How does electrons propagate in the absence of any electric or magnetic field?

A Maltese Cross Tube (also known as Shadow Cross Tube) is used to answer this question. A electron gun produces an unfocused diverging beam which is detected by a fluorescent screen at the end of the evacuated tube. In the center of the bulb a aluminium cross is suspended. It absorbs the colliding electrons and produces a "shadow" on on fluorescent screen.
Layout of the experimental setup of a maltese cross tubeLayout of the experimental setup of a maltese cross tube