Thomson scattering diagnostic in the boundary layer of ASDEX

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Abstract
The divertor experiment ASDEX has been equipped with a Thomson scattering system, designed to measure radially resolved electron temperature and density profiles in the boundary layer between the hot plasma core and the wall. Thus, it is possible to obtain detailed information about plasma edge phenomena as a basis of divertor physics. The measured electron temperature at the magnetic separatrix can be described by the Coppi-Mazzucato (1979) scaling law for the electron heat conductivity in ohmically heated plasmas. This is analyzed over a wide range of ASDEX plasma parameters and discharge conditions. During additional heating by neutral injection the Te-profiles show a steepening in the scrape-off area, which can be a consequence of a local decrease in thermal conductivity responsible for the good energy confinement observed for 'H'-regime discharges.