What size should the foil capacitor plates be?
The capacitor plates can be almost any width or length. A good rule of thumb is to make the foil capacitor plates approx 3 inches wide and about the same length as the electrodes. I have tried many different sizes of foil plates and they all work. The only critical thing is to make the two capacitor plate edges straight and have about 1/8 inch spacing between them. While experimenting with the “Double L” electrode configuration, I used 1 inch wide angle aluminum. These electrodes each had a one inch flat bottom that would sit intimately against the surface. I was able to get very observable laser action while these electrodes were just sitting on the dielectric, without any top foil plates at all. There was more laser output of course when I did use capacitor plates below these electrodes.
