Laser/Materials Interactions: CW DF Laser Ablation of Carbon

Abstract

DF chemical laser interactions with isotropic (graphNOL) and anisotropic (pyrolytic graphite, diamond) carbons have been studied in order to analyze the intrinsic ablation performance of these materials and to measure their responses and properties under well-characterized laser irradiation conditions. Several hundred experiments were performed over a broad range of intensities in order to determine burnthrough times, reflectances at DF wavelengths, and front and back surface temperatures during irradiation. Burnthrough data were analyzed to provide Q^⋆ values (energies of ablation per gram of material) as a function of laser intensity and to understand energy and mass balances associated with laser-induced ablation. In addition, a laser probe absorption spectrometer was used to observe quantitative time-resolved spectra of carbon vapor species in laser-ablated plumes. All of the experiments are used to examine the physical and chemical processes that produce the phenomenology and effects characteristic of pure thermochemical ablation of materials by cw infrared lasers.

This work was supported by the Defense Advanced Research Projects Agency under Contract Number MDA903-82-C-0359 and Subcontract Number BDM-S309-OL7200 to the BDM Corporation and by the Robert A. Welch Foundation under Grants C-812 and K-099B.