Maybe some of you remember when i've posted a design with a cilyndrical grid system. That was before i read the fusor patent. I wasn' very suprised when i found the same arrangement in the patent as a possible fusor. But i've also found the toroidical grid design which really got my attention, since nobody here has tried it yet (at least not that i know of). I understand that it is somewhat harder to fabricate such a grid system but for some reason i think it should be tried (don't know why...i feel it should be, you know that 6th sense ). The "fusing" area in this case would be a circular string of plasma. Probably more energy would be required to achieve the same plasma density as with a spherical design at lower energy levels. I was thinking about building such a system. Also putting in thermionic cathodes (twin circle), and elevating the outer grid a couple hundred volts higher then the shell (as written in the patent) and using the usual 10 kV+ negative voltage for the cathode inner grid. This would be a "simple" DC fusor system. Now my plan is to excite the plasma by modulating the input voltage with a high voltage RF signal, tuned to the resonant frequency of the fusion plasma in the center of the toroid. Well i don't really know what kind of oscillation it is, but that is what i would like to find out. It can be the resonant frequency of the plasma, or it can be a resonant mode where in the center the electrons and ions are constantly switching places (in one period the electrons are in the center, the other they jump outwards and ions are compressed in the center). This would require quite a modulation amplitude. But with a couple of GS-15Bs (cheap and reliable) or other RF power tubes, or by using resonant cavities (DC to RF like in a magnetron) it could probably be done. In fact the fusor chamber itself can be a resonant cavity, with wave mirrors on the inside of the wall that focus waves right in the middle (or alond the string in case of the toroidical design) Well...this was my latest crazy idea . Now prove me wrong!
Constructing a toroidal fusor would be a real pain in the rump, unless you can split the whole toroid like a bagel. It really doesn't sound worth the effort.
Well, the camber would be a "donut" like toroid cut in half horizontally (as for a sphere).Doesn't sound that hard. Infact welding such a grid may be easier, due to its structure. All you have to do is to weld big circles onto small circles. See images below. The top image shows the outer and inner grid from the side, the bottom from the top. The only setback would be to keep the toroid's distance from the chamber wall, so at least two support points (one would be the insulated feedthrough ) are needed. Yeah i know what you say:"Then build it". Gladly! But first i have to collect some equippment and funds.
I like it mainly because it effectively increases the amount of plasma undergoing fusion into a stream. There are other whacked out possibilities here perhaps.
It would look real purdy in glass. (impractical)
Whose gonna' do it?
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
Okay so here it is. The vacuum chamber would be a stainless steel toroid cut in half horizontally and ofcourse bolts would hold it together (the same as a spherical chamber). Now you may be wondering how to put the cathode grid inside the anode grid. Well yes that is a tad bit complicated. There are some ways. One is to make two half toroids (vertically cut) and weld them together, or make the outer grid with a large enough opening in the bottom, and so on. So it can be done. Another idea is to make the grids from a single wire each, by winding the wire onto some sort of cilynder and then extending it (we would have a siral like a spring) and then connect the two ends , and presto we have a cathode or an anode grid. Ofcourse it might need more supports to keep it in place. To sum it up this setup can be easier can be the same can be harder to fabricate than a spherical system.
And I would WANT to do it. Hopefully i'll have a vac. pump soon (couple of weeks, maybe a month, i've talked to some guy in a small shop that sells a whole pile of "junk", everything from pressure gauges to gasoline generators)... The rest will come slowly but surely, i hope.
It still sounds like a real pain in the posterior. I would start with a cylindrical or spherical chamber first to get all the usual issues with vacuum sealing, power supply, etc. worked out before trying something as complex as what you described. You'll be spending a lot less money, too. The vacuum chamber you describe would be an expensive custom job, and difficult to seal.
I agree with you, i plan to first "get in the hang of it", by building a spherical system, and as you said learn the hard of it.
Why so difficult to seal? The sealing where the two halfs meet would be almost the same as for a spherical chamber wouldn't it?
By the way i think i have an idea to get around the expensive chamber problem. Imagine two pieces of a thick walled aluminium tube. One with a larger diameter one with a smaller diameter. Now we have two thick plates and place these two tube section between them, and use large bolts to press the two plates onto the ends of the tube sections. What we have now is a tubular chamber, with the middle cut out, like a rectangular donut. To keep the symmetry a thin piece of toroid shaped metal tube would be placed inside the chamber, since its inside the vacuum it can be really thin (or just a dense grid), and since its made of conducting material it will act like the inner wall of the chamber. Well? What do you think? I made a small drawing (sorry about its quality) in attempt to show you what i mean.
