Tilted foil polarization of radioactive ions

The tilted foil polarization technique has been applied to a beam of radioactive 23Mg (I = 32, T12 = 11.35 s) ions from ISOLDE. To achieve sufficient energy for penetration of the foils a high voltage platform has been constructed and used for acceleration of the initial 120 keV beam of 2+ 23Mg ions to 480 keV. The resulting asymmetry ϵ of the emitted β-radiation from the 23Mg implanted into a cold Pt stopper has been measured as a function of a holding magnetic field. At B = 0.09 T a value of ϵ = −7.4(1) × 10−3 was found. The asymmetry was reduced to ϵ = −3.3(4) × 10−3 at a field below 0.005 T. It is argued that this hard core asymmetry occurs as a result of the internal interaction between the polarized nuclei and the defects created in the implantation process.