Best-practices for potting a high-voltage circuit

Increase the diameter of the conductors. This will decrease the electric field strength at the surface. It sounds like you only need to halve the field strength, so only need to double the radius of curvature.

Where you use connecting, use thicker wire. Where that wire is a component lead, then you could wrap some wire or foil around it, or slip a metal tube over it. If you have soldered joints, make sure you have not left any sharp edges or points where you've cut wires. Use some extra solder and let it ball up under its own surface tension.

Another thing you need to look out for is air bubbles when you apply the potting, if any air bubbles are present it will drastically reduce the dielectric resistance of he arrangement as a whole.

since this is very important to know the effectiveness of your current setup you need a diagram showing the distances between ground and high voltage, this way other people can give better advice, seeing the datasheet for the compound you mentioned it has 14kV per mm so if you have 2mm of clearance it should be ok.

However, if there are pin to plate geometries(you got a sharp pin with high voltage facing a ground plate) you should derate this dielectric strength by about 30%... again without looking at the geometry and the distances it is hard to give concrete advice. Try to make your pins less sharp and more like spheres.

In our second build we had much better performance.

• clean all surfaces
• smooth points and edges in BOTH the ground planes and on high voltage parts (see below)
• used primer
• vacuum degas of potting compound

One thing we did was expended some effort make smooth all of the ground plane surfaces, since arcs begin at the negative terminal, and we are @ +20 kV. The ground plane smoothness might be just as important as the HV terminals.