GENERALIZED DETECTORS: ISOTOPICALLY SELECTIVE SINGLE ATOM COUNTING OF NOBLE GASES

RESONANCE IONIZATION SPECTROSCOPY (RIS) IS PROPOSED AS A NEWMETHOD FOR COUNTING INDIVIDUAL ATOMS OF THE NOBLE GASES AR, KR, AND XE WITH ISOTOPIC SELECTIVITY. RIS INVOLVES THE STEPWISE EXCITATION, IONIZATION, AND COUNTING OF ATOMS OF A PRE-SELECTED ELEMENT, GENERALLY IN A LARGE BACKGROUND OF OTHER ELEMENTS. BECAUSE NARROW-BAND LASERS ARE USED, SUFFICIENT OPTICAL POWER ENABLES ESSENTIALLY ALL OF THE ATOMS OF THE SELECTED ELEMENT TO BE IONIZED, WHILE THE INTERFERENCE FROM OTHER ELEMENTS REMAINS NEGLIGIBLE. THE IONS FROM THE SELECTED ELEMENT ARE THEN EXTRACTED AND PASSEDTHROUGH A MASS SPECTROMETER, THEREBY ACHIEVING ISOTOPIC SELECTIVITY. THE CAPABILITY OF DETECTING INDIVIDUAL NOBLE GAS ATOMS, DOWN TO THE FEW ATOM LEVEL, WHETHER STABLE OR RADIOACTIVE, ENABLES PURSUIT OF NUMEROUS APPLICATIONS OF DETECTING RARE EVENTS THAT ARE NOT TRACTABLE BY RADIOACTIVE DECAY COUNTING METHODS. BASIC RESEARCH IN NUCLEAR PHYSICS AND WEAK INTERACTION PHYSICS WOULD BENEFIT FROM SUCH A SYSTEM WITH APPLICATIONS IN FISSION YIELD DETERMINATION, BB-DECAY, COSMIC RAY INTERACTIONS AND SOLAR NEUTRINO EXPERIMENTS. SUCH A CAPABILITY WOULD ALSO HAVE APPLICATIONSIN GROUNDWATER DATING USING 81KR AND 85KR, OCEANOGRAPHY USING 85KR AND 39AR, NEUTRON DOSIMETRY USING ANY ISOTOPE OF XE, METEORITE ANALYSIS USING SELECTED ISOTOPES OF XE, AND OTHER USES. SOME OF THESE HAVE BEEN IDENTIFIED TO HAVE COMMERCIAL POTENTIAL BECAUSE OF THE LARGE NUMBERS OF SAMPLESTO BE COUNTED. A METHOD SATISFACTORY FOR COMMERCIAL USE HASNOT BEEN DEVELOPED AND IS THE SUBJECT OF THIS PROPOSAL. PHASE I WOULD PROVE THE GENERALIZATION OF THE ATOM COUNTER TO AR, KR, AND XE BY DEMONSTRATING RIS OF ALL THREE NOBLE GAS ELEMENTS WITH THE SAME LASER SYSTEM. PHASE II WOULD DEVELOP A PRACTICAL SYSTEM BASED ON A MODULAR APPROACH WITH SPECIAL ATTENTION PAID TO VERSATILITY.