Tuneable homogeneous kG magnetic field production using permanent magnets

We present a permanent magnet arrangement that can achieve a tuneable axial magnetic field from 1.80(8)-2.67(2) kG along the z-axis, where (x,y) = (0,0), with a rms field variation of less than 1% over a length of 25 mm. The instrument consists of an arrangement of off-the-shelf N42 neodymium-iron-boron (NdFeB) axially magnetized ring magnets, of varying outer and inner diameters. The magnets are organized into four cylindrical brass holders, whose relative separation can be manipulated to achieve the desired magnetic field strength and homogeneity over the region of interest. We present magnetic field computations and Marquardt-Levenberg fits to experimental data and demonstrate excellent agreement between theory and experiment. 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. The design has a clear aperture of 20 mm in the x-y plane along the z-axis, which opens up new avenues for imaging exploration in atomic spectroscopy.