Probes for the assessment of plasma-limiter interaction in JET
The interaction of the boundary plasma with the limiters has been analysed for two 5 MA, 20 s Ohmic discharges in JET by Langmuir probes and by an all carbon collector probe. The deposition of D,C, Ni and Cr and the erosion on the probe have been measured as functions of the distance to the last closed magnetic flux surface. The values are compared to the particle fluences and their energies as calculated from the measured plasma parameters. The calculated deuterium fluences are about a factor of 5 to 10 larger than the deposition on the probe and the calculated e-folding length is steeper than the measured values. The carbon deposition and erosion at the probe has been determined with the aid of 13C implants as well as from the depth of the metal and deuterium depositions and the interference colours of the deposited films. The distribution of deposited carbon is similar to the trapped deuterium with a ratio D:C of about 0.3, indicating that D trapping is dominated by saturation of the deposited C layer. The metal deposition is small; it amounts to a few times 1.0 E-3 of the carbon deposition, indicating the dominance of carbon in the boundary layer.
Bibliographic Reference: Article: Journal of Nuclear Materials, Vol. 162-164 (1989), pp. 598-603
Record Number: 198911048 / Last updated on: 1994-12-01
Original language: en
Available languages: en