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A New Model of Crater Formation by Arc Spots
Author(s) -
Hantzsche E.
Publication year - 1977
Publication title -
beiträge aus der plasmaphysik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.531
H-Index - 47
eISSN - 1521-3986
pISSN - 0005-8025
DOI - 10.1002/ctpp.19770170107
Subject(s) - impact crater , evaporation , mechanics , shot (pellet) , arc (geometry) , recoil , layer (electronics) , hot spot (computer programming) , chemistry , optics , materials science , atomic physics , thermodynamics , physics , geometry , composite material , metallurgy , mathematics , astronomy , computer science , operating system
The forces acting on the cathode arc spot surface and removing the molten layer from the crater bottom are composed mainly of the ion pressure, the neutral gas pressure and the evaporation recoil whilst electrostatic forces diminish the effective pressure that is in the order of some 10 9 dyn/cm 2 . The motion of the liquid layer caused by these forces is treated with the hydrodynamic equations. A simple solution exists in the special case of constant layer depth, that is achieved a few nanoseconds after spot formation. From this model the layer depths (some 0.1 μm) and the ejection velocities at the crater rims (few 10 4 cm/s) are calculated. The real spot velocity agrees with the velocity of the melting front below the spot surface, but because of the stochastic character of the spot motion the apparent velocity decreases with growing observation time intervals Δt according to Δ t −1/2 .