MS - Sector Mass spectrometer

In sector field mass spectrometers, the ions are deflected in electric and magnetic fields. The radius of the circular paths they traverse in the fields depends on the energy (in the electric field) and momentum (in the magnetic field) of the ions. Knowing the charge, energy and momentum, the mass can then be determined. Sector field mass spectrometers can be built so that ions with slightly different velocities are imaged at a point in the detector (velocity focusing). Ions whose trajectories are slightly inclined can also be imaged to one point (directional focusing). Mass spectrometers that can do both at the same time are called double-focusing. The focusing is necessary to still obtain an acceptable intensity of the measurement signal at high resolution. Sector field mass spectrometers are the most accurate, but also the most expensive instruments. They achieve a resolution of up to R = 100,000, which is why they are often used in stable isotope mass spectrometry.