Plasma Focus Researchers Discuss Progress in WarsawOctober 24, 2018
In addition to LPPFusion, two other experimental groups in Poland expect to be testing hydrogen-boron fuel in a plasma focus device in 2019. This was a key highlight of the annual International Centre for Dense Magnetized Plasma workshop in Warsaw, October 4 and 5. The workshop is a summit meeting for researchers using the plasma focus around the world. LPPFusion’s Lerner attended the workshop, representing the USA on the International Scientific Committee, which seeks to coordinate work on the plasma focus.
The two groups will take somewhat different approaches to mixing the hydrogen and boron. While LPPF will be using a compound of hydrogen and boron, decaborane, as a fill gas, the PF-1000U group in Warsaw, will puff a plume of different gas, boron fluoride, through a hole in the anode just before a pure hydrogen pinch converges on the center. The gas-puff idea, which has been used before in other experiments with deuterium, is intended to allow greater densities in the final stages of compression. However, the turbulence in the puff may lead to asymmetries in the compression, and so to lower final density.
The Krakow group, using PF-24, a device very similar to LPPF’s, will use a laser to vaporize a puff from a block of solid boron in the anode tip, only 1 microsecond before a pure hydrogen pinch converges on the spot. Since the boron block has to sit slightly off-axis to avoid being destroyed by the electron beam from the plasmoid, the problem of potential asymmetry is present in this approach as well. Initial tests indicate that the laser can be tightly correlated with the plasma focus pinch process.
Both Polish groups had hoped to run boron experiments in 2018 (as had LPPF’s team!) but ran into a variety of delays. All three groups will be sharing results and learning from each other’s work.
Possibilities for a number of other collaborations arose at the workshop. Dr. Leopoldo Soto of Chile showed evidence from a tiny plasma focus device that there is a sharp front between the filamented and unfilamented portions of the current sheath. LPPF expects to be able to use Dr. Soto’s clear images to test our theory of a critical velocity needed for filament formation. In addition, Dr. V. Krauz from Russia has initiated a collaboration with astrophysicists using the plasma focus as a model for Herbig-Haro objects in space (Figure 2). These objects form as a cloud of plasma contracts to form a star like our Sun. Like a plasma focus plasmoid, Herbig-Haro objects eject highly focused beams. LPPF will be seeking to enlarge this collaboration to US researchers.
Finally, in the broadest collaboration agreed to at the workshop, the Scientific Committee agreed to start a year-long process leading to a “consensus” review paper, summarizing what we, as PF researchers, all agree to about the device’s functioning, what aspects are still being debated, and what questions are still entirely open. The discussion will start with the circulation of brief statements and will be capped by a special workshop in a year.
Figure 2. Herbig-Haro object 212 (not in the New York area code!) as imaged by the European Southern Observatory in Chile. A star is forming in the dark area between the two symmetrical jets, each a few light years long. The jets are accelerated outwards by electromagnetic forces extremely similar in all but scale to those within a PF plasmoid.