Operation - Secondary ion mass spectrometry
Secondary ion refers to the emission of an ion from a solid target that is under bombardment from primary ions. The primary ion beam requires an ion source, from which ions are accelerated to energies typically in the 10-20 keV range. This primary beam is used to sputter the target and a fraction of the sputtered material is ionized. These ions are accelerated away from the sample through a potential drop of 10 kV and form the secondary ion beam that is passed into the mass spectrometer.
On SHRIMP, the primary ion beam is angled at 45° to the sample surface with secondary ions extracted at 90° to the sample surface.
Sputtering involves the bombardment of a sample with an energetic primary ion beam (red). These atoms physically disrupt solid targets and cause atoms and molecules to be ejected. Some of these atoms and molecular fragments become ionized (secondary ions) and are extracted for analysis in the mass spectrometer.