Experimental Studies of Explosive Instability in an Ion Beam-Plasma System

抄録

When the ion beam-plasma system is stimulated by a pump field with frequency f₀ near the ion Langmuir frequency f_pi, the ion sound wave (f_s) is enhanced and, at the same time, a new wave (f_b) corresponding to the slow wave of the beam appears, and among their frequencies, the resonant condition, f_b=f_pi+f_s, is satisfied. The resonant condition for the wave numbers, k_b=k_pi+k_s, is ascertained by a test wave method. The test wave grows temporally at the frequencies coinciding with the frequencies of f_b and f_pi and, at the same time, the wave with the frequency of f_b−f_pi=f_s grows also temporally. Their growing is affected by an ion beam energy, an initial intensity of the pump field and its frequency. These phenomena will be discussed with a nonlinear theory of the explosive instability for the coherent three-wave interaction.