Archived - Example of magnet effects on plasma

[Carl Willis]

My $200 prize requires making 500,000 neutrons per second in a Polywell apparatus.

If I have to define "Polywell" more rigorously for that purpose, I would say that the necessary and sufficient features are a polyhedral magnetic-trap anode, a surrounding cathode, and the absence of any real electrodes interior to the anode. If people also want to call this or any component or effect therein a wiffle-ball or Polywell, they're welcome to. If they want to call something NOT meeting this definition a wiffle-ball or Polywell, they're also welcome to but will not get the money and will get askance looks from me for perceived jargon abuse. If contenders think that my definition of "Polywell" is not inclusive or exclusive enough...too bad, the $200 is my money (but I will hear your case with some degree of sympathy if the neutrons are in evidence).

I'm glad we cleared this up early or I'm sure some clown would haul out an AmBe neutron source and call it "Polywell" to lay claim to easy money.

If Tom Ligon wants to call Dan's construction a wiffle-ball because it resembles WB1, (notwithstanding the fact that Dan's has an interior grid, and an electrically-isolated magnetic trap that may or may not have any electrostatic confining effect on electrons), that's his business.

-Carl

[Chris Bradley]

Dan DT wrote:
> Concering Chris Bradley's question about current and voltage variations without and with the magnets- The measured voltages tended to be ~ 10% higher (at the same Variac input voltage) and the current ~ 10% less when the magnets were present.

This would be as I expect, a lower conduction load on the supply, and, of course (I hadn't thought of that) a consequent higher voltage from the less-heavily-loaded output transformer, due to interference in the electron's free path to the anode. I see no reason why this wouldn't translate into higher efficiencies, cf. a 'regular' fusor, though may still make no difference to absolute neutrons excepting from the higher voltages that might then be accessible with smaller supply voltage pull-down.

> ps: the magnets were not grounded. They were floated- so were they at the voltage of the cathode?, somewhere in the middle?

They will charge up to some natural balance, according to whatever charged particle flux makes it to their surface. Visual impression is that the shadows off the central grid tend to encourage particular ion flows off to the magnets at defined points, so would then charge up (at those points) to..???. This would be some complex mechanism where ions with enough energy (from nearer the shell, coming through the gaps) are re-routed so that they can make it that far. A pure guess might then be that there is a patterned distrubution of charge across the surface of the ceramic magnets creating electric fields parallel the the magnets' surfaces.

[Richard Hull]

The amateur polywell prize, AKA "Hull Prize", has lots of provisions to limit kludges not true to Bussard's original intent.

Read the rules and addendums it contains all manner of limitations and demands to keep crude, "also ran", kludges from taking the prize.

Key point: No inner gridwork of any sort is allowed, whatsoever.

Bussard sought to totally elimenate the inner grid and its attendant ion loses as well as limit or eliminate electron losses. A lofty and noble goal that would make IECF a possible fusion power contender again. Thus, any winner must show that these tenets are met in the case of their device in addition to the 500K neuts/sec.

We believe what we see and not what is told to us or what seems theoretically doable.

In the end.......Get a magnetically cusped device producing a negative central potential well that is totally gridless which produces a continuous 500,000 n/s and works within the stipulated neuts/watt power range and, then, some prize money will be in th' mail. Until that time a named polywell device means nothing......At that time, you can call it what you wish for you will have done something Bussard never did, but wished he could have.

Note*** I have placed yet another addendum to the prize related to my impending possible retirement.

viewtopic.php?f=7&t=242#p242

Richard Hull

[tligon]

I think it would be there if he supported the magnets on insulators, faced them with stainless steel, and used them as the machine anode.

Needs a headlight filament or ten as an emitter.

Yes, get rid of the grid. Although, in fairness, I did stick a HF grid in PXL1 once, to calibrate a PMT, and maybe to try our H-beta spectrometer looking for doppler broadening. Really kicks up the glow when the magnets kick in.

But he's got most of the parts there.

