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Our new beryllium anode stalk has arrived at LPPFusion’s lab in Middlesex, NJ. (See Fig. 1) The stalk, which will be installed at the very center of the FF-2B device, will carry the current from the intense current filaments as they converge and from the tiny plasmoid where the fusion reactions take place. The anode tip also gets the most intense energy from the plasmoid and the hot plasma around it. To better protect the anode, we’ve moved the inner surface further away from the plasmoid and made a number of other design changes to strengthen the part.
Fig. 1 Our new beryllium anode stalk safely sitting inside a glove box, which protects us from any beryllium dust we may generate in working with the stalk. The upper opening in the part is where the plasmoid will form when the anode is in use inside FF-2B. Note the thinner wall of the new anode, which actually strengthens the part by moving the metal away from the heat source along the device axis.
After a careful inspection, we took the anode to be annealed. This is a standard process where the part will be briefly exposed to high temperatures and then rapidly cooled. Annealing relieves the surface stresses that build up during the machining process, and greatly reduces weak points that can lead to cracking. Once this is done, we’ll treat the anode with a chemical bath that will strip off the thin layer of beryllium oxide. Even though this layer is only 10 nm thick—a hundred atomic layers—it can cause problems. Beryllium oxide is an electrical insulator, so when the mega-ampere currents in FF-2B hit the anode, the oxide will be vaporized. In 2019, this caused a thick layer of dust to deposit everywhere in our vacuum chamber, interfering with subsequent shots. The chemical bath, safely carried out within our sealed glove-box—will eliminate this oxide layer. It won’t have time to reform in the time it will take us to put the anode inside the vacuum chamber.
While the anode is getting annealed, LPPFusion Research Scientist Syed Hassan will be busy starting re-assembly of FF-2B with our brand-new smaller switches. We expect the switches will allow us to generate higher peak currents and more fusion yield once our new experiments get under way, still expected sometime in May.