A Physics Exploratory Experiment on Plasma Liner Formation
Y. C. Francis Thio · Charles E. Knapp · Ronald C. Kirkpatrick · Richard E. Siemon · Peter J. Turchi
Abstract and summary · read the original at the source · none found; the NASA-released manuscript carries the determination GOV_PUBLIC_USE_PERMITTED
In one page
Magnetized target fusion sits between the two mainstream routes: make a ball of magnetised plasma, then crush it with an imploding shell. The hard part is the shell — anything solid has to be built, aimed and destroyed on every shot. Francis Thio, then at NASA Marshall, with Charles Knapp, Ronald Kirkpatrick and Richard Siemon of Los Alamos and Peter Turchi of the Air Force Research Laboratory, propose making the shell out of plasma instead: fire a ring of plasma guns inwards and let the jets merge in flight into a converging liner, so the driver stands well off from the target. This paper designs the first experiment of that programme and shows its arithmetic. Twelve coaxial guns of the Marshall type arranged in a circle, each launching two to four tenths of a milligram of plasma at two hundred kilometres a second, timed to better than a hundred nanoseconds. The authors size the capacitor bank that would do it, name the four phases that lead from this experiment to breakeven, and list the spin-offs on the way.
Why it matters hereChapter 9 is about plasma made to hold a shape, and a liner assembled in mid-flight from a dozen separate jets is that idea at its most demanding. Chapter 12 keeps the ledger of fusion routes, and this is the standoff-driver design the US government’s own non-electric applications panel later singled out as the compact, pulsed approach most suited to propulsion rather than to a power station.
What it claims
01The momentum flux that implodes a magnetized target can be delivered by an array of plasma guns whose separate jets merge in flight into a converging plasma shell, so the driver stands off from the target and nothing solid has to survive near it. The experiment described, PLX, is Phase 1 of a four-phase programme intended to carry the approach to fusion breakeven.Abstract; Section 1, Introduction; Section 6, Summary
Designed, not yet built02The driver efficiency is the argument for the approach. Plasma guns may convert wall-plug electricity to directed plasma energy at up to about fifty per cent, against under two per cent for a laser driver once beam production and hydrodynamic coupling are both counted — so laser-driven inertial fusion may need a gain at least twenty-five times greater just to recover what its driver loses.Section 1, Introduction, second page
Published and peer-reviewed03The gun is a power amplifier as well as an accelerator: kinetic energy is accumulated slowly, over about a metre of barrel and more than five microseconds, then delivered in under a tenth of a microsecond across less than a centimetre, which amplifies the imploding power flux density by three to four orders of magnitude.Section 1, Introduction; Figure 1 caption
Published and peer-reviewed04The design point is quantitative. Twelve coaxial Marshall-type guns in a circle form a two-dimensional cylindrical liner; each jet carries 0.2 to 0.4 milligrams at two hundred kilometres per second from a gun no longer than one metre with a muzzle under 0.2 metres, launched with a timing precision better than a hundred nanoseconds. The full three-dimensional version uses as many as sixty guns, a total liner energy of about 0.4 megajoules and a liner mass of twenty milligrams, at about a third of a milligram per jet.Section 2, Experimental Goals and Parameters; Section 3, The Physics and Technology Requirements; Section 6, Summary
Designed, not yet built05The pulsed power was sized by simulation rather than assumed: a two-section pulse forming network per gun with capacitors of 17.5 microfarads charged to forty kilovolts, an output-stage inductance held under sixty nanohenries and a second-stage inductance under fifty, with the current per capacitor limited to about five hundred kiloamps. The analytic starting point gives a net electric-to-kinetic efficiency near thirty-two per cent, consistent with experience from pulsed plasma thrusters.Section 4, The Plasma Accelerator; Table 1, the fifteen-case parametric scan; Section 6, Summary
