Validation of the edge density profiles from the ICRF antenna reflectometer on ASDEX Upgrade

摘要

A new multichannel X-mode reflectometer diagnostic (RIC) was recently installed in ASDEX Upgrade (AUG) to provide the electron density profiles in front of an ion cyclotron range of frequencies antenna. The diagnostic was designed to measure density profiles up to 2×10~(19) m~(-3) in the typical 1.5-2.7 T magnetic fields of AUG. Profiles can be measured every 25 μs simultaneously in 3 different poloidal positions. The main objective of this work is to assess the measurement capabilities of the RIC diagnostic for the scrape-off layer density profiles. RIC density profiles are compared to radial profiles from lithium beam emission spectroscopy and Thomson scattering over a wide variety of plasma conditions. Although a good agreement between the different diagnostics is generally found at low discharge densities, RIC measurements often show steeper profiles at high discharge densities, particularly at low outer wall clearance. In addition, the location of the start of X-mode upper cutoff reflection is determined as well as the plasma density at the first cutoff layer.