Hello from London

[Doug Coulter]

I think it's more complex than that, and doesn't need to be an ion trap to do it. Electrons go right on through wires, while the protons can't leave the tank in a sealed off system. They can hit the grid and become neutrals, of course, and then leave and be ionized again. If you model the power supply as a pump -- there's a source of infinite electrons, but only so much gas (nuclei).
I know from experience that I can put so much current in there that it has to be mostly electrons that carry it. Easy if you forget to have a ballast on there and dump a charged capacitor into it by accident (of course, after that you have metal ions too).

I think the mechanism is that when a very fast ion hits the grid, it ejects many electrons from the negatively charged conductor....so there can actually be more of them, but the only thing I really care about is that there are a lot and they waste energy like crazy.

You are right, a faraday cup only tells you so much, and this isn't proof exactly, just an indication. In this case, one that is pretty far from the "action" - about a foot away and off any of the axes.
Another indication is that scope trace from the thread here on non isotropic neutron production. You can see the electrons being swept out of the space by the second grid, and how long that takes when it tries to go positive on that trace.

There are ions in valves to be sure, just not many. Nothing is perfect. Otherwise you'd not need grid resistors...but you do, it's a measurable current in there in most valves (we call them tubes here, but I know the other nomenclature). But then I started out in electronics when tubes were all there was, and got pretty familiar with them, including electrometer tubes especially designed to limit that problem, and it's enough to be a problem.

I dunno if you're the first to show possibility of net gain that way, but I never argued that myself -- it's what made me think you were onto something, actually. I'd not seen anything else that made my brain happy before myself on that topic. But hey, lets take this to some thread on theories, we're polluting Jon's Hello thread here -- and we know we can both talk this endlessly.
Why not start it with an upload of that paper you turned me onto about "why fusors can't work"? It's good and still very relevant, and we shouldn't keep that to ourselves alone here. I've forgotten who the author was or I'd do it. Brian something?

[chrismb]

At some point I would like to try introducing heavier fuel mixtures such as deuterium with tritium or boron. I have a little bottle of pure boron metal standing by.

Jonathan, Hello. I gather that tritium may be a little easier to obtain in the UK than the States? Reason I say this is we're pretty much unable to obtain any other than gun sights or watch dials. Exit signs are regulated. Even the tritium key ring I have I had to order from Ebay/UK. You can obtain it over here if you're a university or a business with government ties and only then after extensive paperwork. procedures, safeguards etc. -bill

I think I would like to put in a disclaimer here, for technical reasons if not for any other; I cannot see a single good reason for even considering T in a fusor experiment. This is because, as Doug mentions, there is a simple multiplicand of reaction rate that is well known between DD and DT reactions. What would seem a good step is to get evidence of a big reaction rate whilst minimising any risk/radiation, and you can do this by simply throwing in your multiplication factor from DD. I think it is best to presume there is no prospect of handling T safely, and it is unnecessary. Show the results in DD, and the DT rates are inferred. This is, even, what the tokamak guys do*.

*(though, in their case, because the alpha power input into the plasma is so high, at some stage they do need to run DT because there are destabilising magnetosonic waves that need to be accounted for. In a beam-type device, this isn't significant because the fusion products do not add to the reaction volume.)

If you want to run p-11B then all strength to you. Despite the claim it is 'aneutronic', this simply means that the neutron rate is 1% or less. As we know, detecting 10's k neutrons per sec is not unreasonable, so with p-11B at around 0.5% neutronic (I'm not sure of the exact figure, I'll check it out) you'll be able to detect reaction rates of 10^6/s. I reckon a hydrogen fill and a needle cathode tipped with boron will do you. The tip will sputter and you'll get both beam-tip and beam-background fusions, if the proton energies are high enough (there is a resonance around 163keV proton energy, if you are really that committed!).

[Doug Coulter]

Lerner says (private phone call) the main resonance p-?B is 400kv or so. I think I believe him. P->Li is getting good at half that, and goes over into a loss reaction around a meg and a half if I remember the chart Chris sent me. That one is I think nearly no neutrons unless there is D in there (and 6Li). The P->Li one is attractive to me, as the threshold is low, and the energy gain is much higher than DD is -- 16.8 mev vs 2.5 as it goes to helium (any reaction that does has this property). The thing about DD is you make some T and 3He anyway, or so we think, and they aren't "done yet" -- they are still fuel -- better than the D was!

T would have some differences because of the different charge/mass ratio, so I don't think you can infer except in a pure thermal situation. The only reason I can think of to use it (other than it's kind of a fun idea) is to get super hot neutrons for something -the fast neutron physics guys need that kind of thing and it's one of the easier ways to get them without a really big accelerator. Enough to make power gives you other troubles, of course, as ITER is figuring out how to deal with the materials damage from those.

I don't see the least issue with handling any amount we could get. The amount in one of those tiny gunsights would fill my tank to above fusor pressures. My system exhausts outdoors anyway. It's a tiny fraction of a CC. You might get a whole CC out of an exit sign. No one will sell you a bottle, period, anywhere, as far as I know. Too precious on top of the rest. You'll never get enough to get hurt with. Hydrogen isn't easily assimilated into the body as a gas, most comes right back out and in any case, enough to hurt you would amount to an explosive mix with air chemically!
As a low energy beta emitter, it's just not going to do much harm anyway unless the dose is crazy big -- again, where would one get that anyway?

[chrismb]

I think the mechanism is that when a very fast ion hits the grid, it ejects many electrons from the negatively charged conductor....so there can actually be more of them, but the only thing I really care about is that there are a lot and they waste energy like crazy.

OK, yeah, fair enough. Not only there, of course, but also where the beams meet the chamber, there will be a zone of secondary electrons that I would accept would definitely push your electron population past the ion population.

[chrismb]

Lerner says (private phone call) the main resonance p-?B is 400kv or so.

There is a nuclear resonance at 148keV collision energy, which translates into 161keV lab-energy proton with respect to a stationary 11B. The cross-section there is 0.1 barn.

The peak for p-11B is 550keV collision energy, which is 1.2 barn.

At 400keV, p-11B is still around 0.1 barn (as it dips above the 148keV resonance, then comes back up again).

So if you run at 161kV then you would only get a factor of 10 better, at best, whatever higher voltage you might go on to get. I think 161kV is conceivable in a 'regular lab' (you could run the anode at +80 and cathode at -80, which is pretty much where you are now), but I think >400kV is out of the question. So you could go for a 1/10th of max (in the knowledge that whatever reaction rate you get from that, you could theoretically up it) with a feasible +/-80kV, or you could go for max with an implausible +/-275kV.

Lerner might have been talking in terms of thermal temp, because he's working with the 'thermal' side of fusion plasmas, rather than IEC. The reaction rate for a Maxwellian distribution might well peak around 400keV thermal plasma temp (as it sits between the 148 resonance and the main peak, so would range over both of those energies).

[Doug Coulter]

Hard to say, and then theres the complications of lab frame vs particle on particle. That's just what he told me when I asked him. You know, I have three big 120 uf 10kv maxwells here...