Questions about how much energy has to go into a single pulse

[belbear]

In looking around for more information about DPF’s, I stumbled across this article:

http://nextbigfuture.com/2009/08/previous-dense-plasma-focus-research.html

There are references toward Eric Lerner and Focusfusion.org, and it all seems to be quite interesting.
However there is one thing that seems wildly out of scale: The energy that goes in one DPF pulse to reach break-even in a p-B11 reaction.

More specific it is the graph “ESTIMATE of BREAKEVEN from experiments W < 0,5MeV".
According to this graph, p-B11 break-even would occur at a PF energy storage (=energy of one discharge?) of at least 3000MJ, or 3GJ.
If you up this to 4GJ to exceed break-even, this is equivalent to the staggering energy of a TON of TNT!
Several reactions on this article point the same way.

I cannot imagine Eric’s “baby” will be able to fire that kind of pulses, nor can I imagine that a DPF able to withstand this kind of discharge can be built for LPP’s budget. If it’s possible at all to make electrodes that do not vaporize entirely during one such shot.

A quick back-of-the-envelope calculation based on LPP’s estimates of power output tells me a whole different story:

LPP claims that a commercial 5MW rated focus fusion reactor would run at 330 pulses/sec. This is about 15kJ net output per pulse.
Assuming a Q=2 (twice the energy comes out as goes in) and a 60% efficiency of converting fusion output to grid electricity and input capacitor recharging, I arrive at 84kJ input pulses. With E= 1/2CV^2, this should translate to a 214 microfarad capacitor, operated at 70% of a 40kV rating.
Quite a few orders of magnitude smaller than 4GJ, should fit in Eric’s baby, and actually less than I expected.
Don’t shoot me if I’m wrong with this, I’m not a physicist, just a layman….

Also in the aforementioned article, I read that pulses as large as 1MJ have been fired in DPF experiments, done by a Dr Jan Brzosko at DianaHitech labs in New Jersey.
Hey, isn’t that very near where LPP is? What happened to DianaHitech and Dr Brzosko?

Now I ask myself what is right and what is wrong about all those assumptions for p-B11 break-even in relation to needed input pulse energy. Needing obnoxious input energies can only cause more confusion and skepticism about the claims of focus fusion.

Has it all to do with pulse duration, i.o.w. less energy, but in a much shorter discharge time (greater peak current)?

How much energy/pulse (Joules) will Eric’s baby actually be able to deliver? Or is that a secret? The only thing I have found is that it should exceed 2MA in peak current and that this value will exceed all previous DPF experiments.

[texaslabrat]

I think you have to consider the context here. Those numbers were extrapolated from the tests by Brzosko and team with that particular machine. The energy needed to induce a fusion event is proportional to the volume of the reaction chamber (and ultimately the mass contained inside the plasmoid if you want to be technical)…if you want to heat up/compress a large mass of gas it will require more energy than if you want to heat up/compress a smaller mass of gas to the same temperature and density. I think this is where the numbers seem to diverge from LPP’s….ie I believe the LPP DPF is assuming that a much smaller mass will be heated per pulse than was demonstrated with Brzosko’s setup. That’s just a semi-educated guess on my part, however..and I would very much be interested in hearing an “official” explanation 🙂

[Aeronaut]

Sorry I can’t offer you an official, or even farticularly educated explanation, Tex, but my understanding of this machine is that the envelopment-> compression-> heating -> fusion cycle is based entirely upon massive current for a very minute time frame per pulse. This is why we can (hopefully) get as much as 12GG fields without that incredible apparent wattage flowing more than a microsecond, if that. (Haven’t read the patent or seen the video recently).

This incredibly short time frame is also our cooling advantage- the duty cycle of the heating is actually very low per power cycle, just as the input power per second, at 330 hz. I’m going with the 43kJ from the video’s slide for now, but I’d love to see a timing diagram for the current and heating.

[Lerner]

The new LPP machine will have a maximum electric input of close to 100 kJ. Our calculations indicate that this is what will be needed to get Q>1. A generator would be similar in energy, but would pulse much more rapidly–500 times a second or so, compared with 6/ hr for the experimental device.

