Glossary
This scientific library assumes from its users a large amount of knowledge and a familiarity with a variety of terminology related to the topic. Furthermore, some amount of naming conventions have been created here to encode all the necessary functionality in code. This page serves to briefly explain and define all the terms used throughout the library, both the ones used as a standard in the wider scientific literature, and the ones specified by this library. For more details, please see the Theory pages.
Glossary
Most relevant terms
- resolution
The ability of an instrument to show results in detail. The better the resolution, the higher the detail and the less broad the peaks.
- resolution function
A mathematical function that models the resolution of an instrument, as a function of some physical property, such as energy or momentum.
- instrument
A collection of physical devices used to perform an INS experiment. Different instruments are set up to specialise in different kinds of experiments, and so they consist of different devices placed at different distances and made of different materials. This results in different resolution profiles.
- version
A particular combination of parameters for an instrument. Over time, instruments are upgraded by switching out and rearranging their components, resulting in a changed resolution (hopefully improved!). For past and future compatibility, every time an upgrade significant enough to alter the resolution is done, a new “version” is created for that instrument.
- configuration
A set of options built into an instrument that change the physical configuration of the instrument, affecting the resolution. These are things such as the choice of Fermi chopper or analyser. In the context of this library, this is a set of instrument parameters, grouped by a name (option), which get provided to a model together with the constant parameters.
- option
One of the options that can be chosen for a given configuration. This is tied to a particular version of a particular instrument. Any given INS instrument may have several options for a given configuration for users to choose from, which affect several parameters of that instrument.
- setting
A user-chosen experimental parameter that affects the resolution. In practice, this can be the incident energy and the chopper frequencies, depending on the instrument. In the context of this library, a setting is an argument specifically required by a model.
- model
A method to represent the resolution function. There are different ways of approximating the resolution function, each taking into account different levels of detail. The same model can often be used to describe multiple similar instruments or multiple versions of an instrument, but in the context of this package, a model can only be accessed through a particular version of an instrument.
Neutron terminology
- source
A device that produces neutrons used for neutron experiments. In practice, this is either a nuclear reactor or spallation source (a particle accelerator).
- target
A material used in spallation sources, which is hit by the particle produced from the accelerator. The collision emits neutrons which are used for the experiments.
- moderator
A material used to slow down the neutrons produced by the collision with the target.
- beam
A collection of neutrons. Nuclear reactors produce continuous beams and spallation sources produce short pulses; these may be further manipulated with moderators and choppers.
- chopper
A rotating mechanical device designed to block the neutron beam for some fraction of each revolution.
- Fermi chopper
A chopper designed to select a particular narrow slice of energies from the wide range of energies coming from the moderator. This kind of chopper often has multiple openings, allowing the user to make a choice of which energies to use or how good a resolution to obtain.
- disk chopper
A type of chopper shaped like a disk. Can be used for various purposes, such as improving resolution or removing contamination, etc.
- sample
The material being studied by the neutron experiment. Unless specified otherwise, in this library the term “sample” combines two things: the sample environment and the sample under study itself.
- sample environment
A device used to enclose the sample, usually an aluminium “can”. May consist of extra parts, such as a cooling system. Further parts may also be present, such as a vacuum pump or extra experimental devices like a Raman spectrometer, but these are generally not exposed to the neutron beam and therefore shouldn’t affect the resolution.
- detector
A device used used to detect the presence of a neutron. These are placed at various positions around the sample to determine the energies and momenta of the neutrons scattered from the sample under investigation.