We’ve made more progress on the heating problems we mentioned in the last report, but we have not yet completely resolved this problem. The first part of the problem was not delivering the decaborane gas efficiently to the vacuum chamber because it was condensing on various cold spots on the way. Since the mix chamber and sample container that stored the decaborane had no sensitive components that were heat-sensitive we decided to try higher heat (100 C). This led to the decaborane melting and then boiling, producing plenty of gas, while the high heat eliminated the cold spots enroute to the vacuum chamber. We are now able to get many “fills” of the chamber for a single 4-gm fill of the sample container with decaborane powder.
However, we still have problems within the vacuum chamber itself. We found out that our gauges were not accurately reading the decaborane pressure, so recalibrated them against the pressure of a different gas—hydrogen. We did this just by filling the mix chamber with a known pressure of hydrogen, and then filling the main chamber with decaborane until the gas pressure in the two chambers was balanced and gas did not flow in either direction.
When we did this, we found that we had about half as much decaborane in the chamber as the gauges had earlier been reading. We need to double the amount of decaborane to get to where we should be. But at this point we found that after we filled to the target pressure, the pressure in the chamber fell rapidly, indicating that the decaborane was condensing on cold spots in the chamber itself, especially on the anode, which was much cooler than our goal. As the cleaning shots showed, we can’t get good results, and measurable fusion if we fire a shot with a boron or decaborane coating on the key parts.
We also can’t just arbitrarily increase the heat on the electrodes however, without endangering the heat-sensitive Mylar insulator layers. We are now upgrading the insulation on the anode to get its temperature above our goal. Once we do that, we expect rapid improvement towards boron fusion shots.