Original poster: stork <stork@xxxxxxxxxxxxxxxxxxx>
1) Would not a negative space charge induce a positive charge on a nearby electrometer probe?
No, by eletrostatic induction the normally neutral probe will obtain a negative charge from a negative space charge. Let us not forget though that the electric field from the TC is alternating between negative and positive charge even though there is just a single primary bang.
2) Did Hull ensure that the Keithley front-end was not overloaded during the bang. I have a homebrew electrometer which behaves that way - fine until you overload it momentarily, after which it retains a (in my case -ve) charge on the probe until you manually discharge it.
Yes, from my direct observation of Richard's experiments and from conversations with him, he finally deduced that there is inborn error in the Keithly 610C electrometer design. Ultimately the persistence of negative charge was determined to be instrument error.
Stork