METHOD FOR MEASURING VELOCITY OF FLOW USING LASER INDUCED FLUORESCENT METHOD

摘要

PURPOSE:To measure the velocity of flow in a vacuum region by resonating a wavelength variable narrow-band laser beam at the energy level of the atoms and molecules in a flow field and detecting the Doppler shift of absorption spectra from a change in the intensity of emitted light. CONSTITUTION:A slight amt. of I2 molecules are incorporated into the gaseous N2 blown out of a nozzle 101 and the narrow-band wavelength laser 102 is made incident on an observation point. The light emitted from the I2 is condensed by a lens 103 and only the fluorescence is detected by a detector 105 in a filter 104 and the fluorescent intensity thereof is monitored to obtain the intensity corresponding to absorption spectra. On the other hand, a part of the laser beam is separated by a beam splitter 106 and is made incident on a cell 107 sealed with the I2 molecules. The fluorescence from the I2 is detected in the detector 105 by using the lens 103 and the filter 104. This spectrum and the spectrum from the observation point in the flow are compared and the deviation in the absorption peaks is detected. The velocity of flow is determined from the angle formed by the flow direction and the laser beam.