Newbie pB11 Fuel Questions

[NoSmoke]

Hello all. Have just discovered Focus Fusion and have reading just about all that I have been able to find on this fascinating subject. Personally, I have few physics credentials (I’m a Chem Eng retired) but I have a few questions I would like to pose if I could.

If p-B11 does not result in a viable power producing system, would D-D (or D-T) be a possible fall-back solution for these devices?

If p-B11 does work, and works well, would p-N14 also be a good possibility (not sure if there would be any great incentive to go there though).

If the neutrons produced by p-B11 side reactions are not energetic enough to induce radioactivity, what happens to them (do they decay or just hang around)?

One way of direct conversion of the alphas to electricity is via “venetian blind” collector device which as I understand it produces v high voltages (> 1MV?) which would require expensive hardware to convert to more usable values. Would then the conversion “coil” (if that is the correct terminology) proposed for the FF device produce lower voltages and therefore be advantageous in that respect?

Why would the alphas exit the plasmoid preferentially to the p and B11 ions (all being positively charged)?

I’m wondering what would happen if two or more FF devices were pointed at each other (in the same reactor vessel) such that the plasmoids may combine and possibly augment density or ion energy. Has anyone considered looking at that?

Would a working p-B11 reactor likely have to be fueled with H1 and B11 only (i.e. fuel isotope separation would be required)?

Thanks and good luck to all involved…….. 🙂

[Aeronaut]

Welcome to FocusFusion, NoSmoke. I’ll try to answer the questions I can, and let others fill in the physics parts.

We’re currently burning D-D to confirm that the machine and sensors are working correctly and reliably, as well as proving as much of the theory as practical in the known regime of D-D fusion. But the fuel of choice is pB-11, make no mistake. Like the PolyWell’s venetian blinds, our coil is likely going to be handling some incredible voltages on every single pulse. Fortunately, 5MW at 1MV works out to only 5A, which should help somewhat.

The low energy neutrons are still dangerous, since they drill through flesh just like their high-powered counterparts, which do have the energy to make cells radioactive. These low energy neutrons from the aneutronic fusion side reactions can be shielded to less than background radiation levels using a 1 meter water jacket surrounded by 10cm of boron-10, covered by a few cm of lead. The shielded version would not need much more floorspace than the test rig, except in production units we’d need to add some serious vacuum pumps and power conditioning circuitry. Figure a 2 stall garage with a high ceiling.

In any given machine cycle, the p and B-11 ions are crushed into a near-solid form by the collapsing magnetic field, into what we call the plasmoid- a microscopic magnetic bubble which heats and compresses the fuel gasses into the range where fusion pretty much has to happen if science and theory are both right. This eliminates most of the individual fuel ions, replacing them with the helium ion beam and the electron beam leaving the decaying plasmoid from opposing ends, as directed by the magnetic field. The electron beam is somewhat imaginary, since it is absorbed by the plasmoid, further heating it.

Didn’t know that p-N14 was an option- can’t remember seeing any threads discussing it.

[NoSmoke]

Aeronaut wrote: Welcome to FocusFusion, NoSmoke.

Thank you – I look forward to spending more time here.

We’re currently burning D-D to confirm that the machine and sensors are working correctly and reliably, as well as proving as much of the theory as practical in the known regime of D-D fusion. But the fuel of choice is pB-11, make no mistake. Like the PolyWell’s venetian blinds, our coil is likely going to be handling some incredible voltages on every single pulse. Fortunately, 5MW at 1MV works out to only 5A, which should help somewhat.

I would think either high voltages or high amps or something in between (maybe depending on how many turns in the coil(s)). It would still seem advantageous however to keep the voltage, if possible, to levels that could be used m/l directly on-site to minimize conversion costs. I wonder if it is even practical now to convert 1 or 2 MV DC at 5MW to lower AC voltages with currently available hardware?

