Cryogenics of a superconducting LINAC: SPIRAL2 from commissioning to operation

The SPIRAL2 superconducting linear accelerator (LINAC), which has been operational since 2019, employs superconducting, independently phased rf resonators to deliver a wide range of particle beams. Designed for flexibility in particle types, intensities, and energies, it utilizes superconducting quarter-wave resonators, the performance of which is critically dependent on the reliability of the cryogenic operation. This paper reviews the evolution of the SPIRAL2 cryogenic system from commissioning to routine operation, which was initially commissioned in 2017. It highlights the key challenges encountered, including thermoacoustic oscillations, thermal management, and the abnormal behavior of cavities. In addition, it explores the integration of thermodynamic modelling and machine learning techniques to enhance system control and diagnose problems. This work serves as a comprehensive resource for advancing cryogenic operations and the performance of superconducting LINACs.