Elektrische Leitfähigkeit und Degradation von Isolatorkeramik und Wasserstoffpermeation durch den Edelstahl Manet in einer Fusionsumgebung

Existing fusion reactors are complex machines and future machines are even gaining in complexity. The technical requirements regarding material properties are very specific with regard to the application and therefore a broad spectrum of materials is needed. It spans from superconductors to high temperature electrical insulators, from plastics to high strength superalloys and from fiber reinforced graphite to concrete, only to name a few of them. In the present thesis contributions to two different fusion related topics are presented. The decision to build the first experimental fusion reactor ITER (International Thermonuclear Experimental Reactor - a cooperation of EU, Japan, Russia and USA) is approaching at a fast pace. Thus it is necessary to investigate those two fields that have been quite neglected in the past. The first work deals with the so-called RIED-effect, a Radiation Induced Electrical Degradation of the insulating properties of oxide ceramics und er irradiation with an applied electrical field. According to literature this degradation remained even after the end of irradiation (permanent degradation). Here an experimental setup on the basis of the guard ring technique has been developed and analysed, which eliminates the uncertainties of earlier measurements. Thereby the conductivity changes of two Al$_{2}$O$_{3}$ materials (Rubalit 710 and Wesgo Al 995) under irradiation with 28 MeV $\alpha$-particles at 500 $^{\circ}$C and an applied electrical field of 3 $\cdot$ 10$^{5}$ V/m have been measured. According to several authors these are all experimental conditions under which a maximum in RIED-effect is expected. Up to 0,2 dpa irradiation dose I never measured a significant conductivity increase $\underline{inside}$ the material, although RIED-supporters claimed apparent conductivity increases of several orders of magnitude at far smaller doses. I was able to show that apparent conductivity increases - also occuring in our measurements - were all due to surface leakage currents