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Techniques

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

Bernina runs two technique families, neither of which fits the catalog's tomography Methods, so each is carried pending on the PSI 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.

Femtosecond optical pump-probe

The shared SwissFEL technique, the same one Alvra and LCLS-MFX run. An optical laser pulse excites the sample a controlled femtoseconds before (or after) the X-ray probe pulse; scanning the delay resolves the dynamics in time. The PSEN spectral-encoding arrival-time monitor corrects the residual laser-to-X-ray jitter shot by shot.

  • Spine shape: a pump_probe Method that scans the laser-to-X-ray delay (a LinearStage delay axis on the experiment laser) while acquiring per-shot, with the PSEN monitor correcting jitter.
  • 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 eco lxt timing chain). Bernina is the third deployment to reach this gap (after LCLS-MFX and Alvra).

Time-resolved hard X-ray diffraction and scattering

Bernina's reason for existing, and what distinguishes it from Alvra. After the pump, the sample's structural response is read by diffraction: Bragg peaks and diffuse scattering recorded shot by shot on the area detector, as a function of pump-probe delay. The sample is oriented and the detector positioned by the GPS six-circle or XRD You-geometry diffractometer.

  • Spine shape: a diffraction Method binding the diffractometer (a Goniometer for the sample circles, a RotaryStage 2-theta detector arm, and a reciprocal-space PseudoAxis), composed through the graduated Diffractometer Assembly (DIFF-1), over a per-shot acquisition. The reciprocal-space layer resolves the hkl inverse kinematics, and for the XRD platform the kappa-to-Eulerian conversion (DIFF-2).
  • Gap it leans on: the per-shot, pulse-ID-tagged event DAQ (DAQ-1). A time-resolved diffraction run is a free-running shot stream tagged by pulse-ID and delay, not a trajectory of points the spine walks. The diffractometer itself is fully covered by the existing Assembly; the acquisition is the gap.

Why neither 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 diffraction station shares none of them: there is no rotation tomography, no flat / dark frame pairing, no storage-ring energy ramp. The diffraction Method is genuinely new for the fleet (the synchrotron diffractometers at 4-ID and 8-ID carry their own pending Methods), and coining it now, before the per-shot acquisition axis it depends on exists (DAQ-1), would be inventing a recipe for a spine that cannot yet run it. So it is carried pending. That a diffraction technique reaches the same acquisition gaps a spectroscopy technique (Alvra) and a crystallography technique (LCLS-MFX) reached is the reinforcement Bernina adds: the gaps are about the XFEL acquisition paradigm, not about any one technique. See Model for the gap register and the Diffractometer Assembly design.