Methods for creating HV Direct Current?

I want to get a power source of about 3 KV at very low current, using as a power source a 12 Volt Battery.

I'm making the next:
Battery---Inverter---HV AC Transformer---Bridge Rectifier

I want to know more ways to create High Voltage Direct Current.

The main thing I want to do with the HV-DC is to charge a HV Capacitors.

A fun but labor intensive and bulky way would be to use your 12v to drive a motor coupled to the belt of a Van de Graaff generator or the wheel of a Wimshurst machine...

the Van De Graaff generator might be more effcient than most discrete circuits, but will depend on ambient humidity and air conditions. I've gotten 6+cm spark gaps off a plastic tube at work that contains the flow from a ceramic bead blast chamber, on dry days.

HV supply

Here is a simple one. Check out the update for fixes.

**broken link removed**

you do not say how much current you want ... "charge a HV Capacitor" is meaningless as well unless you say what the value is and how fast you need it to charge