I am simulating the circuit shown below. I do not understand how this works and how this will help in generating high voltage pulses for NDT ultrasonic testing.
This circuit produces high negative voltage pulses at the output.
C1 will initially be charged to the voltage of V1 via R1, R2, R6 and R7. When M1 turns on, a falling edge of 300V can be seen at the drain, which is directly forwarded via C1, D2 and R3 to the output.
R3 limits the output current to an acceptable level for the ultrasonic transducer. R4 and R5 damp the resonance ringing of the transducer.
There may also be an inductive part in the transducer. Diode D1 can protect M1 when voltage spikes above Vin come up.