Velocity ratio measurement diagnostics and simulations of a relativistic electron beam in an axis encircling gyrotron

This paper reports on diagnostic experiments and simulations of a large-orb it, axis-encircling gyrotron, The electron's perpendicular to parallel velo city ratio alpha is measured. The experimental diagnostic consists of an ap ertured portion of the beam which is passed through a cusped magnetic field then collected on a glass plate. The cross section of the beam is recorded on the glass plate in a radiation darkened pattern. From the gyro-radius, B-field, and beam energy, alpha can be calculated. Particle distributions o f the radiation darkened plate are in excellent agreement with numerical si mulations of single particle orbits derived from the relativistic equations of motion. The experimental measurement of alpha yields values from 0.9 to 1.4, The simulations predict an alpha of 1.0 to 1.5.