Stability of the resistive wall mode in cylindrical plasmas confined by surface currents is investigated for the δ-function and step-function equilibrium surface-current profiles. For the former, it is shown that the perturbations oscillate and even decay for all locations of the initial perturbation. The entire system is stable and the plasma flow has little effect. For the step-function surface-current distribution, it is found that the thicker the surface current layer, the more stable is the system even if the largest initial perturbation is located on the rational surface, but the plasma flow also has little effect on the system.

Solid state nuclear track detectors have been used for measuring axially emitted protons from a 2.2-kJ energy plasma focus device. The flux of the protons emerging out from the pinched plasma column of the plasma focus device has been found to saturate the CR-39 detectors. Aluminum filters have been used to avoid the saturation effect. By varying the aluminum filter thickness as well as the etching time of CR-39 detectors, proton tracks have been analyzed. Proton energy above 200 keV to about 1 MeV has been measured by using different thicknesses of aluminum filters. On increasing the etching hours, the most probable track diameter is found to be shifted from lower to higher values. The track number density decreases on increase of the filter thickness, whereas the track diameters increase linearly with respect to the etching time.

A study on the generation of unstable electromagnetic wave through nonlinear wave–particle interactions in an inhomogeneous plasma has been presented. Drift wave turbulence, which is one of the common features of inhomogeneous plasma, is found to be strongly in phase relation with thermal particles. The plasma particles, accelerated by drift wave turbulence field, may transfer their energy to electromagnetic O-mode through a modulated field. This process has been described by Vlasov Maxwell system of equations. From the nonlinear dispersion relation for O-mode the growth rate has been estimated. It has been observed that growth of unstable O-mode may predict magnetospheric electromagnetic radiation phenomena.

The propagation of electrostatic waves is studied in plasma system consisting of pair-ions and stationary additional ions in presence of the Sagdeev potential (pseudopotential) as function of electrostatic potential (pseudoparticle). It is remarked that both compressive and rarefective solitary waves can be propagated in this plasma system. These electrostatic solitary waves, however, cannot be propagated if the density of stationary ions increases from one critical value or decreases from another when the temperature and the Mach number are fixed. Also, when pseudoparticle is affected with a little dissipation of energy, it is trapped in potential well and can oscillate. Oscillations generate shock wave in the media, and in the negative minimal point of the well it is possible to compute numerically the shock wavelength for the allowed values of the plasma parameters.

Beam–plasma interaction is investigated in a model of plasma microwave oscillator: waveguide with spatially separated plasma and beam layers of finite thicknesses. Investigation is carried out in general form without specifying shape of the waveguide in cross section. Approach is based on perturbation theory over wave coupling. Spatial separation implies weak beam–plasma interaction that exhibits many specific features. Developing instability is caused by the growth of the negative energy beam wave. It is shown that upon weak coupling presence, dissipation leads to a new type of dissipative beam instability. Its maximal growth rate is inversely proportional to collision frequency in plasma. The growth rate of this instability is obtained for an arbitrary level of dissipation. Basic parameters of instability show that its properties cannot be neglected upon design of high-power, high-frequency plasma-filled generators/amplifiers based on relativistic e-beams.

The operation of the quantum free-electron lasers (QFELs) with a helical wiggler and in the presence of ion-channel guiding is considered. The quantum Hamiltonian of single particle has been derived in the Bambini-Renieri (BR) frame. Time dependent wave function and three constants of motion are obtained. The Raman-Nath equation (RNE) and its approximation solution have been calculated, and then the resulted solution has been employed to obtain the quantum gain, photon statistics parameter and squeezing parameter. A quantum approach has been used to get quantum statistical properties of the FEL and the photon gain formula for the small signal gain limit. It is found that the ion-channel guiding decreases the squeezing. Also, the conditions for positive (bunching) and negative (antibunching) gain have been studied numerically.

Nonlinear ion cyclotron and ion-acoustic waves have been studied in an electron–positron–ion plasma. Using Boltzmann distributions for the electrons and positrons and fluid equations for the ions, a set of nonlinear equations in the rest frame of the propagating wave is derived and numerically solved for the electric field. A scan of parameter space reveals a range of solutions for the parallel electric field, from sinusoidal to sawtooth to highly spiky waveforms. The results are compared with satellite observations.

The terahertz (THz) frequency radiation produced as a result of nonlinear interaction of high intense laser beam with low-density ripple in collisionless magnetoplasma has been studied under the paraxial ray approximation. The relativistic change of electron mass leads to self-focusing of laser beam when the initial power of laser beam is greater than its critical power. The self-focused laser beam couples with the pre-existing density ripple to produce a nonlinear current driving the THz radiation at different frequency. The applied magnetic field enhances the nonlinear coupling efficiency. Appropriate expressions for the beam width parameter of the laser beam and the electric vector of the THz wave have been evaluated. Theory and numerical simulations show that this THz source is capable of providing power of Giga watt level.

The ion wake-field effects on the elastic electron–dust collisions are investigated in complex dusty plasmas. The eikonal method is employed to investigate the behaviors of the scattering phase shift and scattering cross section due to the variation of the strength of the wake-field. It is shown that the eikonal phase shift decreases with an increase of the Mach number and increases with an increase of the impact parameter. It is also shown that the eikonal phase shift decreases with increasing Debye length. The eikonal cross section for the elastic electron–dust collision is found to be increased due to the influence of the wake-field. In addition, it is found that the wake-field effect on the eikonal cross section is almost independent of the Debye length.

A general theory for the existence of solitary structure at M = Mc has been discussed, where Mc is the lower bound of the Mach number M, i.e., solitary structures start to exist for M > Mc. Three important results have been proved to confirm the existence of solitary structure at M = Mc. If V(φ)(≡ V(M,φ)) denotes the Sagdeev potential with φ being the perturbed field or perturbed dependent variable associated with a specific problem, V(M, φ) is well defined as a real number for all M ∈ ℳ and φ ∈ Φ0, and V(M, 0) = V′(M, 0) = V″(Mc, 0) = 0, V‴(Mc, 0) < 0 (V‴(Mc, 0) > 0), ∂ V/∂ M < 0 for all M (∈ ℳ) > 0 and φ (∈ Φ0) > 0 (φ (∈ Φ0) < 0), where ‘′ ≡ ∂/∂φ’, the main analytical results for the existence of solitary wave or double layer solution of the energy integral at M = Mc are as follows. Result 1: If there exists at least one value M0 of M such that the system supports positive (negative) potential solitary waves for all Mc < M < M0, then there exists either a positive (negative) potential solitary wave or a positive (negative) potential double layer at M = Mc. Result 2: If the system supports only negative (positive) potential solitary waves for M > Mc, then there does not exist positive (negative) potential solitary wave at M = Mc. Result 3: It is not possible to have coexistence of both positive and negative potential solitary structures at M = Mc. Apart from the conditions of Result 1, the double layer solution at M = Mc is possible only when there exists a double layer solution in any right neighborhood of Mc. Finally, these analytical results have been applied to a specific problem on dust acoustic (DA) waves in non-thermal plasma in search of new results.

The role of static inductance on ion beam emission in plasma focus devices, based on anomalous resistivity, is reported. The effect of gas pressure variation on the process of energy transfer into plasma is investigated and discussed by using Lee's model. The dependence of ion beam production on filling gas pressure along with change in static inductance is studied. The results show that increase of static inductance in a specific range of operating pressure can enhance the efficiency of dense plasma focus device.