Building and Testing a Grid Idea.

[James Parkin]

Hi guys,

I have been away from the fusor communitiy for quite some time working on several fusion device ideas. I'm now currently at university and my research has progressed rapidly.

Currently I've been using genetic algorithms to improve the transparency of the grid and massively increase recirculation. I've finally got a great solution which is significantly better than the standard "ball" electrode approach. My design is a steady state, non ocsilating device, which I just need to build.

My research got picked up on by the Plasma Physics Department at my university and two professors had a look at my findings. They concluded that my assumptions were solid and that the device would operate as expected. One expressed a strong interest, but unfortunately the conclusion was that my university doesn't have the equipment.

I'm hoping that someone in this community has a fusor that I can purchase or use briefly to test my electrode design.

Failing that I'll have to build my own.

Either way I'm happy to release my code to the community at some point so that they can either run their own genetic algorithms or easily try out their new fusor configuration.

Regards,

James, UK

[Chris Bradley]

JamesParkin wrote:
> .... improve the transparency of the grid and massively increase recirculation. I've finally got a great solution which is significantly better than the standard "ball" electrode approach.
.. bold claims, indeed.

You may've noticed, James, that simply eye-balling a fusor in neutron-emitting trim shows up a distinct beaming effect that follows the electrostatic minima. There is a self-organisation to these beams in which ions that do not follow such trajectories will 'die out' and will not liberate further ionising electrons that can then cause ionisation at their collision points with the shell (at the ends of the beam trajectories).

These are only observations, but I would regard them as sufficient to cast doubt on claims that grid transparency is a limiting factor in a fusor's capacity to force a few fusion collisions to happen. I've yet to see a strong argument to the contrary. In fact, come to think of it I have yet to see any argument for that. I've only seen the claim repeated and repeated until it has 'become true'.

But that's not to say efficiency improvement may not be possible. You could reduce the 5 watts or so that go into heating up the grid by a full 500%. That'd represent a full 1% improvement in efficiency of a 400W fusor! (Gee!!)

Even if it is a bigger saving than this, why would it be anything more than just saving a bit of lost electrical power, rather than an increase in fusible collision rate?

I think it would be quicker to simply show the grid design you think is an improvement, and folks can take it from there. Some may even try it out for you, though there would be an expectation that you should back it up with your own work ....

[James Parkin]

I'm curious then, if it's not grid losses, why is there current being pulled by the fusor at all? If the electrodes were charged, further current wouldn't be needed to maintain the voltage of the fusor and the fusor would no longer pull current. Surely the only reason current is being pulled is because ions and free electrons are formed depositing their charge on the electrodes and depositing their charge and thus allowing a current to flow.

Why else would you be pulling current?

Regards,

James

[Chris Bradley]

JamesParkin wrote:
> Why else would you be pulling current?
A fusor is a discharge bulb, in which continuous ionisation of its internal gas liberates electrons and ions. The ions recirculate (a bit) through the grid, whilst the electrons nail the shell of the fusor. Most of the current is from these electrons, completing the circuit between the central cathode and outer shell. The actual ion current in recirculation at any given moment is much smaller than the electron current.

The actual process by which the electrons fed into the central grid, by the PSU, enter the plasma is likely to be a combination of processes. I tend to harbour the belief that this is mostly from the plasma inside the grid interacting with it (because the neutral plasma will diffuse out and come into contact with the grid) and via that interaction electrons flow into the central plasmoid, and so excess electrons in the central plasmoid can then be a source of electrons (and that whole central plasmoid would then take on the electrical potential of the inner grid, increasing the effective area of the grid). The interaction of the plasma with the grid would explain heating effects on it.

Some here have expressed a favourable view towards the grid emitting electrons by thermionic emission, but the problem with that is that it is cold to start with so that doesn't explain why there is a current on start up. However, once in operation then this would also be a source of electrons. Electrons might also come about from pure electrical stress around the grid wires. Again, although this field emission might be a source of ionisation, this should vary in the effectiveness of grids made of thicker or thinner wires, but it does not seem to follow. However, this would also be contributory, no doubt. In short, multiple effects lead to the electron current and it is largely irrelevant what those actually are to be able to comment that there is, indeed, an electron current.

I have previously posited that if a grossly-simplified model [presuming that the operating region remains neutral, so there are as many electrons as ions at any one time] is applied then the ion current will be some 1/60th of the electron current (from the elementary principles of equations of motion).

Once the gaseous density drops below some critical pressure, the rate of electron liberation will drop below the rate of electron losses, and at this point the plasma will 'extinguish'. With a higher density, the flow of electrons through the gas may still cause enough 'cascading' to maintain the electron population, and the plasma 'lights'.