Designed, not yet built06What to watch: three-dimensional smoothed-particle-hydrodynamics modelling with the Los Alamos SPHINX code already shows the jets merging into cylindrical and spherical shells capable of compressing a target to thermonuclear conditions, and a zero-dimensional model indicates gains above seventy; an Air Force Research Laboratory experiment at Kirtland in the late 1980s, following earlier work at Sandia, formed an imploding cylindrical plasma from a circular array of twelve and twenty-four radial discharges. What nobody had done, and what PLX exists to measure, is forming a liner from detached jets carried more than a metre from their electrodes at the momentum flux density this programme needs.Section 3, closing paragraphs and Figure 3(c); Section 2, opening
What to watch
Read it · abstract
Abstract
Momentum flux for imploding a target plasma in magnetized target fusion (MTF) may be delivered by an array of plasma guns launching plasma jets that would merge to form an imploding plasma shell (liner). In this paper, we examine what would be a worthwhile experiment to do in order to explore the dynamics of merging plasma jets to form a plasma liner as a first step in establishing an experimental database for plasma-jets-driven magnetized target fusion (PJETS-MTF). Using past experience in fusion energy research as a model, we envisage a four-phase program to advance the art of PJETS-MTF to fusion breakeven (Q of about 1). The experiment (PLX) described in this paper serves as Phase 1 of this four-phase program. The logic underlying the selection of the experimental parameters is presented. The experiment consists of using 12 plasma guns arranged in a circle, launching plasma jets toward the center of a vacuum chamber. The velocity of the plasma jets chosen is 200 km/s, and each jet is to carry a mass of 0.2 mg to 0.4 mg. A candidate plasma accelerator for launching these jets consists of a coaxial plasma gun of the Marshall type.
Y. C. Francis Thio, Charles E. Knapp, Ronald C. Kirkpatrick, Richard E. Siemon and Peter J. Turchi, A Physics Exploratory Experiment on Plasma Liner Formation, Journal of Fusion Energy 20, issue 1-2, pages 1 to 11 (2001). The NASA-released manuscript is document 20020066592 at the NASA Technical Reports Server.
(Abstract only — no other text of the article is reproduced here; see the rights note above. On this site, the magnetized liner inertial fusion design for the Z facility is at /library/stm-57d0076dfb, the anomalous pressure measured on a magneto-inertial fusion load current diagnostic is at /library/stm-4b4aa19d9f, the twelve axioms of fusion energy research and development are at /library/stm-ec19ca9fbf, advanced nuclear propulsion for manned deep space missions is at /library/stm-c75846c5a6, and the US government panel that cited this work when it put space propulsion on the national list of non-electric fusion applications is at /library/stm-23ddebaf70.)
The way in
https://doi.org/10.1023/a:1019813528507The published article is held closed by Springer. The authors’ manuscript is public as NASA Technical Reports Server document 20020066592, released by Marshall Space Flight Center with the copyright determination GOV_PUBLIC_USE_PERMITTED, no copyright indication and no publisher claim; that twenty-three-page document was downloaded and read in full on 2026-09-08, and every claim below is located to one of its numbered sections, tables or figures. Its scan carries an imperfect text layer — km per second appears as kin/s, several equations and the energy-source table are mangled — so nothing beyond the abstract is reproduced here rather than risk transcribing a garbled number as science. The abstract is the paper’s own, identical in the NASA record and in the publisher’s deposited metadata. Affiliations as printed on the manuscript: Thio at NASA Marshall Space Flight Center, Huntsville; Knapp, Kirkpatrick and Siemon at Los Alamos National Laboratory; Turchi at the Air Force Research Laboratory, Kirtland Air Force Base.
How to cite it
Y. C. Francis Thio, Charles E. Knapp, Ronald C. Kirkpatrick, Richard E. Siemon, Peter J. Turchi (2001) A Physics Exploratory Experiment on Plasma Liner Formation. doi:10.1023/a:1019813528507
Where it sits in the curriculum
Plasmoids, charge clusters and the orbsLattice confinement fusion