Vital Electric Fusion: Proven, Safe, Cheap

Energy device in funding limbo for two decades -- dying on the vine for lack of nuclear weapons potential.

US Physicist Dr. Robert W. Bussard has produced proven, consistent, working prototypes of a fusion device that does not need to release neutrons as part of the fusion process.

Neutrons induce radioactivity to their immediate surroundings. Bussard's method does not do this.

This just one of the major drawbacks of other fusion projects such as the Tokamak project. The massive (30 meters X 110 feet) Tokamak/ITER project (D-T/Deuterium - Tritium) fusion reaction produces about 20 million units of energy mostly in the deadly neutron (neutral charge) production and requires gravitational strength containment/compression.

In contrast, Bussard's Inertial Electrostatic Confinement (IEC) Fusion reaction produces about 10 million units of energy per reaction, requires much weaker electric forces/fields for confinement of the reaction and is only about 2% of the size (about 15 X 12 feet) of the Tokamak reactor.

Radioactive Tokamak technology has received 18 billion dollars of US subsidy with 30 billion more earmarked for future development. There has never been a working prototype of ITER technology. Funding is based on theories and equations. A working model is not even anticipated for another 30 to 50 years. There are many proponents of Tokamak that believe that this technology will never be economically viable and others that believe it will never come to fruition at all. In contrast, IEC/Electric fusion devices are smaller, significantly more economical, non radioactive, has had working prototypes producing 10 kv of energy, much more likely to be a viable option, and could come to reality in about 5 - 6 years from appropriation of 200 million dollars. That is less than the cost of one day of economic support for the Middle East oil wars without a single loss of life; and is a mere 1/90th of what has been spent on D-T fusion.

Dr. Bussard's IEC fusion advancements are based on the 1924 concepts of Langmuir and Blodgett, the efforts of Watson in 1959, and the developments of Philo Farnsworth and Robert Hirsch. These early works all involved the use of a grid which defeats the process involved. The Polywell device using magnetic fields removes the hindrance of the previously required grids in the fusion reactors (fusors). Over the years there have been isolated reports on Dr. Bussard's works similar to ex-NASA employee Kelly Starks' 1996 post, but as usual, the corporate media has been and is still currently ignoring this major breakthrough in energy production.

In 1996, through some awesome diplomatic expertise (along with the assistance of several patriot scientist friends) Bussard landed a deal with the DOD/DARPA for 50 million dollars and 12 years of research. Four moths later when the DOD found out what they were getting, they cancelled the contract by saying that the DOD doesn't do fusion? With the approximate $6 million dollars (by Bussard's general statement and $14 million by the navy's specific statements) he funded a renowned scientist working on revolutionary clean fusion, 5 - 10 members, 35% overhead for filling in 64,000 pages of documents, the first machine (very expensive for its stage), and 12 years of work. One million dollars worth of equipment was saved by transferring it to a propulsion lab. It is amazing what they were able to accomplish with so little money.

Part of the 50 million deal that turned into 6 million was an agreement that Dr. Bussard not publish -- a complete gag order. For 6 million the DOD took away all knowledge of clean, safe energy from The People, virtually assured a non-viable product, and was able to keep massive funding to D-T fusion (Thermonuclear Weapons), and allows continued experiments for the development of thermonuclear weapons, such as the Bunker Buster B-61. When the 12-year contract expired and was not renewed, Dr. Bussard was able to publicize his accomplishments. This knowledge of clean energy must be exposed to the world.

It's been a year since the DOD/DARPA refused to renew the IEC contract. Since then, Dr. Bussard has tried desperately to get exposure for his breakthrough technology and possibly planet-saving technology. He presented a paper at an International Conference in Spain. He has also made presentations to corporations as a profit venture.

Only after his fusion efforts had shown proof of fusion and had won the Outstanding Technology of the Year award did the DOD renew the contract. But they did not fund it. It looks like the DOD has stifled the information and is under-funding it again. However, the crucial information for the technology is available to any scientist, group, or nation that stumbles across it and is willing to invest.

Dr. Bussard's excellent 93 minute taped presentation to Google explains the Electric Fusion process in basic physics context and concepts in a way that most with a minimal background of basics physics can relate. The video contains a lot of the previously noted information as well as his well-founded belief that the physics of IEC is proven and merely awaits engineering development which already exists, but needs to be applied to this particular instance. Data being consistent with IEC fusion statements, it certainly appears the essence of what Bussard says is true. Refinement of semi-sphere electromagnet shapes and placements still needs further evaluation. Significantly more energy is required for the Boron non radioactive fusion reaction. The equipment must be tested for viability, dependability and durability when running in a steady state and will need to be refined. A large number of variables - heat, pressure, introduction, removal, collection, etc - will need to be fine tuned for continuous vs pulsed operation. Time is also of the essence and one year's worth of precious time has already been wasted.

"At 78, he (Bussard) is in ill health and his scientific allies fear that the long-sought breakthrough he appears to have achieved may fade into obscurity before it can be fully developed." Dr. Bussard believes there may only be about 5 people on the planet with the background, experience, training and qualifications to make in-depth evaluations and comments regarding IEC fusion. Bussard is the foremost expert on IEC fusion. His loss would surely be a significant hindrance to the completion of the project. Is the DOD trying to stall to insure massive continued funding for nuclear weapons and oblivion of safe and cheap energy?

The title 'Technology for the Year" hardly does this discovery justice. Electric Fusion is the "Technology of the Century". Millions could gain access to cheap energy and pure water as a result.

The potential of one Electric Fusion reactor is impressive. Google rumors IEC output to be in the range of between 100 MW and 1,000 MW (100,000 to 1 Million kW). To be able to grasp the amount of energy produced, the average home usage peaks at 3 to 4 kW for about 4 hours a day. One Electric Fusion device would provide the peak power for 25,000 to 33,000 home with an on demand output of 100 MW. Or, 250,000 to 330,000 homes at peak output with an on demand output of 1,000 MW.

US Physicist Dr. Robert Bussard, a Princeton graduate, has 57 years of research and development experience working in the energy field. His credits range from rocket propulsion to fusion. During that time Dr. Bussard has had significant roles at Los Alamos National Labs, Oakridge Labs, TRW Systems and was the Assistant Director of the US Atomic Energy Commission. He conceived the aptly name Bussard Ramjet propulsion system and has 3 patents on his non-neutron (no radiation) fusion device. In 2006, he won The Outstanding Technology of the Year Award from the International Academy of Science (an insightful basic partial summation of the process) for his achievements regarding fusion.

The PDF document referenced above contains the following text:

http://www.askmar.com/ConferenceNotes/2006-9%20IAC%20Paper.pdf.

