Measurement of lower hybrid waves in scrape off layer using microwave scattering technique in Alcator C-Mod

Abstract

The direct measurement of lower hybrid (LH) waves in plasma can provide information on the propagation and absorption of LH waves in tokamak plasma and validate numerical simulations. Here, we propose to utilize the scattering of probe waves (60 GHz) off LH waves (4.6 GHz) to diagnose LH waves in the scrape off layer. We develop an analytic model to describe the scattering process in weakly inhomogeneous plasma based on the three‐wave coupling problem. We then present first experimental results obtained by upgrading an ordinary‐mode reflectometer system in Alcator C‐Mod.