Techniques¶
What the modelled part of 4-ID POLAR is designed to do, as intent. First cut.
A technique is a portable Catalog Method; a Practice is how a facility adapts it. POLAR's techniques are diffraction, magnetism, and polarization, none of which exist in CORA's imaging-heritage catalog yet, so the Methods below render unlinked and are carried pending until one enters the pilot scope (TECH-1). The function view survives the eventual hardware and catalog choices, which is why it can be written before the Methods are coined.
Single-crystal diffraction¶
The Huber diffractometers at 4-ID-G orient a single crystal and scan reciprocal space, measuring scattered intensity as a function of momentum transfer.
| Technique | Catalog method | Notes |
|---|---|---|
| X-ray diffraction | diffraction |
reciprocal-space scans on the Eulerian or high-pressure diffractometer; Method not yet in catalog |
| High-pressure diffraction | diffraction |
the high-pressure diffractometer with a pressure cell; a Plan setting over the same Method |
Both need the diffractometers and the detectors. Whether the reciprocal-space coordination (hklpy2) is modelled as a PseudoAxis inside an Assembly(Diffractometer) is the design recorded on Model; the world-fact half (the circle geometry) is DIFF-1.
Magnetic and resonant scattering¶
POLAR's signature: resonant scattering across an absorption edge, in an applied magnetic field and at low temperature, to probe magnetic and electronic order.
| Technique | Catalog method | Notes |
|---|---|---|
| Resonant magnetic scattering | magnetic_scattering |
scattering in field (2 T or high-field magnet) at low temperature; Method not yet in catalog |
| Resonant elastic scattering | resonant_scattering |
energy-resonant scattering across an edge; Method not yet in catalog |
These need the sample environment (magnet plus temperature controller) and the monochromator's energy control.
Polarization analysis¶
The phase retarders set the incident X-ray polarization, and the polarization analyzer resolves the scattered-beam polarization; together they enable dichroism and polarization-dependent scattering.
| Technique | Catalog method | Notes |
|---|---|---|
| X-ray magnetic circular dichroism | xmcd |
circular polarization set by the phase retarders; Method not yet in catalog |
| Polarization-analyzed scattering | magnetic_scattering |
the analyzer crystal resolves the scattered polarization; a Plan setting over the scattering Method |
These need the phase retarders and polarization analyzer.
Not modelled yet¶
The Raman station's techniques are out of this cut (TOPO-2). The concrete acquisition recipes (scan sequences, energies, fields, exposures) are not written yet; they join as the deployment approaches the point where CORA drives 4-ID. Whether diffraction and the polarization / magnetism Methods enter CORA's catalog at all is an owner-scope decision recorded on Model; see Open questions for the world-facts to confirm first.