physics
02More than thirty laboratories worldwide currently use these devices in radiation material science. The named areas of implementation are testing materials that are candidates for use in modern fusion reactors of both types, modification of surface layers to improve their properties, and production of nanostructures on those surfaces.Abstract, third and fourth sentences
Settled physics
03The physical mechanisms the paper treats are named explicitly: jet formation, the current abruption phenomenon, super-Alfvén ion beam propagation both inside and outside the dense plasma focus plasma, generation of secondary plasma, and the formation of shock waves both in the plasma and inside a solid-state target.Abstract, the sentence beginning ‘Among them mechanisms of a jet formation’
Published and peer-reviewed
04The experimental results illustrating those mechanisms come from four dense plasma focus devices whose bank energies span the range from one kilojoule to one megajoule — the same class of physics examined across three orders of magnitude in stored energy.Abstract, the sentence beginning ‘In this paper, the most important issues’
Published and peer-reviewed
05The events are resolved with nanosecond time-resolved techniques — electric probes, laser interferometry, frame self-luminescent imaging, x-ray and neutron probes — and the irradiated specimens are then analysed with optical and scanning electron microscopy, local x-ray spectral and structure analysis, atomic force microscopy, a portable x-ray diffractometer combining single-photon detection with high spectroscopic and angular resolution, an x-ray microCT system, and microhardness measurements.Abstract, the two closing sentences on instrumentation
Published and peer-reviewed
06Gribkov frames the whole exercise as a prerequisite rather than a result: to use a dense plasma focus correctly in these applications it is necessary first to understand how the radiations are generated, how they move inside and outside the pinch, and how those streams interact with targets. That is the open work the paper sets out to advance.Abstract, the sentence beginning ‘To use a DPF correctly in these applications’
What to watch

Read it · abstract

Abstract

The dense plasma focus (DPF) device represents a source of powerful streams of penetrating radiations (hot plasma, fast electron and ion beams, x-rays and neutrons) of ns-scale pulse durations. Power flux densities of the radiation types may reach in certain cases the values up to 10¹³ W cm⁻². They are widely used at present time in more than 30 labs in the world in the field of radiation material science. Areas of their implementations are testing of the materials perspective for use in modern fusion reactors (FR) of both types, modification of surface layers with an aim of improvements their properties, production of some nanostructures on their surface, and so on. To use a DPF correctly in these applications it is important to understand the mechanisms of generation of the above-mentioned radiations, their dynamics inside and outside of the pinch and processes of interaction of these streams with targets. In this paper, the most important issues on the above matter we discuss in relation to the cumulative hot plasma stream and the beam of fast ions with illustration of experimental results obtained at four DPF devices ranged in the limits of bank energies from 1 kJ to 1 MJ. Among them mechanisms of a jet formation, a current abruption phenomenon, a super-Alfven ion beam propagation inside and outside of DPF plasma, generation of secondary plasma and formation of shock waves in plasma and inside a solid-state target, etc. Nanosecond time-resolved techniques (electric probes, laser interferometry, frame self-luminescent imaging, x-ray/neutron probes, etc) give an opportunity to investigate the above-mentioned events and to observe the process of interaction of the radiation types with targets. After irradiation, we analyzed the specimens by contemporary instrumentation: optical and scanning electron microscopy, local x-ray spectral and structure analysis, atomic force microscopy, the portable x-ray diffractometer that combines x-ray single photon detection with high spectroscopic and angular resolutions, an x-ray microCT system with Cobra 7.4 and DIGIX CT software, microhardness measurements, etc. Some results in this area are presented.

V A Gribkov, Institute of Plasma Physics and Laser Microfusion, Warsaw, and A A Baikov Institute of Metallurgy and Material Science, Russian Academy of Sciences, Moscow. Plasma Physics and Controlled Fusion 57, 065010 (2015).

(Abstract only. The complete paper is at https://doi.org/10.1088/0741-3335/57/6/065010 — see the rights note for why the full text is not reproduced here.)

The way in

https://doi.org/10.1088/0741-3335/57/6/065010Published as Plasma Physics and Controlled Fusion 57, 065010 (2015); received 20 January 2015, accepted 25 March 2015, published 22 April 2015. Author affiliations as given on the article: the Institute of Plasma Physics and Laser Microfusion, Warsaw, and the A A Baikov Institute of Metallurgy and Material Science of the Russian Academy of Sciences, Moscow. LICENCE. No Creative Commons statement exists on either side: the Crossref record for this DOI carries only IOP’s copyright and text-and-data-mining pages, and the Unpaywall record returns oa_status bronze with a null licence, which means free to read at the publisher and nothing more. TEXT. The full text could not be reached. IOP’s server answers automated requests for both the article page and its PDF with a bot-manager challenge, the Semantic Scholar record has the abstract elided at the publisher’s request, no repository or preprint copy is recorded for this DOI, and the Internet Archive holds no snapshot of either URL. The abstract below was therefore taken word-for-word from the publisher’s own article page and is complete; superscripts lost in extraction are restored, so the power flux density reads ten to the thirteenth watts per square centimetre. The summary and the claims are drawn from that abstract and from the verified bibliographic record, and the locators point to it rather than to sections of the body.

How to cite it

V A Gribkov (2015) Physical processes taking place in dense plasma focus devices at the interaction of hot plasma and fast ion streams with materials under test. doi:10.1088/0741-3335/57/6/065010

Where it sits in the curriculum

Plasmoids, charge clusters and the orbs Lattice confinement fusion