These search terms have been highlighted: iac paper
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57
th
International Astronautical Congress
Valencia, Spain
October 2-6 2006
The Advent of Clean Nuclear Fusion
:
Superperformance Space Power and Propulsion
Robert W, Bussard, Ph.D
EMC2-0906-03
Energy/Matter Conversion Corporation (EMC2)
680 Garcia St., Santa Fe, NM 87505
ph/fax 505-988-8948; e-mail, emc2qed@comcast.net
Sponsored by the
International Astronautical Federation (IAF) and the International Academy of
Astronautics (IAA)
The Advent of Clean Nuclear Fusion:
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Superperformance Space Power and Propulsion
Robert W, Bussard, Ph.D
EMC2-0906-03
Energy/Matter Conversion Corporation (EMC2)
680 Garcia St., Santa Fe, NM 87505
ph/fax 505-988-8948; e-mail, emc2qed@comcast.net
ABSTRACT
Success has been achieved from research and development work conducted since 1986 on a unique concept
for creating and controlling nuclear fusion reactions, in an inertial-electrodynamic fusion (IEF) device of
special, quasi-spherical configuration. Final design insights were proven by experiment in Oct/Nov 2005,
from which full-scale designs can be determined. This allows demonstration of full-scale, clean, nuclear
fusion power systems, based on use of p+B11 -> 3 He4. This demonstration will require about $ 200 M
(USD) over 5 years, with an IEF machine of 2.5-3 m in diameter, operated at over 100 MW. It will open
the door to superformance, practical, economical spaceflight, as well as clean fusion power, and mark the
end of dependence on fossil fuels. The main point of this paper is to present these results of EMC2‘s 20
years of study and research of this approach to clean fusion power.
This concept derives from early work (1960‘s) of P. T. Farnsworth and R. L. Hirsch (F/H), who used
spherical screen grids biased to high potentials to energize and accelerate ions to the center, where fusion
occurred. Ion collisions with grids gave unavoidable losses, limiting power gain to less than 0.001. The
EMC2 device avoids these by using energetic electrons, trapped in a quasi-spherical polyhedral magnetic
field, to generate a spherical electric potential well. Ions dropped into this well at its edge will accelerate
towards its center increasing in density and kinetic energy, collide at high energy, and make fusion. By
this unique design, the power loss problem is shifted from grid collision of ions (F/H) to that of electron
transport losses across high B fields to the confining magnets. The two competing phenomena, power loss
and fusion generation, are thus decoupled by the basic design approach, and each can be optimized
separately.
The concept was invented by Dr. R.W. Bussard in 1983, patented in 1989 (and lastly in 2006), and studied
by EMC2 since 1986. Design studies of IEF-based space propulsion (AIAA Prop. Conf, 1993,97; IAC,
Graz, 1994, Toulouse, 2001) show that this can yield engine systems whose thrust/mass ratio is 1000x
higher for any given specific impulse (Isp), over a range of 1000 < Isp < 1E6 sec, than any other advanced
propulsion means, with consequent 100x reduction in costs of spaceflight.
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INTRODUCTION AND SUMMARY
EMC2 has been conducting Research and Development (R&D) on its unique
concept for controlled inertial-electrodynamic-fusion (IEF) power generation since its
invention in 1983/84 (Ref. 4, and other patents filed in 2006), with detailed studies since
1986/87. The EMC2 concept is electrodynamic, rather than electrostatic, as initially
studied by earlier workers (Ref 1,2,3) in which fixed (static) grids were used to generate
confining electric fields. R&D work on the physics issues of the concept has been carried
out under EMC2 and US Department of Defense sponsorship since 1987, with
experimental work since 1989. Early work (1987/94) was reported at meetings of the
American Physical Society‘s Division of Plasma Physics, and in a wide array of internal
and external technical reports and journal articles (Refs. 2-16). However, by direction of
its USNavy sponsors, EMC2 was precluded from publishing technical papers on its R&D
work and results from late 1994 through 2005.
During this eleven year period it was acceptable to publish technical papers on the
potential application of this new high-performance fusion energy system to space flight
systems and applications without disclosing the means to achieve such energy systems.
And, of course, one very important application of this concept, if successful, has always
been to provide power to drive superperformance propulsion systems for vastly improved
spaceflight. To this end, a series of technical papers was written and presented at
meetings and conferences in this period (Refs. 20-23).
Results of these studies showed that IEF power sources could be used for a wide
variety of aerospace propulsion applications, ranging from HTOL vehicles from earth-to-
orbit, to fast transit vehicles to the orbit of Saturn and throughout the solar system, along
the lines first laid down by Hunter (Ref 24), and even to the fringes of interstellar space
(Ref. 22). Their potential performance exceeded that of all other rational alternatives by
a factor of the order of 1000x; that is the engine systems provided Isp 1000x higher at the
same thrust/mass ratio, or thrust/mass ratios 1000x higher than others at the same Isp.
Figures 1 and 2 show schematic outlines of the types of engine systems considered, and
the general performance spectrum just described.
Figure 1
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Since the R & D program has now
concluded, for want of further funding, just
as it reached final success, it is now
possible to publish the results of the work
of the past 12-19 years. Accordingly, this
paper presents an informal short summary
of these results and conclusions of the R&D
work of EMC2, over the period since 1987, on the Polywell inertial-electrodynamic
concept for clean (non-radiative) nuclear fusion and fusion-electric power. This
summary presumes a general knowledge of the classical basic physics phenomena that
this embodies and on which its performance is based. It also summarizes the present
prospects and needs for the major next step to clean fusion net power systems, following
the groundwork and fully established knowledge from work carried out to date.
The most important result and conclusion from this work is that it is now
possible to design, build, construct and test a full-scale demonstration fusion power
plant, with a high degree of confidence. If designed to run on deuterium (D) the
RDT&E cost is estimated at about $ 150 M over 5 years, while a plant designed to run on
the unique fusion reaction between hydrogen (p, or H) and boron-11 (B11) œ which is
totally neutron-free œ will cost about $ 200 M.
It is important to note that this Polywell concept and device is the only fusion
system that can utilize this clean pB11 reaction, which yields only charged alpha
particles (Figure 3).
Figure 3
BACKGROUND OF PROGRAM
This work has been supported since its
beginning by the DoD (SDIO/DNA, DARPA,
and the USNavy). It reached final success in
proving the ability to control e-losses
sufficiently to ensure that net power, clean
fusion systems could be built at larger sizes
from the EMC2 device, in a series of critical
experiments conducted in November 2005. However, the lab was shut down in the
ensuing 2 months due to the failure of funding in the FY 2006 budget to complete the
present USNavy contract under which EMC2 has been conducting this work. The EMC2
labs and offices in which it has been conducted have been closed. Ironically this
shutdown was at the time of the program‘s final and greatest success in experimental
results!. This is discussed further below.
TECHNICAL HISTORY OF RESEARCH AND DEVELOPMENT (R&D) WORK
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The EMC2 experimental R&D effort began in 1994 with design and test of a
small machine (R = 5 cm), called WB-1, to verify polyhedral B field effects. This device
utilized uncooled solid-state magnets in a truncated cube arrangement, and was simple to
build and test, but inherently had circular line cusps on all its main face magnets. This
resulted in large electron loses through these line cusps, but experiments showed electron
trapping within these limits.
This was succeeded by WB-2 (1994-95) another truncated cube configuration,
with an interior half-width of R = 5 cm, but with uncooled wound coil magnets on all six
main faces. Figure 4 shows WB-2. WB-2 tests proved the principal effect of internal
cusp confinement of electrons under high current drive conditions, as shown in Figure 5.
Subsequent tests were made on similar but larger machines, WB-3 (1998-2001) and WB-
4 (2001-2003) with R = 10 cm and R = 15 cm, respectively. Figures 6 and 7 show these
devices. All of these machines were tested inside vacuum tanks and had open faces on
all cusp axes (the main faces and corners) to allow full circulation of electrons out and
back along the polyhedral B fields produced by the magnet coils. WB-4 produced
fusions in DD under a short-pulsed-mode drive in December 2003, at about 1E6 fus/sec
at 12 kV drive energy and 10 kV well depth.
Figure 4
Figure 5
In parallel with this work, a closed-box machine (PXL-1) was built and tested to
study electron cyclotron resonance (ECR) ionization of internal background neutral gas,
and ion focusing in negative potential wells. Even though it was driven by a single
electron emitter, its tests showed good ion focusing to the potential well center of the
