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Mass spectrometers can accurately measure even very small concentrations of ions, and thus are useful tools for chemical analysis. Specialized techniques based on mass spectrometry include secondary ion mass spectrometry (SIMS), Auger spectroscopy, electron 5 scattering for chemical analysis (ESCA), ion probe mass spectrometry, and inductively coupled plasma (ICP) mass spectrometry. Mass spectrometers can also be used as leak detectors and residual gas analyzers. A mass spectrometer includes three basic components: an ion 10 source, which produces a beam of ionized particles from a sample; a means for separating different ion types in the beam by e/m ratio; and a detector, which measures and records the intensity of each of the types. Many different ion sources are available. For example, gas 15 samples may be ionized by an electron beam in an ionization chamber; solid or liquid samples may be vaporized by a laser beam, resulting in ejection of neutral atoms and charged particles that form a plasma; actinide samples may be obtained by using thermal ionization filaments. Recent developments include ion production by inductively 20 coupled plasma torches, fast atom bombardment of liquid surfaces, and ionizing the surface molecules of a liquid sample with weak laser light. In a typical mass spectrometer, ions exiting the source are formed into a beam and accelerated by an electric potential V before entering the magnetic field where they are separated according to their 25 mass and charge. The radius of curvature of the path of an ion with mass m and charge e in a magnetic field H is
