Lau C, Hanson G, Lin Y, Wilgen J, Wukitch S, Labombard B, Wallace G
MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA.
Rev Sci Instrum. 2012 Oct;83(10):10E309. doi: 10.1063/1.4731002.
A swept-frequency X-mode reflectometer has been built on Alcator C-Mod to measure the scrape-off layer (SOL) density profiles adjacent to the lower hybrid launcher. The reflectometer system operates between 100 and 146 GHz at sweep rates from 10 μs to 1 ms and covers a density range of ∼10(16)-10(20) m(-3) at B(0) = 5-5.4 T. This paper discusses the analysis of reflectometer density profiles and presents first experimental results of SOL density profile modifications due to the application of lower hybrid range-of-frequencies power to L-mode discharges. Comparison between density profiles measured by the X-mode reflectometer and scanning Langmuir probes is also shown.
