Basudev Ghosh

Amplitude modulation of electron plasma waves in a quantum plasma

Using the one dimensional quantum hydrodynamic model for a two-component electron-ion dense quantum plasma the linear and nonlinear properties of electron plasma waves are studied including ion motion. By using the standard method of multiple scales perturbation technique a nonlinear Schrodinger equation containing quantum effects is derived. From this equation it is shown that with immobile ions an electron plasma wave becomes modulationally unstable in two distinct regions of the wavenumber. Numerical calculation shows that the stability domain of the wavevector shrinks with the increase in quantum diffraction effect. It is also found that the growth rate of instability in the high wavenumber region increases with the increase in quantum effect. Ion motion is found to have significant effect in changing the stability/instability domains of the wavenumber in the low k-region.

Modulation Instability of Ion-Acoustic Waves in Plasma with Nonthermal Electrons

Modulational instability of ion-acoustic waves has been theoretically investigated in an unmagnetized collisionless plasma with nonthermal electrons, Boltzmann positrons, and warm positive ions. To describe the nonlinear evolution of the wave amplitude a nonlinear Schrodinger (NLS) equation has been derived by using multiple scale perturbation technique. The nonthermal parameter, positron concentration, and ion temperature are shown to play significant role in the modulational instability of ion-acoustic waves and the formation of envelope solitons.

Dependency of temperature on polarization in CH4/N2 dielectric barrier discharge plasma: A crude assumption

We have investigated the variations of polarization (P) and the temperature (ΔT) at the electrode surfaces during the deposition of C–N layer in CH4/N2 (1:2) dielectric barrier discharge plasma. The reactive deposition process influences the surface temperature, polarization, and the value of the in situ dielectric constant. We have developed a crude model that correlates the surface temperature and surface polarization with thin film properties. We assume that during the thin film deposition process, the atomic mean kinetic energy is equal to the electrostatic energy stored in the electrode surface area. Theoretically estimated temperature is found to agree well with the experimental results. However, the linear model thus developed cannot be used to explain the phenomena in the interfacial polarization stage that requires a nonlinear theory.