Optimization of Open Midplane Dipole Design for LHC IR Upgrade

This paper presents the optimized designs of an “open midplane dipole” [1] for “dipole first optics” [2] for the proposed luminosity upgrade of the Large Hadron Collider (LHC). It was found [3] that in this design at luminosity of 10³⁵cm^-2s^-1, the peak power density in the coils can be up to two orders of magnitude higher than that at the present baseline luminosity (10³⁴cm^-2s^-1). This comes from a large quantity of spray particles from Interaction Point (IP) that is mostly concentrated at the midplane. The “open midplane dipole” design is the only design so far that has been found to provide reliable quench-stable operation with a lifetime of the critical components of at least ten years. In addition to a summary of magnetic, mechanical and energy deposition calculations for various iterations, the inherent benefits and challenges associated with the “open midplane dipole” design are also discussed. Results are presented for a recently proposed attractive option with the dipole splitted in two with a warm absorber placed between the two [4].