DianaHitech, which was located in NJ, unfortunately went out of business and the device no longer exists. It was never fully built, so I believe the peak current obtained was about 0.9 MA or so. We’ve had several discussions with Dr. Brzosko and the cross arrangement of our device was inspired by his.

By the way, in a generator, some of the electric discharge energy that is not actually absorbed by the plasma can be recaptured by well-designed circuitry, so the energy that needs to be captured from the plasma for break-even is less than 100 kJ.

[texaslabrat]

Lerner wrote: The new LPP machine will have a maximum electric input of close to 100 kJ. Our calculations indicate that this is what will be needed to get Q>1. A generator would be similar in energy, but would pulse much more rapidly–500 times a second or so, compared with 6/ hr for the experimental device.

DianaHitech, which was located in NJ, unfortunately went out of business and the device no longer exists. It was never fully built, so I believe the peak current obtained was about 0.9 MA or so. We’ve had several discussions with Dr. Brzosko and the cross arrangement of our device was inspired by his.

By the way, in a generator, some of the electric discharge energy that is not actually absorbed by the plasma can be recaptured by well-designed circuitry, so the energy that needs to be captured from the plasma for break-even is less than 100 kJ.

First, thanks for the direct response..but it really doesn’t answer the concerns regarding the huge discrepancies between your numbers and Dr. Brzosko’s.

That “some of the electric discharge energy” you mention seems like a LOT when you are talking the difference between DianaHitech’s calculated 4GJ and your 100kJ. Unless there’s a volumetric/mass scale issue as I alluded to in my prior post, it seems that *someone’s* calcs are off by a few thousand-fold or some vital background information has been omitted.

[stream of consciousness]
Perhaps the issue could be cleared up if the “W” in those graphs were better defined. Is that energy that must be input by the electric arc each pulse or is that the net total after some energy has been released from fusion events or other input not considered in your calculations? How does it conceivably even build to 4GJ if it has to be delivered electrically in a matter of nanoseconds? Why do they seem to need 4GJ in *their* field and you only need 100kJ? Is that 4GJ perhaps built up over a much longer period of time with “pre-heating” prior to initiating the electrically-driven plasma pulses and thus assumed to be a sort of prior condition in your calcs versus a closed-system calc in theirs?
[/stream]

Thanks in advance for contributing to my nascent education in plasma physics 😉

[Lerner]

Yes there is a big difference–different approaches were used to obtain these predictions. We are basing ours on what we think is a quantitative theoretical understanding of the DPF and how to improve its performance. Dr. Brzosko’s are based more on an extropolation of past performance, without an attempt to use a detailed quantitative theory. For example, I can tell from his graphs that he is assuming an average ion energy of around 60 keV. But we hope to reach 600 keV, with a 50 times higher reaction rate.

In short we think we know how to improve the DPF performance by a large amount. Our experiments will test if we are right.

[texaslabrat]

ah, ok..it’s a matter of a massive increase in efficiency from one process to the other. That’ll work, and for all of our sakes I hope your calcs are right! 😀

As a related aside..how are the simulations going? Were you able to get together the software for gpu-based computation? I’m sure my fellow computer-geeks would appreciate a quicky article sometime on the technology behind the simulations (if/when you can spare a moment). 🙂

[belbear42]

Lerner wrote: The new LPP machine will have a maximum electric input of close to 100 kJ. Our calculations indicate that this is what will be needed to get Q>1. A generator would be similar in energy, but would pulse much more rapidly–500 times a second or so, compared with 6/ hr for the experimental device.

DianaHitech, which was located in NJ, unfortunately went out of business and the device no longer exists. It was never fully built, so I believe the peak current obtained was about 0.9 MA or so. We’ve had several discussions with Dr. Brzosko and the cross arrangement of our device was inspired by his.

By the way, in a generator, some of the electric discharge energy that is not actually absorbed by the plasma can be recaptured by well-designed circuitry, so the energy that needs to be captured from the plasma for break-even is less than 100 kJ.

Thanks for answering, Dr Lerner. Seems to be that my estimate for pulse energy was not that far off. 🙂
How much of the 100kJ discharge energy should actually end up inside the plasmoid at p-B11 fusion ignition conditions to reach break-even?
My guess is that reaching a good enough discharge-to-plasmoid conversion efficiency is actually the main challenge of focus fusion?

Wishing you all the best with your fascinating project…

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