A dynamic fusor

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A dynamic fusor

Postby Doug Coulter » Tue Mar 04, 2014 5:42 pm

Hopefully, this "speculation" is not utterly unfounded. Along the way - many hours of runs and fun in the lab, we've noticed a few things.
Some of that is due to our unique lashup, and sometimes, our failings, but we try to keep obvservant no matter what.

We are running our main fusor grid, cylindrical, usually about 1.5" long and almost 1" diameter, in a 6" by 6" sidearm of a much larger tank, about 14" by 26" ID. While we've tried a number of ion sources (mostly documented here) the easiest one is simply another 2 loop grid out in the main tank, off to the side. There are some videos here of us switching the main grid, with 50kv on it - on and off with a mere 10kv or less on that "ion generator" grid. If we push a little into the little guy, the big guy fires off, we turn off the little guy, and the big guy goes off too. In fact, some coarse measurements show that as a "vacuum tube" or more correctly, plasma triode, we've created a PNP tube (polarity speaking) with a power gain of something over 100, and a current gain of at least 5-10. Hmmm.

We also have had a number of faraday probes (really just rods or wires) in the big part of the tank, and when things are going, they always tell us that we have an enormous negative net charge imbalance (and this conflicts with a lot of theory posing as fact in a lot of literature, but there it is).

We've even measured the time it took for whatever negative it was - probably electrons, probably also some D- or D2- - to reach the faraday probe, one time using the secondary ion source grid itself as the probe (important for what follows) and the propagation time appears to be in the 10 us range. That's aweful slow given the voltages involved...either this stuff isn't getting full speed of the voltage, or what we're really seeing is something heavy and negative - as in charge-exchanged D- species.

An apparently unrelated observation is that we see highest Q at the lower gas pressures (which is borne out by the theories of space-charge defocusing we've known since the early days of electron tubes). We also see pulses of the very highest Q - 500-1000 times more than normal, during onsets, not in steady state, and it would be better had I not edited out "outliers" that were 100 times more Q than what I left in the data set, being conservative and all.

Let's put that together for a minute. Highest Q when it's hard to start, and only at the start. Low gas pressure. An incidental "valve" or tube with a crap-ton of power gain. What does that suggest?

Well, to me, it means I should be either driving this, or making an oscillator - we don't know which is best, and the math is kinda like fractal to figure out, so we are more or less reduced to just trying stuff. Could be that the idea driving waveform will be the opposite of what we get as an oscillator if we should make one - but we just don't know. And the idea that we could do this as an oscillator is just to elegant to ignore.

So, I'm making an oscillator. I will report in the proper place here when I run it, but of course I hope to be reporting far higher Q than normal, and various expected and unexpected results - that's the very nature of science. Why am I saying this first, then testing later? Well, good science predicts, and takes its lumps depending on whether the predictions come out true or not.

I therefore predict that an oscillator, or a driven system, will have far higher Q than a steady state fusor, which to me has appeared as what a math guy would call a "strange attractor" for dynamics that are not best, but worst case for actual fusion. We will know soon - why guess?

I just finished winding the secondary coil for the transformer. The primary is in series with the DC feed to the main grid. It has about a 3-4::1 stepdown (turns ratio anyway) and even though fine-pitch, may not go low enough in frequency to "go the right speed" - after all, we DO certainly have more than one species here - and we don't even know which one we want to be driving the oscillation! But we'll know...that's what lab time is for.

Since a picture is worth a lot of words and so on...
XfrmrMockup.JPG
Mockup - sitting over the huge power supply we might use to drive it (100kv@100 ma, which we'll never use all of)


Obviously I have a little more to do before this sees power. The bigger pipe is sched 80, for insulation. There is an 8" diameter wire-screened outer pipe not shown - this whole mess is more or less the center conductor of a large piece of coax, to keep EMI out of my other stuff - it can get pretty fierce otherwise. The secondary here will be connected in series with the little supply (and ballast) that normally drives the secondary grid. Both supplies have a lot of series R, for safety. We have so much power gain, I'm not going to worry about the losses there for now, it almost oscillates by itself anyway, from coupling inside the tank, but at some wierd, very high frequency (working more like a regular electron tube it seems). This should put it more on a basis of us choosing the frequency and which particles are sloshing back and forth how far and fast.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: A dynamic fusor

Postby Doug Coulter » Sun Mar 16, 2014 4:00 pm

Here's a paper I wrote up on all this. I'll be making a youtube vid soon about it, which due to the large number of new subscribers, will probably bring a lot of people here.

