Overview of the Iseult 11.7 T MRI cryoplant operation

The Iseult whole-body MRI delivered its first images in October 2021. The masterpiece of this MRI is an actively shielded NbTi magnet providing a homogeneous magnetic field of 11.7 T within a 90 cm warm bore. A dedicated cryoplant was constructed to cool the magnet at 1.8 K using a superfluid helium bath and it is in nominal operation since March 2019. This paper will present the cryoplant design, as well as the connection of the cryogenic ancillary equipment with the magnet. Estimated thermal losses will be compared with experimental data collected since the beginning of the cooling phase. Then, we will describe the system maintenance and the periodic controls of the various pressurized components performed keeping the continuous nominal operation of the MRI. Finally, we will present the first lessons learned on this unique cryogenic system operation and possible options to improve its reliability.