[Frank Sanns]

Dan,

I commend you on your work on this. To my knowlege, you are the only one of the amateur polywell crowd (besides maybe Tom L.), that has built anything related to the PW design. It is good to see you actually investigating how the configuration and its iterations REALLY behaves. You will no doubt find that making neutrons with a grid is tough enough. Channeling ions just to where you want them and noplace else is much, much easier said than done. Your work should be a goo model for the amateur polywell crowd. Keep up the good work and keep us posted.

Frank Sanns

[Dan Tibbets]

Thanks for the responses. I'm surprised it had not been done befor. But, mostly it was something to do with the surplus magnets from microwave ovens I had butchered for thier transformers, diodes, and capaciters (one also provided a fan that replaced my defective bathroom vent fan).

I had observed that the magnets would draw a concentration of the glow when they were waved around the outside of the fusor. I was surprised that I got as much definition of the cusp glows that I did. I thought that the magnets were probably two weak, and of the wrong design,and that they would not show a similar appearance to the described behavior of the Polywell magnet layout. I did find that having all 4 of the opposing magnets on each side was critical for showing the glow 'confinement' (for lack of a better word). I wonder if only the four lateral magnets (or more) would give a similar appearance in this gridded design due to the feedthrough stock on the bottom and the convergence of the wires of the cathode on the top. Once I get around to making a more robust and adaptable cage I might try different combinations of magnet numbers, distances, and cathode grids. A four lobed cathode (two crossed wires) gives me 4 diffuse electron/ ion/ glow beams. What happens if I aim them at the centers of the magnets, the edges? What happens to the voltage and current? I'm not in a position to test any positive or negative effect on actual fusion. I suspect it could be harmful (interfering with ion production and survival), unless some variation of magnetic fields (with effects mostly on the more easily controlled electrons) could be made to steer the ions away from the cathode grid- ie effectively increase the transpearency of the grid, while also perhaps decreasing the streaming of the electrons to the shell (ground).

Obvously, electromagnets would work much better (no face cusp as T. Ligon pointed out). But, that represents another whole level of complexity.


Dan Tibbets


ps: 1) I have no idea of the strength of the ceramic Microwave magnatron magnets I have harvested, except that there are two in each magnatron and they seem to be of similar strength across the three old microwave ovens.. Does a strength of ~100-200 Gauss sound reasonable?

ps: 2) I did a casual search on electromagnets, but did not find any immediate referances to strength vs amp turns. The closest I got was deived from some examples from which I calculated that ~ 30 amp turns produced 1 Gauss of magnetic field strength. Is this reasonable?

[MSimon]

Current loop simulator:

http://hyperphysics.phy-astr.gsu.edu/hb ... urloo.html

30 amp turns in a 0.18849555 m (0.61842372 ft) radius loop = 1 gauss at the center of the loop.

[Dan Tibbets]

Thanks. I have used that link befor ( it is a good capsulated physics reference), but I didn't even think of it. I just crossed my eyes looking at dozens (well, maby 10) of Google search possibilities.

Dan Tibbets

[Richard Hull]

This discussion might best be moved to the theory or construction forums. As this is where it might be searched for in future.

Try starting a new related thread.

Richard Hull

[Dan Tibbets]

Two additional images with magnets.

The first is ~ same as the initial image in this thread, except the magnets are spaced a little closer together.

The second image shows the same setup, except there was a 5 Mega Ohm ballast resister. At low Variac settings there was a red tinged glow- relative anode glow?
As the Variac voltage was increased this glow was pushed outward, then replaced with the more typical blueish glow. I wonder if this corresponds to an increasing electron pressure, changing the plasma interaction with the magnets- ie something similar to the "Wiffleball" effect (one can dream at least) at very low voltages and current.

Dan Tibbets

[Dan Tibbets]

Another picture of plasma appearance with perminate magnets in a Polywell type geometry. This time smaller weaker ceramic magnets from RadiaShack.

Dan Tibbets