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Ion Beam Transport Glossary

Brief definitions to beam transport terms used in an accelerator. We will try to add one or two links, typically to more complete definitions and/or more specific information on the particular devices students will use in the Lab Course.

Electrostatic Triplet 
A set of three electrostatic quadrupoles. A triplet/dipole combination (perhaps with a pair of bender plates) can be anastigmatic.
Inflection Magnet 
This author does not know why it is traditional in the near-barrier nuclear physics community to refer to the dipole after the ion source as the inflection magnet. This magnet provides mass selection.
Analyzing Magnet 
This author believes that it is traditional in the near-barrier nuclear physics community to refer to the dipole after the Tandem Van de Graaff as the analyzing magnet because this element separates the mix of energies and charges which emerge from the Tandem.
Switching Magnet 
Or Switcher. This magnet selects the beamline. It is a dipole which can reverse field and contains a vacuum chamber with ports at fixed angles. The CASE NSL switching magnet allows beamlines on +- 15, +-30, +- 45 and Zero degrees.
Magnetic Dipole 
A bending magnet, often used to select mass, charge, momentum or beamline. A dipole naturally focuses in the horizontal (bending) plane; to add vertical focusing the pole pieces are beveled to add a small horizontal component to the magnetic field.
Magnetic Quadrupole 
A magnet with 4 poles, alternating N-S-N-S. By itself, an element which focuses weakly in one plane while defocusing in the perpendicular plane.
Magnetic Quadrupole Doublet
An ion optical element consisting of two magnetic quadrupoles with poles differing by a 90 degree rotation. The Doublet will focus in both the horizontal and vertical planes, acting as a converging/diverging lens in one plane and a diverging/converging lens in the other. This is an example of Strong Focusing. It is essential that the separation between the two singlets is small compared to the focal length of each singlet.
Magnetic Quadrupole Triplet
A set tf three magnetic doublets. In a triplet the outer pair act together and the central element is rotated by 90 degrees. A Triplet can be free of astigmatism, ie, the horizontal and vertical beam waists can coincide. A Triplet and Dipole combination can also be anastigmatic.
Magnetic Steerer 
Simple beam optical element using small dipole fields to steer the ion beam. Usually made without a core.
Strong Focusing 
The use of 2 or more magnetic quadrupoles in an alternating gradient, used to focus the ion beam in accelerators. We at SBU and BNL are proud of the contribution that Ernest Courant made to the discovery and application of this principle.