Research On Determining The Radiation Parameters Of Particle Materials Based On Mie Theory And K-K Dispersion Relation

The complex refractive index of particle materials is a critical parameter in the research on the radiation character of particle. Also it is difficult in this research area of radiation parameters. From the recent researches, the method which is used in study on the complex refractive index of particle material is totally different from the one used on bulk and film material. The method which is widely used in this area is to get the transmittance spectrum of particle material by experiment and choose a good inversion model to fit this spectrum. If the calculation spectrum curve and the experimental one are perfectly fitted, it is the complex refractive index of the particle material.This paper used the electrostatic-levitation theory to make the particles suspend in the air, then the transmittance spectrum could be easily measured. Both of the theoretical and experimental analyses are showed that the extra DC electrostatic field is no effect on the radiation measurement. The thickness and concentration of the particle media could be changed by choosing different aperture of two top plates and the number of powder ejection respectively. The experimental result showed that the thickness of the particle media could strongly increase the extinction ratio. However, due to the limitation of charges the particle carried, the number of powder ejection is no obvious influence on the extinction ratio.In theory, this paper used an inversion method based on Mie theory and Kramers-Kronig dispersion relation. The transmittance spectrum obtained in experiment and the log-normal size distribution function of particle material obtained by Marlvern particle size measurement instrument and curve-fit software are two input parameters, by changing the independent variations--- L p, n (∞) and F---to fit the experimental curve in the program, the complex refractive index spectra could be obtain. The result showed that (1) When the searching area is constrained, the inversion program would not appear several solutions. (2) The geometric mean radius--- rg and geometric mean standard deviation---σg changed in a certain area, these two parameters have no effects on the transmittance spectrum, but both of the real part and imaginary part of complex refractive index spectra curves rise with the increasing of these two parameters. Three similar complex refractive index spectra were obtained by this inversion program from three different transmittance spectra measured in different experimental methods with the same particle sample. The result showed that this inversion method and program are reasonable.