DEVELOPMENT OF AN IMPROVED DETECTOR FOR KR-81 AND OTHER NOBLE GAS ISOTOPES

THE IMPORTANCE OF COUNTING NOBLE GAS ATOMS WITH ISOTOPIC SELECTIVITY STEMS FROM THE PRACTICAL FACT THAT THESE ATOMS CAN BE REMOVED FROM LARGE QUANTITITES OF MATERIALS, AND IF COUNTED INDIVIDUALLY, OFFER OPPORTUNITIES FOR PARTICLE PHYSICS, DATING, ENVIRONMENTAL, AND MEDICAL APPLICATIONS. RESONANCE IONIZATION SPECTROSCOPY (RIS), COMBINED WITH MASS SPECTROSCOPY, HAS LED TO A SYSTEM FOR COUNTING KR-81 (OR OTHER ISOTOPES OF KR OR XE) DOWN TO ABOUT THE LEVEL OF 1,000 ATOMS IN A SAMPLE. HOWEVER, A MUCH IMPROVED DETECTOR (RISTRON) WOULD UTILIZE A NEW PRINCIPLE WHEREIN THE SAMPLE ATOMS ARE STORED IN A SEMICONDUCTING TARGET SUCH AS SILICON OR GERMANIUM AND RECOVERED BY LASER ANNEALING. THIS ARRANGEMENT WOULD PERMIT ISOTOPIC ENRICHMENT BETWEEN EACH RIS-LASER PULSE AND WOULD NOT REQUIRE ISOLATING THE DETECTOR FROM THE VACUUM SYSTEM. IN PHASE I, WE WOULD ATTEMPT TO SHOW THAT NON-SELECTIVE IONIZATION (AS A BY-PRODUCT OF TARGET ANNEALING) DOES NOT INTERFERE WITH THE ION-OPTICS USED IN THE MASS-SPECTROMETER. ASSUMING THIS TO BE THE CASE, PHASE II WOULD ALLOW THE CONFIGURATION OF A COMPLETE COUNTING SYSTEM. APPLICATION OF KR-81 ALONE INCLUDES A BR-81(V,E-)KR SOLAR NEUTRINO EXPERIMENT, POLAR ICE-CAP DATING, OCEANOGRAPHY, GROUNDWATER TRANSPORT STUDIES, AND OTHER EARTH SCIENCES USES. OUR MARKETING RESEARCH SHOWS THAT A RELIABLE SYSTEM FOR KR-81 COUNTING WOULD HAVE CONSIDERABLE COMMERCIAL USE.