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The motion controllers, the timing gap, and the seam between CORA and the floor.

Triggering: a gap in the source

A coherent-imaging measurement is a gated exposure, often one synchronized with a scan: a ptychographic map steps the sample and takes a frame at each point, a Bragg-CDI series rocks the goniometer and takes a frame at each angle. At the other NSLS-II coherent and scanning beamlines a Zebra or PandA box gates the detector frames against the motion. The CDI profile collection, as read, exposes no such trigger box: there is no Zebra or PandA startup file, and no shutter PVs. The EigerDetector and MerlinDetector carry internal and external trigger modes in their device classes, but how an exposure is gated and synchronized with the scan on the floor is not in source. This is the headline controls question (TIMING-1): it is carried as a deferral, modelled by what is real (the detector trigger modes), not invented.

Motion controllers

The optics, KB, goniometer, and tower axes are EPICS motor records whose controller boxes, firmware, and IPs are not in the profile collection (DRIVE-1), so EndstationMotionController is carried as a single MotionController family with the specifics blank.

The seam: CORA and the floor

This is where CORA's design meets the CDI floor. The shape matches the other NSLS-II beamlines'.

CORA owns (its conducting engine, over the ControlPort):

  • the coherent-imaging acquisition: aligning the KB nanofocus, setting the incident energy, positioning the sample on the goniometer, and arming the area detector for a forward-CDI frame, a ptychographic scan, or a Bragg-CDI rocking series;
  • the choice of technique, detector, scan grid, and exposure, gated by the trust boundary.

CORA drives through (the floor it actuates and observes, and does not replace):

  • the EPICS IOCs via the ophyd hardware abstraction: the ControlPort boundary;
  • the DCM / DMM drives, the mirror and KB axes, the goniometer and tower motion, the PSS interlock, and the Eiger2 / Merlin detector IOCs;
  • the facility filestore where the per-run frames land. CORA moves them, over the TransferPort, into CORA's own Dataset of record.

So CORA brings one conducting engine to CDI, working over the ports: coherent-imaging orchestration over the ControlPort, the phase retrieval and ptychographic reconstruction over the ComputePort, and data egress over the TransferPort into the CORA Dataset. The reconstruction is a clean ComputePort leg, the imaging analogue of the correlation analysis at CHX and the reconstruction legs at the tomography beamlines.

The software IOCs (Eiger, Merlin, Prosilica, the TetrAMM and i400 / i404 electrometers, the TDMS tower IOC) are referenced by PV namespace only, never registered as Assets.