I like the use of the 566 and TL081 for frequency and duty cycle. Simple design and functions.
I personally think the right portion needs corrected.
The "Gas Rate Control" will be shorted to ground during pulsing with the IRFP460.
While I'm not sure who has seen the inside of the box, I will post this as my understanding of the system.
Resonant Action control is "Va" and is always held constant "on" with variable amplitude from the “Resonant Amplitude” control knob (variac).
Gas Rate control would be “Vb, Vc, ….Vn” (variac).
I’m including a high resolution photo and adding my opinion on the controls:
CP = Constant Pulse
GP = Gated Pulse
SP = Single Pulse
PF1 = Pulse Frequency 1
PF2 = Pulse Frequency 2
Whatever the frequency was – it wasn’t controlled in this unit, only the x,2x,3x,4x (Low and High). No base frequency adjustments seen.
HGG = Hydrogen Gas Gun