Yep that's clear now, do you know the typical pulse length?
I've only used HE sensors for simple stuff like a speedo sensor on a tail shaft, that's pretty slow and of course I don't care about the pulse length. I don't know if they would be good for this but I assume they would be. You would have to look at response times (they may not be fast enough) and also if the rising and falling edges are symmetrical.
For example the ATSD682 is good for 8kHz which should be fast enough but it may not be able to detect a 3uS pulse.
Rob