The LPPF research team has begun the re-assembly of the Focus Fusion experimental device for the long-awaited experiments with beryllium electrodes. With the new glove box for handling the electrodes now installed, the first step was to attach new windows to the vacuum chamber (Figure 1). Two of the new larger windows are now protected by shutters that will be closed during firing. This will allow them to be used later in the experiment if the main window becomes too coated for use by the ICCD camera. While this did not occur in earlier experiments, the research team plans for a much longer experimental run this time, with 1,500 or more shots. In addition, the use of hydrogen-boron fuel later in the experimental run might lead to heavy coating with boron. The shields will allow for many more shots if coating becomes a problem.
The next steps in assembly will be to mate the beryllium electrodes with their steel connecting plates, using soft indium metal between the parts to ensure good electrical contact. As with the earlier tungsten electrodes, all electrical contacts will be outside the vacuum chamber, eliminating any possibility of arcing into the plasma. The silicone vacuum seals will be baked out at high temperature in our new vacuum oven. Then, the team will carefully center and mount the electrode-plate assemblies onto the rest of the Focus Fusion device. The new vacuum chamber and auxiliary vacuum system will then be installed, sealed and pumped down. After that we will re-install the ICCD camera and other upgraded instruments, including a new electron-beam spectrometer. The final step will be to re-assemble the capacitor switches with new Lexan and ceramic insulators. So we still have a bit of work to do!
Figure 1. Dr. Syed Hassan bolts a window to the new vacuum chamber, which is coated with golden-colored titanium nitride. The protective shutter has already been installed on a second window, facing the viewer. Note the small silver lever extending below the window, which can open and close the shutter without breaking the vacuum. This window is protected by a plastic cover during assembly.
At the same time as Research Physicist Syed Hassan and Chief Scientist Eric Lerner assemble the hardware, Chief Information Officer Ivy Karamitsos and System Administrator Jose Varela, helped by Electrical Engineer Fred van Roessel are upgrading the data processing system. The new system will automatically download all data, process it to produce an estimate of plasma parameters (density, temperature and others) after each shot, and store the data into a new database, with a user-friendly interface. We expect this will greatly accelerate analysis of the data during the breaks between firing the machine, allowing the fine-tuning of the experiment on the fly.