Requiring a barium ion at the location of an event eliminates all backgrounds. Tagging of a single ion of barium has been demonstrated and progress has been made on a method for extracting ions out of the liquid xenon. A freezing probe method has been demonstrated, and gaseous tagging is also being developed.
To eliminate background noise at a specific location, a barium ion must be present there.  The tagging of a single barium ion has been confirmed, and methods for extracting these ions from liquid xenon are being developed. A freezing probe technique has been successfully tested, and gaseous tagging is also under development.