Abstract
A thermionic cusp gun is proposed for use in a 3 MW second harmonic X-band gyro-TWA with a helically corrugated waveguide interaction region. The passage of an electron beam through a non-adiabatic magnetic field reversal converts part of the electron beam's axial velocity into axis-encircling transverse velocity. The paper presents the design and simulation of this cusp-based electron gun, yielding a 12 MW, 81.5 A axis-encircling beam with an axial velocity spread Delta v(z) < 15% suitable for use in harmonic gyro-devices.