In any given machine cycle, the p and B-11 ions are crushed into a near-solid form by the collapsing magnetic field, into what we call the plasmoid- a microscopic magnetic bubble which heats and compresses the fuel gasses into the range where fusion pretty much has to happen if science and theory are both right. This eliminates most of the individual fuel ions, replacing them with the helium ion beam and the electron beam leaving the decaying plasmoid from opposing ends, as directed by the magnetic field. The electron beam is somewhat imaginary, since it is absorbed by the plasmoid, further heating it.

Not sure what is meant there – are you saying that the fuel ions are “eliminated” by being (mostly?) converted to fusion products or that they are expelled from the plasmoid by some other means that distinguishes them from the alphas (after only some have fused?).

Didn’t know that p-N14 was an option- can’t remember seeing any threads discussing it.

It wasn’t here that I saw it – could have been the Polywell forum. In any case, as I understand it, the advantage of p N14 is that there are no side reaction neutrons at all. It is the tail end of the CNO fusion process that goes on in large stars but I’m not sure if the final step would actually happen in an earth bound reactor.

N14 + proton -> O15 + gamma_ray
O15 -> N15 + positron + neutrino
N15 + proton -> C12 + He4

I was able to find this (possibly fanciful) description of a CNO reactor designed to power an interstellar spacecraft:

http://projectark.net/projectark/fusion_drive.asp

N14 occurs in the atmosphere in small but usable concentrations so the fuel is there if the reactor can be developed.

One other comment if I may. I have gone through the

“Introduction to the Plasma Focus-
Machines, Applications and Properties
S Lee & S H Saw ”

presentation and have noted there are many plasma focus devices in operation (or were). Yet I did not notice any mention of developing a power producing device – only machines to generate neutrons and gammas etc. or, any mention of p-B11 devices other than the FF effort. I’m wondering then what technology sets the FF project apart from the others?

Thanks Aeronaut for responding to my post…..

[Aeronaut]

No problem, Nosmoke. Lee’s program is designed to teach plasma physics in countries that lack the budget to build tokamaks. Their main use seems to be making X-rays for integrated circuit wafer plant photolithography. Lerner designed FoFu-1 specifically as the third and final scaling experiment to verify his and Aaron B’s theory that the DPF could fuse hydrogen and boron-11 for commercial power generation. Our chief advantage over the other pB-11 designs is that we don’t need to build electromagnets. We may also have something of an edge in detail of the theory, but that’s just my speculation.

Yes, the ion beam is fusion products, rather than either of the fuel ions.

I’d like to see the 5MW expressed as lower voltage and higher current, but we have to work with what the plasmoid and coils send us. Maybe some smoke and mirrors with paralleled coils and or phase shifting?

[jamesr]

Aeronaut wrote:

Yes, the ion beam is fusion products, rather than either of the fuel ions.

I understood it is mix of products and unburnt fuel from the plasmoid. The fusion products start with high (8.7/3=2.9MeV) energy but are confined in the plasmoid recycling their energy and keeping the plasmoid hot (100’s keV) for ~50ns (ie thousands of orbits of the plasmoid). When the magnetic field collapses the rate of change in B-field creates the huge E-field which accelerates the ions in one direction at ~2.6±0.2MeV and the electrons in the other.

Also regarding the CNO type reactions, apart from the higher temperatures needed – the reliance on the beta+ decay of intermediates means the products must be confined for many half-lives of the radioactive decay – ie hours not nanoseconds. ie impossible in all but large hot stars.

