Spectroscopic measurements of the ion temperature profile in front of a limiter in TEXTOR-94

Ion temperatures have been measured in front of a limiter in TEXTOR-94 under various plasma conditions by means of the Doppler broadening of the C5+ line (lambda = 529 nm), which is excited by charge exchange processes with hydrogen (deuterium) atoms recycled at the limiter surface. The ion temperatures have been compared with electron temperatures measured by atomic beam techniques. It has been found that the ion temperatures are considerably larger than those of the electrons. In the scrape-off layer (SOL) the ratio between the ion and electron temperatures (T-i /T-e) can reach values of up to three at low plasma densities, but this ratio decreases with increasing density. The SOL e-folding length of the ion temperature is much larger than that of the electron temperature. The influence of the test limiter position r(L) on the ion temperature measurements has been investigated but found to be of no significant importance.