University of Washington

Battelle Development Corporation

Institute for Tropospheric Research, a German Non-profit Organization

Robert J Charlson

Norman C Ahlquist

Jost Heintzenberg

Alan P Waggoner

Sabine Wurzler

Frank Stratmann

Theodore L Anderson

Manfred Wendisch

Sarah J Masonis

The present invention relates to a method for investigating the behavior of particles or droplets in a gas-vapor mixture inside a flow device, which is useful for studying cloud dynamical and microphysical processes. The invention allows adjustment and/or control of the thermodynamic system parameters based on the observed behavior of an internal standard with known properties, thus achieving a well-defined vapor concentration and saturation field inside the flow device. By injecting particles or droplets to be investigated into this well defined flow device, and measuring the size of the particles or droplets, the activation and growth or shrinking behavior of the particles or droplets may be determined using a mathematical model of the fluid, thermodynamic, and chemical conditions of the flow device.

Method and apparatus for investigating temporal development of particles or droplets in gas-vapor mixture

An integrating nephelometer is modified to measure 180&deg; backscattering from an aerosol. A laser is mounted outside a housing of the nephelometer and produces a coherent light beam that is directed into a sample volume of the nephelometer, substantially along an optical sensing axis (<4&deg; off the optical axis). Light from the laser beam that is reflected by an aerosol travels back along the optical sensing axis toward a photomultiplier tube (PMT) light detector, which thus produces a signal indicative of the backscattering from the aerosol. A portion of the laser beam is conveyed into the housing of the nephelometer through an optical fiber for use as a reference beam. A motor-driven chopper disk disposed across the optical axis is divided into an open sector, a calibration sector (with a very low transmission), and a flat black light absorbing sector. During a calibration mode to monitor the stability of the laser, the calibration sector diffuses the reference beam so that only a portion of it is measured by the PMT detector. A background noise of the PMT detector is measured when light is blocked by the flat black light absorbing sector. The latter two measurements are used to correct the backscattering measurement for the aerosol. A lidar ratio of the aerosol is determined as a function of the backscattering measurement, a measurement of light extinction due to total light scattering by the aerosol, and a measurement of its light absorption.

Measurement of the lidar ratio for atmospheric aerosols using a 180 degree-backscatter nephelometer

An improved integrating nephelometer having superior sensitivity and long-term stability to previous designs includes a container defining a measurement chamber. A continuously energized light source, such as a tungsten filament incandescent bulb, illuminates the measurement chamber through an opal glass diffuser. The intensity of the light source is regulated in one embodiment by a simple optical-electric feedback system, and in another embodiment by a voltage regulated supply. A cone of observation of the chamber is defined by a plurality of spaced, apertured plates located in the chamber, at right angles to the light source. A measuring photomultiplier tube views the cone of observation and provides an output signal including components resulting from detected photoelectrons, noise, and thermally emitted 'dark current' electrons. A photon-detecting apparatus removes the noise component and provides an output pulse for each photoelectron and 'dark current' electron. The output pulses are counted, and converted into an analog signal representing a desired extinction coefficient b.sub.scat by any one of a number of apparatus, including an averaging circuit, or a second counter and a D-to-A converter. Dark current compensation, if necessary, is effected by either subtracting a fixed value, or a value dependent on some environmental variable, from the measured value of b.sub.scat, or by utilizing a reversible counter apparatus and light source apparatus. Variations of this nephelometer are also described, including an instrument for automatically compensating for the component of b.sub.scat due to Rayleigh scatter by gases, an instrument which is sensitive to a plurality of wavelengths, and a self-calibrating instrument which is adapted for the measurement of total light scatter and back scatter at a plurality of wavelengths.

Photon-counting integrating nephelometer

Growing community of inventors

Seattle, WA, United States of America

Robert J Charlson