it can be easily done with a flyback ( or multiples ) having several outputs - say 3 of, stacked in series 500V each,
you can then charge the required caps on each output - to allow you to get the 4kA pulse for 400uS
there will be some droop of course - we have done 1.5kA this way no problem, you just need more 500VDC rated electro's
i/c = dv/dt, so for a droop of 50V over 200uS, at 4kA average, you need 16 milli - Farad total
or 48 milli-Farad on each 500V part of the series stack ( 48 mF = 48,000 uF )
To charge these caps is 10 sec say - total energy = 0.5 C. V^2 = 18 kJ ( / 10 sec = 1800 watts )
so 3 flybacks at 600W each, or choose a longer charge time, say
20 sec
this gives 3 sections at 300 watt each - much more do-able for a newbie doing a flyback.
For the caps - say we use 470uF, 550V rated, this is 103 caps per section ( 3 sections in series )
as these are about 35mm dia x 65mm high - this is starting to get a little on the biggish side already ( 25 litres just for the caps - say 20cm x 20cm x 80 cm to allow for the pcb and standoffs )
the good news is that a well laid out pcb for each section will easily handle the 4kA, ( 39A per cap - easily done repeatedly by good quality electro's - won't even get warm )
So there you go - 1 x psu for your rail gun prototype - just designed for you
- you 're welcome
@newbie_hs
EP.