Ultra-sensitive measurements of36Cl and236U at the Australian National University

Abstract

Some potential applications of the isotopes36Cl and236U require higher sensitivity than is normally required or achieved. For36Cl, one such application is the measurement of the36Cl/Cl ratio of seawater. We show that, with appropriate precautions to reduce the effect of ion-source memory, it is possible to reach blank levels below 10-16in the36Cl/Cl ratio. Measurements of a series of seawater and sea salt samples yield a blank-corrected36Cl/Cl ratio of present-day sea water of 0.71 ± 0.08 × 10-15. For236U, one potential application is as a prospecting tool, where sensitivities in the236U/238U ratio at the 10-13level are desirable. We demonstrate that this sensitivity can be achieved for 24 MeV uranium ions with time-of-flight detection over a 6.0 m flight path. Show more