[Ivy Matt]

I’d think neutrons would be preferable to gamma rays. You’re probably thinking of a couple of threads on Talk Polywell, here and here. The reaction under consideration was the p+N15 reaction. The advantage of the reaction is that it uses nitrogen, which is plentiful and gaseous at room temperature. The output is a C12 and a He4 ion, with a total of 5.0 MeV, as compared with 8.7 MeV from p+B11. As nitrogen is plentiful in the atmosphere it seems like a good candidate for a SSTO vehicle. The disadvantages of the p+N15 reaction are that it is more difficult to achieve than p+B11 (but see the next paragraph) and produces somewhat less energy. However, if net power from p+B11 fusion is possible, net power from p+N15 may not be far behind. Another disadvantage of p+N15 fusion is sort of the mirror opposite of a disadvantage of p+B11 fusion (using decaborane, at least). Whereas the input of the p+B11 reaction (decaborane) is solid at room temperature, an output of the p+N15 reaction (C12) is a solid at room temperature and would tend to coat the walls of the vacuum chamber in an ordinary fusion device. In a plasma focus device I imagine most, if not all, of the carbon would end up in the tube containing the coils and possibly on the coils themselves. But that would be an engineering problem….

Regarding D+D fusion, my understanding is that, according to Lerner’s theory, fusion is actually easier with heavier gases in this particular device, so there’s no reason to go with lighter elements that produce more neutronic reactions.

A p+B11 reactor will still need neutron shielding, but the neutrons are short-lived and will decay soon after the reactor is shut down, making maintenance of the reactor relatively safe and obviating the need for long-term storage of spent reactor materials.

I’m with James. I would expect all positive ions within the plasmoid to be expelled in the beam, but the high-energy alpha particles are the most interesting for generating electricity.

I believe I read somewhere on these forums about an experiment in which two plasma focus devices being pointed at each other, but I don’t recall if there were any interesting results. I don’t think LPP is currently looking into it.

Regarding the fuel for Focus Fusion, LPP is considering decaborane (B10H14), which is a solid at room temperature. I’m not sure where they get the B11 from…by enriching decaborane, maybe? There are other boranes that are gases at room temperature but, as boranes are toxic, they would prefer to work with one that is a solid at room temperature, as solids don’t tend to sneak up on you the way gases do.

As to what separates FF-1 from other plasma focus devices, I would say the main difference is that Eric Lerner has a theory for how fusion could work in a plasma focus device and, on a physical level, FF-1 is a small, high-voltage plasma focus device. Other plasma focus devices are either large and high-voltage or small and low-voltage. According to Lerner’s theory the combination of small size and high voltage should produce the best environment for nuclear fusion.

[Arvid]

Since the heading is “Newbie Questions” maybe nobody will mind me sticking in a couple of mine, rather than starting an identical thread….

A) On the subject of neutrons created by the boron-11 occasionally fusing with a helium nucleus: Why is any helium sticking around? I can see where this would be a problem in a tokamak, but the alpha particles created in the focus fusion device are going to be heading for the other end of the machine at about 12,000,000 m/s; couldn’t you peel them off after they’ve passed through the coils and given up their kinetic energy and sequester them so they don’t go back and come in contact with the fresh fuel? And….

2) When I first started reading about proton-boron fusion 40 years ago, they never mentioned that side reaction with helium—it had probably only been done in colliding beams at that time, so I suppose it never came up. They did say, however, that every once in a grand while when a boron-11 nucleus absorbed a proton, it would manage to get rid of enough energy by emitting a gamma-ray photon that it could stay together as carbon-12, but in an excited state that would still emit another shakedown gamma—kind of like cobalt-60, only with a half-life of 12 hours instead of 60 years. Does that really happen, or would the kinetic energy with which the reactants come together in the focus fusion machine be too high for that?

[Rezwan]

Hi folks, great discussion. I just changed the title to reflect the topic a bit more.

[vansig]

jamesr wrote:
When the magnetic field collapses the rate of change in B-field creates the huge E-field which accelerates the ions in one direction at ~2.6±0.2MeV and the electrons in the other.

I thought the ions in the exit beam would average around 600 keV?

[jamesr]

vansig wrote:

When the magnetic field collapses the rate of change in B-field creates the huge E-field which accelerates the ions in one direction at ~2.6±0.2MeV and the electrons in the other.

I thought the ions in the exit beam would average around 600 keV?

