HENDO POLYWELL

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JamesC
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HENDO POLYWELL

Post by JamesC »

Hi Guys,

So I was pretty amazed by the HENDO kickstarter. Apparantly a fast spinning array of permanent magnets can produce a magnetic mirror of some kind.. who knew..

Check it out : https://www.kickstarter.com/projects/14 ... hoverboard

I am tempted to pick up 6 'white boxes' and put the 'magnetic engines' on the sides of a cube pollywell style in place of electromagnets used by the original pollywell and just 'see what happens'.

Any feedback on viability and related thoughts of these magnetic hendo engines as applied to containment for fusion appreciated.

Cheers,
James
prestonbarrows
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Re: HENDO POLYWELL

Post by prestonbarrows »

Those are basically just a linear induction motor. Same idea as a maglev train. Hereis a really good video about how they work. Basically, you just have a set of coils and run AC current through them; play some games with the arrangements and phases and you can make it stable and provide motion. Quite like a transformer where the ground is the secondary

Depending on the power and frequency, you could probably use one of these to light a plasma discharge, but not much more than that. Inductively coupled plasmas are a standard method for generating discharges for semiconductor production and so forth. (quite like a transformer where the plasma is the secondary)
richnormand
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Re: HENDO POLYWELL

Post by richnormand »

Liked the video you referred to Preston.
Reminded me of the old PSSC physics program videos of the early 70s in an era when science was "good" for our future and with an experimental approach.
Not the case these days from what I gather from my kids experience with math, chemistry, physics teachers these days just following blindly a mediocre textbook with no understanding.

Funny that in the video they never mentioned the heating effects on the Al plate. In particular if driven by a 50Hz field....

Hope you get a chance to ride the Shanghai maglev from the airport to see how that has progressed!
JamesC
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Re: HENDO POLYWELL

Post by JamesC »

I don't think the HENDO is using electromagnets/AC Coils. This is the patent
http://www.google.com/patents/US20140265690
In one embodiment, the moving magnetic field can be generated by one or more rotors with arrangement of permanent magnets.
So its using spinning permanent magnets which is a much more accessible way of generating a field than coils because you don't need to deal with high currents, power supplies, hand wound coils all that stuff that makes the pollywell almost impossible to make.

I wasn't thinking about lighting a plasma with it but rather containing one, with a configuration like the pollywell. With the simple minded thought that if a spinning magnetic array can cause a hoverboard to lift up then the force it is applying to the charged particles in the metal plate must be away from the hendo engine. Having said that - I suppose it will be acting on electrons! - I wonder if it means it will attract ions.. LOL

Anyhow this is just a thought experiment that could be (relatively) easily tested in practice so I was wondering if there was anything too it.

Cheers,
James
JakeJHecla
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Re: HENDO POLYWELL

Post by JakeJHecla »

Sorry to be the bearer of bad news, but your plasma confinement idea is doomed by the large timescale associated with rotating the halbach array. A reasonably hot (read: fusion) plasma will have ion speeds so high that the rotation of the arrays won't even be apparent in their flight time. It's physically doomed (for that reason and many others).
JamesC
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Re: HENDO POLYWELL

Post by JamesC »

plasma will have ion speeds so high that the rotation of the arrays won't even be apparent in their flight time
Good point. A couple of crazy counter points to consider

* Actually, just thinking about it, it's the electrons the pollywell configuration has to confine and they don't need to be high speed at all. Actually it's best if the electrons confined are very cold and slow ( for electrons ) so maybe the flux of the rotating magnets could be interesting. Furthermore electrons are more easily influenced.

* It's a scaleable thing, so making a bigger container of a polyhydra shape could maybe help

I guess the most obvious issue is if the 'eddy current' effects seen in the metal also applies to free moving electrons and indeed yes, if free moving electrons are just simply too fast to 'give a damn' about a magnetic field such as this.

Thanks for the feedback.

Cheers,
James

[edit] saleable => scaleable
Dan Tibbets
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Re: HENDO POLYWELL

Post by Dan Tibbets »

Sorry, but by my limited understanding, the electrons in the Polywellhave to be hot, probably very close to the average temperature of the ions. There are mysteries for me, but. The Polywell creates a potential well by having a small excess of confined electrons. They are hot and flying around at speeds ~ 60 times greater than the ions (because of their reduced mass). If the ions are traveling at a average speed of ~ 500,000 M/s, the electrons are traveling at a average speed of ~ 30,000,000 M/s.

They have to have this speed to create a deep potential well. Another view is the pressure of the electrons. Like a gas, the energy is the product of the (1/2) the mass and the velocity squared. A cold gas has proportionately less pressure. PV=nRT . It is the electron pressure that inflates the Wiffleball- opposes the magnetic pressure of the magnets. More specifically it is the electron pressure on the edge, where they are fast/ hot. On the edge the ions are actually cold because they are at the top of their potential well. Because of this the ions do not contribute much to the magnet opposing pressure. This results in much less magnetic strength needed to keep the plasma from expanding further. If the ions were as hot as the electrons on the edge, the resultant pressure might be ~ 60 times higher. That would be impossible to contain, unless you reduced density . The Wiffleball effect might still be achieved, but at densities much smaller. This would hurt output v, but it in mentioned in the patent application.

