Authors: S I Kudryashov A A Tikhov V D Zvorykin
Publish Date: 2010/08/05
Volume: 102, Issue: 2, Pages: 493-499
Abstract
Optical reflectivity removal rate and ablative recoil pressure magnitudes were measured as a function of laser fluence during highpower UV nanosecond laser ablation of graphite At low fluences only melting and weak surface vaporization of molten carbon were observed At moderate fluences there is a very narrow fluence interval where the reflected fluence starts to saturate while the removal rate and ablative recoil pressure rise drastically in a correlated manner indicating the onset of a nearcritical surface phase explosion Then at higher fluences the reflected fluence removal rate and recoil pressure saturate with an appearance of a luminous plume altogether indicating negligible specular reflectance and absorbance on the target surface due to its complete screening by the highlyabsorbing laser plume The overall strong correlation between the removal rate and recoil pressure magnitudes may indicate rather quasicontinuous removal of the nearcritical superheated molten carbon layer by a propagating unloading wave in the absence of a crucial subsurface temperature maximum in the layer
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