Detector¶
The flat-panel area detectors, the distance stage, and the flux diagnostics. PVs verified against startup/80-areadetector.py, startup/18-ion-chamber.py, startup/16-electrometer.py, startup/10-motors.py.
XPD's measurement is the diffraction pattern on a large flat-panel detector. For powder diffraction the panel records the Debye-Scherrer rings; for total scattering / PDF it sits close to reach the wide Q that a pair distribution function needs.
| Asset | Family | PV | Role |
|---|---|---|---|
AreaDetector |
Camera | XF:28IDC-ES:1{Det:PE1} |
primary PerkinElmer flat panel |
DexelaDetector |
Camera | XF:28IDC-ES:1{Det:DEX} |
Dexela flat panel (commented-out in source) |
DetectorStage |
LinearStage | XF:28IDC-ES:1{Det:PE1-Ax:} |
sets the sample-to-detector distance (Q) |
IonChamber |
FluxMonitor | XF:28IDC-BI{IC101} |
incident-flux normalization |
QuadElectrometer |
FluxMonitor | XF:28IDC-BI{IM:02}EM180: |
I0 intensity |
ExposureShutter |
Shutter | XF:28IDC-ES:1{Sh:Exp} |
gates the detector exposure |
The distance stage and the Q-range¶
Unlike a fixed flight tube, the DetectorStage Z axis (pe1_z) genuinely translates the panel along the beam, setting the sample-to-detector distance and hence the accessible Q. A PDF measurement uses this directly: a close distance reaches the high Q the Fourier transform into a pair distribution function needs, and the two-distance acquisition combines a near and a far position. The ExposureShutter gates each frame.
Reuse, not new vocabulary¶
This is the reinforcement point of XPD as a CORA exercise: a powder / PDF beamline with a flat panel (the PerkinElmer; a Dexela panel is defined but currently commented out in source, DET-1), a distance stage, and flux counters that needs no new Family. The flat panels reuse Camera (also the Eiger-to-Camera precedent at CHX and SRX); the ion chamber and quad electrometer reuse FluxMonitor (graduated in #353); the exposure shutter reuses Shutter. The detector chain is the same shape Diamond I15-1 carries for PDF (a large detector on the two-theta arm at fixed high energy); XPD shows it porting to a second facility unchanged.