If their temperature (ie random spread in velocities) were 600keV then the beam would be ~2.6±0.6MeV. The energy in the beam comes from the huge, tightly wound, B-field transferring its energy to an E-field, which in turn transfers to the ions, accelerating them into the beam. The ions thermal motion is just superimposed over the top.

Also note, I have assumed all the fusion product He ions have completely thermalised in the plasmoid before the beam is formed – transferring the fusion energy partly to maintain the plasma temperature against X-ray losses, but also maintaining the B-field, until it’s eventual collapse.

[rickPS]

Hello everybody, new to the FF forum myself. I am extremely excited by the work the FF team are doing and follow them with a keen interest.

However, I have a question that has been puzzling me for some time, concerning capturing energy from the ion beam, particularly the ions created by the fusion itself. I can understand that when the magnetic field collapses the ‘original’ ions in the plasma will move along the axis of the device (with the electrons moving in the opposite direction), but I don’t understand why the He ions resulting from the fusion reaction will do the same. My ‘gut feeling’ is that the energy of the fusion will be carried away by the 3 He nuclei in different directions (just like the DPF animation), which is not only intuitive but would also conserve momentum. If so, how then could the kinetic energy of the He nuclei be captured along one axis? Does the collapsing field impart a change of momentum to the nuclei so that they move off in one direction? If so, shouldn’t there be an equal and opposite movement of something (electrons or the plasma residue) in the opposite direction?

[zapkitty]

The helium nuclei have no electrons, and thus carry a net charge. That charge is what the field grabs and propels out along the axis.

The electrons have a net charge as well, one that is opposite the He ions, and thus are also grabbed and propelled… but in the opposite direction.

But unlike the ions the electrons don’t get far, instead they are absorbed by the plasmoid that generated the beams, heating it further and causing more fusion events.

Added note: the forces are opposite but due to the setup the resulting effect is unbalanced… and that’s why NASA originally funded DPFs: they wanted a fusion space drive.

[jamesr]

There seems to be a bit of confusion between the energy/direction/velocity of the He ions and the formation of the beam. They are more or less completely unrelated. I guess the important thing to consider is that you still get a beam of ions out of a collapsing DPF pinch (hypothesized to be a self contained plasmoid structure) even if you don’t get any fusion.

A collapsing DPF pinch will always create the electric field accelerating ions and electrons into a opposing beams. As Zapkitty says the electron beam losses a lot of its energy as the electrons try and plough through the plasma, but the heavier ions have enough inertia to carry on out through the surrounding plasma.

rickPS: Yes the He ions will be emitted in random orientation away from each other – although not all three out from a point in a triangle, instead the excited C12 spits out one He4, then the leftover Be8 almost immidiately splits into the other two He4, conserving momentum in each case. These He ions although traveling very fast don’t get very far as they are still bound to spiral around the magnetic field lines.

If B = 1GG = 10000 Tesla, and the 2.9MeV He4’s have a velocity of ~1.2e7m/s then in the ‘worst’ case when the He ion is emmitied perpendicular to the B-field the radius of curvature is: 0.02mm

So the He ions will just spiral around in a small volume the field having collisions with the other electrons & ions in the dense plasma of the pinch, heating it up. Such that each He will lose all its excess energy and become thermal within a few picoseconds, compared to the 10’s of nanosecond life of the pinch

[NoSmoke]

Ivy Matt: My bad – it was p+N15 (and what I read was the Polywell thread so thanks for finding it).

I have read Lerner’s (is that the polite way to refer to him here?) comments that p+B11 goes easier at or around the ideal temperature for that reaction but, does it necessarily follow that D+D (for example) would not be as favourable (as p+B11) at the ideal D+D fusion temperature (i.e. a much lower and presumably easier to reach temperature)? Perhaps it has to do with the greater magnetic field that accompanies the p+B11 fusion conditions (?). Anyhow, that’s why I was wondering earlier if D+D could be a possible fall-back route to take.

