Terahertz radiation from glow discharge in coaxial resonator

The orbitron in which a low pressure glow discharge is produced between the center and outer conductor by applying tens of kilovolts across them is capable of generating Terahertz radiation. A typical discharge can be divided into a plasma region with equal electron and ion densities and an electron-rich (positive wire potential) sheath region. The outer surface of the sheath constitutes a virtual electron emitter. Electron orbital motion around the thin wire (typically about 10⁻³ cm) is negative mass unstable and Terahertz radiation can be generated. In comparison with the current popular source that uses table-top laser-driven high-speed photoconductors as transient current sources for radiating antennas, the compact orbitron is far better in output power and efficiency. Particle simulation results will be given to elucidate the physical mechanism of radiation generation. Only eccentric orbital electrons are considered. The instability has strong growth rate and is rich in harmonics and can reach Terahertz region.