Miniature Annular Permanent Magnet Assembly with Fast Far Field Decay and Majority Collimated Central Field

We report on a 3/8" OD x 1/4" ID x 3/8" long NdFeB assembly of 1/16" thick annulars boasting half the 1/100 far field transverse decay distance compared to an ID Helholtz-spaced pair of similar annulars; and greater than 50% of ID collimated better than 1/1000. The device is applied to a He-3,-4 laser spectroscopy experiment.