We have developed an atom trap trace analysis ( ATTA ) system to measure Kr in Xe at the part per trillion ( ppt ) level , a prerequisite for the sensitivity achievable with liquid xenon dark matter detectors beyond the current generation .
Since Ar and Kr have similar laser cooling wavelengths , the apparatus has been tested with Ar to avoid contamination prior to measuring Xe samples .
A radio-frequency ( RF ) plasma discharge generates a beam of metastable atoms which is optically collimated , slowed , and trapped using standard magneto-optical techniques .
Based on the measured overall system efficiency of 1.2 \times 10 ^ { -8 } ( detection mode ) we expect the ATTA system to reach the design goal sensitivity to ppt concentrations of Kr in Xe in < 2 hours .