LPP at American Physical Society 2012 Plasma Physics Conference: Strengthening our lead in the race towards fusion power
This update was part of LPP's November 2012 progress newsletter. Download a PDF of the full newsletter here.
LPP Chief Scientist Eric Lerner, accompanied by visiting scientist Dr. Hamid Yousefi of the Plasma Physics Research Center in Tehran, and Ahmad Talaie of Utah State University (our most recent summer graduate research fellow) participated in the annual American Physical Society Plasma Physics conference in Providence, RI, October 29-November 1 (conveniently riding out Superstorm Sandy away from NJ while LPP’s Derek Shannon held down the fort.) The conference provided new information and opportunities, but the most important conclusion for us was the lead that LPP’s Focus Fusion effort maintains over other approaches. This, of course, is no guarantee that our approach will actually get to a practical fusion generator first, but it is a snapshot of the fusion race right now.
Tri Alpha Energy, which is pursuing aneutronic fusion with a different device from the plasma focus, presented their past year’s progress with a half-dozen poster presentations. The clear and thorough presentation of their results was due a shift in management approach to a new openness, according to several of the researchers participating. Tri Alpha’s device, called a Field Reversed Configuration or FRC, generates two large rings of plasma and heats them with an externally accelerated ion beam. Their most recent results show that they have confined plasma at about 100 eV energy for about 2 milliseconds at a density of 2x1013 ions/cm3. A rough measure of overall progress is the product of these three numbers, called “ntT”, which for Tri Alpha is 4x1012. By comparison, LPP’s FF-1 with an ion energy of 160 keV, confinement time of about 30 ns and density of 3x1019 ions/cm3 has a ntT product of 1.4x1017, a factor of about 30,000 larger than that of Tri Alpha. This puts LPP far closer to the goal of net energy for now. Tri Alpha has raised about $140 million in private investments and works with a staff of 30 physicists.
LPP feels strongly that all possible routes to aneutronic fusion should be researched, as long as we don’t know for sure which one will work. We expect to continue discussions with the Tri Alpha team about possible avenues of cooperation.
Lerner’s presentation on LPP’s experimental progress was attended by about 60 researchers, a good turn-out. We explained our latest progress on understanding how arcing affects the formation of filaments and our efforts to overcome this. Our latest work shows that arcing lays down irregular deposits on the insulator and anode which in turn leads to an uneven spacing of the filaments. When closer-spaced filaments collide during compression, they generate the “early beam” phenomenon and prevent full compression and high density of the plasma.
Our new micro-ohm meter allowed us to test for the contact resistance that causes arcing without assembling and testing the whole machine. But continuing small resistances forced us to switch from the copper cathode plate with tungsten ring to an all-tungsten plate. We did not have time to test that new plate before the conference (and the simultaneous storm). Despite this anti-climatic conclusion, our presentation was well-received with good questions and several researchers complimenting the work afterwards. Several researchers appreciated our addressing the detailed technical problems that are often overlooked in reporting scientific results and were impressed by the progress we are making.
The sawteeth below are one solid piece with the tungsten base, eliminating a current contact that had caused arcing. The teeth concentrate electric fields to enhance filamentation in the plasma sheath that extends outward to the copper rods.
Talaie and Lerner’s theoretical description of heating due to plasma viscosity and the currents induced by the electron beam unfortunately reached a smaller audience, in part because our poster happened to be located in the far corner of the hall, but the insight this work provides for further progress is no less valuable.
At least two possibilities for collaboration arose at the conference. University of Alabama has received some funding for fusion space propulsion from NASA, and researchers there are interested in a possible collaboration with LPP in designing plasma focus devices for a new, powerful mega-ampere facility there. Researchers at Lawrence Livermore National Laboratory have developed a computer simulation of the compression phase of plasma focus functioning and may be willing to collaborate with LPP to benchmark their simulations against our detailed experimental results. We will be following up both possibilities in the coming month.