////
Extensions of the Farnsworth fusor

What we are doing in my lab currently does bear quite a bit of similarity to the original Farnsworth fusor, and it seems to be confusing many. We certainly owe the man and a few who came after a serious debt, intellectually. But they never truly succeeded, no one really has yet, although some, including my team, have done far better than the originators have.

Or maybe not, in some sense. Going back through history, papers, private communications, it seems many fusor builders report hard-to-repeat huge Q factors (defined as power out divided by power in). Since they are hard to replicate even in the same lab, they have been dismissed as “outliers” or “equipment errors”.

That same attitude would mean that if a modern biologist was brought Fleming's famous contaminated petri dish, some lab assistant would be in trouble, and we'd also not have penicillin. Luckily, Fleming was the sort of guy who paid attention to “outliers” and “equipment failures” - and also luckily, it turned out to be rather easy to reproduce in his case. Not as much so in a fusor, but philosophically speaking, it seems the same attitude would serve well in fusion research, and it's largely absent in other investigators. With ever better data acquisition, storage, and analysis, I've been able to “catch these in the act” a number of times, and now the challenge is simply to understand and reproduce them, as there is no longer any possible doubt that they do happen – bursts of Q many orders of magnitude higher than “normal” such that on an autoscale plot, the Q of regular fusion operation shows as “zero” by comparison to “thousands and higher” when these events occur. This seems worth the chase, the game is clearly worth the candle.

This document will describe what we've done differently here, and what we intend to do that's even more different.

Our setup is a bit unconventional. We are running our main fusor grid, designed to be a very good electrostatic lens (unlike all others we know of) inside a 6” cylindrical side-arm in a much larger tank.
Early on, we found that going to reduced gas pressure improved Q, but had power supply and other limits that prevented the fusor from “lighting off” at the lower pressures with the gas pressures we wanted to explore. We therefore developed various ion sources to allow us to go ever lower in gas pressure (another way of looking at that is “longer mean free path” over which a particle can travel without an accidental wasteful collision). While most of those worked at some level, what we've been doing of late, and which is a “little odd” is simply using another fusor grid (this one not so precise) out in the main body of the larger tank, to take advantage of Paschen's law, which shows that breakdown is a function of p times d – or in other words (counter-intuitively for many), below a certain gas pressure, electricity would prefer to take the longest path, not the shortest one. The reason is obvious in hindsight – if an electron can't get up to ionization energy of the gas before it is slowed down by collision with a gas particle in the extant E field, you get no ionization, and therefore, no discharge.
(put wikipedia link here for Paschen's law – nah anyone worth his salt will just type it into a search box and do their own homework)

Somewhere along the way, we also noticed that our extra grid could not only act as a switch for power draw and discharge on the main grid, but that we had created something that also had a moderately linear gain region, and amplifier, not just a switch. Tiny changes in the input to the “ion source” grid could control large power in the main one. In fact, we'd built a rather complex triode. In fact, it would even go into parasitic oscillations under a variety of conditions, as any amateur radio operator who has built a linear amplifier knows, these parasitics are usually NOT at a desirable frequency. In our setup, the frequency is very high – MHz, which is much faster than would sync with transit times of the various ion species we have in the fields we might reasonably have. The real resonance is beyond actual numeric computation ability at this point, we've asked the simulation software guys and they tell us this and refuse to take our money (and guys, thanks for being honest about that).

Further, we noticed that this happened most often at the edge of stability (the small more or less linear range of power gain between the grids), and while onsets were occurring. The steady state turned out, after quite a lot of data acquisition and analysis, to be the absolutely worst case for Q!

This happened a lot, with these crazy-high-good Q measurements, and I'm convinced that this is what others have reported the entire time, but dismissed. We did not do anything special here – it just “went off” into the mode, presumably tuned by the parasitic capacity, inductance, resistance in the circuits, and the transit times of the various species involved. Remember, this is a complex mix of electrons, D, D2, (and those two can be neutral, positively charged or negatively charged via charge exchanges). That's a lot of “stuff”, and it seems to have emergent behavior – it's quite difficult to do the math here in practice. Who would have imagined such a simple equation in complex numbers, like Z = Z2 + C, would ever have such a complex set of results as the Mandelbrot set, for example? The basic particle in field equations are about as simple as that, with the same idea – iteration – the last output of the system is the next input, except that we have attraction, repulsion, an imposed field, the field generated by the particles themselves, and various spring-mass systems going on, where the spring if the particle's charge and the true field it sees (not what we think we imposed, which is affected by the particles in it), while mass is simply its mass.

