Design of prototype magnets for FETS-FFA

Fixed Field Alternating gradient accelerators (FFA) hold promise for pulsed high intensity applications. No such FFA has been constructed to date; therefore a prototype - the Front End Test Stand-FFA (FETS-FFA) has been pro- posed to explore the feasibility of using FFA technology for the next generation spallation neutron source, ISIS-II. A key component of this prototype is its main magnets, which must meet several critical requirements: maintaining zero chro- maticity during acceleration, offering tune point flexibility, and providing a large dynamic aperture. The selected lattice incorporates a doublet spiral magnet design for more flexi- ble operations in the tune space. The magnetic field profile is generated by distributed conductors wound over the pole face; a 3D analysis using OPERA software was conducted to evaluate the settings necessary to produce the desired field. The cell tune variation was found to be within ±0.0015 hor- izontally and ±0.002 vertically, for four different working tune points.