Dispersion Effects on Millimeter Wavelength Attenuation Efficiencies for a Variety of Fibers

Abstract : Results of several field experiments have been used to determine extinction efficiencies primarily of graphitic fibers and to relate these efficiencies to length distributions. Of the three dispersion techniques employed, two were driven by constant air pressure and the third dispersed fibers by explosive force. Generally, the latter significantly altered the distribution. When a significant proportion of the fibers was, fragmented to lengths shorter than a half wavelength, the efficiency decreased notably. Extinction efficiencies for almost all the explosively dispersed clouds were in this category. For frequencies of 35 GHz and lower, efficiencies for explosive dissemination typically were reduced by factors of 2 to 4. Efficiencies at 94 GHz were much less affected because the ratio of particle length to wavelength remained, on the average, higher than one-half. In contrast, length distributions for fibers cut from spools and immediately disseminated by constant air flow almost always sharply peaked near the cut length and had efficiencies near to that calculated for the cut length. Calculations and measurements are in agreement on this issue. Extinction, Efficiency, Fibrous aerosols