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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//F'iA. 'iFFllilCk l,llilii 'iClk;y Jet Extraction To obtain thrust from an IEC device, a valley or trough must be created in the electrostatic potential, and a hole must be physically cut into the ground sphere. This allows high-speed ions to escape in the form of a plasma jet as described in the preceding section. Ions are generated near the ground potential with the aid of electron emitters and additional grids. A central spherical electrical grid accelerates ions to the core region. A cylindrical "channel" grid with the same electrostatic potential as the central spherical grid creates a passage through which ions can escape to the outside. Thus this trough in the electrostatic potential profile across the centerline (thrust axis) of the IEC thruster is a unique feature compared to the linear profile for a planar device. The ion beams finally exit through an opening in the ground sphere of the IEC device. The channel grid must be well insulated from the ground potential to prevent short- circuiting or arc-over; thus a separate insulated feed-through cable maintains the negative potential on the inner spherical and channel grids. Makeup propellant gas is fed into the ionization region through needle-valve-controlled tubing located around the chamber wall. Ionization of the propellant uses the electron emitter-guide grid design described earlier. The inner grid serves to both extract and accelerate ions, forming the microchannels. To control neutralization of the plasma jet, additional electron emitters are attached close to the jet discharge hole. A combination of electron emission rates and jet grid bias can be used to control the beam space charge, hence the growth of focusing of the beam during propagation. In present experiments, however, the electron rate is fixed at a suitable value while the jet grid bias is varied. Control of the jet diameter and focus is obtained in two ways: first, the channel grid will be separately hinged with a small servo motor such that its axis can be moved over a volume defined by a 10 percent cone angle; second, the grid bias can be varied over a range up to the chamber potential to provide focus control over the jet flow. A large negative grid bias will cause a narrow focus while small potential values will allow the plasma to expand giving a broad cross section beam. Experimental Jet Design and Performance Figure 3.3 shows the thruster experiment components. It is also of interest to consider the typical dimensions involved to illustrate the compactness of the unit. The experimental studies use an existing spherical IEC chamber of ~30-cm with a 1-cm diameter port on one side of it for beam extraction. (This is somewhat larger than envisioned for application to micro-satellites). An 8-cm diameter spherical electrical tungsten or tantalum wire grid, having a geometric transparency of ~90 percent, will mount inside the chamber. A ~1-cm diameter hole will be cut into the side of the wire grid, and this hole will be aligned with the hole in the chamber wall and connected to it by a 2-cm diameter cylindrical guide grid. The insulator covering the grounded wall must be of sufficient size to prevent arc-over from the ground to the cylindrical grid. The inner electrical grids are connected to a 500-kV de power supply through the insulated feed-through cable. A positively-charged outer grid with a variable voltage of ~ 10-100 Vis mounted on a swivel connector at the outside of the beam extraction port of the chamber, in combination with four electron emitters, generates ions. The choice for the voltages on the outer grids is flexible, so long as a sufficient ion 26 UNCLASSIFIED/ ,u;oAt OFFIGIPk IP&'i Ollk¥
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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.