Isotope-resolved atomic beam laser spectroscopy of natural uranium

We present our results on the development of a technique for conducting laser absorption spectroscopy of uranium in a collimated atomic beam using a compact and potentially fieldable device. A solid natural uranium metal sample is vaporized in a modest vacuum of several mTorr via resistive heating of a tantalum foil micro-crucible. A temperature of over 2000 degrees C is reached by applying only 200 W of electrical power to the crucible. At this temperature, the vapor pressure of uranium is large enough to generate a stable atomic beam. A diode laser is tuned around the 861.031 nm uranium transition, which allows the observation of absorption bands from both the U-238 and U-235 isotopes. The isotopic composition of uranium Standard Reference Material 960 is obtained from the absorption signal, in excellent agreement with the nominal value. Our approach can be readily applied to the isotopic analysis of other actinides, and it is expected to lead to the development of compact, fieldable instrumentation.