Spherical Microwave
Confinement
for the preliminary exam
November 15, 2007
Bill Robinson
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History
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February 1995: Scientific American article on
sonoluminescence and fusion got me started
looking for exotic energy sources
1996-99; investigated various cold fusion ideas,
usually shock waves through hydride aerosols;
gave up for lots of reasons
July 2000; started investigating idea of helical
antennas in a sphere—and thought of coming to
NCSU for physics
2003; started interest in Ball Lightning (BL)
2004; began grad school in hopes of building a
reactor
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More History
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2004-2006; went through large number of
possible designs with this geometry (including
Inertial Electrostatic Confinement [IEC]); ended
up with magnetic SMC theory, BL on the side,
formal papers
August 2006; started construction in 102-A
Research II with Dr. Aspnes as advisor
Spring 2007; obvious that magnets are beyond
my capacity in cost, manpower, time; found
flaws in theory; concentrating on BL and SMC
with no magnets
September 2007; first plasma
October 13 2007; back to SMC as IEC idea
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SMC Reactor Design
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20 helical antennas for 2.45 GHz
circularly polarized RF, 1 wavelength
long, 4 ½ turns; aluminum sphere is
groundplane at 4th zero of
j1 = sin kr/(kr)2 – cos kr/kr (TE)
20 magnetrons (1kW each) fire from
cap bank (6kV to 4kV), ~1/10 sec
Each hemisphere mounted on
independent framework on casters
2 windows 2” diameter
Polar pipes (1 ¼”) for access, gas
in/out, probes, sparker, fiberoptic
Can accommodate either
hemispherical magnets or neutron
shields 1 ½ inches off of surface,
totally enclosing the sphere
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A Tour of the Lab I
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A Tour of the Lab II
Back of control
panel and upper
capacitor bank
Baffles keep the
‘trons from going
KERPOW
From 5 magnetrons to coax
Distributing power to the ‘trons
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Video Stills
Early shot; 3 torr, sparker loaded with flour and graphite; 30 fps; sparker
should be delayed to have maximum during microwave discharge (is now!)
1) Sparker explodes aerosol
2) Magnetrons start breakdown
3) One of 3 frames, hot plasma
4) Winding down, helix cores last to cool
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Abstract for Ball Lightning Research
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By experimenting with a variety of targets, gases, and pressures,
the objective is to create an analog to natural ball lightning (BL),
discover optimal conditions more favorable than atmospheric, and
investigate the anomaly
The spherical aluminum chamber confines the gas and aerosol at a
wide range of pressures
A strong pulse of circularly polarized microwaves from all directions
hits vaporized organic material
As natural BL emits microwaves, the BL should resonate in the
chamber and move to the center
Any microwaves emitted can be gathered by the antennas and the
power rectified to DC with high efficiency
A wide range of measurements and analysis would be possible for
the first time, instead of just field reports, leading to theory of BL
and reactor design
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Abstract for SMC-IEC Research
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Using the same geometry as for BL, with
addition of bias rings at the antenna
bases, waves of electrons flow into the
center and cause a virtual cathode at the
center, to which ions flow
As long as electrons are turned back
before collision with the antennas, the
result is gridless IEC with the potential for
neutron production and possibly fusion
power
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Ball Lightning
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We KNOW it does exist, unlike other exotic
schemes. Ideal power source when harnessed
Extreme BL (EBL) has unmatched energy density
(109 J/m3), beyond any chemistry from
energy/molecule; no neutrons or gammas
EBL emits high levels of microwaves which are easily
rectified (90+% efficiency) to DC
Hardly likely that Nature gives optimum conditions,
but does give possible conditions
Can be made with common materials. Fuel likely to
be abundant; best fuel unknown
Key is to take field observations at face value when
possible without modification to fit preconceptions
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Mysteries of BL: confinement
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Typical lifetime is 10 sec (range 1 to 150 sec typically)
instead of microseconds to cool, recombine
Neutral buoyancy; tends to hover over ground and can
move upwind instead of rising
Can’t have separation of charges sustained in conductor,
thus no E
B requires current which would need superconducting
loop; plasmas have finite resistance. Density is too high
for B confinement due to high collision rate >>
gyrofrequency (density is atmospheric).
