Mission Statement

POWGEN is a third generation powder instrument that enables structural characterization 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, or less, to 8 Å in a single measurement ideal for both traditional Rietveld data and PDF measurements albeit for longer collection time. Rietveld measurements for traditional neutron-size samples (2-3cc) can be completed in a few hour or less, with a < 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

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 and thermoelectric materials. Fast data collection allows looking at processes in situ while the availability of long d-spacings also enables the study of magnetic materials such as high-Tc superconductors, metal-insulator phase transitions, charge and orbital ordering transitions, and molecular magnets. POWGEN capabilities can contribute to understanding materials such as zeolite and aluminophosphate frameworks; metals and semiconductors; dielectrics, ferroelectrics; and ab initio structure solutions of complex polycrystalline materials such as pharmaceutical compounds.

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 Intensity or High Resolution sections.
Detector angular coverage	10 ° < 2 θ < 170°
Solid detector coverage	1.2 steradians (12 m2)
Bandwidth	1Å (tunable incident wavelength from 0.533 Å -4.797 Å)
Frame 1	0.1-3 Å @ 60 Hz
Frame 5	2.2-15.2 Å @ 60 Hz
Resolution	0.0008 < Dd/d < 0.025 (in a single measurement)
d-spacing range (optimal)	60Hz: 0.1-8Å (in single measurement), up to 35 Å with multiple measurements.
Sample environment	Sample Changer: 24 slots, 10K-300K Orange Crysotat (50mm): 2K-300K Cryofurnace (100mm): 5K-500K or 30K-700K Vacuum Furnace: RT-1200° C Gas Flow: RT-850° C (pO2 sensor + RGA)