Laser oriented K36 for time reversal symmetry measurements

We have produced very large nuclear alignments in radioactive K36 (half-life 0.34 sec) through laser optical pumping techniques. The K36 was created through (p,n) reactions using a 50 nA, 22 MeV proton beam, and a 3.3 atmosphere Ar36 target. Measurements were made with the target cell at room temperature, when direct optical pumping produces nuclear orientation in the K36, and at elevated temperatures 160°C and 180°C) where the K36 is oriented through a combination of direct optical pumping and spin exchange. The fraction of the maximal nuclear alignment for the 180°C data was determined to be 0.460.07 stat0.05 syst through measurements of the -ray anisotropy following positron decay. Roughly 105 or more decays of oriented K36 occurred each second. The application of the superallowed decay of K36 to measurements of time-reversal symmetry in decay is discussed.