Basic principle of materials choice for a contact pair in electrodynamic accelerator

The current transfer between an armature and electrodes in a rail accelerator is considered in the paper using the analytical model based on the solution of the magnetic field diffusion and energy equations written in the integral form, with a one-parametrical approximation of the sought functions. The system of algebraic equations is received for definition a critical speed of a projectile, which corresponds to beginning of the contact surface of an armature evaporation. The influence of the main physical factor as the conductivity of contacting materials on a critical speed has been studied. Computation of a critical speed has been spent in a wide range of problem criteria. The comparison of results with known experimental data has shown, that the offered method has acceptable accuracy. It was possible to formulate on this basis the main principle for the selection of contact pair materials: to reduce the influence of high-speed skin-effect, the coefficients of conductivity for contacting materials must differ strongly, irrespective of what materials are used on the armature and the electrode. To simplify the technical realization of such a principle, it may be recommended to use an armature of graphite when the electrodes are made of a good conducting material.