Samples taken in Iraq are screened using thermal ionization mass spectrometry for measuring very tiny amounts of uranium or plutonium.

(Source: Dean Calma/IAEA)

A technique (also called surface ionization mass spectrometry) whereby picogram to microgram quantities of a sample are deposited on a metallic filament which is then heated to 1600-2000ºC in a high vacuum; this results in ionization of the sample. The ion beams from the different isotopes present in the sample are separated in a mass spectrometer and collected either sequentially in a single detector or simultaneously in a set of multiple detectors to yield isotopic ratios. The technique is extensively used at the Safeguards Analytical Laboratory. Highly accurate results require that sample cross-contamination be minimized.