Abstract: An apparatus for determining the rate of flow of particles in a vacuum deposition device using the relationship that the rate of flow of the particles is equal to the density of the particle current times the mean velocity of the particles comprises establishing a flow or current of particles in the device and the directing of a laser beam through the current of particles in order to measure the attenuation of the beam after it has passed through the particles and thus to determine the vapor density within the current. The absorption wavelength shift of the laser beam provides an indication of the velocity component of the current because the shift is produced by a Doppler effect by the velocity component of the particle current in the direction of flow from the source of the particles to the substrate to be coated.

Abstract: A method of determining the rate of flow of particles in a vacuum deposition device, using the relationship that the rate of flow of the particles is equal to the density of the particle current times the mean velocity of the particles, comprises establishing a flow or current of particles in the device and directing a laser beam through the current of particles in order to measure the atteunation of the beam after it has passed through the particles and thus to determine the vapor density within the current. The absorption wavelength shift of the laser beam provides an indication of the velocity component of the current because the shift is produced by a Doppler effect by the velocity component of the particle current in the direction of flow from the source of the particles to the substrate to be coated.