Design of high-density electron spin-polarized test masses

We present a method of designing test masses with a high density of electron spins for use in mechanical experiments searching for weak spin interactions. Nested arrangements of rare-earth permanent magnets are shown to achieve spin densities of order 1024spins kg-1 together with stray magnetic fields at negligible levels. A full magnetostatic analysis of the proposed designs is presented, the mechanical feasibility is analyzed and the related manufacturing issues are addressed.