D ipartimen to d i EnergeticaCorso D u m degli Abruzzi, 24 20229 Torino -ITALY In a recent paper' a new technique has been proposed to study the classical problem of Landau damping in a collisionless unmagnetized plasma. This technique, alternative to the classical one, is based on a time integral equation for the amplitude of the plasma density perturbation. The method is particularly useful to calculate the full evolution of a given initial perturbation. In this work the procedure is extended to magnetized Vlasov plasmas. For an electron plasma, the density perturbation ni(r,t), due to an initial phase spacecan be written as n,(t)exp(ik 9 r) , and % ( t ) obeys an integral equation of the type:where the functions at) and at) depend on the plasma parameters and the external magnetic field; moreover, at)is a functional of the initial perturbation. The above equation can be solved analytically in simple cases or numerically in more general cases. Results for situations of special physical interest will be presented and discussed.References 1. V. Colombo, G. Coppa, P. Ravetto, New Approach to theThe possibility of the significance of inelastic processes in plasma resistivity when the ions are not fully stripped was suggested by Morel. In this work we study the role of inelastic electron-ion interactions (collisional excitation and de-excitation, collisional ionization and three-body recombination) in plasma resistivity, particularly in dense plasma. In Spitzer's theory of low density plasma resistivity only elastic electron-ion collisions are considered. In dense, degenerate plasmas like liquid metals Ziman's theory, which assumes elastic electron-ion collisions, is applied. There the assumption of elastic collisions is justified by phase space limitations on the degenerate electron gas. In dense, strongly coupled, high temperature plasmas this limitation does not exist and the role of inelastic processes should be considered. In these plasmas the ratio of the excitation and ionization energy to the thermal free electron energy is such that the role of inelastic electron-ion collisions becomes relatively important.The contribution of inelastic processes to the resistivity is calculated, employing the average ion model to evaluate the ionic levels and transition probabilities. The significance of this contribution is demonstrated in the case of plasma produced by ultra-short pulse (sub-picosecond) lasers.1. R.M. More, UCRL Report 84991 (1981) 2P12aThe electrical conductivity of copper has been studied in the range of densities from 0.5-5 gmlcm3 and in the temperature range from 8,000 to 25,000K. Copper wires in glass capillary tubes were vaporized by means of a short pulse of current derived from a capacitor bank. The glass confines the copper plasma in a fairly well-defined cylindrical volume for the short interval of time required for the shock wave induced by the high pressure of the plasma to propagate to the outer wall of the capillary and reflect back to the inner wall. The conductivity is measured in this ...

A technique recently proposed to study the classical problem of the evolution of small perturbations in a collisionless unmagnetized plasma is extended to a magnetized plasma. A time-convolutive integral equation for the plasma density is obtained from the Vlasov equation for a homogeneous plasma in a uniform, stationary magnetic field. The equation can be solved by means of simple numerical algorithms and, in some cases, analytical solutions can be obtained. The procedure proves to be analytically simpler than the classical one and is more convenient from a numerical point of view. Techniques of solution are presented and analytical and numerical results for electrostatic perturbations are discussed.PACS 52.20 -Elementary processes in plasma. PACS 52.35 -Waves, oscillations, and instabilities in plasma.