Observation of bifurcation phenomena of unstable waves in an electron beam plasma system

By investigating the behavior of unstable wave motion in plasma, the motion of the system can be understood. In this research, by studying the physical mechanism of the bifurcation phenomena in the wave motion system in electron beam-plasma system, and analyzing the state of the system in which bifurcation phenomena occur from the viewpoint of chaos, the possibility that these phenomena are the chaos of the wave motion system which is the nonlinear behavior of plasma was found. The experimental method using the double plasma device of a stainless steel vacuum container is explained. The typical plasma parameters in the experimental region were 108/cm3 of electron density and 0.8 eV of electron temperature. The wave motion in plasma was detected with a flat plate type Langmuir probe, and measured by interference method and a spectrum analyzer. Electron beam energy and density were measured with a Faraday cup. The results are reported. The unstable waves were identified as the beam mode excited by the instability of electron beam-plasma system. In electron beam-plasma system, the beam mode and two or three subharmonics were observed. (K.I.)