Thoughts on a fusion device: Project Sparkplug

More than enough time spent reading internet articles on the subject of fusion devices and developments around Lockheed's recent announcement got me into thinking about the general idea of how such a thing might work. As for the name "Project Sparkplug", it really is descriptive of the most basic and rudimentary underpinnings of the design. I think once the truth of the thing gets out, this is a tech that will spread like wildfire. (Most barriers to development are that low. Not just something governments in various countries will achieve, but in the college lab and garage scientist realm.)

But before that... Some thoughts on existing fusors, including those not necessarily over unity in terms of power output vs. input.

Obviously of course there are the H-bomb weapon devices, the supposed bringers of Armageddon. Thus the whole MAD scenario and playing a substantial role in creating the politics of the Cold War. These could be considered the granddaddy of the concept, as they were proof of the math and theory put into practice. The brute force example that nuclear fusion was possible for mankind to achieve. More or less involving an initial fission event to trigger fusion at a secondary or tertiary stage. I'm not going to go into detail, but interesting to read up on.

Then we have the plasma focus, something of an "electric toy". In relation to fusion, it's kind of along the right idea and where it all began. These date back to Tesla's own experiments. You have a circular device with a strong discharge, and the plasma streamers emanating from it accelerate charged particles of hydrogen. Every now and then, a chance collision occurs and you have a fusion event. Very low probability of fusion, so the power going in obviously is much greater than anything from the fusion going on.

From observations in behavior of the plasma focus, some clever old men stepped it up a notch trying to see if they could get more out of it. From there we have the Farnsworth/Bussard/Polywell type fusors. These used larger surfaces, higher currents, and more optimal geometry to achieve the same task as the focus fusor in a similar manner. I consider these an evolution of that device, just stepped up, scaled up, and producing more fusion vs. the power put in. For the most part, collisions are still random and not getting more power from the fuel than power being input. (And some like the Polywell were supposedly near break-even in later iterations.)

Tangentally, but no less important are the tokamaks and (circumferential flow?) spheromaks. (The type of reactor I'm getting to will technically also be a spheromak, but a few key operating differences.) This involves creating a plasma ring out of gas ions and magnetically compressing them. They're big and expensive, need a lot of precision, and yet they have some properties which I would consider flawed. Not that they're entirely wrong, far from it. The use of magnetic containment is quite key, and some ideas are sound, but the whole approach seems to be ridiculously difficult. The analogue of what they're trying to do with magnetic fields and plasma to initiate fusion is much like a popular toy of the 1970s and early 1980s, the water weenie. The more one tries to squeeze, the more energy and effort is involved in keeping it in place. (Good luck CERN, but you're doing it the hard way!) I consider Spheromaks of a related design a modest improvement, as it gets rid of unnecessary physical obstructions from the center of the reactor but the approach to fusing the plasma is still flawed in the same way.

Next up, the Z-pinch machine. Great, awesome, lots of lasers. But it's more or less a research setup better suited for heavy element fusion. Some aspects of the field collapse are what I'd consider "spot-on". But what they're doing with it is overkill in some regards. But it's great what they get with the research data, it should pay off later.

Next on are various "ball lightning" experiments and machines. None of these attempted to produce fusion as far as I'm aware of. However the principle of operation in some of these devices relates very strongly. Particularly in how they exemplify an alternate operating mode for the spheromak, efficient containment field generation, and some similar behaviors in particle collision to both the focus and Z-machines - but at the "happy medium" of the two.

Before I go on and follow up with a later post explaining the build as I imagine it... I'll leave everyone reading a video of experiments with ball lightning done by some guy in the Russian Tesla Club. Obviously it's done in a most crude, hacky, and dangerous way. Yet, to me - short of proper containment, it appears as a valid approach. This shows just how simple and relatively low power part of the fusion device I'm picturing can be. Some aspects of fusion are low-tech, so yes "Project Sparkplug" is a good name as any.

If you could get all the original notes (ha!) it would be interesting to go back to Farnsworth's first fusor. It is NOT a Farnsworth-Hirsch design. Farnsworth stated that he could initiate a reaction and shut down the device, and the fusion would continue until the D-T was used up. Grant you, the volume where it was going on was about 1-2mm across, but he reportedly demonstrated it on demand.

Neat... The ones I've seen documented seem to have a grid area or central volume where accelerated particles are left to collide on a fairly random basis. In some designs the particles are aimed at an area, but when talking about atoms/ions that's still pretty huge.

