LPPFusion Chief Scientist Eric Lerner has announced the long-awaited start of tests with hydrogen-boron fuel in the FF-2B fusion experimental device. He made the announcement during his November 11 presentation at the 17th International conference on Plasma Science and Applications in Kuala Lumpur, Malaysia. The first shot using decaborane, a compound of hydrogen and boron, occurred on November 1, with a second shot on November 4.
These initial tests did not yet reach the conditions needed for fusion reactions. Due to imperfections in the heating system, the research team was not yet able to fill FF-2B’s vacuum chamber with the needed 1.5 torr for decaborane, with the shots using only 0.8 torr. As a result, only a very small “pinch” was achieved, meaning that the compression of the plasma was too small to create the density and temperature needed for fusion reactions.
The research team, possibly assisted by a thermal engineer, expect to find and plug the “heat leaks” that are preventing the chamber from reaching the necessary 80 C in all parts. This temperature is needed because decaborane is a solid powder at room temperature and needs to be heated to emit enough vapor to fill the chamber. Like water vapor condensing on a cool surface, the decaborane vapor will condense on any cooler surfaces within the chamber. However, such cool spots can’t be avoided just be turning up the heat. Decaborane melts at 100 C, which would greatly reduce its surface area and make vaporization too slow. As well, the Mylar insulation in the device must be kept cooler than 110 C to avoid damage. So, the tricky part is to keep all parts of the vacuum system between 80 and 90 C. The team expects to achieve this goal in December.
Even without fusion conditions, the tests produced some encouraging results. First, the fact that the November 1 shot produced a pinch (as shown in the dip in the current race in Figure 1) even if a small one, with only half the gas needed, is an indication that a strong pinch should not be too difficult to achieve with the right pressure. Also, Lerner had expected that the chemical breakdown of the decaborane after the shot would coat the windows of the vacuum chamber so heavily that they would be totally obscured. However, this was not the case and the windows were clear enough in the second shot that a good optical spectrum was obtained, showing the anticipated lines of boron (Figure 2).
Based on these initial results, we hope to perfect the heating system and attempt fusion-producing shots before year-end.
Figure 1. This graph of the rate of change of the current in the first shot with decaborane fuel shows the small dip at 2.7 microseconds, indicating a small pinch occurred.
Figure 2. Spectrum of second decaborane shot, showing the lines of boron (labeled with B) as well as beryllium (Be) from the anode(leftmost) and oxygen (O) from oxides(rightmost).
