STM-D-0573Paper2004Published and peer-reviewed

Pinch evidence in a fast and small plasma focus of only tens of joules

Patricio Silva · Leopoldo Soto · Walter Kies · José Moreno

Abstract and summary · read the original at the source

In one page

A plasma focus is a beautifully simple machine: dump a capacitor bank into a pair of coaxial electrodes filled with gas, and the current sheet it drives runs down the barrel, folds over the end and collapses onto the axis into a dense, hot pinch. For decades that only worked in machines storing kilojoules to megajoules. Patricio Silva, Leopoldo Soto, Walter Kies and José Moreno built one storing tens of joules and showed that it still pinches. Their device is small and fast — a 160 nanofarad bank, 38 nanohenries of inductance, charged to between 20 and 35 kilovolts for 32 to 98 joules, with the current rising in about 150 nanoseconds — and the whole point of the design is that the energy density matches that of the big machines even though the stored energy is thousands of times lower. Running on deuterium at 50 and 67 joules they see both classic pinch signatures: the dip in the current derivative and the peak in the voltage.

Why it matters hereChapter 12 needs a compact, high-density plasma source that a small team can actually build and iterate on, and this paper is the measurement that moved the plasma focus from a hall-sized machine to a bench-sized one without giving up the plasma conditions. Chapter 9 studies self-organising, self-compressing plasma structures, and the pinch is the cleanest laboratory example of one.

What it claims

01A deuterium-filled plasma focus storing only tens of joules produces a pinch: the typical dip in the current derivative signal and the typical peak in the voltage signal — the same signatures associated with pinch compression in devices of 1 to 1000 kilojoules — were observed at 50 and 67 joules.Abstract, first and third sentences; title
Published and peer-reviewed
02The device is a fast, small system: a 160 nanofarad capacitor bank, 38 nanohenries of circuit inductance, charged between 20 and 35 kilovolts for a stored energy of 32 to 98 joules, with a current rise time of about 150 nanoseconds.Abstract, second sentence
Published and peer-reviewed
03The design rule the work demonstrates is that the quantity to hold constant when a plasma focus is scaled down is the energy density, not the stored energy: the small device maintains the same energy density as large devices while operating three to four orders of magnitude lower in stored energy.Abstract, second sentence
Published and peer-reviewed
04The time to pinch and the time to peak current were measured as functions of the deuterium filling pressure, giving the operating map a small plasma focus needs in order to be tuned to the pinch.Abstract, final sentence
Published and peer-reviewed
05The evidence presented here for the pinch is electrical — the current derivative dip and the voltage peak — so the measurement that extends the result is a direct fusion yield from a device of this size, which is the line of work the Chilean group carried forward into progressively smaller devices.Abstract, third sentence
What to watch

Read it · abstract

Abstract

The pinch evidence in a deuterium-filled plasma focus (PF) of only tens of joules is presented. The system operates at a very low energy in the tens of joules range (160 nF capacitor bank, 38 nH, 20–35 kV, 32–98 J, about 150 ns current rise time), maintaining the same energy density as in large devices. The typical dip in the current derivative signal and the typical peak in the voltage signal observed in PF devices with energies of 1–1000 kJ, which are associated with pinch compression, were observed in a deuterium-filled PF operating at 50 and 67 J. The time to pinch and time to the peak current versus deuterium filled pressure were also obtained.

Patricio Silva, Leopoldo Soto and José Moreno, Comisión Chilena de Energía Nuclear, Santiago, Chile; Walter Kies, Heinrich-Heine-Universität, Düsseldorf, Germany. Plasma Sources Science and Technology 13 (2004) 329–332; received 15 December 2003, published 4 May 2004.

(Abstract only — see the rights note above. On this site, Eric Lerner’s progress report on proton-boron-11 fusion with the dense plasma focus is at /library/stm-05100e66da, and Sing Lee and Sor Heoh Saw’s numerical experiments on plasma focus scaling are at /library/stm-fbd01b5713.)

The way in

https://doi.org/10.1088/0963-0252/13/2/020Published in Plasma Sources Science and Technology and marked ’© 2004 IOP Publishing Ltd’ with no Creative Commons statement. The article page is subscription-gated — the open-access flag carried by the aggregator indexes is not borne out at the publisher — so this page carries the summary, the claims and the authors’ own abstract, and sends the reader to the source.

How to cite it

Patricio Silva, Leopoldo Soto, Walter Kies, José Moreno (2004) Pinch evidence in a fast and small plasma focus of only tens of joules. doi:10.1088/0963-0252/13/2/020

Where it sits in the curriculum

Plasmoids, charge clusters and the orbs Lattice confinement fusion