SOL Electron Temperature and Density Profiles using Ratios of Minority Helium-I Emission in ICRH-heated Tokamak Discharges on TEXTOR

Characterizing the scrape-off layer (SOL) and last-closed-flux-surface (LCFS) region around an ion cyclotron resonant heating (ICRH) launch antenna during high-power RF heating of tokamak discharges is needed to better understand the heating mechanisms on the core plasma. A new diagnostic that uses a 1-D array of filtered photomultiplier tubes has recently been installed in front of an ICRH antenna on TEXTOR. This diagnostic uses narrow-bandpass (10{\AA}) visible filters to isolate various emission lines of helium-I. The helium is a minority species ($<$ 1{\%}) of an otherwise pure ($\sim $ 98{\%}) deuterium discharge. Using this data and an enhanced collisional-radiative model, the electron density and temperature are determined at high spatial ($\sim $ 1 mm) and temporal (down to 1 ms) resolution. Simultaneous profiles of electron temperature and density from $\sim $ 1cm in front of the antenna out to $\sim $2-3cm inside the LCSF have been obtained -- giving a $\sim $ 5cm full profile. Details of the diagnostic technique and profile data from discharges with ICRH power up to 1.2 MW will be shown.