“BEAMS”43 pages
- p. 5 …Sketch of Two Opposite Limits of the Beam·Maxwellian Equilibrium .. 38
Figure 4.5. The Definition…
- p. 6 …Comparison of Analytical and Numerical Estimates of Q-Values in a
Beam-Dominated Solution -- for a…
- p. 8 …shows the "Star
Mode" discharge where ion beams are created that pass through the grid openings…
- p. 9 …discussed later where the recirculating ions possess
beam-like trajectories passing through the center of the…
- p. 10 UNCLASSIFIED/ ;raA 8FFIIItliL ~81!! SHL'f
beam-like ions. Since electron energy loss processes such as…
- p. 11 …In addition, its beam-like reactions (highly non-Maxwellian)
make the IEC very well suited for…
- p. 13 …a beam created at the anode and accelerated by the applied cathode
voltage; a low-energy…
- p. 14 …Good convergence is required to achieve
optimal beam-beam reactivity scaling for the application that require…
- p. 15 …The observed
loss of convergence with decreasing pressure and increasing current makes achieving
significant beam-beam…
- p. 16 …For a power reactor the objective is to obtain ion
beam-beam collisions in this central…
- p. 17 …the "conventional" beam-like
one. A key issue for this concept is how much plasma compression…
- p. 19 …The
main beam observed is a direct path along the injector
angle. Other faint light channels…
- p. 21 …Note that six ion "guns" were used to create a low energy ion beam that entered…
- p. 22 UNCLASSIFIED/;SflHl 8FFIIItliL ~81!! 8HL'I'
was obtained from recirculation beam-beam reactions in a potential…
- p. 23 …The key physics point is
that the beam-beam fusion rate scales as the ion current…
- p. 26 …Scoping calculations of beam-background fusion rates predict that a 3 He- 3 He reaction
product…
- p. 27 …of the ion density squared
scaling for beam-beam reactions.
REFERENCES
2.1 R. L. Hirsch…
- p. 28 …As such, the beam convergence (compression) is
limited to lower values, hence lower core densities (an…
- p. 30 …by
the intersection of the multiple ion beams, serves to deflect ions into the escaping jet…
- p. 31 …The result is the
formation of the intense space charge neutralized ion beam (or "plasma jet…
- p. 32 …in the
symmetric microchannels into a directed beam or jet.
Comparison to a Conventional "Plasma" Thruster…
- p. 33 …The ion beams finally exit through an opening in the ground sphere of the IEC device…
- p. 35 …These devices operate with ~ 80- keV D-ion beams using the non-Maxwellian
character of the…
- p. 36 …Two ion sources inject
40-keV deuterium and helium-3 ion beams toward the center of…
- p. 37 …Indeed in this case fusion is dominated by beam-beam (non-
Maxwellian reactions). Also, the dipole…
- p. 38 …the center potential and consequently allow incoming
beam ions to penetrate into the core region. In…
- p. 39 …Comparison of Analytical and Numerical Estimates of Q-values in
a beam-Dominated Solution -- for a…
- p. 40 …Hora, "Converging Beam Neutron Source for
Driving a Sub-critical Fission Reactor", Proceedings, ICONE 8, CD…
- p. 41 …Namely, the time scale for
collisional degradation of the beam-like ion distribution function is crucial…
- p. 42 …For example, a tightly focused monoenergetic ion beam is in
fact a pessimistic scenario, because different…
- p. 44 …Thus, weak sinks and strong sources will result in a
large beam population, increasing the beam…
- p. 45 …Sketch of Two Opposite Limits of the Beam-Maxwellian Equilibrium. The solid line
corresponds to a…
- p. 46 …injected beam current, average injection energy, energy spread associated
with the velocity component in both parallel…
- p. 47 …As stated in Section I, the current scaling
for beam-beam reactions is strictly 12. However…
- p. 48 …is very encouraging for formation of deep wells
in IEC devices designed for reactors using beam…
- p. 49 …To do this, it is
assumed that the electrostatic confinement equilibrium ion beams are proportional to…
- p. 50 …When an ion beam is hot, the waves excited by the instability are ion acoustic
type…
- p. 51 …Rider was particularly interested in the claim that due to its beam-like non-
Maxwellian plasma…
- p. 52 …Diagram Showing Equipotential
Surfaces of the IEC Cathode Grid and Their
Focusing Effect on a Beam…
- p. 59 …of detectors, the detector configuration, the collimated
beam size, the acquisition time, and other scan-related…
- p. 63 …Alternately, for space
propulsion, the proton beam, augmented by injection of heavy atoms to increase the…
- p. 68 …Due to its inherent non-Maxwellian (beam-like)
plasma, the IEC is especially well suited for…
- p. 70 …This configuration is highly
non-Maxwellian due to the beam
dominated nature of the trapped ions…
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gridded IECs. Further, the model provides more insight into operation in the STAR
mode. This effect, described earlier in Section 1, is summarized in Figure 4.11.
For higher pressure operation, charge exchange severally limits the number of passes
possible through the grid despite the very high effective transparency achieved by the
STAR mode. This is emphasized by results for the calculations in Reference 4. 7 shown
in Figure 4.12. (Note that related calculations by J. Khachan discussed earlier in Section
II show similar results, but emphasize the role of molecular ions at lower operating
voltages).
Figure 4.11. Diagram Showing Equipotential
Surfaces of the IEC Cathode Grid and Their
Focusing Effect on a Beam of Ions in the star
Mode Discharge at High Voltages(> 50 keV)
Ion Energy Distributions 1st paH
2 cm grid radius, &O kV, 4.8 mTorr
2 .OE+07 ,--------:-c----i
• 1.5E+07
•.2 1 OE:+07 t- --=~
- 5.0E-+00
O.OE+OO
0 20000 """"
ton Energy leVI
1--= lwf ....-Cnll-il
'1--- ...... •c...,.. 'I
--- ..... ~ C.r'4
~ I
Figure 4.12. Results for Calculations for Ion Energy
Distributions is• Pass
These computational results are for the UIUC IEC "A-device" using a diameter grid with
conditions of 50 kV, 10 mA, and 4-cm, and background gas pressure of 4.6 mTorr. At
this pressure, charge-exchange (CX) collisions occur quite frequently for D+ ions. In
their first pass through the IEC, about half of these ions CX within the cathode region
and are lost. After only four passes, most of the remaining ions have lost a large
amount of their original potential energy and the fusion rate from subsequent passes
becomes negligible. D2+ ions have a smaller CX cross section and it takes about 20
passes for most of the D2+ ions to lose their energy and be lost to the grid. (D2+ ions
and also D3+ ions are naturally produced at diminishing quantities in ionization reactions
along with o+. As pointed out by Khachan his work noted D2+ becomes more significant
in lower voltages).
In summary, the design of an optimal IEC neutron source is seen to be quite different
from a power-producing IEC. In the source design, the grid parameters, grid/vessel
diameter ratio, chamber diameter, surface conditions, background pressure, current,
and voltage all become important parameters. In power-producing devices the ion
injection parameters-- including ion current, ion energy relative to height of the well
potential, the ion angular momentum, and the ion to electron temperature ratio, along
with the chamber diameter ---determine performance. The calculations and simulations
cited here provide much insight into these issues and also provide insight into
theoretical and computational tools for IEC study.
45
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