Study of chaotic phenomena in ion beam plasma

Abstract

This thesis presents the experimental investigations of some nonlinear phenomena associated with ion beam plasma in double plasma device, where multi-dipole magnets are used for surface plasma confinement. Low frequency instability is excited in the system when negative voltage is applied to the grid, for both Ar plasma and multicomponent plasma. This instability is dependent on different plasma parameters. When this internal sheath oscillation are coupled to the external oscillations under the threshold values of Vg and Vs period pulling and synchronization are observed which lead to chaotic behaviour. The complete sets of experiments are performed in a double plasma device. The experimental arrangement and its diagnostics are described in chapter II of the thesis. The Langmuir probe, emissive probe and energy analyser are the three diagnostics used in the whole work of this thesis. The emissive probe was constructed and for this inflection point technique is used in the experiment to get the plasma space potential. The energy analyser is used to measure the ion temperature and the ion distribution function. Langmuir probe is used to measure the electron temperature and the density and it receives the plasma signal. which are fed to different instruments for analysis. Ar plasma is produced by a de discharge between the filaments and anodes of the source and the target chamber. The typical plasma parameters are n = 108 - 109 cm-3 and Te = 2-3 eV. Where n and Te are plasma density and electron temperature respectively. The excitation mechanism of low frequency instability at different density ratio of source and target chamber is studied for Ar plasma. The instability observed under low density ratio condition of source and target chamber is of special interest, as it leads to the observation of chaotic phenomena by nonlinear coupling with external signal (discussed in the Chapter-III). In such condition the low frequency instability is excited under a frequency resonant condition, between the oscillating...