Tunable homogeneous kG magnetic field production using permanent magnets

We present a permanent ring magnet arrangement that can achieve a tunable axial magnetic field from 1.80(5) to 2.67(9) kG. The apparatus has been designed to accommodate a cylindrical atomic vapor cell of length 25 mm and diameter 25 mm to lie within the bore of the ring magnets, providing an alternative route for imaging through atomic vapors in large magnetic fields. The measured axial magnetic field has an rms variation of less than 4% over the length of vapor cell, while the calculated field inhomogeneity is less than 5% radially and 12% longitudinally across a cylindrical volume with diameter 20 mm and length 25 mm. The instrument consists of layered concentric off-the-shelf N42 neodymium-iron-boron axially magnetized ring magnets. The magnets are organized into four cylindrical brass holders, whose relative separation can be manipulated to achieve the desired magnetic field strength. We present magnetic field computations and Marquardt-Levenberg fits to experimental data and demonstrate excellent agreement between theory and experiment.