I'm thinking of a very simple circuit to generate high voltage pulses, like this:
The MOSFET in this case will turn on until the current through L1 ramps up to 10A, then turn off. The pulse output is connected to a load which can have a wide range of impedances. If the impedance is low, then the energy in L1 goes there. If the impedance is high (higher than 600V / 10A = 60 ohm), then the 600V Vds on the MOSFET can be exceeded. If I understand correctly, that means it will go into avalanche, and conduct until the current goes below some kind of threshold (or the voltage drops??). This MOSFET happens to be rated for repetitive avalanche energy of 41.7mJ, and avalanche current of 47A. The energy in L1 is (1/2) * 6uH * (10A)**2 = 0.3mJ which is much less than the rated energy.
Is this something that the MOSFET can survive? (Let's say pulses at 10kHz, repeated indefinitely) I've never used a MOSFET in this way, it seems like it would stress the device a lot.
When does a MOSFET in avalanche mode turn off? Is there a way to make it turn off?
What is Vds during avalanche?
P.S. It is possible to limit the peak pulse voltage to less than 600V using some kind of RC pulse shaping network, or zeners or TVS diodes, but that makes things more complicated and is not preferable in my case.