device. Figure 8 shows this machine. It did not allow electron recirculation from the
interior of the device and thus was limited (by wall collision losses of electrons) in its
ability to reach high electron densities.
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Figure 6
Figure 7
Also in parallel, two single-turn, water-cooled, polyhedral tube/coil devices
(MPG-1,2) were built and tested at low B field but high voltages (2001-2002). Both
showed DD fusion reaction output with deep potential wells. And, also in parallel, a fast-
pulsed adiabatic compression device (PZLx-1) was built and tested (2002-2003) to study
hydromagnetic stability of the polyhedral fields under static and dynamic conditions.
Figure 9 shows this device; a single-turn solid copper coil system driven by a fast
capacitor bank energy system to 35 kG central fields, in ca. 2 msec. This was limited by
Paschen arcing to starting energies (of electrons) of about 300 eV, but produced 1E6
fus/sec in DD at its pulse peak.
Figure 8
Figure 9
Finally, a larger version of the closed box device (PXL-1) was built as WB-5
(2004-2005), to test improvements in magnetic insulation by use of external surface and
cusp coils at high fields. Figure 10 shows this system. Its test results showed 1000-fold
improvement (in ability to reach deep fractional well depth at given starting pressures;
early work was limited to 3E-9 torr, while WB-5 ran at 3E-6 torr) from early work (1989-
91) on a larger closed-box machine (Ref. 6) but its inability to be driven beyond this
increase illuminated the critical and dominating effect of unshielded surface losses of
electrons, on overall system performance. This is discussed further, below. The insights
gained from test of this device led to new engineering physics design constraints, which
avoided all such loss phenomena, and which were immediately and rapidly embodied in a
new machine, WB-6 (2005), shown in Figures 11-13.
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Figure 10
Figure 11
Figure 12
Figure 13
This was hastily built and tested (October/November 2005) with impressive and
startling results, giving DD fusions at over 100,000x higher output (at 1E9 fus/sec) than
all prior similar work at comparable drive conditions (Ref. 3). All testing was necessarily
short-pulsed (discussed further below), but all basic engineering design conditions were
proven by this machine (together with the results from its predecessors), to enable design
of a full-scale power plant system.
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RESULTS OF PROGRAM WORK
Thus, all of the individual physics issues and effects required to make the concept
work HAVE been proven by the extensive experimental tests made since 1994 in the
EMC2 R&D program. These include:
The WB cusp trapping effect (explained further below; WB-2,3,4,5), its physics and
numerical rates
The need for electron recirculation through all cusps of the machine, so that cusp electron
flow is not a loss mechanism
The consequent elimination of the WB trapping factor as a measure of —losses;“ it is
simply a measure of density ratios inside and outside the machine
The ECR means for neutral gas wall reflux suppression (PXL-1 WB3,4),
The ability of machines to act as electron extractors from e-emitters located on axes
(WB-2,3,4,6),
The appropriate on-axis positioning of such emitters relative to machine dimensions
(WB-4,6),
The restrictions on machine relative dimensions due to electrostatic droop from emitters
and external walls (extensive electrostatic computer simulations/codes),
The proper positioning of external walls and choice of neutral gas pressure for
suppression of arcing (every machine tested),
The conditions for arc faulting in machine operation (every machine tested),
The need for injection of neutral gas INTO the machine interior, and for Immediate
ionization of same (WB-4,5,6), or
The requirement of ion gun injection at the interior edge of the Polywell potential well
within the machine (WB-4,5),, while keeping external neutral gas density low by
extensive pumping,
The inherent hydrodynamic stability of the Polywell trapping polyhedral B field
configuration (PZLx-1),
The production of predictable fusion reaction rates within the interior of deep- well
Polywell devices, at both low and high B fields (WB-4,6, MPG-1,2),
The ability to run Polywells at current drives up several thousand amps of electron
injection (WB-4,5,6),
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The determination of electron transport losses across Polywell B fields, and verification
of the electron transport loss phenomena (MG transport coefficient) by extensive
experimentation in all Polywell machines.
The absolute necessity of avoiding all magnetically-unshielded surfaces in any machine
design
The understanding of the effects of finite coil dimensions on the role of the —funny cusp“
losses at corners, and the resulting need for precise construction at these points (see
above), i.e. spacing at several gyro radii.
The need for magnetic field coil containing structures to be conformal with the B fields
they produce, to avoid excessive electron impact losses (as above)
The need for independent electron guns to provide adequate drive power
The ability of ion-impact secondary electron emission to supply large drive current
capabilities in proper Polywell machine/shell systems (WB-5)
The requirement of large drive power, as defined in the original Polywell design and
configuration concept
SUMMARY OF TECHNICAL RESULTS
The results of all this work, and their meaning, are as follows:
1.
Essentially all the research and development work that can be usefully done at the
small scale available with the program-limited budgets has been done. Two small scale
device tests of value remain, as does work on e-guns for full scale machines.
2.
All of the basic physics effects and engineering design and construction constraints
have been done, needed to make the concept work, lacking only their extension to full
scale sizes (1.5 m for DD, 2 m for pB11). The next logical and practical step is to
undertake a five-year program to develop and test a full-scale net-power (e.g. at 100
MW) IEF clean fusion demonstration system.
3.
The results of all of the experimental studies to date have shown very stringent
physics limitations that drive the engineering configurations and designs to use of fully-
electron-recirculating machines, within external vacuum shells or Faraday cages, with
only the internal machine at high electric potential. In this preferred arrangement, the
electron emitters/sources and the external shell are all at ground potential.
4.
An alternate potential arrangement could be used, in which the only elements at
high negative potential are the emitters, but this can work only if it employs driven,
negatively biased repellers at every cusp axis position, to prevent excessive electron loss
by streaming out along each axis. Such repellers could also act as secondary electron
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emitters (from ion bombardment) to the degree that the primary driven emitters may be
turned off œ as proven in tests on WB-5..
5.
In these systems electron loss phenomena are solely to (metal) surfaces of the
machine system. Cross-field losses are well understood and can be controlled.
However, losses to poorly shielded (by fields) or unshielded surfaces can constitute major
loss channels. From WB-5 and WB-6 it has been proven that that the fractional area of
unshielded surfaces must be kept below 1E-4 to 1E-5 of the total surface area, if electron
losses are to be kept sufficiently small so that net power can be achieved. And, further,
that no B fields can be allowed to intersect any such internal surfaces of the machine.
6.
This requirement has two main consequences: (a) All coil containers/casings
must be of a shape conformal to the B fields produced by their internal current
conductors, and; (b) The finite size of real coils forces design so that no coils/containers
can ever be allowed to touch each other, but all corners MUST be spaced at some
distance from the adjacent coils, to avoid B field intercept.
7,
This is the principal criterion for design and construction of any real, finite
material coil and system, no matter the plan-form SHAPE of the coils, which is of no
major significance (i.e. round, square, polygonal or triangular, etc). The spacing between
coils should be such that the central plane B field is approximately the same as that of the
B field on main face axes. Typically, this may be at minimum the order of a few (5-10)
electron gyro radii at the inter-corner field strength, but not greatly larger than this (to
avoid excessive degradation of the internal WiffleBall œ WB œ electron trapping factor in
the machine main field).
8.
This Wiffle Ball trapping factor (Gwb) is NOT a measure of losses in any
recirculating machine, thus its value need not be as large as those potentially possible
with high B fields (1E3 vs 1E6), thus greatly relaxing the need to strive for super-high
Gwb factor values.
9.
Wiffle Ball behavior is of value (and is essential) ONLY to establish the density
ratio from the machine interior to its exterior, and this is important ONLY to assure
suppression of Paschen arc breakdown outside, which destroys the electron injection
drive and well potential.
10. These considerations have been driven by the long array of experiments that have
been done at EMC2 since 1994, first on WB-2, then some on WB-3, then the last series
of WB-4, with parallel tests of unique-feature other devices, MPG-1,2 and PXL-1, PZLx-
1. Finally experiments were run in tests subsequent to these on WB-5, and lastly onWB-