Another viewpoint. A potential well is just that- a potential. And potential is ofter referenced as Volts. Current is not directly involved until you start considering things like voltage droop.
For a high/ deep potential well, you need a high potential- Voltage. Voltage is essentially the kinetic energy per electron. To generate a potential well to accelerate positive ions to high energy, the potential well generating element has to be at the same voltage. It is a direct conversion between potential and kinetic energy. If you want ions accelerated to 100,000 eV, the cathode, or rather the virtual cathode made up of electrons must have that average kinetic energy. You can play games with the speed of the electrons in different parts of the machine, but the average energy must match the ion accelerating voltage. The potential well for the ions and electrons must match, it is just that they are pointed in opposite directions.

Dan Tibbets
JamesC
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Re: HENDO POLYWELL

Post by JamesC »

Before I bust this HENDO POLYWELL myth it just occurred to me the mechanism for electron confinement would be quite different. The electromagnetic polywell has static magnetic fields and probably does need hot electrons to create the potential you describe as it's just bending electron paths so to speak.

The hendo concept though uses changing magnetic fields and is actually using Lenz and to generate an opposing force directly - not just bend a path.
Lenz’s law explains how eddy currents are created when magnets are moved relative to a conductive material. These eddy currents in turn create an opposing magnetic field in the conductor
If this also works with free electrons then maybe the electrons can be the opposite to hot, cold actually. Even more so if the eddy currents actually produce losses (bremsstrahlung?) if this were true it might even produce a cooling effect which would be the ideal situation cooling electrons into the center of the device where they would work as the virtual cathode.

I am sure there must be a good reason why it doesn't work this way or you will point me to a 1870's paper of a device that does exactly this.

Cheers,
James
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Dave Xanatos
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Re: HENDO POLYWELL

Post by Dave Xanatos »

I've often wondered about a Halbach Sphere in combination with electrostatic confinement. Interesting topic... one of those things that seems sort of "intuitively headed in the right direction", but...

Of course it would probably cost a small fortune to construct a vacuum chamber within a Halback Sphere :)
It would take decades of work, by thousands of scientists, in a particle accelerator powered by dump trucks of flaming grant money! - Professor Farnsworth/FUTURAMA
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Richard Hull
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Re: HENDO POLYWELL

Post by Richard Hull »

Everything about fusion containment will cost a small fortune until it doesn't work at all, but the people employed in the effort find a way to spend a big fortune to make it bigger and better.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
JamesC
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Re: HENDO POLYWELL

Post by JamesC »

Anyhow* I backed the project to get myself a white-box. I plan to run some basic experiments by pointing a TV electron gun at it and seeing what happens. I will report back the experimental results but it will take a while, the white box's won't even ship until July 2015 and that's if they ship on schedule.
Dan Tibbets
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Re: HENDO POLYWELL

Post by Dan Tibbets »

In the Lenz law quote,eddy currents induced in the conductor- in this case the plasma may heat the plasma, but it would not aid confinement in a polywell. In a tokamak, with it's edge instabilities and various modes and techniques to control edge instabilities (eddies) locally applied or global warpage of magnetic fields, etc might be applied. This extremely complex and dynamic interaction may be necessary for tokamaks, but one of the key properties of the Polywell is that eddies/ edge instabilities are naturally suppressed due to the constant shape of the magnetic fields. This basic concept is basic to Polywell operation. It is true that this ideal condition may need to be manipulated, but not for containment. Electron injection is a big issue now and some dynamic time based variation in the fields either globally or locally, perhaps combined with POPS effects may be needed for both maintaining adequate confinement and efficient electron injection. Again, though, due to the tremendous speed of the electrons such timely modifications to the plasma behavior will probably be due to radio wave (microwave) input or curent/voltage variation of the electrodes. These can be changed rapidly. Even electromagnets consisting of just wires would have difficulty responding this fast due to inductance, hysteresis (?), and other effects, Electric motors with their rotating masses are even slower. In many ways the motors are stabilizing for a magnetic field. The inertia of the mass impedes rapid changes in the magnetic field. Variations over seconds or even milliseconds may be reasonable, but needed changes are more in the time scale of less than a microsecond.

Electric motors are associated with magnetic fields. Such fields could even have the geometry you wish. But, simple electromagnets without a rotor or moving mass does the same thing, probably more efficiently, and have faster (but still relatively slow) strength variation capabilities. There is no obvious reason to use electric motors as a magnetic field source in this application (that I know of).

Dan Tibbets
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