Research on the Whifle Ball

[mattman]

Hello,

I am starting to do research on the Whiffle Ball. A few months ago, someone on this forum (I think it was Dan Tibbets), said they had proven the Whiffle ball effect in Japan.

Do you have a paper, or author, or group name, for this research?

I think I may have found a mistake in Rider's Work having to do with the mirror ratio. I need to get more details on this. I have seen several definitions of the mirror ratio - here is one definition below:

Mirror Ratio = Weakest Magnetic field strength/Strongest Magnetic Field Strength

If the whiffle ball effect is happening, I am trying determine how high the mirror ratio would be. From this, I think it is a safe bet Rider significantly underestimated the mirror ratio in his paper.

[KitemanSA]

Look for IEC2010 papers here.

http://www.plasma.ee.kansai-u.ac.jp/iec2010/Agenda.html

[hanelyp]

As I understand the wiffleball vs. simple mirror confinement:

In a mirror machine there is a loss cone proportional to minimum magnetic field strength/maximum.

In a wiffleball machine the field ratio and shape is such that the loss area is effectively reduced to the particle gyro radius at the cusp.

[KitemanSA]

I think Dr. B. said ~8 gyro-radii. At least along the line-like cusp between magnet coils. ICBW.

[mattman]

Look here:

http://www.plasma.ee.kansai-u.ac.jp/iec ... hachan.pdf

Slide 8.

They are doing a Fusor - an inner wire cage surrounded by an outer wire cage. There inner grid is pretty small: 2 cm, about the size of a big marble. They are running at 10 kilovolts - the same voltage Bussard ran WB6 at.

They notice a small dip in ion energy in the center. The dip fills about 40% of the inner volume - maybe 8 mm in diameter. It is about 1,500 electron volts in energy. The slide states that this is: "Possibly due to virtual anode..."

If I were the investigator looking at that I would guess there were 3 reasons for this:

1. My ion energy measurements were wrong.
2. The ions were attracted to the metal cage in the center - causing the dip in the middle.
3. The ions were repulsed by each other - AKA the virtual anode was happening.


I have lots of reading to do. I will look for papers.

[rcain]

iirc, the japanese efforts were to demonstrate multi-well (potential) formation ('Pollywell' if you will), using mutli grid fusor. also focussing effects.

dont recall seeing any work on Wiffleball' formation, japanese or otherwise.

best hints on Wiffleball i've seen so far come from early works of (the mighty) Indrek and others, looking at mag fields. plus Busards own work of course - eg. Valentzia paper.

do you know of something else?

(ps. i dare say Rick Nebel must have been concerned with your question at some point, since it has always been deemed critical to the whole Bussard concept).

[KitemanSA]

the Sydney U group and Joel Rogers both had some info about it, IIRC.

[D Tibbets]

I do not recall mentioning that the Japanese efforts expanded on Wiffleball claims, but as rcain said, they do serve as a separate source for evidence of deep potential wells being formed in an IEC device. This is a separate issue from the Wiffleball.

The only Wiffleball evidence that I know of is that Bussard, etel were satisfied that it was real based on their photomultiplier tests- the glow of the plasma (due to recombination, etc) were brightest when the Beta= one condition was reached/ passed. This brightness was proportional to the density of the plasma and this apparently was proportional to density increases of several thousand fold. Knowing the electron current into the nearly neutral (1 ppm deviation) magrid internal volume, the external pressure (easily measured with vacuum gauges), and the brightness difference between the inside and exterior allow the calculation of the Wiffleball trapping factor. and resultant electron leakage rates (?).

Nebel was reluctant to depend on the photomultiplier results only so EMC used another method to confirm the PMT data.

That Nebel emphasized that Wiffleball confinement was essential and a potential show stopper, and that WB7 results were generally considered positive and that research continues is a lose and perhaps optimistic conclusion that the Wiffleball reality is confirmed.

