Detector¶
The per-shot area detector and the DAQ data plane it feeds. Design-phase. This is where the family folds and the acquisition ontology does not.
The detector folds; its acquisition does not¶
MFX's science detector (a Rayonix MX340-XFEL, ePix10k, or Jungfrau, depending on the experiment, DET-1) reuses the Camera Family and presents the Detector Role, exactly as the Eiger does at I03 and FXI. As a device, it folds cleanly.
What does not fold is how it is read. At a storage-ring beamline CORA arms a detector and polls its Acquire_RBV PV until it reports Done, one frame per trajectory point. At an XFEL the detector is one source in a free-running stream: the LCLS DAQ records every shot, tagged by pulse-ID and fiducial at beam rate (120 Hz at LCLS, up to roughly 1 MHz on LCLS-II), and a "run" is millions of events correlated downstream by pulse-ID, not a walk over points. CORA's acquisition bodies (collect / discrete / continuous) and its sub-Hz scalar observation logbook have no representation for this (DAQ-1).
How CORA references the data plane¶
The posture this exercise lands on (sketched, not built) is the one CORA already uses for reconstructions: the per-shot data plane lives in SLAC's psana / DAQ, and CORA references a Dataset, exactly as it references a reconstruction artifact through ComputePort. The Run aggregate stays as the provenance envelope (it binds a Plan, a Subject, and a Method, and records what ran); the per-shot frames are not CORA rows. What is missing, and what the event-stream-axis design note sketches, is the actuation side: a primitive to begin and end an event-tagged DAQ run (events or duration, record on or off), with pulse-ID as the correlation key. That is a new event-stream axis, gated on a real trigger.
The detector translation and geometry¶
The detector sits on a translation stage (a LinearStage) that sets the sample-to-detector distance, and carries the experiment geometry (distance, beam center) that serial-crystallography indexing needs. These calibrated values are not in pcdshub's device database and are carried confirm (DET-1).
See Controls for the DAQ and timing systems, and Open questions for the detector items still to confirm.