But now, to go back to describing something which I think might work. (Still short on some things with radio-chemistry and such, since my information is limited. But I may get roughly in the ballpark.)

In this case, I'll be describing a research style device. One intended to be broken down and adjusted, and troubleshoot and learn principles for later production models. The design isn't too concerned with getting a usable power output at this stage, but instrumentation would be used to measure heat out vs. power in, etc.

General appearances:
The main containment of the device is an empty cylindrical tube, a casing mostly of metals and ceramics. Bolted or welded together. It is a lab bench apparatus, somewhere between 3 and 8 ft long. (Components spread out initially for ease of modification, but the design I'm picturing has development geared to a portable design. Intended footprint of the fully engineered model should be comparable to a small-block V8 engine, so everything needed to operate it would fit in an engine bay of something like a light truck.) Materials are based on resistance to temperature and having high strength, but also in some cases radio-properties due to exposure to high-energy particles. (Don't want to get X-rayed unintentionally, exposed to UV, or other hazardous radiation.) Stainless steel/monel, ceramics, boron alloys, graphite, and there may be some moderator or other absorber materials. The majority of the operation of the device is electrical. It has more in common with the focus fusor devices than not. Capacitor banks, coils, switching circuits, control electronics. But it also requires some gas feedstock of hydrogen (gas lines and associated tanks going to it), and also uses lithium metal as a consummable internally. And of course supporting cooling systems with water jackets, hoses, pumping systems as needed. Interestingly enough, this device also borrows a lot from all the previous known fusors mentioned in the previous post, key operational aspects are heavily based upon them.

General operation:
This fusion is mostly a linear process, going from inside one end of the tube to the other. Plasma is magnetically compressed in a manner like that of a spheromak which is accelerated and fired into a reaction chamber where it is fused during a high energy collison event.

Process of operation:
Priming. First the fusion device is evacuated with some vacuum apparatus, and filled with hydrogen. This is kept at a low pressure below atmospheric. At the target end of the tube, an array of plates or grids are energized to disassociate and ionize the hydrogen in the tube. Power input in this case is not at the level of a focus type fusor, although it looks very similar.

The initiator. The initiator is at the other end of the tube. It consists of high voltage electrodes to pulse a spark across a gap. (Pretty much the main reason why this is called "Project Sparkplug", other than a commonality of shape in overall physical appearance.) A lithium (preferably of a heavy isotope) feedstock is fed into the initiator like a small welding rod. However very little is used. (It is actually about the size of a carbon lead in a mechanical pencil.) This is used to seed lithium ions from the tip into the arcing plasma. As the arc bridges the gap, a microwave beam from a magnetron is fired from a side chamber. (Strongly borrowing from "ball lightning devices", same principle.) This initiates an eddy current in the arc. The arc then separates from the electrodes. As this occurs one of two things will happen: either the arc will form a single loop and blow out, or the loop will fold over itself into a spiral toroid. The second state with a magnetially stable toroid containing hot lithium ions is what is desired from the initiator.

The pumping chamber. The pumping chamber magnetically isolates the toroid (which has it's own magnetic field due to the flow of current in the plasma ions) and via pulsed magnetic coils increases the amount of current in the toroidal ion plasmid until it becomes semi-unstable. In a way this stage resembles a spheromak, but at about 90° offset to compress plasma in a complex circumtoroidial loop instead of a single loop. Ions within this plasmid are being accelerated similar to a ring vortex, and the field of the lithium ion plasmid is much like that of a toroidal solenoid.

The accelerator. A good portion of the tube is like a short railgun. This is sufficient though, as the mass of ions is very small. But the goal is to accelerate the ion plasma to relativistic speeds while compressing it. The rails of the accelerator are actually a type of split ring coil that run parallel to the tube. The geometry is arranged to ramp up the energy density of the plasmid into an even more confined volume. Ion temeperature is boosted by some order of magnitude.

The braking (or is it breaking?) chamber. This is another set of coils similar to the railgun part of the accelerator, but with a different geometry. It has some minor similarity in operation to that of Z-pinch apparatus, as the field creates an EMP event. What this does is it pulls the outer shell of the toroidal plasma stopping it, and compresses the ions out through the very center as they swirl back around. Outside of the fusion, this is probably where the hottest temperatures occur. (But the fusion itself creates more heat, considering temperatue vs. volume.) This event breaks apart the lithium ions and atomically disassociates it, essentially a minor fission event that sprays out relativisitic hydrogen ions.

