Parametric Excitation of Electron Plasma Oscillations

Abstract

Nonlinear phenomena in parametric resonances of electron plasma oscillations predicted and partially found out in previous papers (J. Phys. Soc. Japan 30 (1971) 309 and Rep. Fac. Sci. Shizuoka Univ. 5 (1970) 9) are investigated. A frequency of externally applied electric field f_ex swept automatically near twice the plasma frequency 2f_pe and an amplitude of oscillations excited with resonance frequency f_r\simeqf_pe are displayed on the X- and Y-axes of a monitor scope, respectively. Threshold values of pumping voltage V₀ for the parametric excitation of the oscillation and nonlinear shift of the resonance frequency due to the input voltage V_in were measured, and the asymmetrical hysteresis curve of the excited oscillation amplitude for increasing and decreasing f_ex was easily observed by convenient method in which the detection frequency f_r was swept by a servomotor. Parameters including a collision frequency and an electron density gradient are also determined from experimental data.