Pertinent quotes from Nebel taken from other threads in this forum:

Actually, you need to click on “read more” under the design section, then “main parameters” then on the “more” button. What you will find is that the average density of ITER is ~ 1.0e20/m**3. If you use the formula I sent you for the Polywell, you will get a density ~ 2.5e22/m**3. The upshot of this is that the Polywell has a power density that is ~ 62500 times bigger than ITER EVEN IF THERE IS NO ION CONVERGENCE! Thus, a Polywell should far outperform a Tokamak even with a constant density Maxwellian plasma. Even if Rider and Nevins were correct (which Chacon has pretty clearly shown they aren’t) this isn’t a show stopper. It has a lot more significance for Hirsch/Farnsworth machines that have low average densities than it does for the Polywell.
The best analogy that I can think of is that the wiffleball mode is the jet engine and the ion convergence is the afterburner. The 2.5e22/m**3 density is what the Polywell should have on the edge, and then it hopefully goes up a few orders of magnitude as it goes into the interior. I don’t mean to imply that ion convergence isn’t important. This power density boost is what enables the Polywell to be built in small attractive unit sizes and to easily use advanced fuels.
However, the wiffleball mode is essential and the ion convergence simply makes things better. If we can’t get the wiffleball, then we can kiss our behinds goodbye. That’s why we are focused on achieving the wiffleball and we aren’t paying any attention to Rider and Nevins. They’re just a distraction. Does this kind of make sense?



A few comments on scaling laws….
To a certain extent we are in the same boat as everyone else as far as the previous experiments go since Dr. Bussard’s health was not good when we started this program and he died before we had a chance to discuss the previous work in any detail. Consequently, we have had to use our own judgement as to what we believe from the earlier experiments and what we think may be questionable. Here’s how we look at it:
1. We don’t rely on any scaling results from small devices. The reason for this is that these devices tend to be dominated by surface effects (such as outgassing) and it’s difficult to control the densities in the machines. This is generally true for most plasma devices, not just Polywells.
2. Densities for devices prior to the WB-7 were surmised by measuring the total light output with a PMT and assuming that the maximum occurred when beta= 1. We’re not convinced that this is reliable. Consequently, we have done density interferometry on the WB-7. We chose this diagnostic for the WB-7 because we knew through previous experience that we could get it operational in a few months (unlike Thomson scattering which by our experience takes more than a man-year of effort and requires a laser which was outside of our budget) and density is always the major issue with electrostatic confinement. This is particularly true for Polywells which should operate in the quasi-neutral limit where Debye lengths are smaller than the device size.
3. As discussed by several people earlier, power output for a constant beta device should scale like B**4*R**3. All fusion machines scale this way at constant beta. Input power scales like the losses. This is easy to derive for the wiffleball, and I’ll leave that as an “exercise to the reader”. This is the benchmark that we compare the data to.
4. As for Mr. Tibbet’s questions relating to alpha ash, these devices are non-ignited (i.e. very little alpha heating) since the alpha particles leave very quickly through the cusps. If you want to determine if the alphas hit the coils, the relevant parameter is roughly the comparison of the alpha Larmor radius to the width of the confining magnetic field layer. I’ll leave that as an “exercise to the reader” as well.

Dan Tibbets

[rcain]

its good to see those summaries of the state of the art wiffleballwise - thanks Dan.

seems to me this would be a moderately accessible area of research for other labs, at this time; that is, WB-X is still proceeding with Navy labs, so basic Wiffleball method should be ripe for replication (without legal protection/penalty).

i see the point of inaccessibility of reliable scaling data from small machines, but verification of the basic 'pinch-off' effects, and net flows, e tc, at Beta=1 would be very interesting (and one hopes, heartening).

perhaps justification of some further 3rd party funding/initiatives? who knows. would be nice.

[D Tibbets]

Hello,

I am starting to do research on the Whiffle Ball. A few months ago, someone on this forum (I think it was Dan Tibbets), said they had proven the Whiffle ball effect in Japan.

