A simple low power low current N channel fet could easily be used to trigger an SCR. You'd only need the nfet a single resistor and the SCR. The only caveat is you haven't mentioned if this application requires the ability to terminate the discharge BEFORE it's complete, an SCR can't do that, a directly connected NFET can. Again typically in these situations the voltage of the capactior is altered to control the output pulse's total power, just easier that way.