Laser spectroscopy of radioactive atoms

A new helium jet target cell was installed having a smaller capillary. This reduced considerably the helium flow rate, but the transported radioactivity remained at about the same level. However, large fluctuations in the yields were still present. Extensive checks using electric fields of both polarities showed that the transported radioactivities were not associated with charged species, since no change in yields was observed with the electric fields. In order to check that the optics in the helium jet chamber were performing properly, an oven was constructed and installed under the elliptical cylinder light collector. With natural Ba loaded into the oven, strong resonance fluorescence was observed with the laser. Finally the laser system was employed to search for resonance fluorescence with radioactive 126Ba made by a beam from the tandem linac system. No signals were seen above background. Activity measurements showed several hundred 126Ba nuclei/s were passing through the laser beam, and the optical sensitivity was such that a factor of at least a hundred fewer atoms would have been easily observed. A test using a beam of Na ions from the tandem accelerator stopping in the target cell was tried. With the laser tuned to one of the Na Dl components, no resonance fluorescence was observed