6, the definitive final machine, with greatly reduced losses, and record-breaking DD
fusion output.
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DISCUSSION OF TECHNICAL CONCEPT AND EXPERIMENTS
The basis of the EMC2 concept for inertial-electrostatic-fusion (called the
—Polywell“ concept) is the idea of trapping high densities of energetic electrons within a
quasi-spherical magnetic field, into which a current of high energy electrons is injected to
form a deep negative potential well, without use of mechanical grids. Only a very slight
fractional negative deviation (1E-6) from charge neutrality (of ions vs electrons) is
required to make potential wells nearly as deep as the electron drive energy.
Ions then —dropped“ into this well, at its edge, will fall to its center, with 1/r
2
increasing density, and gaining energy sufficient to make fusion reactions among them as
they collide in the central core region of this configuration. If scattering occurs, the ions
simply recirculate back up the well and fall in again when they reach its edge. They are,
of course, finally turned by their gyro motion in the increasing edge B field of the system,
just as are the electrons. The critical element in power balance (fusion power generation
vs. electron drive power losses) is the ability of the magnetic field to keep electrons
inside the quasi-sphere œ ions remain trapped by the electron-driven electrostatic
potential well. The phenomena of fusion generation and of electron trapping and losses
are essentially decoupled in this system.
The original patent concept, which provides the basis for the physics of this type
of machine, presumed coil conductors of zero cross-sectional radius, placed exactly along
vertex edges, with sharp corners where coils came together. This led to an odd
point/radial-line at such corners which had zero field over zero radius. This was called a
—funny cusp“ by the very first reviewers of the concept (1987). It is, of course, not
attainable with any realistic coil conductors of finite size, and (as discussed further
below) this engineering fact has profound and dominating consequences for the design of
any machine hoped to be useful and practical for net power production.
The two single-turn MPG devices (MPG-1 and MPG-2), which were invented to
try to mock up the patent configuration of the coils, but with full recirculation of
electrons (called MaGrid machines), did yield very deep fractional (90+%) wells, as
expected. This was because the e- sources were all exactly on-axis, and were relatively
distant from the main faces. This geometry yielded only a small angle subtense for the
injected electrons, and thus only a small transverse spread of electron energy (relative to
radial energy) at the device inner boundary (fractional well depth tends to vary as the
square of the sine of the angular spread at injection). However the machines ran only at
cusp-axis fields limited to 70-100 G, because of engineering limitations on drive power,
cooling, and system size. These simple devices were also built with spacings at the coil
corner positions, so did not suffer from the unshielded loss problem alluded to above.
They did work and produced fusions in DD.
They functioned by trapping electrons in the polyhedral fields, to make deep wells
œ 30 kV e- drive with 27 kV well depth - with ions generated near the outer edge falling
in along the well gradients, as they should. Limited drive currents (e.g. 0.3 A) gave low
ion densities, such that the trapped ions could not reach ion energy much above 4.5 kV
before charge exchange with the background neutral gas prevented their further heating
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by ion/ion collisions. The limited small drive currents completely prevented burnout of
this background gas. This resulted in the generation of significant beam/background
fusion reactions (at about 1E4 to 1E5/sec) due to fast ions colliding with the background
neutrals. Device badly limited by limiting drive power and very limited cooling ability
on the coils. These machines did prove the efficacy of Polywell trapping and produced
DD fusion output.
Gwb (The WB trapping factor) in these two devices was of order 2-8, which is a
very small Wiffle Ball trapping factor. Much higher Gwb values could be attained if
machines were built with much larger B fields and at larger sizes, well beyond the
program budget. In the MPG series, cooling limits prevented higher currents, and
multiple turns to get higher B fields were out of reach (insulation breakdown in simple,
multi-turn coils, at high drive voltages) with the available effort.
Technical Design Considerations
In order to make net power in a Polywell, there must be no more than about 3E-5
fractional metal surface area unprotected by magnetic field insulation. Otherwise, direct
field-free electron losses will exceed both WB and MG transport power flows, and
system will not be able to yield positive gain. Corollary: No closed box configuration
can be made to function as a net power Polywell, with any conceivable practical
magnetic coil surface protection windings. I.e. it is not possible, in a practical,
constructable system, to cover all but 1E-5 of a closed box system with protective fields.
This means that the ONLY Polywell systems that can be made to work are those in which
there is NO metal surface exposed œ this requires open cusp, recirculating electron flow,
around B field coils that are spatially conformable to the magnetic fields surfaces that
they produce. And this forces the coils to be spaced at a significant interval at their corner
—touching“ points, to allow free electron flow through these points. This also makes the
WB trapping factor simply a measure of electron density ratios (inside to outside) rather
than a measure of —losses“ to containing walls and structures. And, because of this, it is
not necessary of achieve Gwb values greater than, at most, 1E4 œ rather than the 1E6
required for non-recirculating machines.
Electron Recirculation and Thermalization
Thus, in order for a Polywell to be driven in the mode described for the basic
concept, open, recirculating MaGrid (MG) machines are essential. This, in turn, requires
that the entire machine be mounted within an external container surrounding the entire
machine, and that the machine be operated at a high positive potential/voltage (to attract
electrons) relative to the surrounding walls. Note that this was the electric potential
configuration used in the earliest MG machines, the WB-2 device, that proved internal
magnetic trapping of electrons, called the Wiffle-Ball (WB) effect. And in the first proof
of Polywell fusion reactions, in MPG-1,2, and in fusion production in the later devices,
WB-4, 6.. Questions have always been raised concerning the ability of the device to
maintain its quasi-monoenergetic energy distributions among the ion and electron
populations. These are, of course, driven by the dynamic injection of fast electrons, and
their subsequent loss to structures.
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12
If electrons live sufficiently long in the machine they could become
Maxwellianized (thermalized) and develop high energy loss distributions. However, this
has been found not to be the case. The same arguments have been found for the ions, as
well. Detailed analyses show that Maxwellianization of the electron population will not
occur, during the lifetime of the electrons within the system. This is because the
collisionality of the electrons varies so greatly across the system, from edge to center. At
the edge the electrons are all at high energy where the Coulomb cross-sections are small,
while at the center they are at high cross-section but occupy only a small volume for a
short fractional time of their transit life in the system. Without giving the details,
analysis shows that this variation is sufficient to prevent energy spreading in the electron
population before the electrons are lost by collisions with walls and structures. Similarly,
for ions, the variation of collisionality between ions across the machine, before these
make fusion reactions, is so great that the fusion reaction rates dominate the tendency to
energy exchange and spreading.
Ions spend less than 1/1000 of their lifetime in the dense, high energy but low
cross-section core region, and the ratio of Coulomb energy exchange cross-section to
fusion cross-section is much less than this, thus thermalization (Maxwellianization) can
not occur during a single pass of ions through the core. While some up- and down-
scattering does occur in such a single pass, this is so small that edge region collisionality
(where the ions are dense and —cold“) anneals this out at each pass through the system,
thus avoiding buildup of energy spreading in the ion population (Ref 14). Both
populations operate in non-LTE modes throughout their lifetime in the system. This is an
inherent feature of these centrally-convergent, ion-focussing, driven, dynamic systems,
and one not found (or even possible) in conventional magnetic confinement fusion
devices.
Tests made on a large variety of machines, over a wide range of drive and
operating parameters have shown that the loss power scales as the square of the drive
voltage, the square root of the surface electron density and inversely as the ½ power of
the B fields. At the desireable beta = one condition, this reduces to power loss scaling as
the 3/2 power of the drive voltage, the ³ power of the B field, and the square of the
system size (radius). Since the fusion power scales as the cube of the size, the fourth
power of the B field, and a power of the E drive energy equal to the E-dependence of the
