A detection pulse is about 0.2 Vpp(Voltage Peek to Peek).
Since the signal of 0.2 Vpp is insufficient to input 0.6V(ON) of a transistor, BIAS 0.4V have been applied.
Thereby, a transistor will be turned on if detection pulse 0.2Vpp + BIAS 0.4V amount to 0.6V.
The noises from the Cockcroft Walton circuit are about 0.07 Vpp.
In order to avoid this noise, exquisite BIAS is set up.
In case of signal under a noise, a shield is required.
The signal of transistor observed with an oscilloscope.
A noise is separated and 5 Vpp outputs from a transistor. A pulse is about 50[us]. This signal is counted.