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Techniques

What MFX is designed to do, as design intent. Design-phase: these are Methods CORA would earn, not Methods it has.

MFX runs three technique families, none of which fits the catalog's tomography Methods, so each is carried pending on the SLAC Practices until it is earned. They are listed here as design intent, with the shape each would take over the spine and the gap each leans on.

Serial femtosecond crystallography (SFX)

A stream of microcrystals is delivered into the focused FEL beam (liquid jet or fixed target); each X-ray pulse destroys its crystal but records a diffraction pattern first ("diffraction before destruction"). The dataset is millions of single-shot patterns, indexed and merged downstream.

  • Spine shape: a serial_crystallography Method binding the focusing lenses, the sample delivery, the pulse picker, and the area detector, over a Run that is a free-running per-shot acquisition rather than a trajectory of points.
  • Gap it leans on: the per-shot, pulse-ID-tagged event DAQ (DAQ-1). This is the technique that most exposes the acquisition-ontology gap: there is no trajectory to walk, only a shot stream to tag and reference.

Femtosecond optical pump-probe

An optical laser pulse excites the sample a controlled femtoseconds before (or after) the X-ray probe pulse; scanning the delay resolves dynamics in time.

  • Spine shape: a pump_probe Method that scans the laser-to-X-ray delay (a LinearStage delay axis) while acquiring per-shot, with the timetool correcting residual jitter shot by shot.
  • Gap it leans on: the cross-timing-domain synchronization (LASER-1). The delay axis itself is a positioner; what CORA cannot express is the femtosecond synchronization between the optical-laser and FEL timing domains (the lxt_ttc SyncAxis).

X-ray emission spectroscopy (XES / HERFD)

The von Hamos 6-crystal spectrometer disperses the X-ray fluorescence emitted by the sample onto a 2D detector, resolving emission energy; in HERFD mode the incident energy is scanned at a fixed emission line.

  • Spine shape: an xas_spectroscopy Method binding the emission spectrometer and, for HERFD, the incident-energy choreography (the DCCM), over a per-shot acquisition.
  • Gap it leans on: the emission spectrometer binds the EmissionSpectrometer family it introduced, since graduated once ISS earned the 2nd sighting (SPEC-1 now tracks only the analyzer-crystal composition), and HERFD's incident-energy scan reuses the energy-change choreography CORA already models well.

Why none is in the catalog yet

The catalog's Methods are all tomography-family (tomography, dark_field, flat_field, the alignment and energy-change methods). An XFEL shares none of them: there is no rotation, no flat / dark frame pairing, no storage-ring energy ramp. Coining XFEL Methods now, before the acquisition axis they depend on exists, would be inventing recipes for a spine that cannot yet run them. So each is carried pending, naming the Method it would earn, and the deepest dependency (the event-stream acquisition axis, DAQ-1) is sketched as a design note rather than built. See Model for the gap register.