Techniques¶
What the modelled part of ID28 is designed to do, as intent. First cut.
A technique is a portable Catalog Method; a Practice is how a facility adapts it. ID28 runs momentum-resolved hard X-ray inelastic scattering, a Method not yet in CORA's catalog, so the Method below renders unlinked and is carried pending until a technique enters scope (TECH-1).
Momentum-resolved inelastic X-ray scattering¶
ID28 sets a meV-resolution incident energy with the high-resolution backscattering monochromator (scanned by tuning the crystal temperature, not a Bragg angle), places the multi-analyzer spectrometer arm at a scattering angle that selects the momentum transfer, and scans the incident energy against the fixed-angle analyzer crystals, counting the energy-analyzed scattered photons. The measurement is the intensity surface I(Q, energy-loss): how much energy the sample exchanges with the photon at a chosen momentum transfer, the signature of phonons and collective excitations.
| Technique | Catalog method | Notes |
|---|---|---|
| Momentum-resolved inelastic X-ray scattering | inelastic_x_ray_scattering |
the momentum transfer Q is set by the spectrometer-arm two-theta; the meV incident energy is scanned on the backscattering monochromator against the fixed-angle multi-analyzer crystals; the energy-analyzed signal is counted per analyzer; reuses the NSLS-II IXS Method, the second consumer; Method not yet in catalog |
It needs the incident-energy chain (the backscattering mono for the meV resolution), the sample stage and its temperature environment, and the multi-analyzer spectrometer arm and its detectors. The arm scattering angle sets the magnitude of the momentum transfer; the analyzer crystals fix the analyzed energy so the incident-energy scan reads out the energy loss.
The same inelastic axis, in the hard X-ray regime¶
ID28 is the fleet's hard X-ray IXS instrument. The catalog already anticipates inelastic scattering (the SIX soft RIXS arm, the NSLS-II IXS beamline, the ID32 soft RIXS / XES arms), and ID28 reuses the inelastic_x_ray_scattering Method the NSLS-II IXS beamline left pending as the second consumer, deepening the case for that Capability without coining anything. The device that ties the inelastic beamlines together is the dispersive spectrometer arm: ID28's multi-analyzer crystal arm is a further consumer of the SpectrometerArm family, the sighting that reinforced the graduation earned at ID32, now landed as a catalog Family (see Model).
Not modelled yet¶
The concrete acquisition recipes (the per-Q energy scans, the analyzer alignment, the counting times, the analyzer-crystal array calibration) are not written yet; they join as the deployment approaches the point where CORA drives ID28. Whether momentum-resolved IXS enters CORA's catalog is an owner-scope decision on Model; see Open questions for the world-facts to confirm first.