Do you have a paper, or author, or group name, for this research?

I think I may have found a mistake in Rider's Work having to do with the mirror ratio. I need to get more details on this. I have seen several definitions of the mirror ratio - here is one definition below:

Mirror Ratio = Weakest Magnetic field strength/Strongest Magnetic Field Strength

If the whiffle ball effect is happening, I am trying determine how high the mirror ratio would be. From this, I think it is a safe bet Rider significantly underestimated the mirror ratio in his paper.

Concerning the mirror ratio, I assume this is equivalent to the number of passes before escape. In the EMC patent/ patent application 2008, the ratio of an optimized(?) opposing magnet mirror machine was ~ 5-8 passes. The 'cusp' confinement of the Polywell ('14 all point like cusps' replacing the two polar point cusps and equatorial line cusp of a typical mirror machine) was ~ 60 passes, and with Wiffleball inflation, the passes before loss increased to 'many thousands'.

In a sense this is better confinement, but it is similar to mirror point cusp losses, except in the truncated cube these cusps are increased to 14 from two. This total point cusp loss area is worse than the mirror point cusp losses, but eliminates the vast majority of the horrendous equatorial line cusp losses. Thus the ~ 10 fold improvement in 'cusp' confinement. The Wiffleball effect is improving confinement further, but it could also be considered as not changing the cusp loss areas much if any. What it does do is increase the relative volume that is contained, and in doing so it increases the surface area of the contained plasma 'balloon' so that the chances of a charged particle hitting the surface and rebounding is proportionately greater than the chances of hitting a cusp. The resultant angles into the cusp proper may also be changing- effectively decreasing the loss area, but this is more complicated than the simple Wiffleball analogy. Apparently this inflation adds up to the ~ 1000 fold advantage over simple mirror confinement (or ~ 100 times better than simple ' point cusp' confinement?).

To calculate the wiffleball effect you would need to know the effective volume of the spiky ball of plasma confined by the 14 point like cusps at low Beta. Then compare this to the inflated plasma ball volume/ surface area with Wiffleball inflation. The cusp holes/ loss cones could be considered unchanged (I think). How these two volumes would be determined is uncertain, but the ratio between them should be directly proportional to the B field strength.

EG: The 'cusp' contained volume in a 1 Tesla B field might be ~ 1 cubic meter, under 10 Tesla, this area may be 0.001 cubic meters. And, because of the increased B field strength the Cusp surface areas may be 100 times less (1/B^2). This doesn't look good (assuming I'm not completely off track). But, while the plasma area is 1000 times less, the resultant surface area is 100 times less. It is a wash, the confinement is less, but so is the effective confined volume. The ratio of plasma surface area to cusp hole loss area would be unchanged so the density at any given input rate would be unchanged. As the volume is decreased another order of magnitude, the number of confined charged particles would actually be 10 times less- not good.

Now enters the effect of increased charged particle populations (essentially electrons). These increased density of electrons is driven by input rates greater than cusp losses. As this progresses, the electrons push out against the magnetic fields (comparable to gas pressure pushing outward against a balloon). Up to a limit this will inflate the internal volume under constant B-field strength. This is limited by the available radius / starting plasma radius within the machine. This equates to the Beta= one condition- the maximum size allowed. This limits the volume gain- surface area gain over cusp loss hole size to this contained radius proportion. In this constant B condition the volume is increased while the density and loss rate is unchanged. This would scale as r^3 within the constraints of the available radius change.

