I have copied the full report
from Focus Fusion and we are seeing solid progress. An upgrade in hardware design should be very
rewarding this coming year.
My one thought here is that a
larger robust design may be practical a lot sooner. The geometry may support just that and may
make success that much easier. A collapsing
plasmoid may just need more room.
Often design processes latch on
to an apparent economic solution that works against the physics. One recalls that the first aircraft were
kites and never quite practical.
Lawrenceville Plasma Physics are working towards commercial
nuclear fusion using dense plasma focus fusion. They have their
December, 2010 report. They have had problems with switches that has cost them
a few months of time to resolve. They have repeatably fired the bank with 10 capacitors attached, giving reliable shots above 1 MA
at 33-34 kV. They believe that they now clearly understand the previous
pre-firing and insulator-breakage problems. This will enable them to
continue gathering data and testing their theories while they prepare a
thorough ruggedization of the switches that will enable them in a few months to
reach full power with all 12 switches at 45 kV, and push on to their goal of 2
MA current. They are implementing a redesign which will take until March to
complete because delays to get some components. So in April, 2011 they will be
able to push ahead with 12 switches at 45 kV.
LPP has completed 3.5 of their 8 milestones. They are a year behind the
original schedule, which can mostly be blamed on the switch problems, but they
are making good progress. In 2011 their plan is to finish the trigger electrode
revision, which will allow them to achieve 45kV and 2MA, optimize the gas pressure for that configuration with deuterium,
switch to helium and nitrogen while continuing to optimize, then switch to
hydrogen and boron. At that point they hope/expect to see a shot that generates
33,000 Joules of fusion energy, and all of their milestones will be
complete. Unless they run in to more unexpected problems it is realistic that
they might finish that by the end of the year.
We ran into a number of problems that had to be resolved in turn.
Perhaps most importantly, we learned from our experiments that the pre-firing
inevitably gets worse with more capacitors.
This is because the pre-firing is caused by a slow breakdown of the gas related to a phenomenon called “corona discharge”. With more capacitors attached, the power supply’s fixed output charges the bank more slowly, so the switches stay longer at high voltage. Because of this problem, the present configuration of the switches will not work with all 12 capacitors attached. Ten capacitors is our current maximum.
However we know the cure for this. We’ll move the electrodes in the switches further apart (see the attached diagram for further explanation). We will be doing this in our general redesign over the next few months. In addition, if the tungsten trigger rods get worn down so they are too thin or too rough, the field gets too concentrated, and this also leads to pre-firing. Temporarily, we have replaced the thinnest rods and are sanding the others carefully on a regular basis. In our re-design, we will use much thicker rods—probably one-quarter-inch diameter instead of one-eighth inch.
We also had trouble eliminating breakage. While our large stabilizer block prevented any cracking of the insulator above the plate, the rapid movement of the tungsten rods was still breaking the Lexan insulators near the tip. After several tries, we have used a solid cylinder insulator to provide maximum strength. So far, they have lasted 40 shots with only two cracking, so this is adequate for now, although too soon to tell their real lifetime. Again, we know the solution to the mechanical breakage: making the rods thicker so they bend less, and making the insulators thicker so they are stronger. These changes require replacing the top plates of all the switches and making the spark plug holes larger. This hole size has limited our past efforts with the spark plugs.
Finally, to prevent the electrical break-down of the insulators, we also have to make them thicker. All of this can be calculated, based on the experiments we have done, and we hope to complete design work very soon, probably early in January. However, there are considerable ordering delays on some items, such as the tungsten rods, and some additional testing will be needed, so realistically we will not complete the new switches until March. Until then, we will be running with the existing 10–capacitor bank.
Focus Fusion Report
December 30, 2010
Summary: LPP’s Focus Fusion project has demonstrated that ions with
more than 100 keV energy (equivalent to more than 1 billion degrees C) are
confined in a dense plasma focus. This
breakthrough is based on both new evidence from the past month and a
re-analysis of shots made earlier in the year, and resolves a long-standing
controversy within the field on whether the ions are confined in a small space,
and thus can potentially heat the fusion fuel up to ignition, or are in a beam
running freely through the cold background plasma of the chamber. A combination
of evidence from many instruments, fit together like a jig-saw puzzle, has
demonstrated that the ions are trapped in circulating beams in very dense plasma.
