How can I control high voltage signals? (1 to 15kV.)

I'm an embedded s/w guy, but I'm able to do low voltage circuits without too much trouble. So I will try to ask this question on high voltages!

I've got a power supply running at 1 to 15kV. It runs constant voltage, always on. The power supply provides a charge for ejecting water droplets. See this video to see what I'm talking about: http://www.youtube.com/watch?v=5h8I6J_p6AM

I need to control the charge (on or off) for the electrode. What approaches might work?

Spec wise: 1-15kV, KHz-level frequency for switching.

Here's what I got brain storming wise:

• Control from the low voltage side. Don't apply an AC signal to the transformer. (But currently using off the shelf PSU.)


• IGBT. They're on the expensive side the higher max rating. Also seem to be focused on high current applications. And apparently they can be slow (haven't gotten very deep with the specs).


• Cascode. I saw some circuits and papers that seemed to suggest I could use this approach, but there is a lot I don't understand.


• Some kind of virtual ground method? Say 10kV and 9kV. (AC coupled control signal?)

This is a beyond my abilities. Some thoughts would be very useful. :)