Estimation of Cool-Down Speed Affected by Mass Flow Rate and Inlet Pressure in JT-60SA CS Module

The JT-60SA central solenoid (CS) module is cooled to 4.5 K using liquid helium. This cool-down operation of the coil is planned to take about one month. During cool-down, the maximum temperature difference in the coil (dT _C-M ) must be kept below 40 K to avoid excessive thermal stress. Thermometers are attached only at the inlet and outlet on the outer perimeter of the coil. However, because the maximum temperature inside the coil occurs near its inner edge, dT _C-M cannot be measured directly. Hence, estimating dT _C-M is important to allow the cool-down process to be completed within one month without excessive thermal stress on the CS. In the present study, based on the results of the JT-60SA cool-down test performed in 2020, a temperature simulation model of the CS module, including the strands, jacket, and He in the bundle and hole regions was created using MATLAB, and dT _C-M was estimated during the cool-down test. This model was then used to evaluate the effect of the mass flow rate and inlet pressure on the cool-down speed.