Glossary
Sample
The NMR sample is the material placed in the magnetic field, whose proton spin resonates when an RF field of the right frequency is applied.
Search
Before being able to measure, an NMR teslameter has to search the range of the probe to find the NMR resonance frequency.
Shimming
In magnet production, the process of making a magnetic field more homogeneous, by placing pieces of iron (shims) in the appropriate place, or by adjusting the current in special shim coils.
Site preparation
Preparing a site in a hospital or clinic for the installation of an MRI system. In particular, the area has to be magnetically and electrically (RF) shielded and structurally reinforced to support the weight.
Shielding
In magnetics, this refers to shielding the outside world from a magnetic field generated by a magnet, or vice versa. The brute force way of doing this is to build a big, soft-iron box. The more subtle approach, called active shielding, is to use a magnetic measurement system and coils in the walls surrounding the magnet to cancel the unwanted fields.
Solenoid
A magnet in the form of a cylindrical coil, concentrating the field inside the cylinder. See Bore.
Spin
Electrons and protons have spin; in other words, they act as if they were spinning on their axis. This means that they act like little bar magnets, and tend to align in an external magnetic field. NMR, ESR, ferromagnetism and permanent magnetism are all phenomena involving spin.
Stabilisation
See regulation.
Standard
A standard is the internationally agreed-upon physical representation of a unit. For example, a caesium clock is the standard for a second. It should always be possible to trace a calibration back to a series of standards. The tesla doesn't have a convenient standard, so NMR teslameters are used instead, a so-called secondary standard.
Standards laboratory
Usually a government laboratory whose responsibility it is to maintain and develop standards, in cooperation with international standards bodies.
Superconducting magnet
An electromagnet built with superconducting wire. To remain superconducting, the coil has to be maintained at cryogenic temperatures, so it is enclosed in a cryostat. Superconducting magnets can achieve very high fields, don't consume any power once ramped up, and provide a nearly perfectly stable field.
Switching magnet
In accelerators, a magnet that acts as a switch, steering the particle beam in one direction or another.
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