The tube from the diode experiment
were also used to se if it was possible to demonstrate a cathod
ray tube. A very simple television tube of course without
deflection coils.. A high voltage plate with a hole in the middle and a
wehnelt chathode to conform a electron beam. a phosphorescence
screen was maid by using ZnS-paint.
Some concerne were if the mean free path was enough soan electron
could reach several cm. But an evaporation of aluminum foil
around the glowing cathode made a fine metal coating on the
glass surface so if evaporated aluminum could reach the inner glass
surface electrons would also do that.
In this setup it was unsertain if it really worked. The light
emitted from the cathode filament made it difficult to
detect if there was any phosphorescence on the screen caused by
impact of electrons.
