Pinch Oscillations in Electron-Hole Plasmas. II. Experiment

Most of the measurements concern the spontaneous pinch oscillations that occur when the current exceeds a threshold value. Some properties of oscillations driven at subthreshold conditions are described also. The oscillations are characterized by several parameters: threshold current, amplitude, frequency, and wavelength. The dependency of the spontaneous oscillation properties on current, temperature, and time are reported. An applied longitudinal magnetic field has remarkable effects on the oscillations. In particular, the oscillations are stabilized at a critical magnetic field which depends on the current. The variations of the oscillation amplitude and the mode type with applied magnetic field are also shown. At subthreshold conditions, a driven pinch ($m=0$) oscillation can be readily launched in a pinched plasma; its spatial growth is reported. This type of oscillation is attenuated strongly by the application of a longitudinal magnetic field exceeding 50 G. In a prepinched plasma (low current levels), the driven helical mode ($m=1$) oscillation can be made to grow, if the appropriate magnetic field is applied. The results are divided into two groups for discussion, those results explained by the theory presented in the preceding paper and those not formally explained.