About Magnetic Sector Mass Spectrometers
A double-focusing magnetic sector mass spectrometer has at least four components:
- An ion source in which ions are formed and accelerated to energies of up to as high as 10 kilovolts.
- A magnetic sector with a magnetic field that exerts a force perpendicular to the ion motion to deflect ions according to their momentum.
- An electric sector with an electric field that exerts a force perpendicular to the ion motion to deflect ions according to their kinetic energy.
- A detector that produces a response that is proportional to the number of ions.
Slits are placed in the ion path to define the positions and energies of the ions that strike the detector. In general, decreasing the slit widths increases the mass resolution but reduces the number of ions that are detected. Additional electrostatic lenses are commonly used to shape and deflect the ion beam to optimize peak shape and maximize ion beam transmission from the source to the detector. JEOL uses octapole and quadrupole focusing lenses to simplify the ion optical design.
Collision chambers in the first field-free region (just after the ion source) and second field-free region (just after the magnet and before the electric sector) are used to induce ions to fragment in collision-induced-dissociation experiments (MS/MS).