[psupine]

Might be a good time to draw attention to turbines based on supercritical CO2.

A quick google give a short summary which also links to the main report (which is 6.5MB):

http://nextbigfuture.com/2009/06/supercritical-co2-recompression-cycle.html
http://web.mit.edu/jessiek/MacData/afs.course.lockers/22/22.33/www/dostal.pdf

The advantages of CO2 compared to steam, are that the turbine is much smaller and the operating temperature is lower for the same efficiency (53%). The main disadvantage is that the pressures involved are higher, but with a lower temperature, the metal will have less tendency to creep.

The other alternative is Helium, and if we are already cooling electrodes with helium then running the turbine on that would bypass the need for heat transfer to another working fluid. Helium could also be run through any old X-ray to bulk heat converter mass. Pb is cheap.

[psupine]

I think there’s something important in the tuned circuit view of things. It could be an LC resonator, or something like two “fusion chambers” bouncing energy back and forth, or it might even be something like a giant cavity magnetron. I would (personally) like the elegance of the formation of plasmoids being self repeating, but it may be difficult to get the system’s natural resonance down to a few hundred Hertz.

In any case, getting unity out of a single shot is a far more important step.

[psupine]

and there is a book on signal propagation black magic
http://tinyurl.com/33nrh8p

I have this fantastic book. It is mostly about measurement and keeping the loop areas as small as possible so the high frequencies are still visable.

The emphasis with DPF is I think slightly different in that we are trying to get as much energy into the plasma as we can before it detaches from the electrodes and forms the plasmoid.

Maybe we should be thinking about what can be done to delay the plasmoid formation so that the energy transfer can be maximised?

(edit) Actually, a lot of the book is about good termination too

[psupine]

I was imagining something in a standard shipping container for quick install or swap out, and centralized construction, service and refueling. The dimensions discussed here, and the fast radiation decay to safe levels would make transport feasible.

Even if the energy recovery from excess heat ends up being a turbine housed in a separate container, (supercritical CO2?) the elements are small enough to be containerized. Although perhaps this portability makes the chance of outright theft somewhat harder to deal with.

[psupine]

Is there any reason why the sides of the anode have to be parallel? I understand that the cathodes in the cage have to be parallel to the anode surface, but what would happen if the whole thing was kind of conical? One thing is that it would allow more surface area and more internal plumbing volume but still let the business end stay on a tight radius? Or would the conical shape do something nasty to the plasma run down?

[psupine]

As I understand it, one of the techniques used in electron tubes (aka valves) to reduce electrode erosion is to a maintain a negative potential on the “target” electrode. This decelerates the free electrons (that had been accelerated by the grid potential) so that most of the energy has been taken out of them and the electrons impact the plate at low energy. This is a bit like a lunar lander game played out on a very small scale.

If the same situation applies here, then allowing the residual e-beam to contact the +ve anode is the actually making the electrode erosion problem worse, because the electrons are accelerated towards the +ve anode. (Maybe it’s no longer positive after the discharge that formed the plasmoid, but in any case the following should still apply)

Couldn’t we instead have a hole up the middle of the anode and a negative electrode (insulated from the anode) whose task it is to slow the electrons and allow the e-beam to touch with the minimum erosion? The accumulated negative charge would be bled back into the power supply, even if that energy contribution was small.

The unanswered question I’m left with is what is this electrode negative with respect to? The plasmoid is going to be sitting in an electric field at some potential, but I don’t know what that is.

[psupine]

Lerner wrote: Two things can absorb the momentum of the ion beam–the motion of the plasmoid, or the magnetic field that the plasmoid is tied to. It is probably mostly the latter, since otherwise the plasmoid would smash into the anode before the pulse ended.

jamesr wrote: As far I was concerned the plasmoid is the field by definition. ie. when the magnetic field lines break and reconnect to form an closed structure, that is called a plasmoid.

1) Is there any evidence that the the plasmoid does smash into the anode? Do we know how much it will move before total collapse?

2) What happens to the e-beam? Does it go through a hole in the anode for the charge to be re-cycled into the following shot, or is the energy so small that it isn’t worth the trouble and it simply shorts out into the positively charged anode?

[psupine]

OK, so it’s partly that the plasmoid itself is considerably more massive than the electron stream, but are you also saying that there is some residual magnetic field that the plasmoid pushes against, ie some magnetic lines of flux still attached to the electrodes?

I’m still confused though; the charge of the electron beam has to balance the charge in the ion beam. I had imagined the electrons firing back through a hole in centre electrode to provide a negative charge path back to the outer electrodes. Rather, is the goal here to hold the electrons close to stationary trapped in the plasmoid so that the alpha particles go zooming off even faster towards the “decellerator coil”.

[psupine]

I’m still trying to understand some of the subtleties too (I bet we all are!), so please excuse me if this question is so bad that it isn’t even wrong …

Doesn’t conservation of momentum require a significant e-beam to balance the ion-beam from which we hope to extract significant energy? So if optimality has the e-beam energy reduced as much as possible, I’d have thought that the ion-beam is similarly down to nothing or else the plasmoid shoots sideways (or rather in FuFu, up).

I’m sure someone can set me straight. I hope to get there eventually.
Thanks

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