Detector¶
The XAS detectors read at each energy point. PVs verified against startup/BMM/user_ns/detectors.py.
XAS is measured two ways, and BMM does both. The detectors here are the primary signal, sampled once per energy step of the scan.
| Asset | Family | PV | Role in a scan |
|---|---|---|---|
IonChambers |
FluxMonitor | XF:06BM-BI{EM:1}EM180: |
I0 (incident), It (transmitted), Ir (reference) currents |
FluorescenceSpectrometer |
EnergyDispersiveSpectrometer | XF:06BM-ES |
fluorescence yield from the sample (dilute samples) |
ScalerCounter |
GenericProbe | XF:06BM-ES:1{Sclr:1} |
scaler / point counter for alignment |
Transmission XAS¶
The IonChambers are a quad electrometer (class BMMQuadEM) reading three ion chambers: I0 before the sample, It after it, and Ir after the reference foil. Transmission absorption is ln(I0/It) versus energy; the reference channel ln(It/Ir) gives a simultaneous known-edge spectrum for energy calibration.
These ion chambers are the primary measurement detector here, not auxiliary flux monitors, but they are the same device kind as the FluxMonitor Family (graduated in #353 from the Diamond i03/i15-1/i22 ion chambers), which BMM reuses rather than coining a synonym. The role nuance (primary signal vs auxiliary monitor) is a Method concern, not a Family difference; the gas fill and per-channel bindings are the open detail (DIAG-1).
Fluorescence XAS¶
For dilute samples, the absorption is measured as fluorescence yield: the FluorescenceSpectrometer (an Xspress3, available in 1-, 4-, and 7-element configurations in source) records the fluorescence spectrum per energy point, and the element line of interest is integrated. It reuses the catalog EnergyDispersiveSpectrometer Family (graduated once 2-ID and 7-BM shared it), presenting the Sensor Role. Which element count is the installed default, and the vendor, are pending (DET-1).