Detector¶
The flux and beam-position monitors that measure the delivered dose, and why XFP has no imaging detector: the footprinting structural readout is offline mass spectrometry. Reverse-engineered from NSLS2/xfp-profile-collection (startup/); PVs read from the profile collection, carried confirm.
This is the page where XFP departs most sharply from the rest of the fleet, so state it plainly: XFP has no scattering, area, or imaging detector at all. It is a dose-delivery beamline. The thing it "measures" on the instrument is the incident flux, which together with the exposure time and the attenuation is the delivered dose. The structural readout, which residues of the macromolecule were modified, is done offline by mass spectrometry, downstream of the beamline and entirely absent from the profile collection. So the detection side models flux / dose monitors plus the offline-readout seam.
Detection chain (flux / dose monitors)¶
| Device | Family | PV | Role |
|---|---|---|---|
FluxMonitor |
FluxMonitor |
XF:17BM-BI{EM:1}EM180: |
the primary QuadEM electrometer: incident flux plus a per-exposure time-series, the basis for the delivered dose (DET-1, DOSE-1) |
BeamPositionMonitor |
BeamPositionMonitor (loose) |
XF:17BM-BI{EM:BPM1} |
the Sydor four-channel monitor: per-quadrant currents, beam x / y, and a sum-current total flux (DIAG-1) |
The chain measures the beam, not a sample signal. The QuadEM electrometer reads the incident flux and records a per-exposure time-series, which is what lets a run compute the delivered dose; a DIODE PDM array-logger (XF:17BMA-CT{DIODE-PDM:1}) accumulates the dose array as a further monitor, and a second electrometer (XF:17BM-BI{EM:2}) adds channels. The Sydor monitor reads the beam position (for stability and alignment) and a sum current (a further total-flux readback). Beamline alignment is done by scanning a motor against one of these flux monitors and taking the centre of mass, not by imaging (there is no alignment camera in the profile collection).
The flux-to-absorbed-dose calibration, the conversion from measured photons to the hydroxyl-radical dose the sample actually received, is not in the profile collection; it lives in offline analysis. CORA records the measured flux and the exposure as the dose evidence and treats the absorbed-dose calibration as a seam constant to be sourced from staff (DOSE-1, READOUT-1).
Why there is no imaging detector: the offline-readout seam¶
A footprinting experiment is read out by mass spectrometry, which is a separate instrument in a separate lab. The beamline's role ends when it has delivered a known dose to a sample and captured the irradiated aliquot. So what a CORA run at XFP produces is:
- a footprinted sample, the irradiated aliquot, often captured into a fraction-collector tube (see Sample); and
- a dose record: the exposure time, the filter thickness, the flux time-series, and the well or tube identity.
There are no measurement frames to store. The mass-spectrometry analysis that turns the footprinted sample into a structural map is the offline-readout seam: it happens downstream, off the beamline, and is absent from the profile collection. CORA is the system of record for the dose and the sample provenance; the structural readout is a separate, later step that a future integration could link back to the run, but is not modelled here (READOUT-1).
This is the genuinely-new shape XFP brings to the fleet: a beamline whose product is a dosed sample plus a provenance record, not a detector image.
Why no new detector family¶
The detection side reuses the catalog: the QuadEM electrometer binds FluxMonitor, the same role the fleet's other flux monitors fill, and the Sydor monitor binds the loose BeamPositionMonitor already held under review across the fleet (4-ID, 8-ID, 9-ID, ISS, FMX) pending the sensor fold-versus-promote decision; XFP adds a sighting, not a new Family (DIAG-1). No Camera, no Scintillator, no area detector is modelled, because none exists: the readout is offline. The dose-delivery role is expressed by the Source gating (shutters + TimingController + Filter) and these flux monitors, not by a new detector class.
Families¶
Reused from the catalog: FluxMonitor (the QuadEM electrometer and the DIODE array-logger). Loose and held under review: BeamPositionMonitor (the Sydor monitor, DIAG-1). New families: none; nothing graduates and the catalog is unchanged. There is no Detector-role imaging device; the footprinting readout is offline mass spectrometry (READOUT-1). The flux-to-dose calibration is a seam constant (DOSE-1). See Inventory for the Asset tree, Model for the family decisions, and beamline.md for the source walk.