  The effect of the voltage rise time on nanosecond and sub-nanosecond impulse
breakdown of distilled water is studied. The dependence of anode initiated
streamer inception on this parameter is shown to be more intricate than
previously reported, particularly as it relates to mechanisms directly in the
liquid phase. Dynamics of the emission phase for sub-nanosecond pulses with
600ps rise time are presented to enable comparison with previous work on
nanosecond initiation features. Schlieren imaging is also used to show the
development of optical density perturbations and rarefactions as a result of
electrostriction in the liquid which were previously found for nanosecond
pulses as well. The mechanism of nanopore generation in the liquid due to fast
impulses proposed by Shneider, Pekker and Fridman is used to explain the
results.
