Active Space Radiation Modification using Plasma Waves from a Pulsed Electron Beam

This work is advancing a flight-robust, actively controlled electron-beam source
that can (i) stimulate whistler/VLF waves without a large antenna and (ii) enable controlled studies of wave–particle interactions that govern the trapped-electron environment. Space-based VLF transmitters demonstrate the value of controlled wave injections but also highlight the complexity of antenna–plasma coupling in space; pulsed beams provide an alternate actuator that injects free energy directly into the plasma distribution function. We investigate a tetrode-like architecture in which a dedicated control electrode is placed between the cathode region and the main acceleration stage. The additional electrode provides an extra degree of freedom to shape electrostatic potential and manage extraction/focusing, enabling strong modulation while maintaining beam quality. The design emphasis is therefore: fast switching and minimal beam-quality degradation.