Optimization of the multiparameter ?-? coincidence spectrometry for the determination of iridium in geological materials

A new 1CS system has recently been constructed at the University of Vienna. Using low-energy planar detectors and improved electronic components, the detection limit could be lowered to about ng/g for carbonate rocks. As standards, either synthetic iridium standards loaded on high-purity quartz powder, or well characterized geological reference materials, were used. In a series of test measurements we attempted to optimize external factors, such as sample size, irradiation time and flux, decay time, and measuring time, and to determine the optimal electronic configuration, including shaping time, coincidence time, range, and gain. Further measurements are geared towards the establishment of a simple and effective routine procedure for a variety of rock types containing iridium at concentrations within the 0.02-1 ppb range.