On the Identification of Interferometer Signals in High-k Scattering Data

High-k scattering is a technique used on multiple devices to diagnose short scale (order of the ion gyroradius) density fluctuations with good spatial resolution. In the last decade the method has been used to try to identify short radial scale Kinetic Alfv\'en Waves (KAWs) that are theoretically prediceted to couple to large scale Alfv\'en eigenmodes such as TAEs and RSAEs. The importance of these KAWs is that they contribute an important dissipation mechanism for Alfv\'enic instabilities. However, the use of high-k scattering is problematic for the interpretation of the KAW because even a small level of stray radiation from the beam can produce an interferometric signal that can be mistaken for high-k scattering. This talk discusses several methods that can be used to identify the interferometer effect based on properties of the complex amplitude of the received signal. Data will be used from DIII-D and NSTX to illustrate the method.