Reflectometry with fibre optics for direct observation of the deposition of thin layers in TEXTOR
In future fusion reactors the net erosion of wall material will determine the lifetime of the first wall. A new technique has been developed to measure this erosion. A thin semi-transparent film of the redeposited material (a-C:H, a-C/B:H) is deposited on a glass substrate, to the back of which a fibre optic bundle is attached. Interference between light reflected at the glass/film interface and that reflected at the film/vacuum interface leads to periodic variation in reflectivity, which is measured with a photodiode. The setting of the glass substrate is not affected by vibration or movement occurring during a discharge. Reflectivity is high (12-28 %). Thickness resolution is in the nanometer range. First results show that in ohmic discharges the deposition rates in the scrape-off layer (SOL) of TEXTOR decrease with increasing central plasma density. In the case of discharges in trimethyl boron the rates increase at higher densities.
Bibliographic Reference: Report: Jül-2793 DE (1993) 108 pp.
Availability: Available from Zentralbibliothek der Forschungszentrum Jülich GmbH, Postfach 1913, 5170 Jülich (DE)
Record Number: 199311253 / Last updated on: 1994-11-29
Original language: de
Available languages: de