Charlie was a really, really interesting person. Much of what he knew he couldn't tell us of course. But the few things he could tell us were fascinating and hair-raising in roughly equal proportion. His work is very well summarised in this book
http://www.amazon.co.uk/Martin-Pulse.../dp/0306453029 (sadly too expensive for most people to own, but may be accessible through libraries) and a history of the field from a US perspective is given here
http://lcweb2.loc.gov/pnp/habshaer/m...md1450data.pdf.
As far as monitor design goes, it depends on the source impedance of course and the duration of the pulse. The source impedances I was working with were typically of the order of ohms, delivering tens or hundreds of kilojoules in a few hundred nanoseconds. So I could easily live with a probe resistance of just a few tens of kilohms made up of, say a hundred 470R resistors in series. The bottom resistor would still see a few kV (hence the need for nonlinearity correction). So the monitor across it could be designed for a further 200:1 attenuation, say a further twenty 470R's feeding a 50 ohm co-ax out to a fast scope. This second attenuator would sometimes have to be built into a screening can as noise pick-up inside these machines could be 'an issue' to say the least
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Cheers,
GJ