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Experimental demonstration of mass‐filtered, time‐dilated, time‐of‐flight mass spectrometry

The Trace Element Accelerator Mass Spectrometer (TEAMS) at the Naval Research Lab (NRL) offers a unique opportunity to develop a new type of time‐of‐flight Secondary Ion Mass Spectrometer (TOF‐SIMS). This opportunity derives from use of a Pretzel magnet as a recombinator and mass filter in the injector part to the accelerator. Mass filtering prior to time‐of‐flight analysis removes extraneous species, thereby reducing background for trace element analysis, and shortens the analysis time for a single‐beam pulse, thereby improving the duty cycle. Using this approach, it is possible to obtain expanded portions of a few narrow segments of the entire time‐of‐flight spectrum created by a single‐beam pulse. Additionally, a longer flight path with higher ion momenta in the Pretzel magnet introduces time dilation, thereby improving resolution. This type of TOF system is well suited for precise trace element abundance measurements, for example, the simultaneous measurement of fissionable nuclear material and selected fission fragments.