Reaction chamber. The reaction chamber is a refractory volume, shelled with the necessary alloys needed to focus high energy particle back to the center. During each pulse from the breaking chamber, the fusion event occurs with two peaks. One as the initial event, and a scecondary event due to the bounce-back and the refractory design of the outer fusion chamber walls.

As it is, it's pretty simple. The complexities are mostly in precision alignment/manufacture of coils, and precision timing for the firing of capacitor banks for accelerator and braking stages. Although high voltages and current are used, these are short duration or pulsed events so input power consumption is relatively low. The main output of the device is heat, but obviously there will be things like X-rays, gammas, neutrons, and some other high energy radiation from the fusion process and secondary reactions of anything exposed to it.

I may come up with some illustration later. Of course this may not be how the Lockheed device works, but as I said this roughly based on information around fusion in general and how such an apparatus may work.

I think overall cost to build a prototype could be fairly low as it is a smallish bench device, and materials needed are readily accesible (unlike the stuff for a fission reactor). So yes, it's in the realm of college laboratories and individuals with the extra cash to try tinkering at this stuff. Like I said, if fusion is this simple and it takes off, it'll be everywhere.

Thoughts on this?

a reply to: pauljs75

The original Farnsworth machine was a modification of one of his multipactor tubes. There wasn't a grid. I don't have access to that material anymore but it was very interesting. I don't know that it's not out in the mainstream. If you find any material discussing a fusor that's based off a multipactor, that's it.

It was pretty dang close to a stock multipactor, too, and IIRC the notes had it that he'd noticed these plasma formations inside gassy multipactors. He had a name for them that I can't pull out of the depths of reading through the stuff 15 years ago, but I'd remember if I saw it.

He'd found a way to make a multipactor that was 'gassy' with D-T instead of air, and he added one or two extra structures, not F-H fusor grids IIRC, and there was a method for initiating it that involved the extra plates. Once it fired off, you could power down the tube except for the extra plates that suspended the plasma ball and it would continue fusing until the D-T was used up. He had a lot of notes on how he planned to fire ionized D-T into the ball to keep it going, but then they booted him and wouldn't file a patent or let him license his own IP.

Interesting that you're saying there was another Farnsworth design. The fact you mentioned the fusion event was very small and confined in volume does sound like it's operating along the right lines. (At least regarding the scale of the device itself. It makes sense, as that's the most optimal or efficient way of getting the necessary energy density.)

It would be funny if what I describe half-reinvents the original Farnsworth or is a variation, as the only Farnsworth fusor I remember seeing is similar to the one similar to the Polywell or Bussard type design. I wonder if it's been covered up in the same manner as Tesla's work that went missing?

At least these days, inventors can open up their projects if they decide to do so and post directly to the internet. Which makes it pretty hard to hide if they want to share their work and progress with humanity as a whole. (Of course there may still be attempts to discredit or 404 information where it's posted, but once info is out there it should be reproducable and therefore testable.)

originally posted by: pauljs75
I wonder if it's been covered up in the same manner as Tesla's work that went missing?

ITT suddenly booted him and kept his notes and the multipactor Fusor, but wouldn't let him license it or patent it.

Maybe THEY got it going. Or were co-opted. Who can say?

There's a good bit of stuff out there. The word is "poissor"...

While testing high power UHF tubes Farnsworth discovered an anomalous self­focussiog space charge phenomenon. These space charge plasmoids glowed all the more brilliant with increasing application of voltage ... a control characteristic. He named these point­plasma phenomena "poissors".

"Poissors are brilliant space­suspended plasmoids of star­like appearance. When Dr. Farnsworth operated his multipactors the poissor phenomena manifested themselves with special brilliance. Electron optical focusing concentrates ions just as mirrors concentrate light. Early Farnsworth multipactors utilized twin opposed concave cold cathodes.

The design feature of concave electrodes was a radical departure in the world of electron tube designs at the time. Most electrodes of the day were simple planar surfaces. The concaves permitted the re­discovery of electron optics ... a phenomenon originally witnessed by Sir William Crookes and forgotten. Students are directed to the Crookes tube with its concave cathodes.

Farnsworth multipactors and cold cathode discharge tubes produce optically focused "poissors" and exhibited all the response­control characteristics later sought by plasma physicists in their race toward achieving hot fusion. Control­responsive poissors would shrink in size, increase in ionic density, and produce more brilliant light with increasing voltage application.

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