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This Defense Intelligence Agency reference document, dated 10 March 2010, covers inertial electrostatic confinement (IEC) fusion. It was produced in FY 2009 under the DIA's Advanced Aerospace Weapon System Applications (AAWSA) program. The report focuses on work at the University of Illinois Urbana-Champaign and reviews IEC basics, experiments, theory and applications such as neutron sources, explosives detection and space propulsion. It concludes by proposing a breakeven experiment for p-11B fusion that uses a hydrogen plasma simulation.
“BEAMS”43 pages
UNCLASSIFIED/ /FOR QFFlil.l1ls WfilE 8HLV constraint on any Spherical IEC 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 addition 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 • nbk ~ nb • p while beam-beam fusion goes as nb 2 . 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 applications. 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 openings 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." 8 UNCLASSIFIED/ ,'P8"1 8PPll!l"'I! l!l!il! 8111!¥
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Report, from the dia collection. The PDF is mirrored here; the original link is under it. 72 pages are in the text index: search them above, or from the library's search.