Numerical analysis of cooldown of large magnets for low energy beam line for Facility for Antiproton and Ion Research

The superconducting magnets of the Low Energy Beamline are of superferric type. The cooling of the magnets will be done by a liquid Helium bath. Thermal shield and 4K cold mass will be cooled by one common circuit of helium flow. The main constraint for the cooldown is to limit the thermal stresses of the components. In order to satisfy this condition, a gradual cool-down should be performed in order to maintain a small temperature gradient. For cooldown helium flows into the system at a pressure of 16.7 bar. Helium is supercritical at this pressure. The work presents the mathematical model for transient heat transfer. The mathematical model is then solved numerically and the temperature evolution of the cold mass studied. Effect cool down rate of helium and the mass flow rate on the maximum temperature difference and the cool down time is studied.