Toward a Reduced Helium Content Cryogenic Cooling Scheme at 4.5 K for CERN’s FCC-hh Accelerator

A conceptual design for cooling superconducting accelerator magnets operating at 4.5 K is proposed for the hadron-hadron configuration of the Future Circular Collider (FCC-hh). This is motivated by efforts to reduce helium inventory and energy costs, while ensuring compatibility with the tunnel structure envisaged for FCC-ee, and providing a technically viable solution for the magnets. The study is carried out for the latest configuration of the FCC-hh machine, the so-called F14 scenario, that uses Nb<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{3}$</tex-math></inline-formula>Sn superconducting magnets with an operational magnetic field of 14 T, for a centre-of-mass energy of 85 TeV with a magnetic filling scheme of 83%. The updated heat loads are presented, along with expected longitudinal and radial temperature gradients in the magnet structure. The move from 1.9 K operation, which makes extensive use of He II, towards 4.5 K using single-phase helium significantly reduces the overall cryogenic power consumption by 30%, and the machine’s helium inventory by 50%.