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Detector

Two area detectors, read simultaneously. Design-phase; values are reverse-engineered from dodal or inferred.

The detector-side shape of a scattering beamline is two area detectors run at once: a SAXS detector at long camera length and a WAXS detector at short camera length. They are modelled in the detection stage of the descriptor. Both present the Detector Role (2D frames), the same Role the imaging pilots use; what is new is that there are two of them, the same model at different positions, and the beamstops that protect them.

The detectors and beamstops

Device Family Role Control handle Notes
SaxsDetector Camera Detector BL22I-EA-PILAT-01: Dectris Pilatus3 2M, photon-counting hybrid pixel, 0.172 mm pixel, Si 0.45 mm sensor (dodal); long camera length
WaxsDetector Camera Detector BL22I-EA-PILAT-03: a second Pilatus3 2M, identical hardware, short camera length
BeamStop1 BeamStop (positioned) BL22I-MO-SAXSP-01:BS1: SAXS beamstop, positioned X/Y
BeamStop2 BeamStop (positioned) BL22I-MO-SAXSP-01:BS2: SAXS beamstop, positioned X/Y
BeamStop3 BeamStop (positioned) BL22I-MO-SAXSP-01:BS3: SAXS beamstop, positioned X/Y + roll

How each maps onto CORA

  • SAXS and WAXS are one Family, two Assets. Both are the same Dectris Pilatus3 2M. The difference is the camera length (long for small-angle, short for wide-angle) and the technique role, both of which are settings and placement, not a Family split. This is exactly the per-instance modelling CORA prefers over per-technique subtypes: two Camera Assets distinguished by distance and the Capability they serve.
  • The beamstops are modelled as the thing, not its motion. dodal carries the beamstops as XY (and XY+roll) positioning stages. CORA models them as BeamStop Assets whose positioning is an affordance, not as bare stages: the thing on the beam is a beam-absorbing stop that happens to be positionable. The beam-effect (what fraction it absorbs) stays deferred, the same passive beam-path posture the other deployments take.

What dodal cannot give the detectors

Three detector facts are calibration dodal does not carry, and they are required for real SAXS/WAXS data reduction:

  • Camera lengths as a range. dodal carries a single distance snapshot for each detector. Whether the detector distance is a fixed mount or a settable axis (a movable detector or flight tube) decides whether a detector-translation LinearStage Asset is warranted (DET-1).
  • Threshold energy. The photon-counting Pilatus threshold is None in dodal; it is a beam-energy-dependent calibrated value (DET-2).
  • Beam-center. The per-detector beam-center is None in dodal and is required to reduce a pattern to q-space (DET-2).

Families

Both detectors reuse Camera; the beamstops reuse BeamStop. No new Family is earned on the detector side. See Inventory for the Asset tree and Open questions for the detector calibration still to confirm.