SADIE is our Nu Plasma Multi Collector Inductively Coupled Plasma Mass Spectrometer (or MC-ICP-MS for short). However, since even the shortened version of that is such a mouthful and all the other spectrometers have catchy names like RELAX and IDLE, I wanted a shorter, catchier name, for my mass spectrometer and so SADIE was born.
Unlike RELAX or IDLE, SADIE analyses solutions, therefore meteorite and rock samples have to be digested in acids before they can be analysed – I’ll write more about that soon. SADIE then uses a very hot gas (plasma) held at ~8000oC to ionise the solutions. The ions get accelerated through SADIE using a series of voltages (extraction lenses and electrostatic analyser) and a magnetic field all at very low pressure (vacuum of 10-8mbar). As the ions travel through the mass spectrometer they become separated according to their mass, allowing the different isotopes of a single element to be measured independently on the Faraday collectors.
The ratios of those isotopes can then tell us something about the composition of the meteorite or rock, where it came from and what has happened to it since it was formed. We can even measure isotopes resulting from the decay of radiogenic isotopes to tell us how old the sample is.
During the physical and chemical rock forming processes that happen on the earth and in space when the solar system was being formed, the isotopes of some elements become separated into different reservoirs. The amount that they get separated depends on which process is occurring. Some of these variations are unique and can become like a signature for that process, so if we find similar ratios in our samples we can say that they have been affected by that particular process. In this way we can follow the history of a meteorite from its accretion within its parent body all the way to its subsequent ejection and earth landing.
I am currently using SADIE to analyse silver isotope ratios in iron meteorites. Come back soon to read more about that.