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AAWSAP DIRD, Inertial Electrostatic Confinement Fusion, March 2010

U.S. Department of War · 2010-03-10 · 72 pages · text from the file's own layer

This Defense Intelligence Reference Document, dated 10 March 2010, was prepared by the Defense Intelligence Agency's Defense Warning Office under the Advanced Aerospace Weapon System Applications Program. It surveys the basics, experimental status, theory and possible uses of inertial electrostatic confinement (IEC) fusion, with emphasis on work at the University of Illinois Urbana-Champaign. It covers neutron sources, explosives detection and space propulsion. It ends by proposing a 12-gun hydrogen plasma experiment meant to show breakeven conditions for p-11B fuel.

From the source: Release of 2026-09-18 Incident: 3/10/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys inertial electrostatic confinement (IEC) fusion, a relatively unconventional fusion concept that uses electric fields rather than the more established magnetic or laser-based approaches to confine ions, and it reviews both the underlying physics and the experimental work associated with the concept. The report emphasizes that IEC may have nearer-term value as a compact neutron, proton, or x-ray source and as a platform for studying experimental fusion approaches, while also presenting more ambitious possibilities such as aneutronic power generation and propulsion applications. At the same time, it makes clear that the concept remained far from practical fusion power, with experimental devices operating several orders of magnitude below breakeven and with major unresolved issues involving confinement, losses, grid damage, and scale-up. Overall, the document treats IEC as a technically interesting but still highly speculative path toward fusion energy, while suggesting that its more limited spin-off applications were more plausible in the near term than its long-range power generation or propulsion applications.

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constraint on any Spherical !EC device planned for these applications. The observed
loss of convergence with decreasing pressure and increasing current makes achieving
significant beam -beam scaling far less favorable ."
In add ition to the issue of beam -background fusion dominating in the gridded systems
at higher pressures, Thomson pointed out the importance of energetic ions undergoing
charge exchange and being lost from the system. This work and others on the small
gridded systems at that time showed several important problems which are best
understood by considering beam-background vs. beam -beam fusion scaling. The former
scales with density and pressure as nb • nok ~lilb • p while beam-beam
fusion goes as nb2 .
Here: nb = beam ions per cm 3 ; nbk= background atoms per cm 3 ; p = background
pressure; is the fusion reactivity averaged over the appropriate beam
background (or beam-beam) distribution functions.
If ions are produced as done in most small gridded experiments by electron ionization
collisions with neutral gas during a plasma discharge between the grid and vacuum
vessel wall, reduction of background gas pressure will also reduce the ion source,
reducing the reaction rate. Thus, it becomes apparent that to get the favorable beam
beam scaling needed to go into the power reactor regime, ions must be produced
externally while the main reaction chamber is keep at very low background pressure to
avoid charge exchange losses. Indeed, without explaining that this was the reason,
Hirsch used external ion '\guns" in his early experiment at Farnsworth labs. The present
author (G. Miley), however, went back to the internal discharge ion source technique to
simplify the device for portable neutron source appli,cations. Power devices will need to
go back to external production of some type however. Again, this issue will be
addressed further later.
While earlier workers sought small grid open ings designed to provide uniform ion flows
for good core plasma convergence (stressed in the earlier papers already noted), Miley
disclosed in a paper in Reference 1.5 that the STAR mode could be produced with wider
grid openings. In fact, Miley noted that three key modes can be formed in gridded IECs
depending on the pressure and grid openings. These are described as:
"Glow discharge operation of the IECGD is categorized by three distinct discharge
"modes": Star, Central Spot, and Halo (illustrated in Figure 1.3). These names are quite
descriptive of the visual appearances of the visible light emitted from the discharges. All
three modes are reproducible and stable; each is associated with a different potential
well structure, hence neutron production rate. The star mode was used extensively in
recent experiments. It is distinguished by microchannels or "spokes" radiating outward
from a bright center spot (Figure 1.4). As verified by magnetic deflection experiments,
the spokes are primarily composed of ion beams aligned so that they pass through the
center of the openings delineated by the grid-wires. This mode is very efficient for
neutron production, since the large effective grid transparency allows numerous passes
of ions through the center spot before being intercepted by the grid or being ion by
charge exchange. The Star mode is typically obtained at lower operating pressures
(30 kV), using a carefully formed grid with good
sphericity and high transparency (>95 percent). The halo (or "jet") mode occurs when
one of the grid openings is slightly enlarged compared to the others."
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 72 pages are in the text index: search them above, or from the library's search.