The evidence ruled out the unconfined beam model. The 100-keV energy is sufficient
to burn pB11 fuel, once we start running with that fuel in the coming year, and
makes us confident that we will be able to achieve at least significant pB11
fusion yield. A press release on these results will be forthcoming shortly, and
will be submitted to the leading physics journal, Physical Review Letters.
In other key developments, we have repeatably fired the bank with 10
capacitors attached, giving reliable shots above 1 MA at 33-34 kV. We believe
that we now clearly understand the previous pre-firing and insulator-breakage
problems. This will enable us to continue gathering data and testing our
theories while we prepare a thorough ruggedization of the switches that will
enable us in a few months to reach full power with all 12 switches at 45kV, and
push on to our goal of 2 MA current. Demonstrating over 100 keV confinement in
a dense plasma.
While researchers have known for a many years that the dense plasma
focus produces high energyions, with energies well into the range where pB11
fuel will burn, some fusion
researchers have long held that the high-energy ions are not trapped,
but travel freely in unconfined beams. These beams, according to this model,
collide with the diffuse, cold background plasma in the vacuum chamber to
produce the observed fusion reactions. By contrast, we and other DPF
researchers have long contended that some of the high energy ions are indeed
trapped for relatively long times in dense plasma spots—the plasmoids. Both
sides agree that high-energy beams are also produced by the device. The
question is if any of the hot ions are confined—moving in closed loops, not
straight lines.
This argument is critical to the viability of the DPF as a fusion generator,
because only if some ions are trapped, circulating around and around within a
dense plasmoid, can they heat the fuel up sufficiently to ignite a
self-sustaining burn that will consume most of the fuel in the dense plasmoids.
A diffuse beam alone, traveling on a one-way trip through cold and much less
dense background plasma, will not be able to do that.
Previous experiments by LPP at Texas A&M
University
researchers, have accumulated evidence that the hot ions are indeed
trapped. But clear proof has been lacking that would rule out the unconfined
beam model. LPP now has provided that clear proof. One big piece of that proof
came from a recent re-analysis of shots we fired back in March. These shots
achieved high fusion yield, over 1011 neutrons, but with relatively modest currents,
between 600 and 700 kA. We wondered how these high yields could be explained by
a beam running through the background plasma. How much energy would it take to
generate such a beam? Because the background plasma is diffuse, with a density
of only 6.6X1017atoms/cubic centimeter, a very powerful beam would be needed to
produce so many fusion neutrons. We calculated that at least 9 kJ of energy
would be needed to produce such an ion beam, about onethird of all the energy
fed into the capacitors.
But not all energy fed into a DPF is available at any given instant.
Only the energy stored in the magnetic field created by the current is so
available. In turn, only part of this energy is drawn into the pinch and
therefore can drive the beams. We found that the energy needed for this hypothetical
beam was more than double all the energy available for forming it, so it could
not exist.
We could measure the amount of this energy drawn from the DPF’s circuit
during the pinch by examining the drop in the current. The energy carried by a
current is proportional to the square of the current times the inductance.
(Inductance is a basic electrical quantity which is explained briefly at the
end of this report.) From our Main Rogowski Coil, one of our instruments, we could
measure the drop in current. But what was the inductance of the total circuit?
In the past month, LPP engineer Fred van Roessel had measured the
inductance of the entire DPF device by matching the current output curves from
several shots with standard electrical models. He checked those results by
calculating the inductance of some key components, such as the switches. So we
knew how much inductance we had, and thus could calculate the total energy in
the pinch as less than 4 kJ—far less than was needed for the hypothetical beam,
even at 100% efficiency. So a beam through the background gas could not produce
this many neutrons.