fusion cross-section (cross-section proportional to E to the s power), minus 3/2. For DD,
s = 2-4, while for DT, s = 3-6 in useful ranges of drive energy. For pB11, the cross
section scales about as s = 3-4 over the system-useful range.
Thus, the ratio of MG power loss to fusion power production will always decrease
with increasing drive voltage, increasing B field, and increasing size. Because of this, it
is always possible to reach a condition of power breakeven in these polyhedral electric-
fusion machines, with any fusion fuel combination. This is not the case in Maxwellian,
equilibrium fusion devices (e.g. the —magnetic confinement“ devices of the DoE, et al) as
these are severely limited by ion collisional losses to their walls, and by bremsstrahlung
losses from the denser but less-reactive distributions in their equilibrium plasmas.
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Design Considerations from Computer Simulation Codes
Device and system operation and performance at startup conditions, at very early
times, have been modelled by complex electrostatic computer codes, that determine the
coulombic interactions between all particles throughout the system and plot trajectories
and densities in the system. Results of these computations show conclusively that B-field
intercepts with containing structures ensures excessive losses of electrons, as previously
discussed. However, these early-time computed results do not show the realistic effects
of collective phenomena beyond startup (from low- to high-beta).
These have been readily modelled successfully by a major plasma
phenomenological code (the EIXL code) developed by EMC2 since 1990. This is a 1.5-
dimensional Vlasov-Maxwell code, in which diamagnetic expansion of B fields is
included, particle collisions are estimated from density and energy distributions, fusion
rates and output are calculated and bremmstrahlung losses are included, and which
includes such phenomena as central core inertial-collisional-compression effects which
can apply to core ion compression in Polywell devices. Figures 14 and 15 summarize
this code and give a sample output for a pB11 system.
Figure 14
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Figure 15
Arcing and Wiffle-Ball Trapping
As previously noted, no Polywell can operate at all if arcing occurs outside the
machine, between the walls and the machine, because this destroys the ability of the
driving power supplies to produce deep potential wells. Thus the mean free path for
ionization outside the machine (inside the container) must be much greater than the
external recirculation factor, times the machine-to-wall distance. Since the mfp for
ionization is inversely proportional to the product of the local neutral density and the
ionization cross-section, this condition can ALWAYS be satisfied, IF the external neutral
gas pressure is made sufficiently small. In order to avoid external arcing, the densities
thus required are very much too low to be of interest for fusion, thus the density inside
the machine (at its boundary) must be very much higher than that outside. This ratio is
the Gmj factor, which is the ratio of electron lifetimes within the machine with B fields
on, to that without any B fields.
In contrast, in order to be of interest for fusion, the interior density must be above
some numerical value for any given size of machine. Typically this requires electron
densities at the interior boundary of order 1E13/cm3, or higher. While the exterior
densities (of neutrals able to be ionized) must typically be below 1E10/cm3 or less. Thus
a minimum value exists for Gmj (here, typically 1E3), below which no machine can give
significant fusion or net power, independent of the unprotected wall loss problem. Both
must be solved simultaneously
In any realistic device, the effective overall trapping factor is reduced from the
pure WB mode by circulation through the semi-line-cusps at the spaced corners, which
allow much greater throughflow per unit area than through the point cusps of the
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15
polyhedral faces. The line-cusp throughflow factor is called Glc. These two effects act
as parallel loss-flow channels, and combine to produce an overall trapping factor Gmj,
which is the inverse sum of each of their contributions, as weighted by their fractional
areas involved. Thus the overall trapping factor for inside/outside density ratios, is given
by 1/Gmj = fwb/Gwb + flc/Glc, where the fractional areas are flc + fwb = 1. Solving this
algebraic identity gives the effect of corner flow paths on the entire Gmj system as
Gmj/Gwb = 1/[fwb + (Gwb/Glc)flc]. If corner flow paths are not to dominate the
trapping, the second term in the denominator must be kept small relative to the first (WB)
term, thus flc/fwb << Glc/Gwb.
Analysis shows that line cusp corner spacing flow factors are roughly equal to the
square root of the mirror reflection coefficient Gmr for point cusps at the corner field
strength, thus Glc = SQRT(Gmr). Gmr values may be as high as 80-100 in such
machines, thus Glc = 10 is a reasonable value for the corner flow. Using this, and noting
that fwb must be close to unity, gives the approximate result that flc << 10/Gwb for
effective operation. In a truncated cube configuration Gwb = (BR)^2/110E, for B in
Gauss, E in eV and R in cm. Typically, machines may have Gwb > 1E4, thus the
fractional corner cusp flow area must be flc << 1E-3 as required to maintain good density
ratios from the interior to the exterior, to prevent arcing, and retain high enough density
inside for useful fusion. Note that this condition does not relate directly to the problem
of electron losses to unshielded structure, which is also determined by the fractional
impact areas involved as well as by the degree to which local arcing may occur to focus
high current density discharges in the system.
Arcing can take place inside the system whenever sufficient deviation from local
B field insulation is driven by —pinch effect“ currents to the otherwise shielded metal
surfaces. The arc pinch B field is given as Bp = 0.2Ip/rp, where Ip is the pinch current
and rp is its radius (gaussian units), and Ip = (pi)(rp)^2(jp), where jp is the pinch current
density (A/cm2), this becomes Bp = 0.2pi(jp)(rp) for B in Gauss. Now the condition for
arc formation is when the pinch field significantly disturbs the shielding main B field Bo,
thus when |Bo-Bp| << Bo. This yields the constraint that Bp/Bo << 1, or that Bo >>
0.2pi(jp)(rp). From MHD stability theory (and copious experiments since 1955) it has
been found that pinch discharges are inherently unstable if current densities and radii are
above some defined levels in any system. The condition is approximately given by rb^2
> 3E9[SQRT(Ee)]/ne; this yields rb > 0.2 cm for typical conditions of interest. Thus, it is
possible to suppress such effects by avoiding all sharp corners and electric field focus
points in the design and construction of the interior of the device, so as to prevent the
attainment of high current densities over very small areas in arc formation.
.
A key issue here is how to reduce capacitor-drive currents to the levels that are
actually needed for useful experiments. This is a matter of controlling the overall circuit
impedance Z of the machine test system as it runs. This impedance is simply the ratio of
electron drive injection energy to the electron current e-losses to the machine (not to the
walls and tanks) in machine operation. This, in turn, is dominated by the three factors in
e-loss phenomena: 1. direct MG transport through the B-shielded surfaces, 2. e-losses to
poorly shielded or unshielded metal surfaces, and 3. losses due to local arcing. Thus Z =
Ee/Iej, where Iej is the sum of these three e-loss current effects.
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As discussed above, arcing can be suppressed and avoided internally, by proper
design of the surfaces to avoid electric field-enhancing sharp corners and small areas.
Poorly shielded areas, such as the interconnects between spaced corners of the coil
systems, can be minimized by careful design to minimize area and avoid sharp corners,
and by use of internal B fields produced by current carriers through the interconnects.
And the main MG transport losses can be controlled by use of the well-developed
transport models and equations obtained from 13 years of EMC2 experimental research.
In general, the impedance can be controlled successfully, but only with proper care in
design and construction of the devices.
On electron trapping: Since the ion density is nearly equal to (and thus set by) the
trapped electron density, it is desired to have the highest possible electron density for the
least possible drive current. This requires that the transport loss of electrons across the
trapping B fields be small, and that their flow along the cusp axes of the polyhedral B
fields also be kept small. Cross-field transport constitutes an unavoidable loss to coil
structure, while cusp axis flow need not be a —loss“ if the device is open and the electrons
can recirculate along the cusp axes to the outside of the machine, thence to return along
cusp axes field lines. This type of recirculating machine with magnetically protected coil
surfaces is called a MagneticGrid (or MagGrid; MG) machine. It requires that the
machine, itself, be centered inside of a containing wall or shell, that is held at a potential
below that of the machine proper, by the voltage used to drive the electron injectors.
Initially, when the electron density is small, internal B field trapping is by simple
