The picture below shows the fluorescent screen image on a Teltron T555 tube.  The centre bright spot  is the straight through electron beam. The circles around the centre spot are produced by electron diffraction.  The anode voltage and beam current are also shown on the digital meters. The applied heater voltage is 5V. Varying the anode voltage varies the diameter of the ring pattern. Increasing the voltage decreases the diameter.

'Click-on' the above picture to change the anode voltage.

'Click on' image to see electron gun

Electron diffraction tube 

The complete cathode ray tube is shown here with the fluorescent coated screen on the right- hand side. The anode connection is via the plug on the neck, seen here above the electron gun.

Teltron T555

Tube schematic 

The exit hole in the gun anode can be seen on the left. There is a fine mesh grid supporting  a layer of graphiticised carbon across the aperture. The beam of electrons passes through this fine mesh on its way to the luminescent screen. The electrons interact with the atomic spacing of the carbon atoms to produce the interference patterns observed. This suggest electrons have 'wave-like' behaviour. 

For particle behaviour see: Crookes Railway Tube.