Further, armchair theorists have hugely misled the fusion community, without experimental data to back up what they say. They claim recirculation through the grid for example. Well, we don't see it here, and we've looked. Yes, a spring-mass system can have oscillations, but not gain – it always has losses, and with a DC input, there's no way to make up for those. Further, via charge-exchange (and other things) what we mostly see here is “once through and out”. Not only have we looked for the field fluctuations with the finest gear money can buy – and not found them – we HAVE seen rather large increases in fusion when the tank inner walls were implanted with fuel atoms. No guessing here, careful measurements that lead to facts are preferred. I often feel like the theorists think they know ecology of an anthill because they've studied just one ant. It's not that simple, guys.

Most fusors are build spherical, there's an emotional attraction to that shape, but we don't do it that way for a variety of reasons. Due to our realization that any shape electrode you put in a tank and put voltage on creates not only a field, but a non-uniform one that acts like an optical element for charged particles, we decided to design our “lens” with malice-aforethought to be a good one. Any book on electrostatic lensing will not show example that look the least bit like all of the spherical grids I've ever seen – and I will note that in 3d space, you cannot tessellate a sphere with uniform circles or anything else that would produce a good point focus. Even a bucky-ball kind of shape or level of complexity would be far too crude to produce the desired “compression ratio” we are looking for here. And with practical materials, you simply can't make even a bucky-ball without making it so opaque it's super-lossy, or simply won't hold up its own weight.

Cylindrical lenses don't have this issue (other than at the ends) and are easy to design and build to generate a line focus. So that's what we do here, and are still making incremental improvements. While we're not even to optical levels of precision, the simpler math would indicate we should (and should be able to) go to levels far more precise – on the order of the wave-function size (At FWHM) of the particles we want to focus would be nice! We are not even within a few orders of magnitude of that at present, so this is one of a few windows for what seems like a very reasonable way to improve.

Of course, at any real density, space charge effects will likely defocus our great lens – something that was worked out long ago by vacuum tube designers – the thing that causes a CRT to lose focus if the brightness is turned up too far. The particles of like charge do repel each other, else we'd not have to force them together in the first place! The one acknowledgment of the fusion community of the space charge issue seems to be when they think they can use it to create a “virtual electrode” that, using electrons, will draw in far heavier ions to collide there.

I hate having to remind people who pretend to be smarter than I that attraction and repulsion are bi-directional, and it's the lighter one that moves the most! That's a pretty huge sin of omission in understanding and only one of them that are widely considered to be “facts”. Anything like a close look into basic physics of course demolishes all such silly arguments. That's just not how it works!

So, it seems we want to go for fairly low power density, short focal lengths to reduce the bad effects of space charge causing “blooming”, and a few other things, like getting actual instead of fictional recirculation of the ions that we had to put in energy to ionize in the first place, that is, if we want Q rather than just a “star in a jar”. We might be able to tolerate very much higher densities if they were “bunched” since by the time the particles “see” one another's fields, they are already “on course for collision” having come from a very diffuse state (2.2 e-2 millibar, or molecular flow) into a much more compressed state at focus – our “compression ratio” if you will let me use that term. We have experimentally witnessed the actual transition from molecular to viscous flow here, many times, but haven't quantified the actual “compression ratio” thus far (it's not trivial to measure with what we have). It is, however visually obvious, particularly if you can then direct that flow through something that would only turn it if it had a very short mean-free-path, as in “high pressure”.
To coin a phrase, “nevertheless, it moves”.

