Supercritical Helium Flow Calorimetry at the MIT Superconducting Magnet Test Facility

This paper presents recent upgrades to the supercritical helium circuit at the MIT Superconducting Magnet Test Facility to support the characterization of REBCO-based cable magnets. In particular, we discuss the design, calibration and installation of dedicated mass flow meters for every conductor layer in a multi-layer magnet. The design and manufacture of dedicated calibration heaters for each flow path is also described. When used in concert with inlet and outlet pressure and temperature sensors, these upgrades allow us to characterize the hydraulic response of each conductor layer. When deployed as a helium flow calorimeter, the configuration provides a cross-check of DC power dissipation in layer-to-layer conductor joints, facilitates the determination of AC loss heating during swept current and exponential current dump discharges, and permits a more accurate assessment of the energy dissipation within a magnet during quenching. Representative examples for each type of measurement are shown.