Extinction performance of superfine graphite smoke to 10.6 μm laser emission

Abstract

The mass extinction coefficient of superfine graphite smoke to 10.6μm laser emission produced by CO 2 gas laser and the granularity distribution of the smoke particles at different time have been tested in a middle-size smoke chamber. The absorption, scattering and extinction efficiency factors of graphite smoke with different diameters to 10.6μm laser emission have been calculated according to Mie scattering theory and the curves of extinction factors varied with wavelength or particle diameter have been drawn too. Experimental results have shown that the superfine graphite smoke has a good extinction performance to 10.6μm laser emission and that the average mass extinction coefficient of the smoke to 10.6μm laser emission is 1.214m 2 /g. By the analysis, the optimal scattering diameter of graphite smoke to 10.6μm laser emission is 9μm while the optimal absorption diameter is 2.0μm and the optimal extinction diameter is 3.0μm. If the scattering diameter of the graphite smoke is smaller than the wavelength of incident laser emission, the extinction effect is dependent on the absorption. The scattering function increases with the enlargement of smoke particle diameter. In addition, the superfine graphite is difficult to effectively diffuse and form a thick concentration in air. The average diameter of graphite smoke particles gradually decreases with the time increment after forming the smoke.