[Carl Willis]

What does this new idea entail?

It's possible that you might get extremely lucky and find someone with a well-instrumented fusor nearby who is willing to let you fool around with it. But it's far more practical to describe your idea, make the case for it (explain the model and its results), and see if any fusioneers take the bait. (If it's a compelling enough idea, lots of people may try it and give you lots of data.) On the other hand--and presumably just as valuable for you--seasoned fusor builders may see holes in the model that discourage the expenditure of resources to test it. As you know if you read this forum much, theories abound from "armchair physicists" that real fusioneers just laugh at. There is no substitute for getting your hands dirty.

-Carl

[James Parkin]

I'm more than happy to release the details to individuals but I'm hesitant to just release the idea. If you consider yourself a seasoned "fusioneer" then I'm happy to fully explain it to you or anyone else directly via e-mail, etc. You can then determine the validity yourself.

I understand this is not a great way of getting results or help, but I have put hours of computational simulations into the design and spent time talking with professors and then repeating the process till everyone thinks it'll most likely be an improved design. I've approached it with a view of assuming it's a load of nonsense and attempting to poke holes in it. Currently the only areas which are uncertain are if the plasma density at the focus will be what is expected. My simulations create jets which are very similar to implemented designs, but obviously what will occur when all the physics is taken into account is another story. I may well reconsider releasing the design to this community however.

Regards,

James

[James Parkin]

The papers that I have read indicate that the current that is pulled by the fusor is due to the free electrons caused by the ionisation of the ions impacting the grounded wall as they are forced towards it, depositing their charge. At the same time the ions which are flying impact the central electrode taking up charge and neutralizing, this process would occur everytime an ion colides with the grid, thus a current flows as charge is transferred.

I'm pretty sure that this is more or less how a discharge lamp operates, so on that point, I'd agree. However I'm attempting to stop the deionisation due to grid collisions to stop or reduce current flow into the fusor.

Apart from this mechanism how else would current flow. Or have I misunderstood your previous explaination?

Regards,

James

[Chris Bradley]

JamesParkin wrote:
> The papers that I have read indicate that the current that is pulled by the fusor is due to the free electrons caused by the ionisation of the ions impacting the grounded wall as they are forced towards it, depositing their charge. At the same time the ions which are flying impact the central electrode taking up charge and neutralizing, this process would occur everytime an ion colides with the grid, thus a current flows as charge is transferred.
So, you're saying that current is from positively and negatively charge ions heading in different directions? Never heard that one before! Where do the negative ions come from?


> Apart from this mechanism how else would current flow. Or have I misunderstood your previous explaination?
I think you might be. You seem to be proffering the idea that as many electrons head to the shell as ions to the grid, and so that means as many electrons get 'neutralised' at the shell as ions at the grid.

This is false, and defeats the laws of physics. At all times, the operating space in any non-magnetic discharge device is under the simple principle that it remains charge neutral (and any deviations from net neutrality would be dynamic, short-lived events or oscillations). If it were -ve then electrons would get pushed out of it, and if it were +ve then it would draw electrons in. This is just the manifestation of Gauss' law. Now, if the total ion current to the grid was equal to the total electron current to the shell, then it would mean that the total fluxes of each would have to be equal, which would in turn mean that they would have to be travelling at the same speed (because, on average, they cross the same distance). However, as they are under the influence of the same electric field, clearly the much lighter electrons will travel much faster than the ions.

For the electrons to travel faster than the ions, but for the operating space to remain charge neutral, means that the electron flux is higher than the ion flux. One way or another (as I mentioned before, we're not particularly bothered how), this means electrons must flow out of the grid and head towards the shell. This is the primary route for current flow in a fusor. The consequential ionisation processes must be charge neutral (because any produced ion will liberate ion charge and electron charge, in equal measure). Some of those ions and electrons from ionisation will get neutralised along their way, some make it to the electrodes. But as the total electron flux has to be higher than the ion flux, so the electron flux is made up of 'conducted' electrons from the grid together with 'ionisation' electrons from collisions in the working space.

Seeing as it takes an electron 1/60th of the time to accelerate across the space as it would take an ion (square root of the ratio of masses, per s=1/2 (F/m).t^2), it seems logical to presume, in the first instance, that the electron current is 60 times the ion current. There are several caveats along with that, but it is a first-pass approximation. So the outcome is that 58/60ths of the measured current is a throughput of electrons from the PSU with the plasma as a conducting element, 1/60th is from electron ionisations being neutralised at the shell, and 1/60th are ion neutralisations at the grid.

