Effect of current distribution on the voltage-temperature characteristics: study of the NbTiPF-FSJS sample for ITER

Various tests, either on full-size joint samples or on model coils confirmed that current distribution may play a crucial role in the electrical behaviour of CICC in operating conditions. In order to evaluate its influence, CEA developed a code (ENSIC) the main feature of which is a CICC electrical model including a discrete resistive network associated with superconducting lengths. Longitudinal and transverse resistances are also modeled, representing either joint or conductor. In our paper we will present the comparison of experimental results with ENSIC calculations for one International Thermonuclear Experimental Reactor (ITER) sample prototype relevant to poloidal field (PF) coils: the PF-full-size joint sample (PF-FSJS). In this purpose, the current distribution has been measured thanks to a segmented Rogowski coils system. Current distribution effects on the basic characteristics (T-CS, n-value...) of the cable compared to single strand will be discussed. This study aims at putting light on the global strand state in a conductor and is also useful to evaluate some intrinsic parameters hardly measurable (effective interpetal transverse contact resistance for example) allowing further application in coils. (C) 2003 Elsevier B.V. All rights reserved.