Detector efficiency (replaces #482)

[tjof2]

Description of the change

Replaces #482 and brings it up-to-date with Rnm. Ideally someone else should take this over, not my area of expertise. Looks like @sem-geologist and @ZanettaPM commented on #482 and may be able to contribute - and #1835 is seemingly related.

Compute the detector efficiency from the layers. The efficiency is calculated by estimating the absorption of the different the layers in front of the detector.

        >>> s = signals.EDSTEMSpectrum(np.ones(1024))
        >>> s.axes_manager.signal_axes[0].scale = 0.01
        >>> s.axes_manager.signal_axes[0].units = "keV"
        >>> s.detector_efficiency_from_layers()
        <EDSTEMSpectrum, title: Detection efficiency, dimensions: (|1024)>

Progress of the PR

• Change implemented (can be split into several points),
• update docstring (if appropriate),
• update user guide (if appropriate),
• add tests,
• ready for review.

[codecov]

Codecov Report

Merging #2535 into RELEASE_next_minor will increase coverage by 0.00%.
The diff coverage is 77.41%.

@@                 Coverage Diff                 @@
##           RELEASE_next_minor    #2535   +/-   ##
===================================================
  Coverage               75.54%   75.54%           
===================================================
  Files                     202      202           
  Lines                   29534    29565   +31     
  Branches                 6436     6441    +5     
===================================================
+ Hits                    22312    22336   +24     
- Misses                   5402     5406    +4     
- Partials                 1820     1823    +3     

Impacted Files	Coverage Δ
hyperspy/_signals/eds.py	77.92% <63.15%> (-0.77%)	⬇️
hyperspy/misc/eds/utils.py	85.89% <100.00%> (+0.76%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 60610f4...26d5123. Read the comment docs.

[pquinn-dls]

If interested in supporting XRF signal it's not general enough.
Ge detectors are still popular but this method only uses Si as the detector material.
In terms of units cm is standard in x-ray applications.
Doesn't seem to deal with compounds - e.g. an air path.
I have code to do this so will suggest something. Many x-ray applications use xraylib to handle elemental properties and x-ray properties related to EDX/XRD. Would there be support for moving across to this ?

[ericpre]

I am not knowledgeable on the details of this topic and I will not be able to comment sensibly on this.
In term of distribution, xraylib should be added as an optional dependency, because xraylib is a C library and it isn't available on pypi. However, since it is packaged on conda-forge, it should be easy to install in an anaconda/miniconda distribution.