[Vo]:Geiger counters and fast rates of change of voltage gradients

[Nigel Dyer]

I have built myself a marx generator which produces an output voltage of 
the order of 20kV and which can produce a very nice fat spark if the 
output electrodes are close enough.   I have a conventional geiger 
counter and I find it beeps if it is within 5cm of the high voltage 
output.  The distance suggests alpha particles, but a peice of card 
makes no difference so I assume that this is an artefact picked up by 
the large and abrupt change in the voltage gradient.  Oddly I could not 
find any reference to this artefact on the internet.   Is this just 
something that everyone knows but no-one writes down?

Nigel