There are some other considerations here. Pauli's exclusion principle (never proven wrong or even a hint of that) says that identical quantum states are excluded (geometrically if I understand correctly) from happening. And D's have spin of =/- 1. Trying to make two fuse that have identical spin would violate this principle, yet to the extent the forces we currently use bring them together, they tend to also align spin in the worst way for fusion – it's only by accident that a collision or something of that nature flips a spin and allows for fusion at all! When we do have them spun correctly we get D+D->He, but sadly, it won't stay that way – this releases about 16 electron mega-volts worth of binding energy, so the resulting He breaks up unless we have a 3 body collision; theres not enough binding energy even in He, which has quite a lot, to hold it together at that energy. A photon can't carry off the extra because photons themselves have spin and there are conservation laws in operation here that prevent cheating on that. Which no one observes being broken, so for now I feel fairly safe standing on the shoulders of the giants of physics past.

I am only one experimenter working in one moderately well-equipped lab, and I can therefore only try so much per run, or do so many runs in a period of time. Theory (and math) has let us down in numerous ways, so it seem the experimental approach is the way to go here. I'm sure some eyebrows will go up over that statement about math. OK, where's my feedforward solution to the very “simple” 3 body gravitational problem? No perturbation and division into tiny time slices allowed, and tell me where Jupiter in a simplified solar system is in say, 100 years or more. I dare ya. Yet that's exactly the sort of math we need to solve this problem without sort of trying everything that may make sense! Has math become merely the princess of science? I'd submit that we're verging on “chambermaid” at this time, for the important questions. I wish I was wrong, but I don't think I am. Even recursive systems (Julia, Mandelbrot) aren't well defined without just trying something, and even though that's well known, Wolfram comes along claiming he invented it (see his book) – years after the real pioneers.
Blind leading the blind in ignorance of history, as far as I can tell.

I'm not claiming to have invented the plasma triode – that seems to have been done by Phillips back in the 50's or so, not the guy 2 years ago who re-invented it and claimed all sorts of interesting applications in what used to be cool – plasma TVs. This was a PhD with no knowledge of things that have happened since my own birth – seems you can get a nice piece of paper without knowing too much these days. Or maybe I should soften that blow by calling it “not enough” these days to actually make a real advance, instead of adding a decimal point to something, or finding something that was already lying there.

But here we have a very interesting use for it. Like any active device with power gain, not only can it sustain oscillations, it can do so at more than one frequency at a time, in several distinct modes, from super-regeneration to reflex oscillations. And here we have a situation where those properties could be extremely useful. We might find that having the electrons bouncing back and forth at one fast frequency, yet controlled by bigger external fields than they alone generate might actually act as a useful virtual electrode for deuterium ions going a lot slower, but oscillating in space themselves. And have this drive them both! Of course, if that turns out to be impractical, we can always just drive this thing like the triode it is, with whatever arbitrary waveform we can generate - a little harder, takes an arb wave-function generator, but we have one of those too.

So, since I have to prioritize or dither endlessly, the next try is going to be taking advantage of this active device to see if we can't pull off something pretty elegant – using its own gain to drive particles around, flip spins, and make a nice transition from the lowest energy state (ions evenly spread throughout the tank) to a lower entropy state – ions of the correct spin all striking at the focus.

This seems to require no actually-new science, or violate any of the “laws”. Yet it would result in fusion Q numbers extremely larger than have been experienced so far – even in those “outliers”.

It's worth a shot, so that's what I'm doing next.

/////////////////////////

Here it is as a pdf:
FarnsworthExtension.pdf
as a pdf
(43.7 KiB) Downloaded 171 times
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: A dynamic fusor

Postby David Ashley » Tue Apr 01, 2014 4:05 pm

Doug Coulter wrote:Or maybe not, in some sense. Going back through history, papers, private communications, it seems many fusor builders report hard-to-repeat huge Q factors (defined as power out divided by power in). Since they are hard to replicate even in the same lab, they have been dismissed as “outliers” or “equipment errors”.

That same attitude would mean that if a modern biologist was brought Fleming's famous contaminated petri dish, some lab assistant would be in trouble, and we'd also not have penicillin. Luckily, Fleming was the sort of guy who paid attention to “outliers” and “equipment failures” - and also luckily, it turned out to be rather easy to reproduce in his case. Not as much so in a fusor, but philosophically speaking, it seems the same attitude would serve well in fusion research, and it's largely absent in other investigators. With ever better data acquisition, storage, and analysis, I've been able to “catch these in the act” a number of times, and now the challenge is simply to understand and reproduce them, as there is no longer any possible doubt that they do happen – bursts of Q many orders of magnitude higher than “normal” such that on an autoscale plot, the Q of regular fusion operation shows as “zero” by comparison to “thousands and higher” when these events occur. This seems worth the chase, the game is clearly worth the candle.


