TFMC Tcs Data: How Do We Compare Conductor Performance to the Strand and What Conclusions for ITER We May Draw

Abstract

This memo is to assess the TFMC test results and compare it with the strand performance. The TFMC is not an ideal object for studying performance of the CICC in a sense that the instrumentation priority was considered secondary to reliability and therefore a lot of assumptions and modeling need to be made to make the comparison against the LMI strand possible. To compare the CICC performance to strand we need to know at least current in the strands, magnetic field and electric field distribution along the strands, temperature profile and strain distribution. In the TFMC we have much less uniform magnetic field and less determined temperature than in the CSMC Inserts, so role of modeling is greater. A code M&M developed by Polito team (R. Zanino and L. Savoldi Richard) evaluates the temperature profile in the conductor. It includes heat transfer in joints, self-heating, heat transfer to the radial plates. From their model it follows [1] that the radial plates do not affect significantly the temperature in the conductor near the area with the peak magnetic field, which is 3-5 m away from the conductor entrance inside the TFMC winding pack. Unfortunately, there are no sensors in between themore » inlet and outlet to establish the validity of the code prediction, but different heater powers and outlet temperatures have good agreement with their code prediction, therefore we assume that their findings are correct. We will assume that the temperature in the TFMC is equal to the inlet temperature detected by the T712 sensor. One of the difficult parts for the TFMC analysis that the magnetic field distribution is not uniform even longitudinally. Due to significant current in the CICC the field distribution in the cable is never homogeneous. In the CS Insert at 40 kA, the field difference between the high and low fields in the cross section was about 0.9 T [2]. In the TFMC at 80 kA, the difference is about 1.6 T [3]. The reason why the CS Insert has less field difference is higher transport current in the TFMC. In addition to that transverse inhomogeneity, there is a strong inhomogeneity of the magnetic field along the length of the TFMC conductor.« less