Tests on the electrical insulation of the FT U tokamak magnet after repeated mechanical stresses at -196°C and 23°C

This paper deals with the work done to define, construct and test a detailed critical part, spatially limited at about 10 cm³, reproducing the essential configuration of the FT-U magnet coil. The tests were performed at room and LN2temperatures in order to study the degradation of the insulating materials after repeated mechanical stresses. We describe criteria required to design a practical model with the possibility to simulate the thermo- -mechanical behaviour of the coil and allowing the measurement of the electrical insulation properties. The experimental set-up is described, as well as the operations for test analysis, optical observations and measurements on the components. Finally some results and typical microphotographs are reported.