[James Parkin]

Chris Bradley wrote:
> So, you're saying that current is from positively and negatively charge ions heading in different directions? Never heard that one before! Where do the negative ions come from?
>

I was unclear:
The papers that I have read indicate that the current that is pulled by the fusor is due to the free electrons, as a result of the ionisation of the ions, impacting the grounded wall as they are forced towards it, depositing their charge. At the same time the ions which are flying impact the central electrode taking up charge and neutralizing taking up charge, this process would occur everytime an ion colides with the grid, thus a current flows as charge is transferred.

I'm saying the current comes from electrons and ions heading in different directions and electrons only being added to the system when an ion is neutralised at the grid.

> > Apart from this mechanism how else would current flow. Or have I misunderstood your previous explaination?
> I think you might be. You seem to be proffering the idea that as many electrons head to the shell as ions to the grid, and so that means as many electrons get 'neutralised' at the shell as ions at the grid.
>
> This is false, and defeats the laws of physics. At all times, the operating space in any non-magnetic discharge device is under the simple principle that it remains charge neutral. If it were -ve then electrons would get pushed out of it, and if it were +ve then it would draw electrons in. This is just the manifestation of Gauss' law. Now, if the total ion current to the grid was equal to the total electron current to the shell, then it would mean that the total fluxes of each would have to be equal, which would in turn mean that they would have to be travelling at the same speed (because, on average, they cross the same distance). However, as they are under the influence of the same electric field, clearly the much lighter electrons will travel much faster than the ions.
>

I agree, electrons do get pushed out of the device and head for ground there would most certainly be a charge on the shell, and as it is earthed the current will flow to earth removing the charge from the shell. After startup, current then continues to enters the system by ions neutralising against the negative grid. These atoms in time ionise and the electrons move to the shell. The repetition of this is your current transfer. The time of flight is irrelavant and current is dependant on the neutralisation ionisation cycle with allows new electrons to enter the system and then exit only as fast as the ions hit the grid.

[Chris Bradley]

JamesParkin wrote:
> After startup, current then continues to enters the system by ions neutralising against the negative grid. These atoms in time ionise and the electrons move to the shell. The repetition of this is your current transfer.

This makes no sense to me as a sustainable description of the general physics of discharge plasmas in the glow-discharge regime.

Good luck with your endeavours with a new grid design.

[James Parkin]

Would you indulge me a little more. I'm interested in your perspective and I could well be completely wrong.

Assuming we agree current enters and exits the fusor and thus electrons must flow some how.

How do you think electrons are released from the central grid. As I believe this mechanism is the crux of this dicussion.

[Carl Willis]

I just think that a detailed and public discussion over the meat of the idea is the only practical way to get it tested in a fusor, short of building your own fusor of course.

We are by name an "open source" community, embodying the ideal that shared contributions improve the quality of the hobby for all participants. In this case, if you share your idea, other people with the physical means to test it may give you proof of the principle, practical feedback, and publicity; and they would get better-performing neutron sources for their own use out of it. The practical alternative to leveraging the open-source hobby community is to follow the commercial approach--keep your ideas to yourself and just hire a consultant to build apparatus or run tests.

-Carl

[Chris Bradley]

JamesParkin wrote:
> How do you think electrons are released from the central grid. As I believe this mechanism is the crux of this dicussion.

I have described the 3 possibilities I think are probably at work in viewtopic.php?f=6&t=3281#p20639 . In reality, it will be a mix of effects.

For further understanding of the way electrons flow from/into a conductor into/from a plasma where plasmas interact with a solid conductor, you should take a look at descriptions of how a Langmuir probe works. It's quite complicated when you get down to the detail and involves accelerating electrons across sheath layers, but it is a well understood process.That should cover it.

If you want a real simple explanation that paints a picture (albeit somewhat inaccurately), imagine metals as 'solid plasmas'. Both plasmas and metals have mobile electrons, and this is why both conduct. So if you put a plasma in between two metal conductors and apply a polarity across the two metal electrodes, the plasma will form an element in the circuit and will conduct electrons, just as if it were another piece of metal connecting the two electrodes.

[Dennis P Brown]

The amount of power released by a fusor is trivial and worse, as shown by others, the issue of Bremsstrahlung radiation losses would dominate any fusor even if you, somehow increased power output by an incredible value of six, or even seven orders of magnitude. This is in no way meant to say improvements are not worth trying but a fusor in the current 'potential well" design just isn't viable and nothing based on that design can achieve viable energy production. Until that issue is addressed, all other improvements are but little more than 'window dressing".