This discussion of outliers keeps coming back to me. It reminded me of a section in New Rose Hotel which is a short story out of the collection Burning Chrome by William Gibson:

He said that there was a certain wild factor in lab work. The edge of Edge, he called it. When a researcher develops a breakthrough, others sometimes find it impossible to duplicate the first researcher's results. This was even more likely with Hiroshi, whose work went against the conceptual grain of his field. The answer, often, was to fly the breakthrough boy from lab to corporate lab for a ritual laying on of hands. A few pointless adjustments in the equipment, and the process would work. Crazy thing, he said, nobody knows why it works that way, but it does. He grinned.


Maybe this is what you're trying to achieve. That is, there is some magical combination of adjustments that will yield amazing results.
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Re: A dynamic fusor

Postby Doug Coulter » Wed Apr 02, 2014 11:41 pm

Well, not exactly. I really like it when others manage to duplicate my work (which has happened on a few key issues) and there's no magic required to do so. I'm really focused on solving this one, as a personal quest - for the love of solving a really hard problem in a complex space.

This one is so complex that even if you can keep many-dimensional trade-offs in your head with ease - there's just too many and too much emergent behavior when you get to the lab for any simple armchair theorist to handle. We quite often see the theorists "shining on" the important phenomena - sins of omission, since they are hard to compute (that's actually being nice, many just commit the sins from intellectual laziness). The intention is really to share this with the human race, once we get there, and we've been making major strides of late.

The trouble with most of the extant theory is it's like, ok, we've studied a single ant or bee to the point where in isolation, we absolutely know how they work. It tells you nothing about how they work in a hive or swarm, where they interact with each other as well as with any external stimulus you apply. Who would have predicted that Z = Z2 +C would produce the Mandelbrot/Julia sets from such simple math? Any recursive process where the previous output is the next input has this set of issues that are poorly understood in a feed-forward or predictive sense, sometimes you just have to go try stuff.

Sometimes it's like the guitarist in my band and I looking at one another after a really hot gig. Hey, we're an overnight success! And then remembering there were 20 years of previous practice to get there and having a big laugh over that. Having done that once or twice already, I know what it's about in that regard. Sometimes the universe is its own best model, and it runs in real time - but only after you spend a lot of time and effort setting up experiments and learning from them.

I think the difference in approach here is that we actually look at our results - expected and otherwise, and make changes based on any new understanding gained - we don't get too hooked on "the way it must be" because...well, humility
(definitely not a trait I was born with, but had to learn). We've been wrong too many times to join a particular religion about all this. We know we don't know it all. So when we get a surprise, we try and learn as much as we can from it, and move ahead, even if it means ditching a lot of previous work, and turning to a new direction. The earlier work wasn't really wasted, it was education required to move to the next level, after all. No point getting all ego-hungup on a particular approach.

That's something where we have a very unique advantage (I say we, as I have this partner who helps a lot but doesn't like his name mentioned too often). We're not beholden to any external source of money. If we find out we were wrong, we can just try something new, something indicated as worth trying as a result of the data we've carefully collected on *everything* that happens, not just what we expected to happen. So we can just "follow our nose" and "keep our eyes on the prize" and fix the problem, not the blame - something that entraps big science badly.

Yes, there have been cases in my engineering past where a system was so complex that if they wouldn't let me in the room to constantly manage/tweak it, no one else could make it work. That's way not the goal here. I want it to work for all.
I expect the answer will be no more, or less, complex than say, a quadrupole mass spectrometer - and that's pretty complex, but manageable, after all, a lot of companies make those now and they work, but the math will make your hair fall out, there are just a lot of dimensions in the parameter space that interact, but once you know that, and have plotted out the shapes of the obvious ones, you can make one to specification without too much trouble. This is just about one or two more dimensions of harder than that is. That's actually a lot, but then, someone already worked that one out, so we only have to add the additional understanding for the 2 or so more. In that case, Q mass specs or penning traps don't work in significant space charge situations, and we have to have that to even get close, but the rest of that math and theory is the giants on whose shoulders we stand. Further, they only worked with one polarity of species and only a limited range of positive charges. We have electrons too - and they both help and hurt and are WAY different in E/M than the ones we mostly are trying to work with - far past the E/M range and with higher space charge interference than a mass spec works with, but a lot of the same ideas in terms of frequencies interacting with amplitudes - there's a "space" where you can increase one and adjust the other to match and get the same results, for example.

