This paper reports the principle of evaluating the size spectra of very small particles using the laser-beam scanning method proposed previously by the present authors 1), and some preliminary experimental results to verify the principle. The principle is to derive the particle-size spectra from the amplitude histogram of time-dependent random pulse signals obtained by detecting the light scattering from the particles passing through the laser beam under illumination. Preliminary experiments were conducted for polystyrene particles of 0.5-1.09 μm sizes dispersing in water and produced satisfactory results. The present method has a disting-uishing feature of measuring the spatial distribution of very small particles without disturbing the circumstance where the particles exist. It has also an ability of measuring the particles in closed vessels.
In order to eliminate the particles contaminating a clean room and to manipulate the pellet containing heavy hydrogen in the laser nuclear fusion technique, it is undertaken to develop a new technique for trapping and controlling small particles. This new technique is very effective in catching and manipulating the particles suspended in air by using the forces of radiation pressure produced by laser light. The behavior of particles trapped or pushed awav near the forcal point of laser beam has been clarified experimentally.