This paper describes a novel method for generating electrical transients. A small charged metal sphere coming into contact with the centre conductor of a coaxial transmission line is used to produce pulses with a risetime below 60 ps and amplitude of 500 V or more. The phenomenon is investigated experimentally to determine whether the gaseous medium in which the discharge takes place affects the pulse shape. Measurements in sulphur hexafluoride, argon and rough vacuum indicate that the breakdown mechanism is not a gas discharge, but the gas does affect the amplitude range, shape and variability of the current pulses. Results are interpreted in the light of previous investigations into arcs between electrodes separated by gaps of less than 100 µm, in which field emission of electrons from the cathode was recognized as the principal source of charge carriers. Potential applications for the contact discharge pulse generator are proposed and aspects of its operation that could be refined to reduce pulse shape variability are identified.

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A review of our theoretical studies and computer simulations with PIC codes of the interaction of ultrashort, high-intensity laser pulses with plasmas is presented. The mutual attraction of the currents inside the self-focused channels, arising from the pulse filamentation, makes them interact magnetically and coalesce into a single channel with strongly enhanced electromagnetic energy density. Pulses of finite length and width propagate in the shape of a 'bullet' and produce a wake consisting of magnetic dipoles correlated with an electron vortex row behind the pulse. The vortices evolve into an antisymmetric configuration which is shown to be stable when the distance between its vortices is greater than the electron skin depth.

Intense microwave beams are proposed to be used for cleaning atmospheric chlorofluorocarbon contamination which is destroying the ozone layer of the Earth. It is shown that it may be possible to excite microwave discharges freely localized in the troposphere. The relation between the quantity of the destroyed chlorofluorocarbons and discharge parameters is established, the energy required for destruction is evaluated and possible unfavourable consequences of the accompanying effects (such as nitrogen oxides production) are analysed. The mechanism of dissociative electron attachment which is manifested in a cold decaying plasma of a pulsed microwave discharge is considered to be a principle mechanism causing dissociation of chlorofluorocarbons (CF2Cl2, CFCl3, etc.). The results are presented of a model laboratory experiment in which, under conditions close to those of free space, a study is made of the efficiency of chlorofluorocarbon dissociation under the action of the discharge produced in air by intense microwave radiation. The experimental results do not contradict the conclusions of the analysis of elementary processes causing the destruction of the chlorofluorocarbon component.