I'm building my own high voltage capacitors, for science, and I'm running into an issue. I'm 90% sure what I'm looking at is coronal discharge but I wanted to be certain. The caps are two aluminum foil plates with 4 layers of some unknown plastic sheeting between them and then hooked up to my 15kV NST.
In this picture you can see the arc that forms after running on AC for a while. The whole thing is much brighter in person but this picture captures the problem I'm having. The thing I'm curious about is that when I hook up diodes to it to make a half wave rectifier this problem does not occur. This only happens on AC and if I reduce the number of layers of dielectric to just 1, it's not so much corona as it is just a constant lighting storm with big arcs like the one seen shooting off all over the place.
So just to confirm, is this coronal discharge? Why does it only happen on AC?