Title: Ion acoustic wave experiments in a high school plasma physics laboratory

We study the influence of ion beam and charged dust impurity on the propagation of dust ion-acoustic solitary wave in an unmagnetized plasma consisting of Boltzmann distributed electrons, positive ions, positive ion beam, and negatively charged immobile dusts in a double plasma device. On interacting with an ion beam, the solitary wave is bifurcated into a compressive fast and a rarefactive slow beam mode, and appears along with the primary wave. However, there exists a critical velocity of the beam beyond which the amplitude of the fast solitary wave starts diminishing and rarefactive slow beam mode propagates with growing amplitude.more » Whereas, the presence of charged dust impurity in the plasma reduces this critical beam velocity and a substantial modification in the phase velocity of the slow beam mode is observed with increasing dust density. Furthermore, the nonlinear wave velocity (Mach number) as well as the width of the compressive solitons are measured for different beam velocity and dust density, and are compared with those obtained from the K-dV equation. The experimental results are found in a well agreement with the theoretical predictions.« less

Dust acoustic waves (DAWs) are spontaneously excited in dusty plasmas produced in dc and rf discharge plasmas over a wide range of plasma and dust conditions. A common feature of these plasmas is the presence of an ion drift relative to the dust, which is driven by an electric field, E{sub o} in the discharge. Using a three fluid model of the DAWs, including the zero order electric field and collisions of all species with the background neutral gas (pressure P{sub o}), DAW stability curves were obtained in the E{sub o}-P{sub o} plane, for various dust and wave parameters. Themore » (E{sub o},P{sub o}) data points from several experiments in which DAWs have been observed are also shown in comparison with the theoretical stability boundaries. This analysis supports the conclusion that the DAWs are excited by an ion-dust streaming instability.« less

Experiments on the excitation of rarefactive ion acoustic solitons using a fine mesh grid in a negative ion plasma are described. The excitation is novel in that a modulated high-frequency sinusoidal wave voltage signal is applied to the grid. An interpretation of the velocity modulation and bunching of free-streaming ions that pass through the grid to which the signal is applied is given. {copyright} {ital 1997 American Institute of Physics.}

A study on the amplification of ion acoustic wave in an inhomogeneous plasma has been made on the basis of a nonlinear wave-particle interaction process called plasma maser effect. The drift wave instability, which is a universal phenomenon of an inhomogeneous confined plasma system, is found to be strongly in phase relation with thermal particles and may transfer its wave energy nonlinearly through a modulated field to ion acoustic wave. Considering a Maxwellian distribution function model for inhomogeneous plasmas under the standard local approximation, we have estimated the growth rate for ion acoustic wave, which is obtained by using themore » nonlinear dispersion relation. It has been found that amplification of ion acoustic wave is possible at the expense of drift wave turbulent energy. This result may be particularly important for stability of various drift modes in magnetically confined plasma as well as for transport of momentum and energy in such inhomogeneous systems.« less