Challenges for the Electric Field Devices for a CERN Proton EDM Storage Ring

In the framework of the Physics Beyond Colliders (PBC) study at CERN, the Electric Dipole Moment (EDM) working group is investigating the feasibility of building an approximately 500 m circumference storage ring to precisely measure the permanent electric dipole moment of the proton. Protons are stored in an EDM ring at the so-called ‘magic’ energy of 233 MeV using only electric field elements in order to ensure that spin and momentum vectors precess horizontally at the same rate. For a proton with longitudinal spin, any EDM manifests itself as a measurable vertical spin precession. This article describes the challenges related to the electrostatic accelerator optics elements composing the storage ring. The demanding vacuum requirements, combined with the large scale and absolute absence of perturbing (residual) magnetic fields are to be taken into account for the design of the electrostatic bends, quadrupoles, as well as injection elements. The feasibility of reaching the required field tolerances is discussed. Finally, a strategy is explored to allow the conditioning of the large number of high electric field devices to assure an extremely low spark rate during operation of the storage ring.