Maltese Cross CRT
cathode rays - electrons - magnetic fields
What it shows:
Cathode rays are seen to travel in straight lines by casting the shadow of a Maltese cross on fluorescing glass.
They can also be deflected by magnetic fields, as seen by the distortion of the shadow.
How it works:
Electrons accelerated down the tube are carried by their momentum to the front wall, where they strike the glass
causing it to fluoresce. However, those electrons on a collision course with the cross never reach the glass,
leaving a dark shadow in the green fluorescence Showing the effect of a magnetic field on the cathode rays, a
magnet brought close to the tube deflects the electrons, distorting the image of the cross.
figure 1. Schematic layout of Maltese Cross CRT
Setting it up:
The Maltese Cross tube uses a 6V DC supply and induction coil.
1
A small Alnico bar magnet is sufficient to deflect the beam.
Comments:
On some Maltese Cross CRTs, the metal cross itself acts as the anode. The effect of the electrons being decelerated
by the glass are shown in Bremsstrahlung. Rating ***
1 Ours are CENCO although are no longer available. Sargent-Welch model 2392A are similar