The shots back in March only reached about 70 keV of energy. In
September, however, we had two shots that our time-of flight detectors showed
had over 100 keV ions. Could we be sure of this result? It came from measuring
the difference in the neutron arrival times at two detectors set at different
distances—11 meters and 17 meters. The more the neutrons spread out, the greater
their range of velocities and thus the greater the range of velocities of the
ions (deuterium nuclei) that fused to produce the neutrons. More velocity means
more energy, so this is a measure of the ions’ energy.
With just two
detectors of neutrons, we could not be positive that something was not
introducing an error. For example, what if there were really two neutrons
pulses? We needed data on neutrons as measured closer to the source.
On our last day of shots in December, on December 24, we got clear
neutron signals from one of our PMTs located at only 1.3 meters from the axis
of the machine. Thanks to a reduction of noise, to 6 mm of copper shielding to
cut back on the X-ray signal, and to the reliable firing of the device (more of
that below), we have clear evidence that we are not getting double neutron pulses
and that our measurements of ion energy are reliable. (see Fig. 1) This is a
second major piece of the evidence for the confinement of 100 keV ions.
Our ICCD images, obtained in October, show that the region where the
ions are confined is only about 120 microns or less in radius.
In addition, our neutron bubble detectors, located along the axis of
the device, as well as
horizontally, show that there definitely are somewhat more neutrons
moving in the axial
direction than horizontally. This means that the motion of the ions
cannot be totally random as in a thermalized plasma with no circulating beams.
Instead, the only explanation of all the data is a circulating beam of ions,
constituting a large fraction of the ions in the plasmoid, that encounters the
most dense plasma as it flows up along the central axis of the plasmoid, thus producing
the most neutrons in the axial direction, but many in all other directions.
This model has allowed us to calculate the plasma density in our best
shots to be in the area of 1-4 X 1020 ions/cubic centimeter, more than 100
times the fill pressure of the gas we started with.
We will be working on the technical paper describing this important
result in January and hope to complete it during the month. We think that it
will add considerably to the credibility of the Focus Fusion project, and thus
ease future fundraising.
Reliable firing of bank with 10 capacitors
On the last day of firing this year, we finally achieved reliable
firing with 10 capacitors—all fired together six times in a row with no
pre-firing. We now are confident that we understand the remaining two problems
of the switches, their pre-firing and the breakage of the spark plug insulators.
Unfortunately it has taken us a total of three months to get this understanding,
from the time that we solved the first problem of achieving simultaneous firing
in late September. We simply have not had enough reliable shots to optimize the
pressure and axial field to obtain the higher yields we are seeking. While we
are able to continue firing the bank in its present configuration, to go to all
12 capacitors firing at 45 kV will require some additional work on the switches.
But we know what we must do.
We ran into a number of problems that had to be resolved in turn.
Perhaps most importantly, we learned from our experiments that the pre-firing
inevitably gets worse with more capacitors.
This is because the pre-firing is caused by a slow breakdown of the gas
related to a phenomenon called “corona discharge”. With more capacitors
attached, the power supply’s fixed output charges the bank more slowly, so the
switches stay longer at high voltage. Because of this problem, the present
configuration of the switches will not work with all 12 capacitors attached.
Ten capacitors is our current maximum.
However we know the cure for this. We’ll move the electrodes in the
switches further apart (see the attached diagram for further explanation). We
will be doing this in our general redesign over the next few months.
In addition, if the tungsten trigger rods get worn down so they are too
thin or too rough, the field gets too concentrated, and this also leads to
pre-firing. Temporarily, we have replaced the thinnest rods and are sanding the
others carefully on a regular basis. In our re-design, we will use much thicker
rods—probably one-quarter-inch diameter instead of one-eighth inch.
We also had trouble eliminating breakage. While our large stabilizer
block prevented any
cracking of the insulator above the plate, the rapid movement of the
tungsten rods was still breaking the Lexan insulators near the tip. After
several tries, we have used a solid cylinder insulator to provide maximum
strength. So far, they have lasted 40 shots with only two cracking, so this is
adequate for now, although too soon to tell their real lifetime. Again, we know
the solution to the mechanical breakage: making the rods thicker so they bend
less, and making the insulators thicker so they are stronger. These changes require
replacing the top plates of all the switches and making the spark plug holes
larger. This hole size has limited our past efforts with the spark plugs.
