[rafal]

I see.

So it’s not that PF does not get DoE funding. It’s just that the funding goes with a disclosure-constraints and we all get an impression, that only enthusiasts do any progress here, which apparently is not true at all.

Anyway. As always (with science :); one answer rises more questions…. surprisingly, I see references to DPF devices used as neutron source (D-D reaction) instead of H-B fussion devices. How come the later is less interesting to the researchers?? bits me.

But still, thenx for the reference and link.

[rafal]

Ha!

It looks like tightening anode-cathode distance to increase energy concentration is not as “innovative” as I thought it was, others came at those conclusions too, like: http://www.google.com/patents/US8487536. I’s pity I haven’t traced any science papers on the influence of cathode-anode final distance on the overall device performance like neutron yields. But may be s I’ll have more luck later.

But along those lines; both inventors listed in that patent are located/residents of las Vegas. I’m not familiar with US science facilities, so: are there any recognized research facilities around las vegas? Or should one think that DPF is becoming so hot issue, that patent trolls already smell fresh meat?

[rafal]

Lerner wrote: There are many studies of neutron distribution. Overall they show that with low current DPF, most neutrons come from collisions of the ion beam with the plasmoid. But in higher current machines, they come from collisions of ions trapped in the plasmoid with each other, which increase faster with increasing current. In FF-1 neutrons are very evenly distributed, showing that the ions are trapped.

by any chance; You don’t have any links to experimental results on that?

The current starts next to the insulator because that minimizes induction and thus the amount of energy in the magnetic field. Currents always minimize the amount of energy they have to expend. Mother Nature is not lazy, just efficient!

I see.

Have there been any experiments on how close the tips of the anode and cathode can be to each other, while the “nature preference” to ignite the arc along the insulator remains “in force”? I’m asking, because it looks to me, that the shorter the “final part” of the sheath “bulb”, the more energy of the arc could be trapped within the plasmoid …. have that been tested, yet?

[rafal]

Oh yes. It’s excellent.

But, as it’s often the case when learning … every answer rises more questions 🙁 So I cannot help myself asking those that occurred to me while reading that Saw+Lee paper:

1. is it not a mistake, that under figure.2 they state: it shows setup results with additional inductance of 33uH … which is gigantic with respect to intrinsic device inductances in the range of 33nH?

2. They say, that for a variety of devices, there is always an “optimal” inductance, where current reaches maximum. And that reducing inductance further does not increase discharge current (and they’ve published that observation earlier). I don’t have an access to that their earlier paper, but …. I was wondering if that effect can also have something to do with sin effects. In particular, one of the LPP devices reportedly had cathode rods fi=10mm, while at the frequencies equivalent to speed of the discharge (e.i. c.a. 20micro-sec), copper effectively conducts only at depths of c.a. 2mm. So having cathodes build from copper bars of 3mm/30mm cross section should do better. shouldn’t it?

3. Saw+Lee describe setups pinching current in pure D2, and measurement of D+D reactions which yield neutrons. Are there papers presenting special/angular distribution of resulting neutron outbursts? As opposed to ion jets from H+B reaction, neutrons could expose something regarding the internal dynamics of plasmoid vortexes. I think.

4. and last and the most important for me question: I cannot find any hints on why exactly the sheath forms at bottom of cathodes along the pyrex insulator, and not at their tops, where electric field between anode and cathode is the strongest. Where should I look for that answer??

So I’d really appreciate any further pointers to published results? (the links three posts above are probably interesting, but as they are mainly raw data, it’ll take me more time to really digest them)

But thenx anyway,

-R

[rafal]

I’m sure people at LPP do a great job of building up knowledge around physics involved – including tedious plasmoid properties measurements. Obviously that’s valuable, and time consuming.

I only tried to say, that:
1. I’d expect that a sort of perturbence (shake-up of a design) of the DPF device structure/geometry is also exorcised … in the spirit of Edison trying every possible filament for his incandescent light bulb.
2. but mainly I wanted to ask if there is any sort of tutorial/beginners guide on the DPF device parameters: like basic dependencies of output-jet total energy, and its ion energy spectrum v.s basic device design like: anode diameter, anode lip curvature, number/diameter of cathodes; length of pyrex insulator; its thickness, etc.

before we fully understand the physics of the process (and thus can “design for” a successfull cross-over to Q> 1), it’s usually worth (blindly) testing various “engineering options”.

I for one would like to know how the density-time varies with the number of cathode rods – may be one does not need that many (like: what if just three would do?) … or if it pays to have a lot of them (in consequence to have as many as possible plasma spokes crossing the sheath) and thus one needs to change the cathode array geometry towards a circular comb of copper blades. Anyone knows what’s better?

And one “engineering option” I’d personally would surely check very early (but haven’t seen done) is to check the D2-B10 filament. This does not require any changes in hardware, while this close to target density-time constraint should highlight any influence spin has on the reaction.

[rafal]

Why exactly: ” reactions suggested here don’t work”? References provided by Francisl indicate they’ve been studied.

I must say, that after reading a bit on the DPF devices I’m truely puzzled why “wariations” of the reactor haven’t been studied. Quite recent publications from LPP indicate that they are fighting some minute metal/oxide impurities, thile the overall structure of the device does not change:
1. they don’t exorcise D2+B10 outcome
2. they don’t change the geometry (like bend the cathodes, so the form a cone instead of a cylinder).
3. there is no info in the influence of anode pyrex insulator length.
… just to mention the most prominent variations.

… while on their 2007 google-talks presentation they stated, that their density-time parameters is just 65 times to low …. e.g. less then two orders of magnitude! I’d expect that in such circumstance one tries every possible (or impossible) variation of his/her device to cross-over. And their recent papers suggest, they only look for minute fine-tuning of the process. that’s strange.

BTW: is there a “beginners guide” which explains what exactly happens within the umbrella shaped current sheath? Because “my everyday experience” with plasma (like thunderbolts) suggest, that current goes through plasma along lines, not surfaces (like spokes between cathode electrode surface and anode). Still, the sheath seem to originate from thin “air” between cathodes? how come?

[rafal]

Hi,

I came here “redirected” from “http://lppfusion.com/fusion-power/dpf-device/” (the dense plasma focus company website). I’m not sure if anybody from there frequent this discussions, but whoever read this: the LPP fusion people colide protons (hydrogen H1) with boron (B11) commpressing the plasma using its instability indused by flow of electical current.

I was wondering, if quantum effects could help them get more dense plasma if they use Deuteron (D2) with spin of 1 instead of proton with spin of 1/2 (and consequently B10 instead of B11)?

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