Mr Lerner;

From what I’m reading, you’re using a spark-plug, without the grounding arm, to initiate a plasma within the switch. The plasma then conducts, via the spark-plug’s center electrode, the current pulse over/along the plasma. Now you’re looking for a spark-plug with a larger center electrode to act both as a better heat-sink, and to lower the current density in the electrode. (with the current density used, I can see why they are beating themselves to death)

The real issue seems to be how do you start a plasma in the plasma switch without overloading the small electrodes that you need to assure that they fire together. Larger electrodes will conduct heat better, but they will not fire together in time as well as the smaller electrodes. In both cases, switch-to-switch timing is affected by the switch-to-switch gap mis-match due to the initial firing pulse ramping-up, as different gap distances will arc at different voltages. (times along the ramp)

If that’s the case, have you considered dispensing with the spark-plug altogether?

It may be easier to initiate the plasma using another means. One that would absolutely insure that all the plugs fired simultaneously, and could give you a way to use a larger diameter electrode. I had suggested this earlier, but the suggestion either withered, or was left off for good reason. Anyway, back to how I would do this.

How about using a LASER to initiate a plasma in the plasma switch? No issues with ramp-time as with the initial electrical pulse used to start the switch, and no issue with the switch-to-switch gap mis-match between the conducting electrodes that will arc at different voltages (times) as the initial electrical pulse ramps-up.

One LASER pulse can be routed to all switches simultaneously, (or tuned by varying the distance between source & destination) insuring that they all initiate a conductive plasma at the same time. Because the main conductive electrodes no longer need to be used to initiate the plasma, they can be made larger in diameter, with better attendant thermal characteristics, and a lower current density.

The issues would be the gas that’s excited by the LASER, and used to conduct the main capacitor bank’s current; finding an off-the-shelf LASER that can do the job; the selection of materials for the construction of the new conductors; and making the switch so that a LASER can be fired across it to start a plasma.

I think it likely that some of this research has already been done in the past, probably connected with lightning strike dampers, or some other current-dump system associated with power generation/switching systems.

From what I read, this is a critical issue; both so that experimentation can proceed, as well as for fielding a robust system in the future. I’m thinking that this means that the electrode heating/current density problem has to be solved, and that the switch-to-switch gap mis-match must be rendered moot as a maintenance issue.

What say you?
Patrick