I think part of this is developing what I think is an all-important "feel" for how these things work by simply experiencing how they do so under a lot of different conditions. And my data mining multidimensional plotting software that can map anything we measure onto up to 4 dimensions and twirl them to look for patterns (something humans do better than computers, presently) helps a lot with that.


At any rate, I'll soon be posting the data from some runs we made based on the ideas above (or make some more formal runs to make pretty data - it's real repeatable just now) - and it's turned out that I was right. We just went a factor of about 2800 up in Q (output power over input power) from where we were, and we were already at record levels for this class of approach - in about 3 years work and about half a million bucks (not all my money, but I've put in my share). Compared to other efforts, I feel pretty good about this at this point, and it really does look like we'll make it in not a whole lot longer. We've been getting orders of magnitude yearly - and in only a few years we've eaten them up from 10e-11 to e-8 to...now e-4 or thereabouts. 10e2 is instant if we go to DT fuel, but I'd like to try to get there without that "freebie" b because it isn't really free - you need tritium for it, hard to get, to make, and also hard to be legal and safe with, along with a few other issues (the 16 mev neutrons that mix makes dislocate atoms in the tank material matrix and turn it to dust at useful power levels, which is why ITER's assumptions they needed it for gain shut them down - it'd take their machine apart in a very short time - if they got it to work at all). Nice to know it's there, but we'd rather get 'er done with cheap, easy, non-radioactive and abundant fuel.

The word is, so far, so good. We got this gain with the very first try at all, no tuning, tweaking etc. We could be WAY off the peak there, and the probability is high that we are, yet we got that much improvement. What if we're an octave off in something that has a Q (electrical sense) of 100? That's pretty likely, and in fact, it's likely that this first try was further off than that. Now to do the boring grunt lab work to find the right octave, and hopefully the peak, one more jewel in the crown. This may not be the last thing we need to get there, but it's almost certainly the next 2-3 orders worth. By the time we get that, I feel pretty confident we'll know what the next tweak will be, just from what we learn doing this.

And that's the point here - we don't allow ourselves to get addicted to one way of thinking - we can leave that to the bureaucrats. We just want it to work, whatever it takes.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: A dynamic fusor

Postby Doug Coulter » Sun Jul 13, 2014 10:54 pm

Just to tie up a few "theory" aspects of what we think we've learned lately. Yes, it appears that spin is important, and that DC "dynamic equilibrium" isn't the best - to the extent it has an effect on spins at all, it's a worst case - it lines them all up. Random is better (and right would be 2x better than that - we want anti-parallel). I think I've verified that in a number of tests, the last of which almost killed me - I picked up 100 msv in 30 seconds before I realized why all my sensitive counters and safety monitors went blank and just turned it off. I've since replicated that, and will soon give the details so others can too. We're now concentrating on more shielding so I don't have that happen again. Rad sickness is no joke, I know that first hand now.

I believe I've also learned that something people don't think about much, or perhaps correctly, is important. We always measure an electron excess when we have fusion going on. Always, and it's a lot, though I don't have exact ratios - getting the data on that is a bit difficult. Here's my theory on that. Well, we know we're going to have excess electrons - secondary emission and by golly, we're using a 50kv negative power supply to pump them in there...but there's evidently a huge difference between bound electrons and free ones - in what amounts to a somewhat polarized or charge-separated plasma vs bound ones.
Not so much that you can have this "virtual cathode" thing - I still believe that it's the electrons that will follow the far heavier and slower ions around, it just makes (Newtonian) sense.
While when electrons are bound, they tend to keep nuclei apart - that's why LLNL for example has to try so hard to push or shock them together (or the tokomak boys have to keep things very hot to keep full ionization even if it wastes 5/6 of the input energy into spurious degrees of freedom) - but unbound and with a large energy-speed differential so they can't recombine with ions - they help neutralize the Coloumb force as the ions approach our focus. That's the good side. The bad side is, of course, that due to their own field, they tend to neutralize the field we try to apply across the volume of the tank. There's no free, so to speak, so we don't get our ions up to anywhere near the energy of our 50kv input, not even close. But it doesn't matter as much because we don't need the speed as much, and actually, more speed would limit our time at tunneling range per pass, anyway.

