The following topics can be discussed with this Neon-gas filled, partial-vacuum electron tube: 
•  Determination of the specific charge e/m for tangential injection and perpendicular magnetic field
•  Observation of the spiral path followed by electrons fired axially into a co-axial magnetic field.
 

The dual beam tube is a partly evacuated electron tube, filled with Neon at low pressure and equipped with both axial and perpendicular electron guns. The electron beams are perpendicular to one another and a common deflector plate is provided for both guns. The electron beam source is an oxide cathode heated indirectly via a heating coil. The electron paths show up as a fine, orange beam due to impact excitation of the Neon atoms.
The dual beam tube can be used to determine the specific charge e/m from the diameter of the path followed by electrons fired into the tube from a perpendicularly mounted gun with a vertically aligned magnetic field and observation of the spiral path followed by electrons fired axially into a co-axial magnetic field.