Setup without grounding the Maltese cross

Setup:

A second alteration of the experiment is isolating the Maltese cross.
For this purpose the power supply and the grounding of the Maltese cross is removed. Now the electrons impinging on the cross cannot flow off.
Skizze Aufbau Schattenkreuzröhre ohne Erdung

Notice:

This experiment is in this setup non-reproducible and matches the theory only sometimes.