8  Mass analyzer design

What’s the difference between an analyzer and a filter? We don’t know.

Short description of advantages and disadvantages of each type.

8.1 Magnetic sectors

Quick recap of why we need magnets and the dispersion equation. Lorentz force.

8.1.1 History of magnetic sector geometries

Dempster, sector field, extended geometry. Focal planes.

8.1.2 Extended geometry magnetic sector in practice

Dispersion, focal plane geometry.

8.2 Electrostatic Analyzers (ESA)

Why use an ESA instead of a magnet? Before or after magnet? Why is it so often seen on ICPs and less often (or even not at all!) on a TIMS. Reference Coulomb force, a figure of an ion traversing a ESA.

Advantage is that you can change a voltage quickly (nanoseconds), for instance to deflect a beam.

8.3 Quadrupole Mass Analyzers

Quadrupoles are a dynamic mass analyzer. Quickly changing voltages. Radio frequency.

Hexapoles and Octopoles. RF multipoles in general.

Rod shapes and resulting EM field lines. Compromises with number and shape of rods.

Advantages: no moving parts, very fast, reliable, inexpensive (see also, vacuum systems and requirements). Disadvantages: One m/z out the back end at a time. Throughput can be low.

Stability triangle figure.

Lots of math with funny symbols.

8.4 Time of flight mass analyzer (TOF)

Some history. Space applications. Nanoparticle and environmental applications.

Geometries: reflection plates or not.

Notch filters. If you have oxygen, you have to notch it because it overwhelms everything else.

Simultaneous collection of all ionized species regardless of mass.

Disadvantages: Much less sensitive for low-z species. Lower sensitivity than quadrupole, also more expensive. Advantages: really fast, very small (fits on a benchtop), suited for imaging applications, portable applications, and extraterrestrial applications.

8.5 Accelerator Mass Spectrometer (AMS)

Large, expensive instruments, very high voltages. Contains several of the mass analyzers mentioned above, plus more components.

8.6 Orbitrap mass analyzer

Max can clean this up later. Thanks Max!

8.7 Ion trap mass analyzer

Stephen can discuss advantages and disadvantages here.