Initiation of Ecton Processes by Interaction of a Plasma with a Microprotrusion on a Metal Surface

摘要

Evolution of rapid (similar to 1() ns) Ohmic overheating of a microprotrusion on a surface in contact with a plasma by emission current is studied taking into account the energy carried by plasma ions and electrons, as well as Ohmic heating, emissive source of energy release (Nottingham effect), and heat removal due to heat conduction. Plasma parameters were considered in the range of n = 10(14)-10(20)= cm(-3) and T-c = 0.1 eV-10 keV The threshold value of energy transferred to the surface from the plasma is found to he 200 MW/cm(2); above this value. heating becomes explosive (namely, an increase in the temperature growth rate (partial derivative T-2/partial derivative t(2)) > 0) and in passing current (partial derivative J/partial derivative t > 0) is observed in the final stage at T similar to 10(4) K and j similar to 10(8) A/cm(2)). In spite of the fact that Ohmic heating does not play any significant role for plasmas with a density lower than 10(18) cm(-3) because the current is limited by the space charge of electrons, rapid overheating of top of microprotrusion is observed much sooner (over a time period of similar to 1 ns) when the threshold is exceeded. In this case. intense ionization of vapor of the wall material leads to an increase in the plasma density at the surface. and file heating becomes of the Ohmic explosion type. Such conditions for the formation of a microexplosion on the surface and of an ecton accompanying g it can be created during the interaction of a plasma with the cathode, anode. or an insulated wall and may lead to the formation of cathode and anode spots, as well as unipolar arcs.