Finally, to prevent the electrical break-down of the insulators, we
also have to make them
thicker. All of this can be calculated, based on the experiments we
have done, and we hope tocomplete design work very soon, probably early in
January. However, there are considerable ordering delays on some items, such as
the tungsten rods, and some additional testing will be needed, so realistically
we will not complete the new switches until March. Until then, we will be
running with the existing 10–capacitor bank. Derek Shannon is ably assisting
while Dr. Subramanian is on vacation.
IEEE Green Engineering to support FFS video on Focus Fusion
Dr. Paul G. Ranky, the Senior Editor of IEEE’s Green Engineering
Series, has offered to
collaborate with the Focus Fusion Society in producing an eight-hour
video series on Focus Fusion technology. The IEEE (Institute of Electrical
The offer came about when Dr. Ranky attended a Focus Fusion Society-LPP
Joint Solstice Seminar in Somerset ,
NJ
On the lighter side—inter-species technical cooperation
Our efforts are already getting help from the international community
of DPF researchers. So what’s the next step—get help from another intelligent
species? Maybe the dolphins can lend usa
As Focus Fusion fans know, our device produces tiny plasmoids which are
a plasma version of a phenomenon also found in fluids—the vortex ring. Humans
can produce a primitive version of the vortex ring—the smoke ring. However such
smoke rings are very unstable, so they’re not very interesting (as well as
having health hazards associated with producing them!).
Dolphins, however, produce highly stable vortex rings and then play
with them, as seen in this
video (http://www.youtube.com/watch?v=5us-v4bntP).
The vortex ring is formed in the water by the way the dolphins blow air from
their blow-hole. Since the vortex has its lowest pressure at the core, the air
stays there. The motion of the much more massive water ring overcomes thebuoyancy
of the air and prevents the rings from rising.
But how do the dolphins learn to produce such thin and stable rings?
Perhaps we can learn something of interest from their play. Dr. Diane Reiss of
Hunter College, a leading researcher on dolphin communication and intelligence,
and LPP’s Eric Lerner are discussing ways of studying this fascinating
behavior. Her long-term research program is also attempting to try tointerpret
the intricate songs and sounds that dolphins use to communicate with each
other. (Dolphins have the second largest brain-to-body-mass index of any animal
on earth, comparable with that of our Homo erectus ancestors). So perhaps one
day the dolphins will be able to explain to us their vortex ring techniques!
Reports
We apologize for the lateness of the report, but at times, it is more
critical to continue the
experiments than take out time for the report. A year-end report will
follow shortly and we will then resume the regular schedule, reporting again in
early February.
Technical note: What is Inductance?
Inductance is a measure of how much magnetic energy is stored in a
circuit (or part of a circuit)for a given amount of current. All currents
produce magnetic fields, and these fields contain energy. The current itself
supplies the energy to build these fields. The inductance of an object is the
ratio of the amount of magnetic energy to the square of the current (to be precise,
twice that ratio). The bigger the inductance, the large the magnetic field of a
given current, so the slower that current must build up. Inductance is affected
by how strong the magnetic field produced is—and thus how concentrated the
current is—but also by the total volume of space affected by the field.
Happy New Year to ALL!
Figure 1. Ready for its close-up. This graph shows the output of the
photomultiplier tube (PMT) located only 1.28 meters from the machine’s axis.
This is close enough so that the neutrons from fusion reactions do not have
time to spread out due to their different velocities, so they reveal the shape
of the neutron pulse as it originated. This shot, 12241009, has a single x-ray
peak, the one on the left. It is filtered heavily by 6mm of copper so only
relatively high-energy x-rays, above 80 keV, can get through. This reduces the
x-ray peak enough so we can see the neutron peak, the broad one on the right.
We can identify it as a neutron pulse because of its timing relative to the
neutron pulses observed at the same time at a much greater distance by the near
and far Time-of Flight PMTs. This graph shows clearly the single-pulse shape of
the neutrons and confirms the high energy that we have calculated for the ions
producing the neutrons. This particular shot achieved “only” over 40 keV, but
other shots in September achieved over 100 keV.
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