Thermal-Hydraulic Analysis of the DEMO CS Coil

Two alternative designs of the central solenoid (CS) coil were proposed by EPFL-SPC PSI Villigen and CEA Cadarache for the European DEMO Tokamak. The DEMO CS coil consists of five modules, namely CSU3, CSU2, CS1, CSL2, and CSL3, the most demanding of which is the CS1. According to the EPFL-SCP design, the CS1 winding pack is composed of ten subcoils, each consisting of two layers wound with cables of the same kind. Our present work is focused on the thermal-hydraulic analysis of the CS1 cables designed by EPFL-SPC at the normal operating conditions during the whole current cycle. We took into account the realistic magnetic field distribution, heat transfer between neighboring turns, and heat generation due to AC losses. The analysis, performed using the THEA CryoSoft code, was aimed at the assessment of the minimum temperature margin and at verification if the proposed design fulfills the acceptance criterion. For the considered current scenario, the minimum of the temperature margin was observed at the end of the dwell phase. The temperature margin in the subcoils 1-9 was above the 1.5 K criterion, but was slightly too small in the most outer subcoil 10.