[Richard Hull]

Chris has pointed out again that there are many modalities in the fusor, all happening in concert, both benficial and detremental.

Carl points out that this is an open source type forum and exhorts for a full exposition or to go off, keep the secret and build and test on your own.

The fusor must glow to work as is commonly found in the simple device. This glow is just like a piece of neon, only we are operating a deuterium lamp that must be operated at a criticalpressure in flowing gas. As a circuit element, the fusor must be treated as a dynamic, almost infinitely variable, impedance.

Breakdown to glow mode is a matter of high field emission as it is in all such glow lamps. At a given potential applied across the high gas impedance load, based on electrode geometry, electrons are shorn from surface atoms and ionizational breakdown occurs. When this happens a vast gulf of voltage hysterisis becomes obvious as a huge current flow develops as the impedance plunges. This forces an often massive reduction in voltage to keep from destroying the power source to some greatly reduced sustaining voltage at a reasonable supply current. The hysterisis between strike and run voltages in a fusor at 25 microns might be as much as 5000 volts!

It is obvious that in a cold fusor, initial glow start is brought about by high field emission for the above reasons. The trigger event near this high field point can be a cosmic ray event or a local radioactive component triggering breakdown. Precision trigger voltage points are often fixed in many discharge devices by highly controlled geometry, fixed internal gas pressures and moderately strong internal radioactive sources of long half-life.

It is the cathode and its geometry in a DC system, especially the fusor, that the first electrons are emitted from to begin the ionization process.

Microampere Tritchel discharges in a dark fusor can trigger bursts of x-ray emission and even tiny amounts of fusion, but these are only noted at the very ragged and razor thin edge before full ionization glow discharge begins.

Richard Hull

[James Parkin]

I'm aware of this issue, however, just as a point of discussion, why can't fusors rival tokamaks, which also emit Bremsstrahlung radiation? Assuming that the ions in a tokamak have the same magnitudes of energy, imply that they also have the same velocities, plus as they are going around in a circle they are undergoing a similar magnitude of acceleration if the radius is the same (a = rw^2 for centripetal force and a = xw^2 for simple harmonic motion). Is it correct that the conclusion of this is that tokamaks have an increased chance of fusion? (Possibly due to increased energy? Or even increased Density?)



Regards,

James

[Chris Bradley]

JamesParkin wrote:
> why can't fusors rival tokamaks
Rival in what way? Fusors can only uselessly burn up a kW or so of power, whereas tokamaks can uselessly burn up 10's of MW of power. 10,000 fusors all working at the same time could waste as much energy as a tokamak!

Have I misunderstood your question? ..

Tokamaks are thermo-nuclear devices, wheras fusors are beam-target devices. The difference is that the former is described as 'hot' [all the ions are at fusionable energies], whereas a fusor is 'locally hot, generally cold' [only a near-zero percentage of ions are at fusible energies]. The former therefore loses energy very rapidly by these bremsstrahlung processes. The fusor does too, but it loses more of its energy by thermalisation processes [where ions lose their energy directly through momentum-exchanging collisions with molecules and ions] and by charge exchange reactions and loss of energy by fast neutrals.

[Donald McKinley]

James
James wrote
>Assuming that the ions in a tokamak have the same magnitudes of energy, imply that they also have the same velocities,

They do not have the same velocities. You can find references to this in a search.

Don

[Carl Willis]

I am on the fence about closing this thread.

On the one hand, it began as a prospective "Construction and Operation" topic. If the grid idea alluded to gets described with enough detail to be considered a blueprint for an actual experiment, then this is a fine place to continue THAT discussion.

On the other hand, the thread's momentum on the original topic has decayed. We are now mired in some theoretical backwater, "beating around the bush" (or perhaps focus has evaporated entirely).

We are either going to have a legitimate discussion about "building and testing a grid idea" (meaning, for starters, that we need to know what the idea is), or we're going to have to move along. Any subsequent posters to this thread need to make up their minds. Thanks in advance.

-Carl

[James Parkin]

No, you have actually given me the answer I thought was the case. I thought thermalisation was the killer not Brunstrang radiation. There seem to be many confilicting opinions and theories on this forum. I'm happy though, it generates discussion and forces one to check literature to determine the facts and the valid theories.

[James Parkin]

I've decided to team up with a few students and begin building the fusor within the university. I've sourced power supplies and vacuum pumps, however, a vacuum chamber is harder and more expensive to obtain. Any suggestions as to where one would get a cheap one or repurpose another piece of equipment?