The problem is still sealing. You will need inner and outer seals. Unless you can find commercial flanges to do the sealing (I doubt this), you will need to manufacture your own. This multiplies the difficulty many times. Ask Richard Hull about his experiences with the home-made flanges on his Fusor III, with only a 6" chhamber size. The seals will also be larger in circumfrence than ones for a spherical or cylindrical chamber, unless you envision a really tiny toroid. This again multiplies the probability of a leak. The next problem is fastening - clamps or bolts? How many clamps, how many bolts? Can you avoid deformation of the flange while trying to tighten it down?. Finally, the o-rings may need custom fabrication, unless you can find large Viton o-rings of the right diameter. I would not try this scheme untill the problems mentioned above are worked out satisfactorily - otherwise it will be an expensive dead end.
Well sealing may be solved as the drawing shows below. This is just a proposal. As you can see on the left there is a hole in the top plate (cover) for a bolt. The black thing between the side wall and the cover is vacuum seal. Can be an o-ring or some kind of more dynamic material (i would like som advices here, is there something like "liquid rubber" or similar?). In this configuration the sealing would tighten as the vacuum increases. I don't think any significant deformation would occur because of the tightening bolts, since the material of the covers and the tubes is thick, and the distance of the bolt from the wall is small. If there is any deformation (like the middle of the cover bulges) the vacuum would most likely compensate. Well yes flanges would have to be home made. And i guess that is not so easy. I would prefer putting the falnges onto the covers, since those are flat. But i repeat that i agree that first i should build a demo system with spherical design. Even that is not a so simple task. And i can learn much from it.
It's funny you should mention this shape of grid; I actually brought a small, roughly made toroidal grid to the recent HEAS meet. I just whipped it up to show to a few folks to see what they thought about the idea.
The grids are easy enough to make. First I made just made one ring out of 0.060" stainless welding rod.
The ring was about 6 inches in diameter, and to it I spot welded a spiral "slinky" of stainless MIG wire (0.030"). Just let the slinky of wire curve all the way around the ring, spot weld as you go, trim off the excess, and viola: a simple toroid.
The best arrangement I've thought of so far for such a grid shape would entail two such grids as mentioned above, of different sizes of course, and with the same center line of circular cross-section.
Simply weld a little extra support to the outer grid and then snip it into two equal pieces along its "equator".
I always figured the easiest way to house it would be to put the whole thing under a nice, thick Pyrex salad bowl or something, with a baseplate.
Larry Leins mentioned some interesting ways one could play with a toroidal grid. One of the ideas I liked was setting up ionizer electron current to flow around the torus near the outer grid. This might allow more ionization than present ionizer schemes (ion guns aside).
There's probably a lot of ideas and speculations one could explore. I do like it as it tend to pack a lot of plasma into a relatively small space, but I definately would build a hot dog style grid first.
If I were serious about this, I would just make a long slinky like inner grid that was highly flexible. Next, I would buy a very expensive and maybe even custom made 4-6" diameter SS welded flex hose about 3or 4 feet long with conflats on the ends. next, maybe a 4-6" diameter stub with flanges about 4 Inches long for my HV connections, view port, etc.
I would then use some sort of standoffs attached to the inner grid ONLY and feed it into the length of flex hose. Bolt one end to the stub. Then form the flex and thus the flexible inner grid to the into a closed ring to the other side of the stub. Make appropriate connections and seal the last flange to the stub. It would work with a lot of proviso's with out to much strain, except on the pocketbook.
Figure about two grand for the custom flex pipe and flange assembly and stub. The outer wall of the torus need not be smooth, per se.
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
Actually that was my first thought. For a demo purpose that would work, because the ionization grid is the anode. Originally the anode is the outer metal shell of the fusor, and the outer grid is the ionization grid elevated to a slightly higher (couple hundred volts) potential than the anode, and a thermionic cathode povides electrons to form a cloud around this grid. Most of the fusor builders don't seem to bother adding such a cathode, nevertheless elevating the outer grid to a higher potential, or is simply just don't know of such an amateur system. Though i did see cathodes in some. So if i want a fusing toroidical fusor (probably first of its kind) the anode should be a toroid because this way the symmetry stays.
This is not an easy or cheap thing to build, but initially (and as many of you have said) there would be a "lot" of plasma involved, increasing the probability of fusion. Ther may be many other possibilities too. But first i simply want to see a shiny dot in the center of my kitchentable demo fusor .
Why wouldn't the chamber i've described work? Or is it just too complicated to fabricate (flanges and all)? Well getting such large diameter ss or Al tube sections may be hard. But sounds cheaper.
Use a Cylinder vacuum chamber, and stick a SS rod in the middle of the toroid . Trying to build a toroid vaccum chamber isn't going to buy you anything, except substaintial hair loss.
