SCR driver diode

[Javier Lopez]

I have made following design to drive two high power hokeypuck SCRs to activate a Plasma compression coil. As long as catode falls below 0V, I do not know if it is needed to insert diodes from the optoisolated driver A1 (and A2) and the limiting current resistor R1 (and R2):

 

[berkeman]

Where exactly would you insert those diodes? And can you show the full circuit for the gate drive circuits?

 

[Javier Lopez]

Here is the complete drawing. U1 and U2 are isolated drivers. I ask if I have to insert a diode between U1 and R1 and another between U2 and R2 (in the forward resistor direction). (The R3 and R4 are set to drain the inducted voltage due high dV/dt at SCR due >10kAmps are drain).
My idea is to charge the 6mF capacitor using R5, then drain the capacitor energy through the coil sorrounding the plasma that is L1 by using a trigger signal named "control". As long as L1 is a superconducting inductor, most of the current will come back to the capacitor then I will switch off the device :)