We report on remote measurements of cross-wind and atmospheric turbulence, using a one-station scheme. As most
remote wind-sensing methods, our method is based on observing the drift of the scintillation pattern across the line of
sight. The scintillations are caused by naturally-occurring turbulence-induced refractive index irregularities in the
atmosphere, which drift at wind speed. Analyzing spatial-temporal cross-correlation function of the signals of two
elements in the array, it is possible to obtain the cross-wind speed. We use the zero-crossings technique for measuring
the cross-wind value, while the cross-wind direction is determined by comparing areas from both sides of the peak of the
cross-correlation function. Here we present results obtained using these techniques in comparison to independent
measurements of the anemometers. The experiments were performed along a uniform path over a flat beach parallel to
the Mediterranean Sea shore. Four white-screen diffusive targets were placed at distances of 300, 600, 850 and 1200m.
Five anemometers were placed along the laser beam path, one near each target and at the measurement station. Each
target was illuminated with a beam from a glass fiber pulsed infrared laser with a repetition rate of several thousand Hz,
and a sub-microsecond pulse-length, and output beam divergence of ~300 μrad. The receiver has an entrance aperture of
80mm, and the incoming radiation is focused onto an array of four 50×250um InGaAs detectors by a lens with
f=500mm. The results show good agreement. From the fluctuations of the signal on the detector array, our system also
measures the turbulence structure parameter Cn
2, using the angle-of arrival technique. The obtained results show
reasonable agreement with independent scintillometer measurements of Cn2, performed with a CW He-Ne laser in a
two-station setup with a detector at a distance of 60m from the laser.
Previous studies in our laboratory have shown that preferential excitation of high lying electronic states of the lead atom is obtained following the detonation of lead azide. However, measurements have shown that the detonation products form an optically opaque medium. In order to overcome this problem, the detonation was conducted via a supersonic nozzle. As a result a transparent medium was formed near the nozzle exit plane. Strong emission from lead atoms was achieved in this medium. Time- and wavelength resolved measurements have shown that the emission intensity of the 3P1° ? 1 D2 transition of the lead atom is significantly enhanced as compared to that from 3P1° to lower lying states. The behavior of the emission is explained in terms of kinetic and spectroscopic (self-trapping) mechanisms. The implication of our results to obtaining laser oscillation following detonation via supersonic nozzles is discussed.
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