Reports of More High-Ion Energy Data


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Posted by Lerner on Jul 28, 2010 at 09:42 PM
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Further detail from the June 22 ICOPS conference.

J. P. Appruzese and his colleagues at the Naval Research Laboratory noted in their presentation at ICOPS that several experiments with pinching machines had achieved ion energies above 10-20 keV, with the highest being the 200 keV previously reported from the big Z-machine at Sandia National Laboratory. Appruzese also mentioned LPP’s results with the DPF as a further example. He pointed out that such high ion energies could be used for fusion with advanced fuels—in his example, D-He3.

Working in cooperation with theoretician Michael G. Haines of Imperial College, London, Appruzese suggested that these high ion energies might be caused by turbulent heating. Such heating of the ions occurs when frictional forces within plasmas get large enough to disrupt the smooth flow of the plasma, leading to energy dissipation and heating, just as turbulence in ordinary fluids heat them up.

LPP’s initial analysis of this suggestion seems to indicate that it does not explain our higher-than-expected ion energies with deuterium gas. Turbulent heating increase rapidly with increasing atomic charge on the nucleus, so may be significant for pB11, but does not seem to be quite enough for deuterium, which has only a single charge on its nucleus. However, the idea is an interesting one and this process should be included in our future analyses.

Our assessment, from discussions with other researches at ICOPS, is that the reporting of high ion energies in other experiments has given considerable credibility to our own results.

In addition to these specific results, we had extensive talks with many other researchers in the DPF field. We strengthened our ties with the team working on the Polish DPF, PF-1000, still the world’s most powerful DPF. A young researcher at Imperial College offered to analyze some of our neutron data with his new algorithm that can provide more information about ion energy distribution. We also had some preliminary talks with researchers from Voss Scientific about a possible joint grant application to the National Science Foundation for work on DPF simulation techniques. Overall, we felt that our participation at ICOPS, which included our whole research team as well as our visitors from Kansas Sate University, greatly benefited our Focus Fusion project. We can’t overstate the importance of collaboration within the world-wide DPF community to the success of our efforts.


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Brian H's avatar

The turbulence issue is confusing; turbulence is not free. It comes at the expense of ordered or laminar flows, etc., so any energy/heat “caused” by turbulence is borrowed from something else. What is that, in this case?

Are you talking about the interior of the plasmoid here?


The energy comes from the twisted magnetic field reconfiguring.

I came across a recent paper today:
A. Lazarian et al., “Fast magnetic reconnection and energetic particle acceleration,” Planetary and Space Science In Press, Accepted Manuscript (n.d.),
http://dx.doi.org/10.1016/j.pss.2010.07.020

That goes through how turbulence can speed up magnetic reconnection and accelerate particles to high energies (in this case from an astrophysical perspective, but the physics should be the same on our small scale)


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