Development of carbonaceous particle size analyzer using laser-induced incandescence technology

This paper presents a new sensing system for carbonaceous nanoparticle measurement using a laser-induced incandescence (LII) technique. Our research group has improved the laser-induced breakdown spectroscopy (LIBS) system used for quantitative analysis. Although the basic principles of LIBS quantitative measurements are well understood, several uncertainties remain concerning complete descriptions-especially for particle size measurement. The elemental composition and density of the particles are determined using LIBS, and particle size measurements are accomplished with the help of LII. In the case of the present system, with temporally resolved LII, measurement of soot primary particle sizes is feasible in a combustion process derived from the ratio of emission signals after a laser pulse because the cooling behaviour is characteristic of the particle size. The LII temporal analysis was performed by a streak camera, which was also used for LIBS analysis. The LII technique allows in situ measurement of the average primary particle size of nanoscale soot particles.