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.

Here, we use the creator() to create a simulated 4-circle diffractometer with the E4CV geometry.

EXAMPLE:

>>> from hklpy2 import creator
>>> e4cv = creator(name="e4cv")
>>> e4cv.core.sample
Sample(name='cubic', lattice=Lattice(a=1, b=1, c=1, alpha=90.0, beta=90.0, gamma=90.0))
>>> e4cv.core.solver
HklSolver(name='hkl_soleil', version='v5.0.0.3434', geometry='E4CV', engine='hkl', mode='bissector')
>>> e4cv.core.sample.reflections
{}
>>> e4cv.add_reflection((1, 0, 0), (10, 0, 0, 20), name="r1")
Reflection(name='r1', geometry='E4CV', pseudos={'h': 1, 'k': 0, 'l': 0}, reals={'omega': 10, 'chi': 0, 'phi': 0, 'tth': 20}, wavelength=1.0)
>>> e4cv.add_reflection((0, 1, 0), (10, -90, 0, 20), name="r2")
Reflection(name='r2', geometry='E4CV', pseudos={'h': 0, 'k': 1, 'l': 0}, reals={'omega': 10, 'chi': -90, 'phi': 0, 'tth': 20}, wavelength=1.0)
>>> e4cv.core.sample.reflections
{'r1': {'name': 'r1', 'geometry': 'E4CV', 'pseudos': {'h': 1, 'k': 0, 'l': 0}, 'reals': {'omega': 10, 'chi': 0, 'phi': 0, 'tth': 20}, 'wavelength': 1.0, 'order': 0}, 'r2': {'name': 'r2', 'geometry': 'E4CV', 'pseudos': {'h': 0, 'k': 1, 'l': 0}, 'reals': {'omega': 10, 'chi': -90, 'phi': 0, 'tth': 20}, 'wavelength': 1.0, 'order': 1}}

Note

The Core class provides key diffractometer features as Python properties. This enables their inclusion in the DiffractometerBase class using ophyd AttributeSignal. One such example is the Solver geometry name:

geometry = Cpt(
    AttributeSignal,
    attr="core.geometry",
    doc="Name of backend |solver| geometry.",
    write_access=False,
    kind="config",
)
"""Name of backend |solver| geometry."""

Using the e4cv simulator, the property is:

>>> e4cv.core.geometry
'E4CV'

From the ophyd diffractometer object reports this:

>>> e4cv.geometry.get()
'E4CV'