Manipulation of the fields to increase the collision rate?

Discuss the technical details of an "open source" community-driven design of a polywell reactor.

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ccain84
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Manipulation of the fields to increase the collision rate?

Post by ccain84 »

First, I'm a web developer who is in WAY over my head, and reading many of these technical posts gives me a huge mental inferiority complex. So, please forgive my ignorance.

Anywho, here's the basic idea I had: subtley manipulate the magnetic fields so as to increase the number and "quality" of collisions.

Here's a specific idea, probably half-crocked, idea of how one might achieve this.

1) Oscillate the magnetic field (and therefore the electron well) along just one of the axis. This might by itself increase the collision rate because the ions would periodically be "running into themselves."

2) Of those ions that escape the grid, use a second set of external magnets (electromagnets or permanent?) to steer as many ions as possible onto the same axis as the internal oscillation. Then as they are re-circulated back into the magrid, they will have a greater likelihood of colliding "head-on" with the internally oscillating ions because they're moving along the same axis.

A not-so-great analogy might be the turbocharging of a car engine; to increase the power, you intentionally jam more air into the engine than would normally be present.

It just occurred to me as I was trying to follow the discussions of collision probabilities that you might be able to increase this probability via manipulation of the fields.

Or is this the same idea as the POPS thingy??
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D Tibbets
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Post by D Tibbets »

Varying the conditions inside the Polywell or any other type of Fusor may have benefits. Dr Nebel who is leading the research at EMC has as much knowledge of such issues as anyone as he was one of the co-authors of papers concerning POPS (Periodic Ossilation of Plasma Systems (?)). This uses microwaves to bunch, manipulate the ions. May, also have other uses such as ash extraction, slowing or recovering from thermalization effects, etc. Varing the magnetic or electrostatic fields would presumably similar end effects as POPS.
Keep in mind that ions that escape confinement are at the top of their potential well, so actual energy loss is at a minimum. Concerns about vacuum and arcing may be more significant. Also, structures that return/ recirculate these ions may interfere with electron recirculation or direct energy conversion.
I don't know if the machine could work with a more oval- cigar shaped Wiffleball. Oval or cylindrical gridded fusors can work in this way, though I'm uncertain of relative efficiencies. I have seen some reports (Univ. Illinois) of two cores side by side, so that the final appearance might be something like an hourglass(?).

Dan Tibbets
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MSimon
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Post by MSimon »

One minor correction POPS runs in the range of 100 KHz to 30 MHz depending on the species of fuel and the size of the reaction volume.
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MSimon
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Post by MSimon »

ccain84,

Welcome!

You would be well advised to note your newbie status in your posts for a while. Some of the folks around here get crotchety (Me. Me.) if they get a hint that you are pontificating above your level of expertise.

BTW you seem to have done your homework. Excellent!
Engineering is the art of making what you want from what you can get at a profit.

zenakuten
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Post by zenakuten »

When I first discovered the polywell this was my first thought - then I saw the video and indeed they applied a microwave to it.

Shouldn't the frequency range match the resonant frequency of the fuel's nucleus? 2.4 Ghz is what a water molecule oscillates at so that's why microwaves are tuned to that frequency. But what does a boron nucleus oscillate at? Is it in the POPS range mentioned above or maybe a harmonic of it is in that range?

Another idea is to apply a carrier frequency from a radio transmitter to the coils in addition to their normal load, tuned to give a constructive wave to the plasma. At the right frequency the energy from the transmitter should be transferred to the plasma, kind of like a tesla coil (the magnets are the primary, the plasma becomes the secondary).

I admit, I am software developer first and have little real knowledge in electrical engineering or physics. The general idea is that once the ions are contained near enough in the magnetic bubble in the middle, coax them to 'hum' just right so they will fuse.

MSimon
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Post by MSimon »

zenakuten wrote:When I first discovered the polywell this was my first thought - then I saw the video and indeed they applied a microwave to it.

Shouldn't the frequency range match the resonant frequency of the fuel's nucleus? 2.4 Ghz is what a water molecule oscillates at so that's why microwaves are tuned to that frequency. But what does a boron nucleus oscillate at? Is it in the POPS range mentioned above or maybe a harmonic of it is in that range?

Another idea is to apply a carrier frequency from a radio transmitter to the coils in addition to their normal load, tuned to give a constructive wave to the plasma. At the right frequency the energy from the transmitter should be transferred to the plasma, kind of like a tesla coil (the magnets are the primary, the plasma becomes the secondary).

I admit, I am software developer first and have little real knowledge in electrical engineering or physics. The general idea is that once the ions are contained near enough in the magnetic bubble in the middle, coax them to 'hum' just right so they will fuse.
All good ideas and they have been extensively discussed here.

1. Polywell is a beam-beam machine not a thermal machine. Microwaves not tuned to the beam frequency would disrupt operation.

2. Applying a phase rotating RF frequency to the grids is an interesting concept. It may have to be tried to prove/disprove its usefulness.

3. Low level microwaves are used for diagnostics of the plasma.

Use the search feature to find the various discussions.
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chrismb
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Post by chrismb »

zenakuten wrote:2.4 Ghz is what a water molecule oscillates at so that's why microwaves are tuned to that frequency.
Just for info, this is a false bit of information that seems to circulate around. 2.4GHz warms up H2O well enough, but is not a resonant frequency for water. It is picked for EM spectrum management reasons, not for optimising warming up your TV dinner.

