A TIEMF model and some implications for ITER magnetic diagnostics

Radiation and temperature induced voltages and associated currents (generally termed RIEMF and TIEMF, respectively) have been found to occur in both MI coaxial cables and ceramic coated single cables. This is an important issue because TIEMF will make extremely difficult, if not impossible, to separate the radiation and temperature effects from the required signal for the ITER magnetic diagnostic coils. For operation in ITER, the problem is expected to be worse, the varying neutron energy spectrum and dose over the whole cable path, will give rise to a non-uniform transmutation and could induce TIEMF effects, even in initially perfect cables. It has been previously reported that TIEMF are generated in well localized regions of the central conductor (inhomogeneities). This paper present a model that explains observed TIEMF features and also some predictions concerning the EMF induced at the integrators input. Of particular importance is that some geometric configurations expected to be problematic, result in almost zero TIEMF despite the above mentioned effects, providing a more optimistic view of this problem. Some solutions are provided to mitigate cabling issues.