Second Harmonic emission by a 20keV Electron Beam in a Laboratory Plasma*

Understanding the interactions between beams of electrons and magnetized plasmas is a fundamental and practical problem. For example, the Sun regularly ejects highly energetic particles due to unstable magnetic fields of the solar atmosphere. Electromagnetic radiation at the second harmonic of the plasma frequency is a signature of the type III radio bursts. These emissions are of great interest as they serve as probes to study the accelerated electrons and the plasma through which they travel. Presented here is an analysis of the plasma parameters for which second-harmonic waves are emitted by a 20keV electron beam in a magnetized plasma in the Large Plasma Device (LAPD) at UCLA. Emission of the second harmonic is observed by both in-situ probes and by an antenna outside of the plasma. Preliminary results indicated a close-to-simultaneous emission of the second harmonic once an amplitude threshold is met by the fundamental mode.