The Refrigeration System for the Superconducting Proton Ring of the Electron Proton Collider HERA

A superconducting proton storage ring will be installed in a 6336 m long ring tunnel as part of a 30 GeV electrons, 820 GeV protons colliding beam facility at DESY (Hamburg). The magnets will be cooled by three refrigerators installed in a central cryogenic building. Each unit has a capacity of both 6775 W refrigeration and 20.5 g/s current lead cooling gas rate at 4.4 K, as well as 20 000 W between 40 and 80 K for the cooling of radiation shields. Coolant will be supercritical helium at 2.5 × 105 Pa, T ∼ 4.4 K being continuously recooled by two-phase helium boiling at 1.1 × 105 Pa within the dipoles. A large transfer line going all around the tunnel will supply individual sections. Sufficient redundancy for the most sensitive components ensures continuous operation in case of individual component failures. The whole system will be automated by means of a process control computer system.