Velocity separation in electron beam by static electromagneticfield of helical symmetry

In a homogeneous magnetic field superimposed one a helically symmetric electrostatic one, the electron drift trajectory depends on the particle energy and on the particle velocity component relative to the magnetic field. These effects can be used (1) to suppress gyrotron magnetron-injection gun instabilities caused by electron reflection from the magnetic mirror and (2) for separation of electron beam energy fractions in multistage depressed collectors