Impact of Void Fraction on Mechanical Properties and Evolution of Coupling Loss in ITER<tex>$rm Nb_3rm Sn$</tex>Conductors Under Cyclic Loading

Abstract

The combination of current up to 50 kA and magnetic field of 13 T in the Cable-In-Conduit Conductors (CICC) for the coils in the International Thermonuclear Experimental Reactor (ITER), cause huge local transverse forces. This results in changes in the transport properties, friction and anomalous contact resistance versus force behavior. The latest design optimizations tend to go toward a lower void fraction (VF). This has an impact on the evolution of the coupling loss and on the possible degree of strand bending and deformation. Toroidal Field Model Coil (TFMC) type of conductors with VFs of 26%, 30% and 36% respectively, are tested in the Twente Cable Press, by which a variable (cyclic) transverse force of 650 kN/m is transferred directly to a cable section of 400 mm length at 4.2 K. The AC loss of the conductor, the inter-strand and strand-bundle resistance ( c ) in the cable and the associated bundle deformation are examined during mechanical cycling. The test results are discussed in view of the previous results on Nb 3 Sn ITER CICCs.

Electromagnetic and thermal stability of the ITER Central Solenoid during a 15 MA plasma scenario

“…Unfortunately, the effects of these two phenomena cannot be easily predicted because it is not possible to directly measure the resistance variation in the conductor during operating conditions. The effect of the Lorentz force on the strand contact resistance was investigated in [15] and [17], but without transport current. The SULTAN AC loss results after cycling of the CSJA8 sample are used to estimate the effects of current and magnetic field variation on the inter-strand contact resistance.…”

Error Estimation in the $T_{cs}$ Measurement of TF Conductors in the SULTAN Facility

“…The contact conductance between the sub-cables was varied in the range from to S/m . These per unit surface parameters of the model were adapted to fit the ranges of experimental results reported in [14]. The -value of the strands was varied in the range from 2 to 30, and was taken independent from and strain.…”

The Effect of Inter-bundle Resistive Barriers on Coupling Loss, Current Distribution and DC Performance in ITER Conductors

“…The round cable with an internal cooling channel is enclosed in a conduit made of stainless steel [1]. The large size of the multi-strand cable goes along with the generation of coupling loss in the NbTi [2]- [4] and CICC's [5], [6]. The low frequency tests with sinusoidal applied field, as standard applied in the Cable Press [7] , provide the representative coupling loss time constants for the loss in typical ITER coil field dump-rate scenario (exponential and linear) [8].…”