Ultrasensitive detection of krypton-85 gas using photon burst mass spectrometry

Although long lived noble gas radioisotopes have been proposed for radiochemical dating and environmental monitoring, their use has been limited by their incompatibility with sensitive methods of detection. Photon Burst Mass Spectrometry (PBMS), by combining the mass dispersion of an isotope separator with the isotopically selective photon burst detection, promises to be a viable technique for the ultrasensitive detection of many isotopes, including noble gases, and specifically Kr-85. The principle of the method is that a beam of krypton ions generated in a microwave source, accelerated through 50 kV and imaged magnetically, is converted to a neutral atomic beam with Rb vapour, and passed along one focus of an elliptical chamber anticolinearly to a laser beam (811.5 nm). Spontaneous emission from the atoms is imaged by the gold coated elliptical surface through a slit at the opposite focus, and onto a photomultiplier tube. By the use of multiple detectors in series, random events such as cosmic rays bursts are ignored. 2 refs