Neutrals may be confined since no cooling from
convection, and “pop” on collapse evidence for internal
pressure >> partial pressure of ionized fraction. No
known mechanism for that. Would be ~15 atm!
If neutrals not confined, then plasmoid should cool and
collapse in < 1 ms; would help explain BL moving
upwind (but leaves most of the mystery)
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More Mysteries of BL
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Power output of BL not associated with cooling or
reduction in size
Energy flows out continuously from visible light
(recombination), RF (static recorded), sometimes heat
Energy out on explosion can include microwaves;
unknown origin. Evidence from cooked meat, hot water
Total energy can be >> initial input especially when not
generated by linear lightning, and energy is generated
during lifetime of BL; evidence of anomalous sustaining
reaction
Most powerful recorded BL formed underwater off coast
of Japan
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Using the reactor for BL
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Magnetron cap bank charged mostly by an oven
Sparker (2kV) throws hot organic material into center
Microwaves hit and react with hot aerosol and fill gas for 50 to 130
ms as capacitor bank goes from 6000 to 4000 V, ~1000 J energy
Current equipment only goes down to 3 torr and cannot withstand
positive internal pressure required to explore full range of conditions
After upgrade with flange, new antenna feedthroughs, and turbo
pump, can do much lower pressures and over atmospheric
May use baffles, especially for higher pressures; requires seed
plasma to absorb microwaves, otherwise can damage magnetrons;
no problem now at 3 torr with baffles. Mysterious malfunction at 1
atm
Recently added Teflon shields at base of antennas to avoid
breakdown, damage
If successful there is potential for explosive dissolution
For low pressures can use biasing rings at antenna bases (-6 kV to
start with, described in next section)
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How to make BL; a Best Guess
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Take field evidence seriously; smell, aerosol, microwave
damage, environment where formed
Smell indicates rotten egg (hydrogen sulfide) and ozone.
O3 ubiquitous with sparks so may not be useful indicator
Solids required for aerosol formation; only solids in air
are biological (birds, bats, bugs), so tests will use
organic fuel for sparker
Closest atmospheric lab plasmas to BL are microwave
discharges; must measure plasmoid duration after
microwave power input stops
If BL puts out microwaves, makes sense to put in a
potentially resonant chamber where it will tend towards
the center
Should get it started with pulse of extreme conditions
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How This Is New for BL Synthesis
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Since microwaves come out of BL, makes sense
to try making BL with a pulse of microwaves
Can expect BL to resonate in a spherical metal
shell and tend to float in center; not tried before
Circularly polarized RF keeps constant
magnitude fields; not tried before
Helical antennas in both rotations will receive all
radiation efficiently regardless of direction
Chamber controls gas pressure and species,
protects from explosions and BL microwaves
Sparker allows controlled introduction of aerosol
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BL Diagnostics
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Easy one is most important; does it last after power cuts off?
Must have accurate measure of when microwave input stops
Currently have video at 30 fps; would like higher speeds,
shielded from EMF
Will set up computer for data acquisition
By using coax relay can divert antenna for outgoing power
after magnetrons stop, rectify and measure DC voltage to find
microwave output. More ideal setup would have hybrid
couplers but too expensive now
Can insert emissive probe along polar axis to find plasma
potential regardless of electron drift [1]
Spectrometer probably via fiberoptic; need to borrow one!
(From NE?)
Need good leak testing to improve vacuum
Gas analysis before and after pulse to detect reactants and
products; gear available in lab
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HOWEVER!
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Making BL in this reactor is a long shot
Next; an explanation of a way of using this same
geometry with minor changes at low pressures for
Electron Accelerated Inertial Electrostatic Confinement
(EXL IEC) without grids for conventional fusion reactions
(D-D, D-T, proton-B11)
Unlike BL, the physics is known; critical point is to
reverse electrons by near-field RF and inward-flowing
electron waves before they reach the antennas, instead
of requiring transit through grids
If this is correct, the existing hardware could produce
large numbers of neutrons. The concept might be
developed for power generation in larger and more
efficient reactors
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Inertial Electrostatic Confinement
(Ref. 2)
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IEC single potential well
[3]
Fig. 2: Single potential well structure. The minimum normalized potential,
Ymin, coincides with the core potential, Ycore = Y(r = 0). The fractional well
depth, FWD is defined as FWD = 1-Ymin.
