LPP Fusion Redesigns to Overcome Hurdles to High Yield Fusion

LPP fusion discovered the FF-2B’s prototype anode was cracked. They have used the shutdown time, necessitated by both the crack and the coronavirus, to complete the design of our new switches, and to redesign the anode. They are aiming to resume firing with these crucial new upgrades in the fall. This will allow us to keep to our plan of initiating experiments with hydrogen-boron fuel in 2020.

Above – Side view of anode shows one of two cracks extending down the sides. Top view shows two cracks, top and bottom extending out of the damage area on the inner lip of the anode.

They had have to be extremely careful to ensure that no beryllium dust escaped to contaminate the experimental room, we had not planned to do any complete disassembly this year. The team came up with a plan to remove just the anode from above, while maintaining a reduced pressure in the chamber, guaranteeing that air would be flowing inwards into the chamber and no dust could escape.

The tricky part was to lift the anode vertically so it would not hit the surrounding ceramic insulator and crack that, too. There is only a 1 mm gap between the two parts. But Research Scientist Dr. Syed Hassan worked out a way to lift the anode with lab jacks and a level to guide a supporting rod. During the delicate operation on March 30, which they recorded, one jack collapsed. Fortunately, Dr. Hassan’s many lab skills include a quick reaction time, so he seized the supporting rod in time to prevent any damage to the insulator. (Fig.1) With Chief Scientist Eric Lerner assisting, Dr. Hassan successfully removed the anode and substituted an older steel plate with an O-ring as a temporary seal.

They have made major design changes to their new switches that will likely eliminate prefires. We will avoid in future shots turning off the preionization and firing at low pressures. In addition, the new anode we will be getting can be strengthened with design changes and annealing, a process of controlled heating to release strains caused during the machining of a part. They expect that it will take about three to four months to replace the beryllium anode and they have already contacted potential suppliers. To avoid a major delay in the work, they will simultaneously be getting the new switches made and installed. They are already soliciting bids on their manufacture. The new switches will not only eliminate prefires, they will also allow for much less downtime for maintenance. Even more important they will increase the amount of current the device produces which will increase fusion yield. When they resume firing in the early fall, they believe they will have a device that can overcome the remaining hurdles to high fusion yield.

While the cracks were bad news, the inspection of the beryllium anode also brought good news. The erosion of the electrode near the insulator has markedly decreased with the beryllium electrode as compared with the previous tungsten electrode.

Laser PB11 Shows Big Advance

An international scientific collaboration using the PALS laser facility in Prague has reported a major advance in hydrogen-boron (pB11) fusion. The report, published in January in Physical Review E, demonstrated a 40-fold increase in fusion yield over previous experiments at the same facility in 2014. Researchers hit a target of boron nitride with some embedded hydrogen with a 2 TW burst of infrared laser radiation, focused down to an 80-micron spot. The research team explained that they achieved the 40-fold increase in fusion yield simply by making the target thicker. The advance is both a step forward for hydrogen-boron fusion, which has the potential to provide cheap, totally clean energy, and an example of the sort of leaps that can occur in fusion research.

The laser approach to pB11 fusion is being promoted by Australian company HB11 Energy, although that company was not involved in the PALS experiment. The main disadvantage of this approach relative to Focus Fusion using the plasma focus device is the very low efficiency of the laser needed to initiate the fusion. The iodine laser at PALS, for example, needs 1.2 MJ input to produce a 600 J laser pulse. The fusion output from the latest experiment was 0.06 J, so the critical ratio of output energy to input energy is still about 80 times less than that achieved by LPPFusion’s FF-1, using a much less reactive fuel, deuterium. To reach net energy, HB11 Energy envisions fusion generators that would be much larger and more costly than will be needed for Focus Fusion.

Despite these drawbacks to the approach, the data obtained in the PALS laser experiments is extremely encouraging to all those, including LPPFusion, working toward pB11-based energy generation.

ABSTRACT
The nuclear reaction known as proton-boron fusion has been triggered by a subnanosecond laser system focused onto a thick boron nitride target at modest laser intensity (10,000 trillion watts per square centimeter) resulting in a record yield of generated α particles. The estimated value of α particles emitted per laser pulse is around 100 billion, thus orders of magnitude higher than any other experimental result previously reported. The accelerated α-particle stream shows unique features in terms of kinetic energy (up to 10 MeV), pulse duration (∼10 ns), and peak current (∼2 A) at 1 m from the source, promising potential applications of such neutronless nuclear fusion reactions. We have used a beam-driven fusion scheme to explain the total number of α particles generated in the nuclear reaction. In this model, protons accelerated inside the plasma, moving forward into the bulk of the target, can interact with 11B atoms, thus efficiently triggering fusion reactions. An overview of literature results obtained with different laser parameters, experimental setups, and target compositions is reported and discussed.

SOURCES – Physics Review E, LPP Fusion
Written by Brian Wang, Nextbigfuture.com