Beam Optics Design for the μSR Facility at the RAON Facility in Korea

The beam optics was evaluated to determine the specifications for the electromagnets in the proton beamline and the surface muon beamline at the RAON facility. Beam optics was evaluated, up to the fifth order by using GICOSY software; fringe field effects were also investigated. The distributions of the position and the angular divergence of 600-MeV protons were assumed to be Gaussian, and the initial beam emittance was 0.125 π mm mrad. The proton beamline was optimized by adjusting the positions and the magnetic fields of the electromagnetic components. The full width at half maximum (FWHM) proton beam size at the muon production target was 2.75 mm (x) × 6.73 mm (y), which met the requirement for achieving the maximum surface-muon production at the target. The designed surface-muon beamline is 23-m long and consists of two solenoids, two dipoles with a deflection angle of 70°, six quadrupoles, and a Wien filter. For an initial muon beam size of 6 cm (x) × 2 cm(y), the expected muon intensity at the end of the beamline, where the muon irradiation sample will be located, was estimated to be 7.7 × 107 per second.