Hannover 2013 – scientific programme

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MO: Fachverband Molekülphysik

MO 18: Experimental Techniques

MO 18.8: Talk

Wednesday, March 20, 2013, 15:45–16:00, F 102

COATEX: Testing optical coatings for resistance against tritium — •Vera Schäfer and Sebastian Fischer — Karlsruhe Institute of Technology (KIT), Institute of Technical Physics - Tritium Laboratory Karlsruhe (ITEP-TLK), Germany

The Coating Test Experiment COATEX is an experiment to monitor the tritium compatibility of optical windows with different reflection coatings. The monitoring of these samples is based on transmission/reflection measurements, which are carried out with the aid of laser diodes, photodiodes and other optical components. The tritium compatibility of these coatings is important for the Laser Raman spectroscopy (LARA). The main component of LARA is the LARA cell, which is totally floated with tritium and has four windows with such optical coatings. During test measurements with a high tritium concentration these coatings were damaged.

This talk gives a brief overview about the experimental setup and the measurement principle of COATEX. A long term measurement showed problems with the reproducibility of the measurement results, because drifts of 11.5 % occurred. Possible reasons for these drifts like a temperature dependence of the photodiodes, electrical noise and an undefined polarisation of the laser diodes will be presented. In addition, mechanical instabilities of the different optical components caused variations of the measurement results. Although not all planned modifications of the experimental setup have yet been realized, the drift has been reduced to 3 %.