But the B field can be varied also. By increasing B strength by 10X, the volume could be unchanged if the density is increased 100 fold. This is dependent on the loss hole size being 100 X (10^2) times smaller with the same volume/ surface area of the plasma sphere.
This is the B^2 density effect.
Various combinations of these competing effects are possible.
In the example of WB100, the radius in increased 10X, the resulting area 1000X, the resulting surface area 100X, while the B field is increased 100X with resulting cusp hole size decreasing by 10,000 * ratio of plasma sphere surface area / loss hole surface area. The increased plasma sphere surface area multiplies this ratio by 100, while the increased distances between the magnets divides this ratio by 100. The net effect is that cusp hole size to plasma sphere surface area remains at a ratio of 10,000. (B^2). This total surface area divided by the B field strength induced cusp hole size cancels out so the only concern is the B- field strength in determining the ratio.Thus, again the B^2 density scaling.
As the fusion rate scales ad the density squared, this gives the final B^4 fusion rate scaling.
The result is (10,000 improved density)^2 * 1000 increased volume = 100,000,000,000 times increased fusion., or ~ 100 MW of fusion power.

The loss scaling is based on the this surface area ratio, which ends up being ~ r^2. This ignores some magnetic loss scaling (B^0.25 I think)), but this is modest compared to the radius loss scaling.
I understand that the power output scaling is well understood and difficult to argue against (this ignores ion confluence which would magnify the advantages?)
The loss scaling is more uncertain. The relative shrinking of the cusp hole loss cones seems straight forward, but there is disagreements. Other losses such as electron injection efficiency through the tighter cusps, Bremsstrulung, etc are additional input energy loss concerns.

Dan Tibbets

[D Tibbets]

its good to see those summaries of the state of the art wiffleballwise - thanks Dan.

seems to me this would be a moderately accessible area of research for other labs, at this time; that is, WB-X is still proceeding with Navy labs, so basic Wiffleball method should be ripe for replication (without legal protection/penalty).

i see the point of inaccessibility of reliable scaling data from small machines, but verification of the basic 'pinch-off' effects, and net flows, e tc, at Beta=1 would be very interesting (and one hopes, heartening).

perhaps justification of some further 3rd party funding/initiatives? who knows. would be nice.

I hope this is one of the goals of the Australian group. Perhaps some news at the next IEC meeting this fall (?)...
It may be in the US somewhere as they have been alternating the meeting site between the US and Japan. Perhaps Nebel or Miles will moderate again, as they are both now 'retired'.

Dan Tibbets

[rcain]

its good to see those summaries of the state of the art wiffleballwise - thanks Dan.

seems to me this would be a moderately accessible area of research for other labs, at this time; that is, WB-X is still proceeding with Navy labs, so basic Wiffleball method should be ripe for replication (without legal protection/penalty).

i see the point of inaccessibility of reliable scaling data from small machines, but verification of the basic 'pinch-off' effects, and net flows, e tc, at Beta=1 would be very interesting (and one hopes, heartening).

perhaps justification of some further 3rd party funding/initiatives? who knows. would be nice.

I hope this is one of the goals of the Australian group. Perhaps some news at the next IEC meeting this fall (?)...
It may be in the US somewhere as they have been alternating the meeting site between the US and Japan. Perhaps Nebel or Miles will moderate again, as they are both now 'retired'.

Dan Tibbets

that would seem to give them just enough time to get something ready/underway, if they get their skates on. its difficult to know exactly what they've been up to so far; their websites say very little, but one suspects 'plodding along', mostly, else we'd have heard.

good to hear Japan is in the frame. wonder if there's anything under the radar we haven't spotted yet.

for that matter, maybe Famulus should do a pitch. he's agile and media-friendly at least, (though, not obviously Japanese, i don't think that matters)

(ps. conspicuously, no Brits in attendance, I imagine. ho hum..)

[MSimon]

Dan,

Excellent summary of the main issues.

[mvanwink5]

How does Dr Rogers dismal R^3 loss scaling simulation results square with EMC2 recent reported .gov positive results.

I wonder if a new paper will shed some light on this?

[D Tibbets]

How does Dr Rogers dismal R^3 loss scaling simulation results square with EMC2 recent reported .gov positive results.

I wonder if a new paper will shed some light on this?

Perhaps. Certainly the paper by Rogers one year earlier was more consistant with EMC2 thinking. This more recent simulation behaves substantially different from EMC predictions.

Dan Tibbets