LPP on the same beam with larger DPF in Warsaw

Posted by Rezwan on Jul 14, 2011 at 11:32 AM
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At the Dense Z-Pinch conference (DZP) in Biarritz, France, earlier in June, LPP’s Lerner reported on our recent results with the production of intense ion and electron beams. These beams are important as an indication of the energy that we are transferring into the dense plasmoid—the tiny knot of plasma where the fusion reactions take place—and are useful in themselves for other applications, such as LPP’s X-Scan infrastcutre inspection concept.

Based on the experimental results from May, Lerner reported that the bulk of the ions in the ion beam had energy of around 300 keV, and the beam had a peak power of 60 GW, about a third to a quarter of our theoretical predictions, showing that we can supply energy more efficiently to the plasmoid, but are close to the ideal. (See final section for our plans to improve performance.) The electron beam, observed indirectly from the intense X-rays emitted when the beam hits the central copper electrode of the DPF (the anode), was measured at a much higher energy, around 18 MeV, but with only 1% of the total energy of the ion beam.

Since the beams are accelerated in opposite directions by the same large electric fields in the tiny plasmoid, they should start out with the same energy. Lerner interpreted these result as showing that, in the case of the electron beam, we are able to observe only the highest-energy tail of the distribution of energies, with a larger number of electrons at lower energy not observable with the current set-up because the radiation they emit is absorbed in the anode itself.

What was encouraging at the conference is that the East European team of scientists working at the DPF located in Warsaw reported very similar results with a much larger machine. Their beams total energy of 20 kJ (for both beams) from a 400 kJ capacitor bank was quite similar to our total energy of 2 kJ for a 40 kJ capacitor bank and their average per-ion energy of 150 keV was somewhat lower than our 300 keV. Like us, they observed the beams forming into tiny micro-beams 100-1000 microns in radius, comparable but somewhat larger than the 60-200 micron radii that we observed from scars made on the bottom of the vacuum chamber. (See last month’s report.)

Closer Collaboration

Dr. Pavel Kubes of the Warsaw group, Lerner of LPP, and Dr. Chris Hagen of NSTec in Las Vegas (which has a large DPF) expect to meet at another conference in Warsaw in September to discuss closer collaboration among the three big DPF groups.