title: Optical particle sizing in backscatter.
abstract: Several possibilities for the use of elastic light scattering in the backscatter range (scattering angle theta(s) > 140 deg) for determination of size, velocity, and refractive index of spherical particles are investigated. First the phase Doppler technique is considered. Numerical simulations of light scattering with the Lorenz-Mie theory are used to show that the phase Doppler technique is unsuitable for such backscatter configurations, except for special measurement conditions. The time-shift (or pulse-displacement) technique is then considered by use of the Fourier-Lorenz-Mie theory. Simulations show that up to four fractional signals can be obtained by use of the technique in backscatter, corresponding to the scattering order or modes: surface wave (long path), reflection, second-order refraction (inner path), and a mixture of second-order refraction (outer path) and surface wave (short path). Signal characteristics as a function of particle size, refractive index, and particle ellipticity are studied. Suggestions for a practical measurement instrument are put forward.
authors.affiliation: Darmstadt University of Technology, Germany. ndamasch@sla.tu-darmstadt.de
authors.forename: Nils
authors.initials: N
authors.lastname: Damaschke
authors.forename: Holger
authors.initials: H
authors.lastname: Nobach
authors.forename: Nikolai
authors.initials: N
authors.lastname: Semidetnov
authors.forename: Cameron
authors.initials: C
authors.lastname: Tropea