We are doing some experiment, the other guy needs 1200V at 1200 amps or so ( the higher current the better) for few mSeconds, my first thought was to use big capacitors in the range of 2000uf 1200 volts, but i'm not sure if I can meet the required specs, so I have to calculate the capacitance required to achieve this goal, any ideas?
well 1200A at 1200V is 1 ohm. So t =RC gives you 1ms per millifard before the voltage drops to 1/3 if all is supplied from capacitors this calculated on your load being resistive. so much depend on what few mSeconds mean. 2000uF with 5 stacked capacitors is 10,000 uF for each layer - quite a large volume.

Anyhow be careful, you are designing something much more efficient than the electric chair.

Erik