A National Network Of Accelerators Dedicated To Material Irradiation (EMIR)
- Hosting Legal Entity
- Lujan Neutron Scattering Center at Los Alamos Neutron Science Center (LANSCE) of Los Alamos National Laboratory
- Coordinating Country
- United States
- RI Keywords
- environment, geoscience, powder diffractometer
- Lujan Center, Group Office TA-53, Bldg. 622, Rm. 220, LANSCE, Los Alamos National Lab, Los Alamos, NM 87545 USA
- High-Pressure-Preferred Orientation (HIPPO) is high-intensity medium resolution powder diffractometer for high-pressure, texture, phase transformation, and stress measurements.
HIPPO Instrument Scientist:
email@example.com, (505) 667-7016
- Application Area
- Materials in Extreme Environments and Geoscience
HIPPO is the first third-generation neutron time-of-flight powder diffractometer constructed in the United States. It achieves very high neutron count rates by virtue of a short (9 m) initial flight path on a high-intensity water moderator and 1,360 3He detector tubes covering 4.8 m2 of detector area from 10° to 150° in scattering angles.
HIPPO was designed and manufactured as a joint effort between LANSCE and the University of California with the goal of doing world-class science by making neutron powder diffractometry an accessible tool to the national user community. D-spacing ranges from 0.12-4.80 ？ (1.31-52.4 ？-1) to 1.2-47.5 ？ (0.13-5.3 ？-1) are available to support studies of crystal orientation distribution (texture), amorphous solids, liquids, magnetic diffraction, small crystalline samples, and samples subjected to non-ambient environments such as temperature, pressure, or govuni-axial stress.
The exceptionally high data rates of HIPPO also make it useful for time-resolved studies. In addition to the standard ancillary equipment (100-specimen sample changer, closed-cycle He refrigerator, furnace), HIPPO has unique high-pressure anvil cells capable of achieving pressures of 30 GPa at ambient and high (2000 K) temperatures with samples up to 100 mm3 in volume. A low-temperature gas cell allows studies in the pressure range up to 5 kbar and temperatures between10K and ambient for instance, to study clathrates. The uni-axial stress-rig CRATES, built by the Technical University Hamburg-Harburg, Germany, allows the study of crystal lattice strains and texture changes in situ during deformation. HIPPO?s sample chamber also accommodates user-provided sample environments.
- HIPPO (High Pressure-Preferred Orientation) is a general purpose neutron time-of-flight powder diffractometer. The short distance of 8.8 m between the high-flux water moderator and the sample provides a neutron flux at the sample position of over 10(exp 7) neutrons/cm2/s (at a proton current of 100 μA). After a re-configuration in 2011, at present 1240 (exp 3)He detector tubes are arranged on 53 detector panels on 5 rings with nominal diffraction angles between 40° to 144°. The combination of high flux and large detector coverage makes HIPPO very efficient for the acquisition of datasets for crystal structure refinements and allows for kinetic studies with temporal resolutions of the orders of minutes or better in some cases. The large number of detector panels probes many sample directions simultaneously, allowing to measure the orientation distribution (texture) of grains in a polycrystalline aggregate with only two or three sample rotations around the vertical axis. A new six-axis robotic sample changer with a capacity of >100 samples for efficient collection of datasets for crystal structure and texture measurements at ambient conditions was commissioned in 2012. A large number of sample environments for HIPPO allows investigations of crystal structure, phase composition or texture at temperatures above (up to 2500 K) and below (7 K) room temperature, at high pressures (8 kbar in gas pressure cells, 8GPa in the TAP98 toroidal anvil press), under applied uni-axial load (up to 100 kN), or in a magnetic field (up to 2 T). Combinations of these, e.g. 5 kbar/10 K in gas pressure cells, 8 GPa/2000 K in TAP98, uni-axial deformation at up to 1200 K, controlled atmosphere at 1000 K, or magnetic fields at 100 K are also available to users. Many of these sample environments allow sample rotation for texture measurements to investigate e.g. phase transformation textures between 10 K and 2500 K or during uni-axial deformation at Temperatures up to 1200 K. User-specific sample environments can be provided by users or can be developed in collaborative efforts. The short flight-path and the 20 Hz repetition rate of the spallatin target provides exceptionally an large d-spacing range from 0.12 ？ to 22 ？. Besides conventional Rietveld analysis, typically using the GSAS or MAUD packages, pair-distribution function (PDF) analysis or maximum entropy method (MEM) analysis were successfully applied to HIPPO data. Engineering diffraction analysis, e.g. single peak fitting for lattice-plane dependent strain evolution or texture analysis, are routinely available.