MSimon
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Post by MSimon »

chrismb wrote:
zenakuten wrote:2.4 Ghz is what a water molecule oscillates at so that's why microwaves are tuned to that frequency.
Just for info, this is a false bit of information that seems to circulate around. 2.4GHz warms up H2O well enough, but is not a resonant frequency for water. It is picked for EM spectrum management reasons, not for optimising warming up your TV dinner.
It may also have had something to do with magnetrons left over from WW2.

I believe Raytheon was the first company to make microwave ovens.

Yes. It was Raytheon.

http://en.wikipedia.org/wiki/Microwave_oven
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tombo
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Post by tombo »

Microwaves heat water by depositing energy in a bending mode. IIRC
I had thought they tuned the frequency to that mode but once you mention em spectrum allocations the true situation becomes clear. Any time politics enters the picture any optimization with physical reality is compromised.

Ionized elemental particles have no bending or vibrating modes. The only spring-like forces to restore position and allow a resonance are the E & B fields. So any pops tuning involves the whole device. This complicates the situation considerably. But, it also creates more knobs to turn on the process.

Have any experiments been done with 2 coil beam-beam machines that operate somewhat like a very simplified polywell? Somewhat like operating an original 2 coil cusp machine to create opposing oscillating beams. My mind's eye sees it somewhat analogous to light bouncing back and forth in a laser's cavity. It would of course have the equatorial loss cusp therefore not work as a reactor, but it would provide a simplified platform to explore and understand the pops process.
-Tom Boydston-
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

zenakuten
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Post by zenakuten »

Thanks for all the info and corrections about microwaves. I was thoroughly misinformed :oops: Upon further investigation it seems the frequency I'm looking for is much, much higher than I previously thought (in the exohertz range for atoms, even higher for ions).

I did some further research and discovered sonoluminescence. I believe this is conceptually the model I was thinking of when said "apply a radio transmitter to the MaGrid".

The mechanism for sonoluminescence remains unsettled, but as far as I understand it can be understood as similar to a note played on a slide guitar; the large mechanical vibration of the soundwave is transformed into higher and higher vibrations until they are vibrations of electrons and ultimately light waves. There is of course much more to it than this of course, but that is the ultimate outcome.

To apply the same principle to the polywell, the radio frequency transmission should be applied to opposing faces of the MaGrid such that a standing wave forms between them. The sound waves are replaced with radio waves, but it's the same idea. The plasma should still react to it, IMO. The frequency would be difficult to calculate but would depend on the plasma's density, pressure, size, etc. and probably best be left as a adjustable knob on the device.

Xardion
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Post by Xardion »

I'm not sure if there's a misunderstanding here about the POPS effect, but POPS doesn't apply RF to the electric field directly. It uses an RF fluctuation at the POPS resonance frequency applied at an amplitude proportional to the voltage of the grid. I.E. a +/-4V amplitude change applied at POPS frequency to a 250V grid, so that the potential changes from 246V to 254V at 450kHz, for example. I think talk of injecting microwaves is referring to using ECR to ionize neutral gas.

zenakuten
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Post by zenakuten »

Actually I think that's what I said :) The RF has to be applied in addition to the MaGrid electrostatic field. Without the electrostatic field the potential well would be weak.

I did more research on the POPS effect and this seems to be the right idea, but it needs more RF frequencies set at frequencies near multiples and harmonics of the the resonant frequency of the plasma. From what I read POPS is good in that it keeps the temperature down while still letting fusion happen, but I think there are a lot more interesting things you can make happen with multiple frequencies. I admit I did not do much research into POPS when it was first mentioned to me, but it is very much the effect I was after, except I'd want to experiment a lot more with different frequencies to achieve different outcomes from the plasma.

I think a similar effect to POPS is happening in sonoluminescence, except in sonoluminescence, multiple frequencies are hitting the plasma due to reflections of the sound waves off the container. Instead of the temperature staying relatively the same as with POPS, here it skyrockets.

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Post by MSimon »

zenakuten wrote:Actually I think that's what I said :) The RF has to be applied in addition to the MaGrid electrostatic field. Without the electrostatic field the potential well would be weak.

I did more research on the POPS effect and this seems to be the right idea, but it needs more RF frequencies set at frequencies near multiples and harmonics of the the resonant frequency of the plasma. From what I read POPS is good in that it keeps the temperature down while still letting fusion happen, but I think there are a lot more interesting things you can make happen with multiple frequencies. I admit I did not do much research into POPS when it was first mentioned to me, but it is very much the effect I was after, except I'd want to experiment a lot more with different frequencies to achieve different outcomes from the plasma.

I think a similar effect to POPS is happening in sonoluminescence, except in sonoluminescence, multiple frequencies are hitting the plasma due to reflections of the sound waves off the container. Instead of the temperature staying relatively the same as with POPS, here it skyrockets.
If you hit a resonant circuit with 2X its resonant frequency nothing happens (relatively).

Now it may be a good thing to pump in at the electron, boron, and alpha frequencies but they are not harmonically related.

And bouncing waves off a wall (unless it is a very special kind of wall) does not change the frequency. It does change the standing waves.
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