—mirror reflection“ and interior electron lifetimes are increased by a factor Gmr,
proportional linearly to the maximum value of the cusp axial B field. This trapping factor
is generally found to be in the range of 10-60 for most practical configurations. However,
if the magnetic field can be —inflated“ by increasing the electron density (by further
injection current), then the thus-inflated magnetic —bubble“ will trap electrons by —cusp
confinement“ in which the cusp axis flow area is set by the electron gyro radius in the
maximum central axis B field. Thus, cusp confinement scales as B
2
. The degree of
inflation is measured by the electron —beta“ which is the ratio of the electron kinetic
energy density to the local magnetic energy density, thus beta = 8(pi)nE/B
2
. Figure 16
shows two means of reaching WB beta = one conditions.
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17
The highest value that can be reached by
electron density is when this ratio equals unity;
further density increases simply —blow out“ the
escape hole in each cusp. And, low values of
this parameter prevent the attainment of cusp
confinement, leaving only Gmr, mirror
trapping. When beta = unity is achieved, it is
possible to greatly increase trapped electron
density by modest increase in B field strength,
for given current drive. At this condition, the
electrons inside the quasi-sphere —see“ small
exit holes on the B cusp axes, whose size is
1.5-2 times their gyro radius at that energy and
field strength. Thus they will bounce back and
forth within the sphere, until such a —hole“ is
encountered on some bounce. This is like a
ball bearing bouncing around within a
perforated spherical shell, similar to the toy
called the —Wiffle Ball“. Thus, this has been
called Wiffle Ball (WB) confinement, with a
trapping factor Gwb (ratio of electron lifetime
with trapping to that with no trapping).
Figure 16
Analyses show that this factor can readily reach values of many tens of thousands,
thus provides the best means of achieving high electron densities inside the machine
relative to those outside the magnetic coils, with minimal injection current drive.
In a recirculating MG machine, this factor is important since it sets the minimum
density that can be maintained outside the machine, for any given interior edge density,
as required for sufficient fusion production. It is desired to keep this outside density low,
in order to avoid exterior Paschen curve arcing, which can prevent machine operation.
To have low exterior density of electrons, and high interior density requires large Gwb
factors, thus, good Wiffle Ball confinement is essential to system operation at net power.
Thermal/Mechanical Limits On Steady-State Operation
From extensive design and experimental studies it has been found that machines
able to operate in steady-state mode require internal cooling of the magnet coil windings.
And this has been found impractical by any means, at the B fields required for useful
fusion production, in machines below a size considerably larger than those which have
been able to be studied in the EMC2/USN budget-limited program. In particular, it has
been found, by detailed design studies, that supercondcting (S/C) magnets can not be
used practically in machines below a size of, typically 1.5-2 m radius. Below this size,
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18
water-cooled copper coils occupy less total volume (because of S/C LHe/LN2 cooling
requirements) thus are more practical to build. However, water-cooled copper coils with
optimal shape and configuration (for minimum electron impact losses to coil structure),
able to reach conditions useful for significant fusion production, also can not be made
practically below a machine size of about 1-1.5 m radius. The limitations of water-
cooled copper coils made it impossible to achieve B fields above about 3 kG in the WB-
4,5,6 test machines
In such Polywell
®
devices, the strength of the B field is determined by the total
current used to create the magnetic field from its driven coils, divided by the system
size/radius. This current, in turn, is fixed by the limiting current density (j+) that can be
used in the coil conductors, times the cross-sectional area of these conductors. This latter
is proportional to the square of the system size (for similar configurations), thus to R
2
, as
for the electron losses, above. Hence the maximum possible B field (for given limiting
j+) is proportional directly to system size.
The engineering design configurations for normal (i.e. copper) coil conductors
that can be properly cooled have been known since the beginning of this program. These
require triple layer shells and internal insulation, and expensive and large scale tooling.
However they can be used only in machines much larger (i.e. 1.5 œ2 m radius and up)
than any built within the program budget and, at these larger sizes, superconductors make
better coils, anyway. Machines below this size can be built with higher B fields (and thus
low electron transport losses) and can be tested in Polywell mode, but only as pulsed,
uncooled-coil machines. This limits their testing ability to, typically, a small fraction of a
second (due to ohmic heating of the copper coils of the magnets).
It is thus NOT POSSIBLE to test at steady-state ALL of the physics working in
concert, in a Polywell machine, in devices below about 1.5 m in size/radius. This
fundamental fact, driven by the realities of mechanical and thermal engineering design
and construction œ to meet immutable constraints of the basic physics -, has made it
impossible to reach the objective of a break-even fusion power machine at the sizes and
scales used in the USNavy IEF program conducted by EMC2 since 1991. To achieve
this objective, it has now been conclusively proven that machines in this larger size range
must be used.
Since the cost of these scales roughly as the cube of their size, the costs for proof
of net power is estimated to be in the range of $ 120-180M, as compared with the
approximately $ 15-18 M that has been spent over the past 13 years in this program. This
estimate turns out to be completely consistent with those made originally in the earliest
studies (1987-91) ever done (by EMC2) for this concept and program, which estimated a
cost to proof-of-breakeven (or net power) in the range of $ 50 œ $ 60 M for DD fuel, and
$ 120 +M for pB11, in 1992. Scaled to today‘s (2005) dollars, these numbers would be
very much larger.
THE FINAL MACHINE, WB-6, AND THE PATH TO FUSION POWER
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Unfortunately, the ability of the program R&D work to reach full scale output
conditions with steady-state operation was always limited by costs and budgets. That is
why the last machine tested, WB-6, was designed as a short-pulsed machine. It was an
uncooled machine, with its magnets able to run only for a few seconds at high field, and
it had to be driven with (almost uncontrollable) big capacitors, to reach the e-drive
currents known from basic theory to be needed (40 to a few 100 amps). These could not
be supplied from the existing lab power supplies or even from the available wall power.
The use of pulsed drives also forced the system to try to achieve large in/out neutral gas
density ratios without steady-state e-driven burnout (as is essential in the basic final
design) but had to make use of puff gas injected into the machine on submillisecond time
scales, trying to match this with the fast discharge time of the caps; into the circuit of the
machine, which was not even fully damped (RLC parameters could not be made fully
stable with the equipment available)
The proper course of R&D to follow, to reach net power production has been
known for a long time. WB-5 was an attempt to revisit to the first large scale closed-box
experimental work (Ref. 6), to see how well electron confinement had been improved by
the understanding of MaGrid insulation reached in the tests of WB-2,3,4 and MPG. It
was expected that greatly increased electron trapping would result in higher electron
densities at higher system starting pressures, at the same currents of e- drive. It was
found that electron trapping was 1000x better than in the earlier large machine (called
HEPS), with comparable electron densities at pressures over 1000x those attained in the
earlier work. .However, when increased drive currents were employed to try to drive the
internal densities to still higher values, the machine was unable to go significantly beyond
this 1000-fold increased level, except with extreme higher currents (30 kA and up).
Extensive detailed experimental studies showed that this was due to e- losses
along B-field intersect lines into the corners and seams (where the B fields run directly
into the tank metal) of the containing tank. WB-5 was a closed box machine, like HEPS,
with its coils outside œ so that it could not allow e- recirculation out and back through its
magnetic cusps. .These losses were extensive, and attempts to reduce them by use of
floating ceramic repellers placed along about ² of the seam lines reduced e-losses by
2.5x but only at the price of opening up huge loss areas for trapped ions. This did show
exactly how bad the unshielded metal problem was; very bad in HEPS, less so in WB-5,
but actually totally intolerable in ANY machine. No matter the SHAPE of the coil/coil
joint (whether sharp-corner touching or line cusp-like) what matters is that (almost) NO
metal must be there at all. The coils MUST not touch and MUST be spaced apart. This
is the e-loss analogue of the effect of line cusp flow paths at the spaced corners on overall