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IEC double potential well
[3]
Fig. 3: Double potential well structure. The double well depth (DWD) is Ypeak
– Ymin. Here, Ypeak coincides with Ycore.
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Existing IEC
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Large increase of plasma density in potential wells, fosters high rate
of reaction there; BUT net reaction rate ~ 1/pressure
IEC with grids cannot (yet) go above Q~10-5
Big advantages: no B fields, easy high T, simple geometry, some
fusion does occur at center and in mantle (zone between grids)
High T makes advanced fuels tempting but elusive so far
IEC operates at too low density for power reactor (need ~1021 m-3 in
sizable volume) [5]
IEC is the cheapest way to fusion by a very large factor; reactors
are mostly vacuum, thus low mass.
Existing grid reactor can be a practical, portable, simple neutron
source (like the STAR reactor), but not efficient enough yet for subcritical fission or large-scale transmutation. Maximum so far; 2x1010
neutrons/sec by Hirsch in the ’60s [6] and Nebel in late ’90s
Other attempts for either gridless IEC (Bussard) or to protect grids
magnetically from collision have failed
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Some recent experiments
Richard Nebel’s Los Alamos
Triple-gridded POPS IEC
1010 n/s, $500 k, 25 kW [4]
Hitachi IEC, Japan, 7 x 107 n/s
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Unavoidable Loss Problems in grid IEC
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Collisions with grids; Pgridloss/Pfusion > 3000; particle paths
MUST cross grids to be confined [5]
Ion upscatter and energetic tail loss time ~10-3 fusion
rate
Ion neutral capture and escape from potential well
Fusion reaction products escape, do not heat plasma
(direct energy conversion probably won’t work) [8]
Ion collisions increase angular momentum and throw
ions out of dense center region (may not be so bad,
double wells can work)
No way to keep plasma non-thermal; collision x-section
>> fusion x-section by factor of at least 105
Bremsstrahlung same or worse as other reactors, makes
advanced non-neutronic fuels probably impractical (fuel
touted as ideal for IEC)
Both ion and electron loss times << fusion time
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Critical IEC Scaling Problem: 1/n
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As density drops, longer mean free path, more
acceleration between grids, higher energy,
increased <sv>, fewer ion-neutral collisions,
tighter focus at center, more head-on collisions.
[9]
Thus fusion reactions scale as 1/n instead of n2.
IEC reactors operate at very high vacuum <<
fusion reactor range (1021)
Might not be true of SMC since mfp of runaway
electrons are long due to velocity; acceleration
from microwaves not grids; less focus anyway
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Critical IEC scaling problem; Power ~ 1/a
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a = radius of spherical active zone, q = total charge, fa
= potential at r = a, ne and ni are average densities in
the active zone, P = power from fusion
For grid IEC, q = |ne – ni| ~ ni
fa ~ q/a ~ ni a3/a2 = ni a2
Since fa is within a small range, ni ~ 1/a2
P ~ ni 2 *Volume, so P ~ 1/a
Probably NOT true for SMC since source of ions,
electrons, and charge balance is not the same as for
grids; q is not ~ ni
Proof of this is the use of ion or electron beams to alter
the charge/density relationship in grid IEC to increase P
Result is IEC devices are very small (a few inches) and
cannot scale up while SMC probably can
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Antennas as e- accelerators
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Antennas are insulated with ceramic and do not short out to plasma
Will apply -6 kV (or more) bias to base rings, 4” diameter, 1” from
wall. Next reactor could put (+) bias on antennas
Microwaves cause breakdown starting in core, rapidly saturates to
critical density (opaque plasma)
Electron cascade bunches in waves and flows toward center; same
process turns back electrons from center (thermalized after crossing
reactor core)
Uncoordinated antenna phases now; may be better in phase for
inwards-moving spherical waves
Existing rig; ~5 x108 e/cycle at ~25 keV (~0.2 amp) assuming
delivering 5 kW to waves from microwaves (efficiency of 0.25)
Bias on base rings limited to no more than electron wave energy ~
virtual cathode potential; 10 kV for D-T reactor, 50 kV for D-D
Ions do not bunch in waves, follow e- inwards; qi(t)= <-qe(t-d)>
Inner charge during microwave increase;
qtotal = qi - qe = - d <dqe/dt> (qe = # inner electrons)
For each 5 microseconds ion delay, can create 1 kV potential if low
electron loss
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Periodically Oscillating Plasma Sphere (POPS)
Uses RF modulation of grids and emitters to oscillate the potential well in
resonance with the orbital frequency of the ions to extend life of virtual cathode
(a) Temporal evolution of plasma potential at the center of the
virtual cathode with and without rf modulation. (b) Delay in the virtual cathode
destruction due to rf modulation as a function of modulation frequency.