However, since they are light and follow the ions closely, they tend to get between them and prevent them repelling one another as well as they might otherwise. This is an interesting picture:
Nuclear_force.png
Nuclear force between two nucleons vs distance.


For once, real numbers! They're a little scary when you talk 10e15 kinds of accuracy, but we now have a lot less to guess at.
Here's the wiki article that's from: http://en.wikipedia.org/wiki/Nuclear_force

According to the wikipedia article (a lot of these have been getting recent edits that make them more useful, the timing is interesting here) - the very right edge, about 1.8fm, is where the nuclear force overcomes the Coloumb force for two protons. Well, our case is a little more complex than that, since we have deuterons (and other stuff I'll ignore for the moment- but be honest about ignoring it).
We have a pair, assuming the correct spin combo (50% chance) so the nuclear force is double what is shown in the graph, though the Coloumb is just what the graph shows, since tne neutrons in the D's don't have any. Outside 1.8 (or a little further due to the more-nucleons, but only a little) fM - we have to hope for quantum tunneling into fusion, which is a probabilstic thing with more probability the closer and longer they are together - and this is where the electrons might be helping us linger longer inside the area where tunneling might be able to happen - the probability goes up with closeness (it's 100% inside 1.8 fm) and time...

There's just about no way we'll ever have a grid that accurate so as to get 100% - it's just not going to happen with stuff we humans can make, out of things we can get, but we can do a lot better than we have (I've proved that many times and it keeps getting better) - but we CAN get good enough to dramatically increase that time-distance product at the "focus" as I call it - that's what it looks like, though it's not looking just like light in a lens, and of course, what we see is the "losers" that recombine and give off light, not the ones "taking care of business" anyway. In essence, we're seeing a map of the lower energy outer edge of where the real action is when we view the poisser. And focus is getting so good it almost takes a magnifiying glass to even see it - that's progress. In fact, my best camera, though the layers of glass, can no longer get a picture of our focus, or sometimes, even the spread out beams, they are that faint and tiny - low losses are good for fusion, not so great if you want to see what's going on.

In our case, each beam is widest where it passes between grid wires, and narrowest at the focus and tank edges. Actually, at present, it's narrowest at the tank edges, the focal length appears a bit "long" for perfect focus at the center, but we're heading in the right direction when an experiment that improves our accuracy from 3-4 mils to 2-3 gives us factor of 10 better performance - that's huge for such a tiny change between horrible and somewhat less horrible - after all, we're talking mils (thousandths of an inch) error here - green light is 530 nm or so - and we want fM - another factor of a million over a nanometer to get to "perfect". (for reference: 1 nm = 3.93700787 × 10-8 inches, 530 is 2.08661417323E-5 in - or 2/100ths of one mil)

We ain't gonna get that down to a fM - the nuclei, much less atoms in our tungsten rods are much larger than that. But what we can do is improve vastly the region where "tunneling" occurs, its density, and time of residence at density (our version of the Lawson criteria, though not thermal, necessarily) to the point of possible gain - we are now getting nearly a milliwatt out of actual fusion, an amount that almost killed me in seconds...and don't need all that much more to start talking about "boiling that cup of tea". I think that's pretty huge, myself, even if I was the one to get there, and first as far as I know, in terms of Q anyway. Other efforts have done more fusion, but with FAR more input power. This is looking more like a compression ratio, or a finesse (in the spectrometer sense - resolution) problem than anything at this point.

We have discovered that grid accuracy in some sense has a very high exponent of "goodness" of fusion result, and have not yet found out how long that trend continues - we haven't found the other side of the evident peak yet. When we do - and we will - then other things come into play.

One is that spin alignment bugaboo. Another is the behavior of those sometimes-pesky, sometimes-useful electrons. Can we manipulate them such that they "get out of the way" at just the right time? An RF field might do that, but the math appears like that of a mass spectrometer - the frequency is dependent on a bunch of other things, it's just one number in the equation. Like a drift-tube accelerator, or a mass spectrometer, a number of things all have to be "right" at once or it doesn't work at all. So for now, more-better grid accuracy for a stable base, then the other stuff. though I must say, any sort of pulsing at all - almost anything that perturbs stable operation, has always shown us far more fusion per watt. I just think that's the spin alignment, and there's another effect to be had on top of that one that will, in the end, be larger and more important. I envision that it's going to look a bit like the Mathieu equation, but with at least one more variable, and that one (which is what makes quadrupole mass specs work) is already pretty hairy - so it's not going to be really easy to find that magic combo. This means our research goes first for the basic stuff, and repeatability, before we can even begin to work that search space, or so I believe at present.

