Measurements of the edge power flow to the ALT-II limiter in TEXTOR

Abstract

Thermographic measurements at the ALT-II pump limiter on TEXTOR have been performed with the following results. (1) The design of the toroidal pump limiter provides a rather uniform temperature distribution and prevents an overheating of the graphite cover tiles. (2) The local measurements of the convective energy flux to the limiter (IR scanner) and of the radiated power (bolometer) show normally a good power balance; this indicates that the power is leaving the plasma toroidally symmetrically. (3) From the analysis of the temperature distribution in poloidal and toroidal direction along the ALT-II tiles a power decay length of 5–7 mm is derived. (4) The ion temperature at the last closed flux surface is obtained from the energy flux along the magnetic field lines. At low plasma densities, the ion temperature is up to a factor of 2 higher than the electron temperature and at high densities both temperatures converge to the same value.