Powder Diffractometer

POWGEN | BL-11A | SNS

Mission Statement

POWGEN is a high-resolution neutron powder diffractometer that enables characterization of the crystal, magnetic and local structure of novel polycrystalline materials.

Instrument Description

POWGEN is a general-purpose powder diffractometer useful for a wide range of structural studies. It can cover d-spacings from ~0.1 Å to 8 Å in a single measurement, ideal for both traditional Rietveld data and PDF measurements with longer collection times. It can also cover long d-spacings up to ~ 38 Å, powerful for studying magnetic order. Rietveld measurements for standard neutron-size samples (0.3-3cc) can be completed in ~ 1 or 2 hours with <0.1% resolution at short d-spacings and <2.5% resolution for nearly all d-spacings of interest. Alternatively, much of this resolution can be traded for intensity, making it possible to take shorter measurements while still maintaining good resolution. It is also possible to collect data from much smaller samples with longer collection time. The adjustable bandwidth-limiting choppers allow for large variations in the incident wavelengths and pulse repetition rate. Interchangeable guide sections and the ability to trade resolution for intensity at the analysis stage allow users great latitude to optimize the data range, resolution, and statistical precision for each experiment.

Applications

Scientific studies at this instrument encompass a wide range of novel materials. These include, but are not limited to, structural studies of energy storage materials such as battery materials, ceramic membranes for solid oxide fuel cells and oxygen sensors, hydrogen storage materials, high-entropy alloys and thermoelectric materials. Fast data collection allows looking at in situ processes (e.g. solid-state synthesis, redox reactions and gas-solid interactions). Long d-spacing coverage enables the study of magnetic materials such as magnetic semimetals, multiferroics, high-Tc superconductors, charge and orbital ordering transitions, magnetocaloric materials, and molecular magnets. The availability of magnetic field capabilities allows the study of field-induced structural and magnetic transitions. POWGEN capabilities can contribute to understanding materials such as zeolite and aluminophosphate frameworks; metals and semiconductors; dielectrics, ferroelectrics; metal-organic frameworks (MOFs), and ab initio structure solutions of complex polycrystalline materials.

Specifications

Moderator	Decoupled poison supercritical H2
Source-to-sample distance	60 m
Sample-to-detector distance	2.5-4.7 m
Flight Path	44m straight guide followed by 6m interchangeable High Resolution or High Intensity sections.
Detector angular coverage	10° < 2Θ < 170°
Solid angle detector coverage	1.2 steradians (12 m²)
Bandwidth	1Å (tunable incident wavelength from 0.533 Å -4.797 Å)
Frame 1	(CWL: 0.8 Å) d coverage of 0.1-8 Å @ 60 Hz
Frame 2	(CWL: 1.5 Å) d coverage of 0.5-12.5 Å@ 60 Hz
Frame 3	(CWL: 2.665 Å) d coverage of 1-20.5 Å@ 60 Hz
Frame 4	(CWL: 4.797 Å) d coverage of 2.2-38 Å@ 60 Hz
Resolution	0.0008 < ∆d/d < 0.025 (in a single measurement)
Sample environment	Sample Changer: 10K-300K, 24 slots Orange Cryostat: 2K-300K Cryofurnace: 5K-500K or 30K-700K Vacuum Furnace: RT-1200°C Gas-Flow AGES: RT-850°C (pO2 sensor + RGA) Slim SAM Magnet: 2K-300K and 0-5 T