Physics

The physics module includes functionality for modeling and treating various signal related to X-ray physics. In particular, we offer modeling of X-ray fluorescence (XRF) emission and X-ray attenuation, and some useful tools for X-ray phase contrast. The back-end of this module is the famous X-ray physics package called xraylib.

X-ray Fluorescence

The physics.xrf sub-module offers mainly two classes: LinesSiegbahn and DetectorXRF. The former exposes a simplified interface for handling XRF emission lines, using the Siegbahn nomenclature. The latter allows one to describe the position and geometry of a XRF detector, that is used in the VolumeMaterial class of the physics.materials sub-module.

The LinesSiegbahn class, exposes two important static methods:

class LinesSiegbahn:
    """Siegbahn fluorescence lines collection class."""

    @staticmethod
    def get_lines(line: str) -> Sequence[FluoLine]:
        ...

    @staticmethod
    def get_energy(
        element: Union[str, int],
        lines: Union[str, FluoLine, Sequence[FluoLine]],
        compute_average: bool = False,
        verbose: bool = False,
    ) -> Union[float, NDArray]:
        ...

The method get_lines returns the list of available lines for a given line family, e.g. the K_α and K_β lines for the K line family. The method get_energy, instead, returns the energy(ies) of the requested line(s) for a given element. If the requested expression matches more than one line, it can either be the list of all the line energies, or their average.

Material modeling

The main class of the physics.materials sub-module is VolumeMaterial, that allows one to model heterogeneous material compositions in the reconstruction volume, with the aim of generating:

Attenuation maps (local linear attenuation coefficient).
Emission cross-sections maps for XRF and Compton.

X-ray Phase Contrast

The physics.phase sub-module contains functions to model the delta-over-beta value and transfer functions encountered in phase contrast problems.