LPPFusion Research Scientist Dr. Syed Hassan, assisted by Chief Scientist Eric Lerner, has completed the successful assembly of FF-2B with our new modified beryllium electrodes. The next step is a bake-out to rid the vacuum chamber of water vapor and then on to our exciting first effort to burn boron—to achieve fusion with the hydrogen-boron reaction.
Dr. Hassan had to carry out a number of exacting steps to complete the assembly, all the while maintaining LPPFusion’s strict safety protocols to prevent contamination with beryllium dust. First, using our sealed glove box, Dr. Hassan merged the new anode onto the anode plate. To ensure ultralow resistance, he used indium to join the parts together. The parts were first heated to melt the indium, then the indium was spread onto the parts with an ultrasonic soldering iron. The ultrasound produced by the iron, similar to that used in a dentist’s office to clean teeth, breaks up the thin layer of oxide on the metal parts, allowing the indium to fuse onto the part. Once the right temperature is reached, the indium spreads as easily as paint. Lerner’s measurements showed that the resistance across the joints was less that 2 microohms, an excellent result.
Dr. Syed Hassan, in full protective gear, does final preparation to put the new beryllium anode plate (with anode hidden underneath) onto the FF-2B device.
To remove the thin oxide layer from both the anode and the reprofiled cathode, Dr. Hassan hand-polished each. This step is important, as it prevents the vaporization and redeposition of a messy oxide layer. This occurred in our first beryllium assembly in 2019 but was avoided by polishing in the second assembly in 2021.
However, in order to prevent the beryllium parts from re-oxidizing when exposed to the air during assembly, the team had to do the entire assembly in a single day. Dr. Hasan and Lerner worked to carefully center the ceramic insulator within the cathode and the anode inside both, to prevent asymmetries in the plasma breakdown (see next news item.) They used a new procedure, suggested by Dr. Hassan, in which the cathode and insulator were first centered on each other and the connecting bolts tightened, while the anode remained unbolted. This result in excellent centering of the insulator, but the anode was 0.125 mm( 0.005 inch) off-center, potentially a big error. However, with a tiny shove of a screwdriver on the anode steel plate, Dr. Hassan flicked the anode into perfect centering and bolted it down. Lerner measured the centering from below the anode to be better than 25 microns, so one side of the anode is not more than 5% closer to the insulator than the other side.
To complete the assembly of the vacuum chamber Dr. Hassan had to work well into the early morning hours of Aug. 23. This is not something we do routinely at LPPFusion! We hope by the time of the next major assembly we’ll have more help to spread the work.
With the bake-out expected to last two weeks at most, we still expect to initiate tests with the new assembly in September. After a preliminary week of shots with deuterium, we’ll move directly to our long-awaited tests with decaborane—a compound of hydrogen and boron.