Reply To: turn heat into electricity

[Lerner]

This is what we’ve decide to do, near-term and medium-term. Since we have gone at times for hundreds of shots without breaking insulators, we don’t think we need a thicker one right now, with 1 MA or so currents. It seems to be a question now of avoiding any lateral stresses that accumulate when we are centering the electrodes and insulator. So first, we are separating the centering of the electrodes from final assembly, so that when we assemble, everything will already be vertical. Second, we’ve enlarged a cushioning gasket to eliminate a small ring of the insulator that was unsupported. Third, we are eliminating a second, ‘centering’ o-ring, so there will be no lateral pressure conveyed from the anode to the insulator. I estimate that together these steps should take any stresses on the insulator down by at least a factor of 5. And, the plastic shims we were using to measure the gap between the insulator and the electrodes could have left behind residue that explosively vaporized when the plasma hit it. So we are changing the probes to eliminate this problem.
In the medium term, stresses will increases as we go to higher currents. So, thanks in part to the ideas from the forum, and searching the literature, we’ve got three “finalists” to look at for a new insulator material—silicon nitride, zirconia, and cubic boron nitride. We’re seeing what suppliers can come up with and quotes. Anybody use any of these?