Quadrupole magnet

Three main types point ion collectors are in use for quadrupole, magnetic-sector, and TOF instruments, and they are discussed here. The multichannel plate collector (or time-to-digital converter)... 

Commercial mass analyzers are based almost entirely on quadrupoles, magnetic sectors (with or without an added electric sector for high-resolution work), and time-of-flight (TOE) configurations or a combination of these. There are also ion traps and ion cyclotron resonance instruments. These are discussed as single use and combined (hybrid) use. 

A simple mass spectrometer of low resolution (many quadrupoles, magnetic sectors, time-of-flight) cannot easily be used for accurate mass measurement and, usually, a double-focusing magnetic/electric-sector or Fourier-transform ion cyclotron resonance instrument is needed. 

Focusing Elements. Two ion optical components are usually placed between the accelerator and the sample chamber. A magnetic field separates any He-, He, or He+ from the He++ beam. A quadrupole magnetic lens then shapes the beam and focusses it into the sample chamber. 

Quadrupole Magnetic sector field Electric sector field Time of flight (ToF) Electrical Ion-trap Magnetic Ion-trap... 

Electric dipole + Electric quadrupole +.. + magnetic dipole... 

If we examine the magnetic held from such a quadrupolar device, we will hnd that the held along the central axis is exactly zero and increases linearly to a maximum value at each pole face. (The pole tips should be hyperbolic surfaces to conform to the shape of the magnetic held, although cylindrical pole tips are often used for ease of manufacture.) Quadrupole magnets are thus characterized by the gradient of the magnetic held, dB/dr, where r is a radial coordinate and... 

Figure 14.11 Schematic design of a quadrupole magnet. The arrangement of the poles will provide x focusing in the usual right-handed coordinate system with the z axis emerging from the page. [From O. Chumberlin, Ann. Rev. Nucl. Sci. 10, 161 (I960).]...

The quantity on the left is the Fourier component of the dipole moment induced by the optical field Max(w). These equations can be generalized to mixed frequency-dependent electric dipole, electric quadrupole, magnetic dipole properties, and similar equations can be written for the Fourier components of the permanent electric quadrupole, aj8(magnetic dipole, ma(co). For static Maxwell fields similar expansions yield effective (starred) properties, defined as derivatives of the electrostatic free energies. 

Mass spectrometers (MSs) are classified by the technology they use to separate ionic masses into clusters. Their examples include the quadrupole, magnetic sector, time-of-flight, and ion-trap mass spectrometers. 

A SPLITT system based on a quadrupole magnetic field combined with annular channel geometry possesses an axial symmetry that not only lends itself to the separation but also to the tractability of the mathemat-... 

M. Zborowski, P. S. Williams, E. Sun, E. R. Moore, and J. J. Chalmers, Cylindrical SPEITT and quadrupole magnetic field in application to continuous-flow magnetic cell sorting, J. Liquid Chromatogr. Related Technol 20 2887-2905 (1997). 

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