Temperature Distribution During the Cooling Down of the R3B Magnet Cold Mass

The cold mass of the R3B magnet consists of a set of six trapezoidal racetrack coils. There are two main coils and two pairs of lateral coils which are connected in series in a butterfly-like shape. The coils are imbedded in the coil-casings and covers which are made of aluminum alloy 5083. There are four coil-casings (two main coil-casings and two lateral coil-casings) and linking components between the coil casings. The cold mass will be placed in a large cryostat. The purpose of the cooling system is to get the R3B-GLAD coils at the proper temperature for running operations under magnetic field. The coils are indirectly cooled. The cool down is ensured by gas helium forced flow. As the coils are imbedded in 5083 (casings + covers) it has been decided to cut off heat loads, like thermal radiation and conduction from room temperature to cold mass, before they can reach the coils. Heat exchangers are thus glued on the casings and covers. There are 20 heat exchanger tubes glued in square grooves in covers and casings over a length of 2 m. In this paper the temperature distribution over all the coils and their support structure during the steady state and transient cooling down process are presented. The orthotropic properties of the thermal conductivity of the winding are taken into account. The non linearity of the thermal properties of the coils and materials constituting the support structure is also considered.