Wavelength#

In diffraction, the wavelength of the incident radiation sets the radius of the Ewald sphere. [1] Only \(hkl\) reflections which lie within the Ewald sphere are accessible to the experiment.

Note

While the energy of the incident beam may be interesting to diffractometer users at X-ray synchrotrons, wavelength is the general term used by diffraction science.

A diffractometer (as a subclass of DiffractometerBase) expects the incident radiation to be monochromatic. Wavelength is used directly in every forward() and inverse() calculation — it sets the scale of the reciprocal lattice and determines which \(hkl\) reflections lie within the Ewald sphere and are therefore reachable.

hklpy2 provides wavelength classes for several common situations:

Wavelength — general monochromatic source (simulated, any radiation type).
WavelengthXray — X-ray source with energy/wavelength conversion (default for most geometries).
EpicsWavelengthRO — read wavelength from an EPICS PV (read-only; control of the PV is outside the diffractometer).
EpicsMonochromatorRO — read both wavelength and energy from a monochromator EPICS PV (read-only).