Core Operations#

A diffractometer’s .core provides most of its functionality. The core conducts transactions with the Solver on behalf of the diffractometer. These transactions include the forward() and inverse() coordinate transformations, at the core of scientific measurements using a diffractometer.

Python class	Purpose
`DiffractometerBase`	ophyd PseudoPositioner
`Core`	The class for a diffractometer’s `.core` operations.
`SolverBase`	Code for diffractometer geometries and capabilities.

In addition to Solver transactions, the .core manages all details involving the set of samples and their lattices & reflections.

Core concepts#

The table below summarizes the main topics managed by .core and points to where each is described in more detail.

Concept	Summary	More detail
Solver	Backend library that implements diffractometer geometries, modes, and the `forward()` / `inverse()` transformations.	Solvers
Geometry & mode	The physical arrangement of axes (e.g. E4CV) and the computation mode (e.g. `bissector`, `constant_phi`) that controls how the solver assigns axis values.	Diffractometer
Wavelength	Beam wavelength used in `forward()` / `inverse()` calculations; defaults to 1 Å.	Wavelength
Sample & lattice	Crystal sample with its unit-cell lattice parameters; multiple samples can be registered and switched between.	Sample, Crystal Lattice
Reflections & UB matrix	Measured orientation reflections used to compute the UB orientation matrix via `calc_UB()`.	Orientation Reflection
Constraints	Limits on real-axis ranges that filter the solutions returned by `forward()`. Act after computation.	Constraints
Axis names	Cross-reference map between diffractometer axis names and solver axis names, set by `assign_axes()`.	Diffractometer Axis Names
Presets	Per-mode constant-axis values the solver assumes during `forward()` instead of the current motor positions; do not move any motor. Act before computation.	Presets