Determination of the carbon redeposition rate in the scrape-off layer of TEXTOR by a new, time integrated collection technique

Abstract

A method has been developed which allows the carbon redeposition in the SOL of TEXTOR to be deduced simply and rapidly from the interference colours of amorphous carbon films collected on targets during a number of discharges. Two sources of carbon — release from the wall and diffusion out of the plasma core — can be distinguished by appropriate arrangements of the poloidal and the toroidal limiters. The deposition rates can reach 2 × 10 16 C/cm 2 s two centimeters deep in the SOL, and the D/C ratio in the films is high (~ 0.4). This may become important for future devices when D-T operation is planned. Observations made after the boronization of the machine and in He-discharges are presented.