Flight of Electrons

Theory of the electron motion after pasing the anode in the electron gun
flight phase
When the electrons pass the anode they leave the electric field.
Then there is no more acceleration.
So the equations for a uniform linear motion are usable:
$x(t)=v_{\text {end}}\cdot t$
$v(t)=v_{\text {end}}$
The electrons move with the velocity they get while passing the acceleration zone.