(Reproduced from Ref. 4.) This is for just a few hundred volts and 10-6 torr
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POPS & SMC?
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POPS in grid IEC cannot scale to a reactor since
Pfusion
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3(ni / ne ) 2 o2 (rmax / rmin ) 2
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v
2
2 e rVC
fusion
With rvc = virtual cathode radius, fo = potential well depth; note change
in radius and compression ratio
Resonant frequency:
POPS 
2eo
2
rVC
mi
At fusion reactor conditions, 10-30 MHz (D-D); milder plasmas down to 1
MHz
Works by throwing a few ions out of potential well. Might use by RF
imposed on bias grid or injected beams of e- or ions
Grid IEC needs addition of electrons at center to reduce ion space charge
and allow compression, may also in SMC
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Magnetic SMC: a possible future addition
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Two hemispherical coils,
counter-rotating
Uses cylindrical cusp to make
electron cyclotron resonance
(ECR) on spheroidal B
isosurface at 875 gauss
Could help make plasma
transparent outside plasmoid
Would heat electrons at ECR
surface efficiently and
selectively
reactor is constructed to
accommodate the coils
Expensive and uses a lot of
power if not superconducting
Could funnel reaction products
out poles and equator for
direct energy conversion
Arrows are B field; center circle is plasmoid
surface; outer circle is magnet coil
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Magnetic SMC
Amp turns
30000
0.3
25000
0.2
20000
0.1
15000
0
10000
-0.1
5000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
coils
-0.2
-0.3
Coil windings in amp-turns for test
reactor, one hemisphere (other
hemisphere is negative of this)
-0.4
-0.2 are
Tickmarks
0
0.2
meters;
contours
are 0.4
B field magnitudes; dark circle is 875
gauss (ECR); outer circle is magnet;
next circle in is pressure wall; dotted
circle is inner end of antennas
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Current and Future Research
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THEORY; Ion heating; magnetrons are a few MHz out of
phase, causes Landau damping [8]
Shock dynamics, if they apply, with antennas in phase or
random (current setup is random); compression, heating
Confinement mechanism for electrons in SMC-IEC (no BL
theory yet)
HARDWARE; Diagnostic tools are first priority; computer DAQ,
plasma probes, spectrometer, gas analysis, and detectors for
x-rays, gammas, neutrons, alphas
Upgrade of vacuum system for lower pressures and secure
use of H2S for BL, or D2 and boranes for SMC
Installation of bias rings at antenna bases, -6 kV for now
GOALS; BL creation then reactor design, or SMC to scale up
for D-D or D-T reactor, sub-critical fission, etc.
FUNDING! And a way to continue doing this after
graduation—here if possible; post-doc?
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References
1) A. Siebenforcher, Rev. Sci. Instrum. 67(3), March 1996
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2) Tom Ligon, Infinite Energy Issue 30, 2000
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3) IEC thesis by Ryan Meyer, U. of Missouri-Columbia December 2007
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4) J. Park, R.A. Nebel, S. Stange, Phys. Plasmas 12, 056315 (2005)
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5) ”A general critique of intertial-electrostatic confinement fusion
systems”, Todd Rider, Phys. Plasmas 2 (6), June 1995
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6) R. L. Hirsch, J. Appl. Physics 38, 4522 (1967)
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7) M. Rosenbluth, F. Hinton, Plasma Phys. Control. Fusion 36 (1994)
1255-1268
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8) F. Chen, Plasma Physics and Controlled Fusion, 1984
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9) “Development of a High Fluence Neutron Source for Nondestructive
Characterization of Nuclear Waste”, M. Pickrell, LANL Technical Report
(1999)
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M. Bourham, class notes
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Many BL articles in Nature over the last 80 years
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Personal interviews with BL witnesses and their relatives (including Dr.
Hallen)
www.billrobinsonmusic.com/Physics for pictures, papers, latest news
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