STM-D-0945Paper2009Published and peer-reviewed

Deuterium anions in inertial electrostatic confinement devices

D. R. Boris · E. Alderson · G. Becerra · D. C. Donovan · B. Egle · G. A. Emmert · L. Garrison · G. L. Kulcinski · J. F. Santarius · C. Schuff · S. J. Zenobia

Abstract and summary · read the original at the source · APS default licence

In one page

An inertial electrostatic confinement machine is a vacuum chamber with a see-through wire cage at its centre, held at a hundred thousand volts negative. Deuterium ions fall inwards through the gaps, oscillate through the middle, and some of them fuse. Everyone had assumed the traffic was positive. D. R. Boris and colleagues in Gerald Kulcinski’s group at the University of Wisconsin–Madison put two instruments on their machine — a magnet that sorts charged particles by mass and speed, and a shielded current collector — and found deuterium ions carrying a negative charge streaming out of it. The energy spectra separate how they are made: ions that pick up two electrons from background gas on the way in, and ions built right at the glowing cathode when a slow electron attaches to an excited deuterium molecule. Some survive as whole molecules long enough to fly forty centimetres to the detector. The negative current is not a curiosity — the team estimates about a milliamp of it, flowing in channels set by the cage geometry.

Why it matters hereChapter 9 studies plasma that organises itself into structure, and this paper shows an inertial electrostatic device sorting its own particles into beams and channels that nobody designed; chapter 12 keeps the ledger of fusion routes, and this is the one an ordinary laboratory can own — instrumented here well enough to reveal a whole population of carriers the standard models of the device had left out.

What it claims

01Deuterium ions with a negative charge stream out of a gridded inertial electrostatic confinement device in quantity: current densities as high as 8.5 microamps per square centimetre were measured at the wall of the Wisconsin machine, forty centimetres from the cathode surface, with a collector of admittance area 0.7 square centimetres.Abstract; Section II E, Faraday trap results
Published and peer-reviewed
02The energy spectrum taken at a hundred kilovolts resolves five separate populations: three born in the space between the grids when fast positive molecular ions capture electrons from the background gas, and two born at the cathode itself when a slow electron attaches to an excited deuterium molecule.Section II B and II C; Figures 4 and 5, the five-Gaussian fit
Published and peer-reviewed
03Whole molecular anions survive the trip. Their flight distance implies a metastable lifetime of at least about half a microsecond, and the ratio of molecular to atomic anions formed at the cathode came out between 0.5 and 1 — many orders of magnitude above the roughly one-in-a-hundred-thousand ratio reported for caesium-sputter sources, and in line with the 0.35 to 0.4 seen in dielectric barrier discharges.Section II C, Discussion of the magnetic deflection-energy analyzer results
Published and peer-reviewed
04Along the line of sight measured, secondary electrons are the minor part of the outgoing negative current, not the major one: switching on a hundred-gauss deflecting field removed only eighteen per cent of the collected current, and raising it to four hundred gauss removed a further two per cent, showing the remainder is genuinely made of ions.Section II E, Experimental results, Faraday trap
Published and peer-reviewed
05The outgoing negative flow is not uniform but channelled: the potential dips around the individual cathode wires focus anions and electrons into beams, the collected current differed by a factor of five between two viewing positions, and scaling one channel to the 230 openings of the cathode gives a total anion current of roughly 0.5 to 1.5 milliamps.Section II E and Section II E 2; Figures 9, 10 and 12
Published and peer-reviewed
06What to watch: the authors name their own next measurement — a multichannel array of Faraday cups to map the angular structure of the anion and electron beams, which would settle quantitatively how much of the cathode current these negative species carry, and how far the same physics explains the divergent flows seen in other hollow-cathode devices.Section II E 2, closing paragraphs; Section III, Conclusions
What to watch

Read it · abstract

Abstract

A magnetic deflection-energy analyzer and Faraday trap diagnostic have been used to make measurements of divergent deuterium anion flow in the inertial electrostatic confinement experiment at the University of Wisconsin–Madison (UW-IEC) [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, I. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)], a device to confine high-energy light ions in a spherically symmetric electrostatic potential well. Deuterium anion current densities as high as 8.5 microamps per square centimetre have been measured at the wall of the UW-IEC device, 40 cm from the surface of the device cathode with a detector assembly of admittance area 0.7 square centimetres. Energy spectra obtained using a magnetic deflection-energy analyzer diagnostic indicate the presence of D2 minus, and D minus ions produced through thermal electron attachment near the device cathode, as well as D minus ions produced via charge-transfer processes between the anode and cathode of the device.

D. R. Boris, E. Alderson, G. Becerra, D. C. Donovan, B. Egle, G. A. Emmert, L. Garrison, G. L. Kulcinski, J. F. Santarius, C. Schuff and S. J. Zenobia, Deuterium anions in inertial electrostatic confinement devices, Physical Review E 80, 036408 (2009); received 18 March 2009, published 30 September 2009. All eleven authors are at the Fusion Technology Institute, University of Wisconsin–Madison, 1500 Engineering Drive, Madison, Wisconsin.

(Abstract only — see the rights note above. On this site, the same Wisconsin device’s space-charge neutralisation is at /library/stm-5c07c85688, the neutron production rate and plasma characteristics of spherically convergent beam fusion are at /library/stm-e386fdbf31, a particle-by-particle model of a cylindrical inertial electrostatic device is at /library/stm-0b806244cb with the experimental study of its discharge plasma at /library/stm-218a859c1b, the Defense Intelligence Reference Document on the approach is at /library/stm-cac9786426, Philo Farnsworth’s founding patent is at /library/stm-3a226d4c01, and the US government panel that put these devices on the national list of non-electric fusion applications is at /library/stm-23ddebaf70.)

The way in

https://doi.org/10.1103/physreve.80.036408Published as Physical Review E 80, 036408 (2009) under the APS default licence, with no Creative Commons statement, so the sheet stays abstract-only. The full nine-page article was read on 2026-09-08 through the APS full-text endpoint at harvest.aps.org, and every claim below is located to a numbered section or figure of it. The abstract is the published one; the subscripts and superscripts of the original (the D2 minus ion, microamps per square centimetre) are rendered inline so the page displays. The work comes from the Fusion Technology Institute at the University of Wisconsin–Madison.

How to cite it

D. R. Boris, E. Alderson, G. Becerra, D. C. Donovan, B. Egle, G. A. Emmert, L. Garrison, G. L. Kulcinski, J. F. Santarius, C. Schuff, S. J. Zenobia (2009) Deuterium anions in inertial electrostatic confinement devices. doi:10.1103/physreve.80.036408

Where it sits in the curriculum

Plasmoids, charge clusters and the orbs Lattice confinement fusion