Determination of optical distortions caused by thermal turbulence

Describes experimental apparatus which enables the optical effects of thermal turbulence to be examined quantitatively. Preliminary results are presented for the RMS positional deviation in the detector plane of a laser beam propagating through liquid nitrogen in a known state of thermal turbulence, and are shown to be in general agreement with the predictions of an empirical theory. Continuing experiments examining the local structure of the turbulent medium are outlined.