I believe a further thing that is helping us is that most probably we're going in "neutrons first" when we start to get close. If I got the math right, the deuteron's natural frequency (quantum wavefunction stuff) is in the range of 10e22 or thereabouts, but when they start to feel that huge repulsive force, I'd have to bet that something so light would tend to line up so as to minimize tons of force. Again, plain old Newton here. There might be a further mumble-de-pegging going on as the electrons get squished out of the way, but...that's for the future to learn and hopefully control.

Right now, we're tooling up to handle the major breakthrough we already have - about factor 2800 or thereabouts. No more 100msv doses in 30 seconds for this worker. But when we do - it's onto the next, more accurate grid, finishing up sweeping that parameter space - the last time we scaled down, things got better and we've not seen the other side of that peak yet - then this RF stuff, and I think just maybe we're about there. And I mean THERE, as in "boil that cup of tea".
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: A dynamic fusor

Postby ScottMc » Thu Oct 23, 2014 3:44 pm

reading about the dynamic firing made me think of an unrelated little side project I had been toying around with. op-amp circuit with glow tubes exploiting the NDR curve. If I hand select the right group of bulbs 3 in series, they will illicit an oscillation between them, however the middle one stays unlit at all times, there is no capacitor or even inductor in the circuit. very interesting behavior. The oscillation is random and unpredictable. I have also played with a simple circuit employing series and parallel bulbs with small capacitance nF and very large inductance (greater then 10H) to exploit the NDR curve as well, the feedback loop produces a memresistor curve. What's the point? hmmm, without really thinking to hard on the nitty gritty details I wonder if what is being seen is attributed to the NDR curve point for that setup. And then I wonder if it's worth chasing down, would holding the plasma in it's NDR region prove usefull? is it even possible? I'll admit I'm very intrigued by that possibility and how it may impact the goal of fusion.
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Re: A dynamic fusor

Postby Doug Coulter » Fri Oct 24, 2014 5:12 pm

It's certainly something to keep one's eyes open for. What we've found so far is that the natural plasma resonance frequencies (or the even slower control loop stuff in our power supplies) are on the too-low side to have the effects we want. That pesky low-fusion dynamic-equilibrium sets in too quickly, or so it seems from what measurements we've been able to make thus far.

Remember, even if you don't put explicit L or C in a circuit, that doesn't mean there isn't any - there are always parasitics, often discovered (like with astronomy) when you get a 10x better scope or whatever. The ions themselves act capacitor like, but very slow motion (completely sub-relativistic) and through influencing the charge on electrodes as they go by - do interesting things indeed. Even the tiny rod through a good insulator on our main feed through looks like 40-something pf to ground when there's no plasma at all in there - it will doubtless change radically when there is, and also depend on what AC signal strength and frequency is added on top of our DC main supply, making things a bit complex to characterize.

Neons are fun - from the old "do nothing" random flasher box in Popular electronics when I was a boy (the '60s?), to use in ring counters and logic, to just plain fun. Even some older tube-type opamps I have used them as "zener diodes" though in that case, since they were in a light-tight sealed box, they painted them with a radium and phosphor stripe to get the strike voltage low and consistent. At the age they are - the phosphor has all been degraded, so you wouldn't know that without a geiger counter, that paint is pretty lethal stuff. I happen to have a lot of neon in a tank here and have made a few, though I've never reached that low strike voltage the pro ones have, even with attempts at a penning type mix. The real ones use odd metals (like cesium) on the electrodes, which I can't do here, which may be part of it, dunno. They look nice when lit, though.

Neons, from the ubiquitous Ne2 on up are great things to have around the lab if there's also HV around. Just corona will light them and warn you not to come near something if you simply stick them here and there - no explicit wiring required.

We are just at the point of beginning to be able to measure group motions, speeds and so forth, of ions and electrons in the fusor under "real" conditions. They largely cancel our imposed field in equilibrium, but can do all kinds of strange things if you can get them bunched up or otherwise oddly distributed. It smells like low-hanging fruit...we'll just have to pick some and find out.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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