If you want to get fancy use a rod that has a varible diameter (ie thicker on one end than the other) Simply weld rods of various diameters end to end. You could connect it to a mechanical feedthough (push/pull) to alter its diameter in the center of chamber to adjust the focus of the toroid without devacuuming the chamber.
The problem your likely to run into is:
Its going to take a beef power supply to run it. Since the toriod will have more surface area to leak electrons, it going to take more power to operate
You run times will probably be short with out active cooling. Because you need more input power to drive it, its going to get a lot hotter than a sphere shaped grid.
I'd like to second the idea of a "hotdog" fusor though as a first pass.
Somehow, I think you can probably find a 6-12" diameter pipe a few feet long and putting spherical end caps on that is lot easier than making a toroid. This would amount to an electrostatic version of the "baseball" type magnetic confinement systems. You'd have a straight ribbon of plasma to work with.
The possibility of "focusing" the fusion reaction say at the ends of the ribbon in an oscillating plasma does provide an interesting way of pulling energy out with a magnetic coupling
I'd like to hear what actually happens with a toroid, although I think you'll get significant synchrotron radiation because of the bent path.
Ahhh... just though of my favorite endeavor... a plasma ribbon just might act as a wakefield accelerator the possibilities...
I'm using Auto CAD 2002 do design the chamber. I'll post the blueprints when i'll finish. I'm already done with one end-plate. I'll also design a chamber for a spherical and a "donut" type system. This may help others to build a chamber in the future. Ofcourse first i'll ask your oppinion on the design.
I do not know how this would affect but spherical design the electrons pass through the centerpoint from all directions in a toroid
electrons will cut through the choroid on a 90 degree plane all the way around giving you less of a negative charge a point and a spherical/toroid design the electrons are going to be unfocused.
Yes, i am aware of the fact that charged particles will not come from all directions, just on a vector that is perpendicular to the axis of the tube/torus. If you imagine a tubular grid with spherical ends , well that is like cutting a sphere in half and putting a tubular section in the middle. If we look at the point that is at the center of where the tube section and one hemisphere meets we see that particles come from all the directions of space in a 180 degree radius. Along the tubular section for a given point this is just a plane that is perpendicular to the axis of the tube. Like expanding one infinitely thin "layer" of the sphere that contains the center point (a plane that halves the sphere).
A torus can be imagined as an infinite tube. There is no end and there is no beggining. If we examine any point in the center of this torus along its center, then we'll see the same, that particles travel towards this center from a plane perpendicular to this center axis. So while a tubular design where there are two hemispheres at the end there will be two points where the plasma is probably more intense (but this may not be true since for most of the particles comeing from that 180 degree hemisphere there is no counterparticle to collide with, or to be more precise the collision will not be head-on, and these particles will not fuse thus the power invested in the acceleration is wasted), in case of a toroid the plasma intensity is the same at any point in the center. In case of a sphere there is only one point, and in that point (a volume of space in reality) there is a given intensity of the plasma, aprticles "flow" from all the directions of space. So in theory which will have the best efficiency, which will give the greatest amount of fusion at a given power level? A tube (with end hemispheres or without) and a torus may have the same fusing efficiency. Clearly a sphere is the most convinient, for its simplicity of design and that it accelerates all particles towards the same single point from all directions. A tube and a torus (given that they are practically the same) creates a string of plasma. All particles are accelerated towards a single line and all collide "head-on" just like in a sphere. A torus is a more elegant solution maybe, and an interesting geometry to play around with. So the conclusion might be that all the grid designs will have the same efficiency for a given power level compared to the size (fusion cross section). So the case might be that the main difference will not show in efficiency, but other ways, such as new experimental possibilites.
The ring of plasma material ain't moving or accelerating.
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
Gee, I woudln't bet on that one. Once you get 65kev into that toroid, something is going to travel down the axis of the plasma filament. Likely at around 4MEV, so a good bit of synchrotron radiation is a definite possibility.
Never the less, I'd love to see Adam's proposal and the results.
If there was any motion down the axis, it would be chaotic, and in both directions at once, not in the same direction. And how could the energy down the axis be greater than the aplied energy?
If there was any coherent on axis motion, then it would immediately hit the grid, since tehre is nothing for it to continue on axis sine the forces inside the inner grid are nearly zero, and there is no magnetic field to bend it (which would be what synchrotron radiation is.)
Greg and I are right on this one. There would be no urging electrostatically or magnetically to get anything in the plasma stream to do much of anything other than get the hell away from where it is now. AND get the hell away in any direction possible. Any direction will look better to the reactants and products than staying in the circular, chaotic plasma stream.
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
. Now prove me wrong!
