Thermally induced EMF in unirradiated MI cables

Radiation and temperature induced currents and voltages in mineral insulated (MI) cables, (generally termed RIEMF and TIEMF, respectively) have recently been the object of discussion and study. The problem is due to a possible electromagnetic force (EMF) generated along the centre conductor of ITER magnetic diagnostic coils in a radiation field, and the difficulty of separating radiation and temperature effects from the required signal. Previous work has shown the importance of temperature gradient effects. To address this problem further, studies of TIEMF have been carried out on an MI cable across the ends of the centre conductor at temperatures up to 550 °C, making point-by-point measurements, as well as annealing tests. It has been confirmed that voltage maxima appear in well-localized regions of the cable, indicating that some inhomogeneity is present. No geometric variations were observed by X-ray imaging of the cable.