This is a 50kv charger made from a Ignition coil which will put out 10-13kv. From the ignition coil the hv is sent to 4step cascades, each step of a cascade multiplies the max output voltage.

FOR EXAMPLE: 2KV to start, if we have a 3 step cascade we do 3x2000 we get 6kv out.

In cascades both the diode's and capacitors must be the same or higher the rating of the initial starting voltage. You do not need large capacitors 1nf, 1pf, 1uf will do just fine.

Here is a schematic sent to me by Astrolite. It is a frequency module circuit for a ignition coil.