Both of them were additionally installed on the SEM chamber. The
discharge was operated using DC source having 1 kV maximum
voltage through a 10 MU ballast resistor (RB) to limit the current in
series. Id was determined from the voltage drop across RB measured
by a multimeter, and Vd was calculated from the difference between
supplied voltage and voltage drop across RB. The discharge current
(Id) waveform was observed by oscilloscope (IWATSU-LeCroy,
LT364) across a 50 U resistance (RM) inserted between the cathode
and ground while the discharge voltage (Vd) waveform was
observed by the oscilloscope probe directly connected across both
electrodes