Main Magnets and Correctors for the CBETA and eRHIC Projects, and Hadron Facilities

The CBETA (Cornell Brookhaven Experimental Test Accelerator) project described in reference C. Mayes (2015) is a prototype electron accelerator for the proposed eRHIC (electron Relativistic Heavy Ion Collider) project, described in reference E. C. Aschenauer (2014). An Energy Recovery Linac (ERL) in combination with a recirculating beam line which is based on the Fixed Field Alternating Gradient (FFAG) principle constitute the electron accelerator. The FFAG beam line of the electron accelerator is comprised of cells consisting of one focusing and one defocusing quadrupoles which are designed as Halbach type permanent magnet quadrupoles which are discussed in reference K. Halbach (1980). Window frame electromagnets surrounding the Halbach magnets will be used as normal and skew dipoles correctors and quadrupole correctors. A Halbach magnet in combination with low field electromagnets to act as dipole and/or quadrupole correctors can also be used in the proposed eRHIC project as well as other hadrons facilities like RHIC. We will discuss some of the advantages the Halbach type permanent magnets have over electromagnets and provide experimental and theoretical evidence of these advantages.