Sector mass spectrometer

[1] Popular combinations of these sectors have been the EB, BE (of so-called reverse geometry), three-sector BEB and four-sector EBEB (electric-magnetic-electric-magnetic) instruments.

Most modern sector instruments are double-focusing instruments (first developed by Francis William Aston, Arthur Jeffrey Dempster, Kenneth Bainbridge and Josef Mattauch in 1936[2]) in that they focus the ion beams both in direction and velocity.

[3] The behavior of ions in a homogeneous, linear, static electric or magnetic field (separately) as is found in a sector instrument is simple.

The force in the magnetic sector is complicated by the velocity dependence but with the right conditions (uniform velocity for example) ions of different masses will separate physically in space into different beams as with the electric sector.

These are some of the classic geometries from mass spectrographs which are often used to distinguish different types of sector arrangements, although most current instruments do not fit precisely into any of these categories as the designs have evolved further.

Since the forces due to these two fields are equal and opposite when the particles have a velocity given by they do not experience a resultant force; they pass freely through a slit, and are then subject to another magnetic field, transversing a semi-circular path and striking a photographic plate.

This geometry is often used in applications with a high energy spread in the ions produced where sensitivity is nonetheless required, such as spark source mass spectrometry (SSMS) and secondary ion mass spectrometry (SIMS).

[8] This geometry is used in the SHRIMP and Panorama (gas source, high-resolution, multicollector to measure isotopologues in geochemistry).