Magnetic design and method of a superconducting magnet for muon [formula omitted]/EDM precise measurements in a cylindrical volume with homogeneous magnetic field

Abstract

A magnetic field design method of magneto-motive force (coil block (CB) and iron yoke) placements for g−2/EDM measurements has been developed and a candidate placements were designed under superconducting limitations of current density 125 A/mm2 and maximum magnetic field on CBs less than 5.5 T. Placements of CBs and an iron yoke with poles were determined by tuning SVD (singular value decomposition) eigenmode strengths. The SVD was applied on a response matrix from magneto-motive forces to the magnetic fields in the muon storage region and two-dimensional (2D) placements of magneto-motive forces were designed by tuning the magnetic field eigenmode strengths obtained by the magnetic field. The tuning was performed iteratively. Magnetic field ripples in the azimuthal direction were minimized for the design.The candidate magnetic design had five CBs and an iron yoke with center iron poles. The magnet satisfied specifications of homogeneity (0.2 ppm peak-to-peak in 2D placements (the cylindrical coordinate of the radial position R and axial position Z) and less than 1.0 ppm ripples in the ring muon storage volume (0.318 m <R<0.348 m and -0.05 <Z< 0.05 m) with 3.0 T strength and a slightly negative BR (magnetic field radial component) at Z> 0.0 m) for the spiral muon injection from the iron yoke at top.