Flow speed measurement using two-point collective light scattering

Abstract

Measurements of turhulence in plasmas and fluids using the technique of collective light scattering have always been plagued by very poor spatial resolution.

In 1994, a novel two-point collective light scattering system for the measurement of transport in a fusion plasma was proposed. This diagnostic method was designed for a great improvement of tbe spatial resolution, without sacrifcing accuracy in the velocity measurement. The system was installed at the W7-AS stellarator in Garching, Germany, in 1996, and has been operating since. This master thesis is an investigation of the possible application of this new method to the measurement of flow speeds in normal fluids, in particular air, although the results presented in this work have significance for the plasma measurements as well. The main goal of the project was the experimental verification of previous theoretical predictions.

However, the theoretical considerations presented in the thesis show that the method can only be hoped to work for flows that are almost laminar and shearless, which makes it of very small practical interest. Furthermore, this result also implies that the diagnostic at W7-AS cannot be expected to give the results originally hoped for.