New Calibration Confirms FF-1’s High Fusion Yields
Tests in early June have confirmed that FF-1 is producing higher fusion yields than have been achieved with any other DPF at the same peak current. The new tests were calibrated with LPP’s silver activation detector and our new commercially-purchased bubble detectors. In our two calibration shots, the bubble detector and our silver activation counter showed excellent agreement. We can now confidently use our previous measurements of neutron yields to compare our results with those of other DPF devices. Figure 1 shows two of the best shots from FF-1 (red dots) compared with the best shots for all non-LPP DPFs (blue dots). The FF-1 results are as much as a factor of ten above the other results and show a sharper increase with higher current. The green dot shows LPP results from 1994, which also lie above the main body of results. We cannot say for sure yet if this improvement in performance is due to our use of the Axial Field Coil or to the small radius of our electrodes or both. Further experiments are needed to determine this.
Figure 1. Neutron yield in various DPFs in the world. Derived from J.O. Pouzo, M.M. Milano in Current Trends in International Fusion Research: Proceedings of Fourth Symposium. NRC Canada pp 33. (2007)
The calibration also allows us to confidently chart our own progress over the course of 2010. Figure 2 shows the increase of fusion yield from FF-1 so far this year. Each point represents a new “record” for FF-1 yield. The figure shows that we have traveled a bit less than half way to our goal of demonstrating scientific feasibility which would involve a yield of 10,000 to 100,000 joules. If we can continue at the rate of progress of the spring, we should reach our goal by year-end.
Figure 2. LPP’s past and planned energy yield per shot in joules.
New Spark Plugs Pass First Tests
Our new spark plugs, which we hope to be far more rugged than the old, automotive ones, have passed their initial tests. Production of the spark plugs was slowed during May, partially because of redesigns needed as we went along. In addition, our first designs, tested in late May, did not work well. We had selected Macro, a tough ceramic, as the insulator for the spark plugs. However, this idea did not work. In our initial tests, all four insulators broke after two shots. Dr. Subramanian suggested using Lexan plastic for the insulator. Lexan is extremely hard to break, being used for bullet-proof glass, but melts at low temperatures. We would also try another plastic, PEEK, which has a much higher melting point, but is somewhat less impact resistant. After an initial eight shots at 24 kV with three new spark plugs, two using Lexan and one using PEEK (plus one old spark plug for symmetry), no wear was visible on the insulators, although there was very slight pitting of the tungsten tip. Since we don’t know how the insulators will react at higher voltages, we have decided to make half the insulators from one plastic and half from the other. The three switches fired within 50 ns of each other, which is acceptable and can be improved with further adjustment of the spark gaps. We expect to have all 12 spark plugs working by the end of this week.
Kansas State Graduate Students Arrive to Help LPP Project
Two Physics graduate students from Kansas State University have arrived for a month of work at LPP’s lab. The two students, Mohamed Ismail and Amgad Mohamed, have worked for six months at the small DPF facility run by Professor Ali Abdou, a former classmate of Dr. Subramanian at the University of Wisconsin, Madison. Dr. Abdou will also be participating in our research for a week at the end of the month, so our manpower will be greatly enhanced in June. The students have dived into the work and have succeeded in reducing the remaining electrical noise on the Near Time-of-Flight instrument by a factor of 75 in their first day of work. We are looking forward to working with our new colleagues this month, and anticipate great benefits from their assistance. The extra manpower will hopefully boost LPP’s progress, just in time for Mr. Lerner to present a paper at the International Conference on Plasma Science in Norfolk, Virginia, on June 20th.