trapping factors, discussed above.
Since it was always known that conformal magnet coil cans/casings were the only
way to avoid B field intersect with their surfaces, but since it was difficult and costly to
build such container shapes, and certainly not able to make the coils steady-state-cooled
at the size/scale affordable, the design and construction of WB-6 had to use uncooled
coils that could only be run in a pulsed mode. The insight derived from the experiments
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on WB-5 was used in the rapid design and construction of WB-6, which did use
conformal coil cans and spaced coils. The last tests of WB-6 were conducted hastily
during October/November 2005. These proved (by beta=one tests) to be an order of
magnitude better in effective e-losses (i.e. losses greatly reduced) than WB-4. That is,
the coefficient in the simplistic one-term MaGrid (MG) transport equation (for transport
across the fields to the metal surfaces) normalized to experiment out at about 0.1 of that
found from the WB-4 test results. This means that the effective unshielded metal surface
fraction was greatly reduced in WB-6 from that of the metal structures (legs, doghouses,
etc) of WB-4. The actual loss equation must have three terms for realistic modelling of
the phenomena here. The first term is the simplistic one, referred to above, the second
term is that concerned with e-losses to less-well-shielded or unshielded metal areas and
the third term is that concerning local arcing, discussed previously.
Final tests of WB-6 were made with the fast puff-gas/cap-discharge system,
starting at < 1E-7 torr tank pressure. These four definitive tests showed true Polywell
potential well trapping of ions at ca. 10 kV well depth (with a 12.5 kV drive), with total
DD fusion neutron output of ca. 2E5 nts over a period of about 0.4 msec; giving an
average fusion rate of about 1E9 fus/sec œ over 100,000 times higher than the results
achieved by Farnsworth/Hirsch for DD at such low energies, and 100x higher than their
best with DD even at 150 kV (Ref 3)
This device then failed by internal coil shorting in subsequent test œ the coil
construction and engineering was just pushed too hard by the forced drive conditions. It
is really very ironic that the program had to shut down the lab and close up œ after 12
years of careful study under USNavy sponsorship - just as these results have shown
world record IEF output.
The only small scale machine work remaining, which can yet give further
improvements in performance, is test of one or two WB-6-scale devices but with
—square“ or polygonal coils aligned approximately (but slightly offset on the main faces)
along the edges of the vertices of the polyhedron. If this is built around a truncated
dodecahedron, near-optimum performance is expected; about 3-5 times better than WB-6.
This is somewhat like a combination of MPG-1,2/WB-6, and it must also be run in the
puff-gas/cap-discharge mode (as for WB-4,6) to reach useful conditions. This will also
incorporate another feature found useful, that is to go to a higher order polyhedron, in
order to retain good Child-Langmuir extraction by the machine itself (which is more
straightforward than relying on stand-alone e-guns for the cusp-axis, very-high-B-field
environment), while not giving excessive electrostatic droop in the well edges. These
small scale tests are discussed further, below.
PHYSICS AND ENGINEERING ASPECTS OF PULSED OPERATION
On fusion output; the two machines that have run best, with ions trapped at near-
electron-drive energies in the e-driven deep electrostatic potential wells, and ion
acceleration by falling into these wells, with subsequent fusion, were WB-4 and WB-6,
both in their last week of life. In both of these, neutral density in/out ratios needed to
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21
avoid Paschen arc breakdown outside the machine (for a very short time), was achieved
by fast puff gas input directly into the machine interior edge.
As the neutral gas filled the machine interior, fast injected electrons created
ionization in this gas. The ion and electron densities produced by this fast ionization
were too low to drive the system to the electron beta=one condition. However, the low
energy electrons resulting from this ionization rapidly cascaded with additional neutral
atoms, being driven by electron/electron collisions with the incoming injected fast
electrons, and made still more low energy electrons. The cascade time e-folds at a rate of
1/(no)(sigmaizn)(veo), where (no) is neutral density, (sigmaizn) is ionization cross-
section for low energy electrons at speed (veo). Typically, for no = 1E13 /cm3 (i.e. ptorr
= 3E-4 torr), veo = 1E9 cm/sec (Ee = 100 eV), and sigmaizn = 1E-16 cm2, the cascade e-
folds with a time constant of about 1E-6 sec (one usec). Thus all of the neutral gas is
ionized and the system is filled with low energy electrons in only a few usec. Wiffle Ball
trapping works very effectively here. If all the electrons were still at ca. 100 eV, the
surface beta would be about beta = 0.01, at B = 1000 G.
However, the low energy electrons are heated by fast collisions with incoming
fast injected electrons. The Coulomb energy exchange time for this process is also about
1 usec. Thus the device will reach beta = one conditions when the mean electron energy
is about 2.5 keV, in ca. 20 usec. Beyond this point excess electron density will be driven
out beyond the beta = one limit; the field will have expanded as far as it can within MHD
stability limits.
This process uses —cold“ electrons to start, with —hot“ electrons as drives, to yield
a beta = one population of —hot“ electrons. Of course, while the terms —cold“ and hot“
imply Maxwellian temperature distributions, these systems do not exhibit this on the time
scales of interest. This is called the —two-color“ electron startup mode, and will work for
any machine which is e-driven and supplied with neutral gas input at the proper rate.
This is the preferred method of startup for reactor-scale systems.
The overall result is that a deep potential well is provided in a few tens of usec,
and the ions formed by ionization are trapped within this well, heated by the fast e-
injection to well depth energy, and thus yielding fusion. However, the cap drive current
ran away as the internal puff gas supplied leaked out into the volume around the machine
and led to external arc shutdown. The arcs were from feedthrough leads into the main
vacuum tank and the tank walls, and had nothing to do with the machine or its containing
cage/shell. This took place over 0.5-2 msec after puff-gas actuation, so little time was
available for true Polywell operation. The cap drive current to the test system then ran
away to over 4000 A to this external feedthrough arcing, as the Polywell formed and
fusions occurred. This destroyed the well depth (due to drop in drive voltage). However
the system did run at emitter currents (to the machine) of 40 A for about 0.3-0.4 msec,
proving the basic concept. Figures 17 and 18 show data from these tests.
Since the electron transit lifetime in the machine is about 0.1 microsec, even 1 msec is
10,000 lifetimes, so the process looks like —steady-state“ to the electrons (and their
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22
trapped ions). Using this pulsed puff-gas technique, DD fusion output was attained from
WB-4 three times in December 2003, and (as noted
Figure 17
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Figure 18
above) world‘s record outputs from WB-6 in four tests during November 2005. These
results show, firstly, that Polywells, driven properly, do work and, secondly, that we
actually do understand how they work and thus can design and build full-scale systems
with confidence.
Of course, for the steady-state operation of the basic concept, what is needed are
large controllable power supplies, much larger machines (but still only to about a
maximum size of 2 m radius), and controllable gas supplies and e-guns able to survive
their B and E fields and gradient environments. With these the machines can be driven
initially via internal neutral gas burnout, and can use the —two-color“ electron
energy/density method (which has been known since 1994) to drive startup. As described
above, this two-color effect (starting with —dense —cold“ electrons and transitioning very
rapidly to less dense —hot“ electrons, by energy exchange collisions with incoming
injected electrons) will occur automatically in any machine, as employed in the pulsed
cap-driven tests of WB-4 and WB-6, if background neutral gas is used by fast electron
injection as a source for initial ionization within the machine.
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FUSION POWER RDT&E FOR NET POWER PLANTS
While all the basic features and engineering physics constraints have been
determined from the R&D work to date, there are several additional tests of small-scale
machines that could yet provide valuable information for further definitive design of the
next step to full-scale machines. These would be modified versions of WB-6, with
emphasis on exact matching to the basic patent descriptions, to best fit the physics
requirements of electron confinement and loss suppression. In addition, some effort
could usefully be put into development of final configurations of cusp-axis electron
emitters, and of cusp-axis repellers able to operate as secondary electron emitters under
ion bombardment, to allow easy supply of electrons to these machines. Unfortunately, all
such remaining small-scale tests must yet be conducted in short-pulsed mode, as