Just another wild thought – since blem radiation is generated by the reaction of electrons with ions in a plasma, could it be reduced by stripping some of the electrons from the plasma by some means? I suppose that might increase confinement difficulties but maybe there is a favourable trade-off there. In the spirit of we need everything we can get since, as I understand it from another thread, the max Q that can be expected from the FF p+B11 device is about 1.5(?) which IMO is very uncomfortably close to break-even – we are going to need some very high and perhaps unrealistic energy conversion efficiencies to surpass electrical break-even (and, by a sufficient margin to also surpass commercial break-even). As a newcomer I don’t want to start by expressing negative opinion but I do wonder sometimes what the realistic odds are of actually reaching here such a difficult goal.

james: If the He ions simply spiral around in the plasmoid until they loose their excess energy, how then would then generate net energy when finally expelled from the plasmoid by the magnetic field collapse? It would seem the energy imparted to those ions would only then be obtained from the collapse of the magnetic field which in turn was created by the input energy (which it seems to me would result in no net gain).

[Ivy Matt]

Ivy Matt wrote: Regarding the fuel for Focus Fusion, LPP is considering decaborane (B10H14), which is a solid at room temperature. I’m not sure where they get the B11 from…by enriching decaborane, maybe?

Oy, clearly I’m not a chemist. That’s B(sub10)H(sub14), or ten borons, fourteen hydrogens. And obviously there’s no hydrogen-14. :red: Boron-11 is actually more common in nature, but B-10 and B-11 generally occur together.

NoSmoke wrote: I have read Lerner’s (is that the polite way to refer to him here?)

To be honest, I don’t know. Referring to people by their last name alone in written communication is a habit I picked up in the university. However, it does happen to coincide with his forum name.

NoSmoke wrote: comments that p+B11 goes easier at or around the ideal temperature for that reaction but, does it necessarily follow that D+D (for example) would not be as favourable (as p+B11) at the ideal D+D fusion temperature (i.e. a much lower and presumably easier to reach temperature)? Perhaps it has to do with the greater magnetic field that accompanies the p+B11 fusion conditions (?). Anyhow, that’s why I was wondering earlier if D+D could be a possible fall-back route to take.

D+D fusion is certainly easier to achieve (in terms of kilovolts and stress to the spark plug insulators), but I’m not sure about net power from D+D fusion. The reaction produces neutrons and three types of positive ions: protons, tritium*, and helium-3. I imagine the ions could generate electricity directly, and the neutrons could generate electricity the old fashioned way, but I don’t know enough to say how feasible either or both methods of electrical generation are. And there would still be a nuclear waste problem.

However, when I said that heavier gases achieve fusion more easily, I was referring to this:

To see what the consequences of the magnetic field effect are for DPF functioning, we
first use a theoretical model of DPF functioning that can predict conditions in the plasmoid,
given initial conditions of the device. As described by Lerner [12], and Lerner and Peratt
[13], the DPF process can be described quantitatively using only a few basic assumptions.
Using the formulae derived there, Lerner [1] showed that the particle density increases with μ
and z as well as with I, and decreases with increasing r. Physically this is a direct result of the
greater compression ratio that occurs with heavier gases, as is clear from the above relations.
Thus the crucial plasma parameter nτ improves with heavier gases.

See section 3: “Conditions In DPF Plasmoids”. I’m not a physicist, so I have little idea how well my ideas match reality (or physics models, at any rate), but I picture the magnetic field “squishing” the plasmoid, and it makes sense to me that the heavier the element(s), the denser the plasmoid would be. Thus, the Focus Fusion device not only uses plasma’s instability against itself, but it also uses boron’s relatively high (compared to hydrogen) atomic number against itself.

*Speaking of tritium, I recall that this question came up in the Talk Polywell forums: What happens to the tritium that is produced in the current D+D fusion tests? Is there very much of it? I suppose this question would come up with regard to any research program involving D+D fusion, but I didn’t have a satisfactory answer with regard to the LPPX.

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