AAWSAP DIRD, Inertial Electrostatic Confinement Fusion, March 2010

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An added long-term potential advantage of developing the !EC-jet thruster is that the
concept can eventually be extended to an ultra high impulse fusion power/propulsion
unit. Indeed, the thruster concept arose from work on a fusion based IEC (Reference
3.5). To move to fusion power, however, would require advances such as discussed for
terrestrial IEC power plants as Section VI.
JET Extraction From a Spherical IEC
A plasma jet can be extracted from the gridded spherical IEC by enlarging a grid
opening. This forms the basis for various exciting applications including a jet thruster
and various plasma processing uses such as gasification of municipal wastes and future
materials recycle. Here, to illustrate this asymmetrical geometry, we briefly consider
the IEC jet thruster for use in satellite operations and maneuvering (Reference· 3.6).
Description of the IEC let Thruster
For conventional star mode operation, such as discussed earlier, the IEC grid is
designed to be highly symmetric so that the microchlannel beams are also symmetric,
providing good convergence. However, experiments have demonstrated that enlarging
one of the grid openings distorts the potential surfaces. This results in the creation of a
very intense, tightly coupled space-charge-neutralized ion jet directed outward from the
central core plasma region (see Figure 3.2) (Reference 3. 7), and it is this mode of
operation (star with jet) that would be employed for the proposed thruster.
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(a)
(b)
Figure 3.2. (a) Jet Operational Mode in Experimental IEC Device and (b) Jet Set-up
The jet formation has been explained theoretically (Reference 3.5) in terms of the large
distortion of the potential surface at the enlarged grid opening. The local gradient
initiates electron flow that in turn drags ions out across the surface. The result is the
formation of the intense space charge neutralized ion beam (or "plasma jet") at that
location. Such operation has been routinely obtained in laboratory IEC devices under
steady-state operation, with the plasma jet being maintained for hours. The power
carried by the jet has been demonstrated by heating a target plate placed in its path.
Over half of the energy imparted to the ions by the accelerating grid is effectively
funneled into the jet, and no major losses of ions to the vacuum chamber wall or grid
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