previously described.
Remaining Small-Scale Experiments
(1) Design, building and parametric testing of WB-7 and WB-8, the final two true
polyhedral coil systems, with spaced angular corners, to reduce —funny cusp“ losses at the
not-quite-touching points, and yet provide very high B fields with conformal coil
surfaces. These would be topologically similar to the original WB-2 and PZLx-1, but
without their excessive unshielded surface losses, and with pure conformal coils and
small intercept fractions. These latter can be achieved by appropriate spacing between
the corner junctions (typically several gyro radii at the central field strength between
adjacent coils) to allow free circulation of electrons and B fields through the —funny
cusp“ regions, without direct B field line impact on or intersection with the coils
themselves.
These should be tested best in an external vacuum system, with capacitor-driven
power supply for the electron injection drive, and be driven to fusion conditions for a
period of several tens of milliseconds. If these achieve true minimal losses (as derived
from WB-6 results), electron trapping factors of Gmj > 5,000 will be achieved and thus
yield significant fusion output, because of the very low loss design configuration of these
machines. To achieve this will require both high e- drive currents (see above re
secondary ion-driven sources), and controllable, pulsed, neutral gas input to the machine
interior.
Tests should be run in both of two possible electrostatic potential configurations.
First, with the machine as the only object at high potential, being placed at high positive
potential, with the emitters and surrounding cage or shell at ground. This ensures that the
only attractor for electrons will be the machine itself, so that electron losses to external
structure will be kept to small levels.
Second, with all of the system components except the emitters (and associated
repeller plates on axes of the cusp systems) held at ground potential, and only the emitters
and repellers at high negative potential. This has the feature that the electrons
recirculating through the cusps must return via magnetic field capture, else they will
—see“ the attractor potential of the surrounding shell and be lost. WB-4 was run in this
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< IAC Paper Sept 2006
25
manner and found to lose 95% of its injected electrons to attractive ground potential
structures outside the machine, through a tight beam along the cusp axes. Figure 7 shows
this effect in operation. Repellers/emitters on all cusp axes may be used to suppress such
losses, but their diameter must be kept small relative to the cusp —hole“ size/diameter,
This loss mechanism may also be mitigated by operating the external surrounding
shell or cage at slightly negative potential relative to the machine, thus providing a degree
of electrostatic trapping for the emitter/repeller electrons. Either system is expected to
operate successfully, from prior results on WB-4 et al.
(2) Building and test of both ion sources and high-output electron guns and
secondary electron emitters, for eventual use in large, full-scale machine drives. These
may use hollow cathode techniques and (possibly) magnetron gun design concepts.
Rugged and survivable e- and/or i+ guns, adequate for the needs of large machines, can
be built based on present knowledge from past work. These may also invoke the use of
neutral gas input through the ion/electron guns themselves, thus enhancing the ionization
of neutrals as they stream into the machine interior. And, in large-scale machines,
experiments to date and design models suggest that ion supply may be best accomplished
by use of the —two-color“ electron/neutral in-situ ionization process previously described
as the main source of ions in the fast pulsed experiments. This effect will occur over only
a few cm of outer radial position in any system that is designed to operate at reactor
power conditions.
Longer-Term Program Needs
To proceed to realistic clean fusion power, what is needed is a long-term
commitment to support this effort at the level cited above (and since 1991). On the main
Polywell development, all the work done to date has been successful in illuminating the
physics and engineering requirements for these systems. However, as previously
remarked, it was not possible to make power breakeven fusion at the much-too-small
machines, equipment, funding and staff available. It was clear from the beginning of this
work (and has been so told to the DoD since 1987) that 10x more funds and people were
needed, and the estimates of program size, scope and scale required for net power fusion
systems have hardly varied over the past 13 years. The achievement of fully reliable e-
guns required a team of 3 people working for 4 years to develop them, same for i-guns,
same for diagnostics, same for microwaves, same for magnet design, same for machine
design, same for theory/codes, etc, and these were needed at a machine scale of at least
1.5-2 m radius.
The work done did study, analyze, and experimentally prove all of the critical
physics and engineering issues at small scale, in a way that allows scaleup to the full
machine size, and it is now possible to build the e- guns and ion sources needed.
Fortunately, scaleup is possible with this approach, because the dominant physics is
classical, and thus readily predictable given the known and proven MG transport loss
models and equations.
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< IAC Paper Sept 2006
26
The only next useful step is to conclude small scale work (as described
previously) and then undertake a full-scale net-power demonstration IEF system, to
show total plant feasibility.
It is important to emphasize that there is nothing significantly new to be gained by
further tests at sub-scale sizes (i.e. less than that needed for net power). This is an
inherent consequence of the way in which the fusion power output (Pf) and system gain
(Qf. ratio of fusion power to drive power) scale with the machine size (R) and electron-
confining magnetic field (B). Fusion power scales as the fourth power of the B field and
the cube of the size, thus Pf = (k1)B
4
R
3
, while the unavoidable electron injection drive
power loss scales as the surface area of the machine, thus is proportional to R
2
.
Assuming the use of super-conductors for the magnetic field drive coils, the electron
losses are the only major system losses. Then, the ratio of these two power parameters is
the gain (Qf), which is thus seen to scale as Qf = (k2) B
4
R
3
/R
2
= (k2) B
4
R.
Because of this B
4
R
3
scaling of fusion output, which makes fusion power scale as
the 7
th
power of size, and the corollary 5
th
power scaling of system gain, it is obvious that
little can be gained short of building the next system at full-scale. Further tests at the
present small scale (1/10 of that needed) will not tell much more than is already known œ
and R&D at 2 or 3 times the present level still does not come remotely close to reaching
the conditions to prove net power.
To demonstrate net power requires a full-scale system, that can be run steady-
state, cooled and with controllable timing and power supplies. And this can be done only
with a funding level of $ 150 M (DD) to $ 200M (pB11), over a program duration of
about five-years of carefully directed and guided effort. Given this level of funding and
the DT&E it will pay for to achieve pB11 net power from a full scale demonstration
system, a full scale demo plant could signal the eventual end of dependence on oil and all
other fossil fuels by CY 2013. Subsequent full scale synthetic fuels and direct electric
power plants could then be built over following decades by ca. CY 2030-2040. And
work could begin on the application of such systems tro superperformance space power
and space propulsion systems, as well. The cost of this program is less than 1/8 that of
the present magnetic fusion program of the US DoE.
It is sufficiently small that such a program could be undertaken by a wide variety
of organizations and countries interested in solving the problem of world energy politics
and economics. Countries which could logically develop interest in such an effort
include China, India, Russia, Brazil, Argentina, Venezuela, Spain, Italy, and others œ but
none beholden to the large scale on-going expenditures in the so-called —magnetic
confinement“ programs of the Western technological nations.
EMC2‘s interest in this effort is simply to see it reach conclusion, and thus to
solve the problems posed by excessive dependence on controlled fossil fuel resources œ
most notably oil. The achievement of full scale IEF clean fusion power systems would
allow easy access to energy, both thermal and electrical, for all nations, and all peoples,
everywhere œ free from cartels and controlled production and pricing. This is a goal
Page 28
< IAC Paper Sept 2006
27
worthy of pursuit, and EMC2 will be happy to work with any organization interested in
undertaking such a venture.
ACKNOWLEDGEMENT
The author wishes to acknowledge the support of this work, from its inception, by the
US Department of Defense, Strategic Defense Initiative Office (through the Defense
Nuclear Agency and the Lewis Research Center of the NASA), the Defense Advanced
Research Projects Agency, and especially the US Navy, under Contract Monitor Dr. Alan
Roberts, of CNO/N042, and of NAWS, China Lake, under Mr. Charles Combs, and other
support from the Electric Power Research Institute and from the Los Alamos National
Laboratory, as well as direct support from EMC2.
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