No, I was referring to a detector tube filled with neon, where
the voltage on the tube is just below the sustained ignition level,
and where the charged particle causes a conducting ion trail, which
discharges the parallel capacitor a little bit, causing the click signal
you can pick off. The feed resistor slowly restores the voltage
accross the tube/cap. The amplitude of the click shows the energy level
of the detected particle. Long ago I built a cosmic ray detector/display
using these tubes.
Name is geiger muller tube I think.

OK I understand. But that's still not the problem, because the unit produces
its own clicks whether the probe is connected or not........