Die Bestimmung von Submikromengen Kupfer in Reinstmetallen und Meteoriten Durch Ein Hochselektives γ,γ-Koinzidenzverfahren

Copper was determined non-destructively by neutron-activation analysis in the high purity metals Be, Bi, Pb, Se, Sn, Tl and in iron meteorite specimens down to concentrations of 40 ppb, while the minimum detectable mass for 1 g-samples as defined recently byCurrie ²⁵ was about 0.1 ppb Cu. γ,γ-coincidence counting of the annihilation radiation of⁶⁴Cu essentially improved suppression of interferences by other γ-cascade emitters. The latter was achieved by increasing the detector distances and by counting in centric and eccentric positions with respect to the detectors. Using the 180°-angle correlation of the annihilation γ-quants of⁶⁴Cu etc. an increase in selectivity—in relation to conventional coincidence methods—was achieved by a factor of about 10³. A goniometer arrangement proved to be very advantageous.