Techniques¶
What the modelled part of 12-ID-E is designed to do, as intent. First cut.
A technique is a portable Catalog Method; a Practice is how a facility adapts it. 12-ID-E is CORA's first Bonse-Hart ultra-small-angle X-ray scattering (USAXS) beamline, and it also runs pinhole SAXS and WAXS on area detectors. The lead technique, USAXS, is a new Capability for the fleet, so its Method renders unlinked and is carried pending until a technique enters scope (USAXS-1); the SAXS and WAXS Methods share the i22 scattering vocabulary and are pending the same owner-scope decision (TECH-1).
Bonse-Hart ultra-small-angle scattering¶
USAXS reaches momentum transfer q far below the pinhole-SAXS regime by rocking a matched pair of channel-cut crystal stages through the Bragg condition: the collimator sits upstream of the sample, the analyzer downstream, and as the analyzer rocks against the collimator a single photodiode counts the transmitted intensity through an autoranging transimpedance amplifier across several gain decades (BONSE-1, USAXS-1). The measurement is the rocking curve, the transmitted intensity as a function of the small angular offset between the two crystals, which maps to q. This angular rocking fly-scan against a multi-decade autoranging point detector is the acquisition shape that is new for the fleet, not a new device class.
| Technique | Catalog method | Notes |
|---|---|---|
| Ultra-small-angle scattering (USAXS) | ultra_small_angle_scattering |
the Bonse-Hart rocking curve: the analyzer crystal stage rocks against the collimator crystal stage through the Bragg condition while the UPD photodiode point-counts the transmitted flux through an autoranging amplifier; new Capability, pending (USAXS-1, BONSE-1) |
| Pinhole small-angle scattering (SAXS) | small_angle_scattering |
low-q on the SAXS Pilatus area detector; shares the i22 SAXS Capability, pending (TECH-1) |
| Wide-angle scattering (WAXS) | wide_angle_scattering |
wide-q on the WAXS Pilatus area detector on its translation; shares the i22 WAXS Capability, pending (TECH-1) |
USAXS needs the incident beam chain (the shared 12-ID double-crystal monochromator and the attenuator filter bank), the sample stack (positioning stage, rotator, and the Linkam and PTC10 temperature stages), the Bonse-Hart crystal stages, and the autoranging photodiode with its flux monitors and scaler for normalization. The same instrument runs pinhole SAXS and WAXS on their Pilatus area detectors, which reuse the existing scattering Capabilities and the same beam.
A new operating axis for the fleet¶
USAXS is genuinely new for the fleet. The catalog already carries pinhole and grazing-incidence scattering on area detectors (i22, SMI) and a range of imaging, microprobe, and spectroscopy methods, but no crystal-analyzer rocking-curve technique. The new axis is the acquisition shape itself: rock one optic (the analyzer crystal) against a second, fixed-geometry optic (the collimator crystal) while a current-integrating point detector autoranges across several gain decades, rather than expose an area detector at one geometry (BONSE-1, USAXS-1). Pinhole SAXS resolves the scattering pattern by where photons land on a 2D detector; USAXS resolves much smaller angles by where the analyzer crystal passes the beam, read as one transmitted current per angular step. That is a new Capability, deferred as a question (USAXS-1).
The new acquisition shape forces no new device families. The Bonse-Hart crystal stages bind the catalog RotaryStage: the operative axis is the crystal rocking rotation, and channel-cut versus multi-bounce is a per-Asset setting, not a new optic Family (BONSE-1). The autoranging photodiode binds the catalog FluxMonitor: it is a current-integrating point detector read through an autoranging Femto amplifier, the same anatomy as the I0 / I00 / I000 / TRD flux monitors and the counting scaler, and the multi-decade gain autorange is a device-state setting (DET-1). The SAXS and WAXS Pilatus detectors bind the catalog Camera. So what is new is the science Capability and the acquisition shape, not a device class; see Model for why nothing graduates and the catalog is unchanged.
Not modelled yet¶
The concrete acquisition recipes (the rocking-curve angular ranges, the gain-autorange behaviour and counting times for the photodiode, the pinhole-SAXS and WAXS camera geometries, and the temperature-ramp sequences) are not written yet; they join as the deployment approaches the point where CORA conducts over the floor. Whether USAXS enters CORA's catalog is an owner-scope decision and is deferred (USAXS-1); minting a cross-facility Method is not done from a modelling exercise until a technique enters a real scope, the same earn-the-abstraction discipline the SAXS and WAXS Methods follow (TECH-1). The Practices are carried pending on the APS Site: 12IDE_usaxs_practice (ultra_small_angle_scattering, USAXS-1), 12IDE_saxs_practice (small_angle_scattering), and 12IDE_waxs_practice (wide_angle_scattering). See Open questions for the world-facts to confirm first.