The blanker thread goes through a sequence of optional time periods

UnblankTime: if this is set, the beam is blanked immmediately and then
unblanked after this time is up

If there is beam scanning, it goes for ScanTime
If there is drift compensation, it goes on for PostActionTime

ReblankTime:  if this is set, it waits for this delay unless drift
compensation was used, then the beam is reblanked then it goes on to
post-actions

Otherwise, if PostactionTime is set and there was not drift compensation,
it waits for this amount of time and goes on to postactions.

ShutterTime is set for a Gatan camera as the amount of extra open shutter time
for the plugin to set up.  This is included in the reblank time.
(If shutter can't be opened, it uses a dark reference (!) specified by
PreDarkExposure and uses PreDarkBlankTime to blank out some of this if needed)