Pulsed magnetic field method for measuring polarization of radioactive beams

A new method has been developed for measuring the magnitude of nuclear spin polarization of a secondary, radioactive beam by making a pulsed magnetic field measurement that does not require advance knowledge of the nuclide's magnetic moment. Using a standard beta-NMR apparatus, a magnetic double ratio is determined from the counting rates in 0 degrees and 180 degrees beta detectors for magnetic field on and off conditions. This ratio provides direct information on the induced spin polarization of a radioactive beam. A demonstration of the method was performed using spin-polarized B-12 nuclei produced by fragmentation of an 80 MeV/nucleon O-18 beam in a Nb target.