Abstract: The method and apparatus of laser-induced incandescence (LII) to analyze characteristics of submicron-sized particles are described. LII is recognized as a good tool for determining the characteristics of small particles in a gas, e.g., volume fraction, particle size, and specific surface area. It uses the fact that the incandescence signal is proportional to the volume of the particles. It also uses the fact that transient cooling is dependent on the specific surface area of the particle, which is related to diameter of the particle. In LII, particles are heated by a pulsed laser light beam to a temperature where incandescence from the particles can be distinguished from ambient light. The temperature of particles and their volume fraction governs the incandescence. The temperature decay rate is proportional to the primary particle size. The invention uses an optical arrangement that ensures a near-uniform laser energy distribution spatial profile.

Abstract: The method and apparatus of laser-induced incandescence (LII) to analyze characteristics of submicron-sized particles are described. LII is recognized as a good tool for determining the characteristics of small particles in a gas, e.g., volume fraction, particle size, and specific surface area. It uses the fact that the incandescence signal is proportional to the volume of the particles. It also uses the fact that transient cooling is dependent on the specific surface area of the particle, which is related to diameter of the particle. In LII, particles are heated by a pulsed laser light beam to a temperature where incandescence from the particles can be distinguished from ambient light. The temperature of particles and their volume fraction governs the incandescence. The temperature decay rate is proportional to the primary particle size. The invention uses an optical arrangement that ensures a near-uniform laser energy distribution spatial profile.

Abstract: The laser-induced incandescence (LII) to analyze characteristics of submicron sized particles is described. LII is recognized as a good tool for determining the characteristics of small particles in a gas, e.g., volume fraction, particle size, and specific surface area. It uses the fact that transient cooling is dependent on the specific surface area of the particle, which is related to diameter of the particle. In LII, particles are heated by a pulsed laser light beam to a temperature where incandescence from the particles can be distinguished from ambient light. The surface temperature of particles and their volume fraction governs the incandescence. The temperature decay is proportional to the primary particle size. The invention uses an optical arrangement that ensures a near-uniform laser energy distribution spatial profile. The invention also uses a low fluence laser beam pulse to avoid evaporation of particles.

Abstract: The present invention relates to a method and apparatus for applying laser induced incandescence (LII) to determine a primary particle size of submicron sized particles. The present invention has found that in addition to volume fraction information, particle size can be determined using LII due to the fact that transient cooling is dependent on the diameter of the particle. The ratio of a prompt and a second time integrated measurement from the same laser pulse has been found to be a function of the particle size. A modeling process involves a solution of the differential equations describing the heat/energy transfer of the particle and surrounding gas, including parameters to describe vaporization, heat transfer to the medium, particle heating etc. The solution gives temperature and diameter values for the particles over time. These values are then converted to radiation values using Planck's equation.

Abstract: The invention relates to a method and an apparatus for the determination of particle volume fractions with laser induced incandescence (LII) using absolute light intensity measurements. This requires a knowledge of the particle temperature either from a numerical model of particulate heating or experimental observation of the particulate temperature. Further, by using a known particle temperature a particle volume fraction is calculated. This avoids the need for a calibration in a source of particulates with a known particle volume fraction or particle concentration. The sensitivity of the detection system is determined by calibrating an extended source of known radiance and then this sensitivity is used to interpret measured LII signals. This results in a calibration independent method and apparatus for measuring particle volume fraction or particle concentrations.

Abstract: A continuous flow chemical laser is described in which chlorine dioxide and nitric oxide are reacted to produce atomic chlorine and hydrogen iodide is then introduced into the flow stream to form hydrogen chloride in an excited state. The hydrogen chloride may itself be lased in a transverse flow laser or carbon dioxide may be introduced which may be lased in a longitudinal or transverse flow laser. The required chlorine dioxide may be generated by passing chlorine and helium or another inert gas through loosely packed sodium chlorite. The nitric oxide may be introduced in two successive steps first to yield chlorine monoxide and in the second stage to yield atomic chlorine. The latter reaction facilitates operation in the supersonic transverse flow mode in which the hydrogen iodide and second injection of nitric oxide are made just as the flow stream is being transformed from a subsonic flow rate to supersonic flow rate.