Hello - (hope this is the right place .. pardon the cross-post)...
I was recently asked to come up with a circuit for rapidly turning off a modest magnetic field (about 100 gauss) in a microsecond or less. Did a little math, some thinking, and came up with a Helmholtz coil pair that seems to do the right thing. Approximate inductance of the coil pair is
8 uH.Turning the field off in under a microsecond was the difficult part.. but a hint in a reference suggested placing a zener across the inductors. This was tried with a much lower current (and a much lower field) and indications are that this will work. However...
Generating a 100 gauss field requires about 15 amperes. Turning off that field by circulating the current through a zener means the zener must (a) handle a pulse of 15 amps and (b) dissipate nearly 1 mJ in less than a microsecond. The repetition rate is once every 5 seconds, maybe a little faster if the research turns the frequency up.
I have found only one maker of pulse-rated zener diodes.. and while I was able to get a few as samples, now a small quantity is needed (