The Multi-Axis Crystal Spectrometer at the NIST Center for Neutron Research is a third generation cold neutron spectrometer that provides ultra high sensitivity access to dynamic correlations in condensed matter on length scales from 0.1 nm to 50 nm and energy scales from 2.35 meV to 16 meV. The project is funded jointly by the NIST Center for Neutron Research, the National Science Foundation, and the Johns Hopkins University.
The Multi-Axis Crystal Spectrometer takes advantage of the large solid angle view of the cold source to deliver a high intensity neutron beam at sample position. The large doubly focusing PG monochromator can deliver up to 5x108 neutrons/cm2/s in a 2 cm x 4 cm area at sample position, providing one of the highest neutron beam in the world. Between the monochromator and the sample there is a focusing super-mirror guide that enhances the flux on sample by approximately 20%. Upstream of the monochromator there is a variable beam aperture that controls the overall angular distribution of neutrons that is incident on the sample. There are also radial collimators that control the energy resolution. It is a remarkable aspect of MACS that the Q and E resolution can be controlled virtually independently through these remote controlled devices. The detection system for MACS consists of twenty independent monochromatic channels with variable final energy. There is also an energy integrating detector in each channel. These channels operate simultaneously and in doing so provide 0.15 Sr monochromatic detection plus 0.15 Sr diffraction detection. This is more than an order of magnitude gain in detection efficiency for surveys as compared to a conventional TAS.
Actual MACS configuration:
Incident energy: 2.3 to 17 mev
Energy resolution: 0.05 to 1.4 meV (FWHM)
Monochromator: Doubly focusing PG002
Analyzer: 20 analyzers vertically focusing PG(002) providing 0.15 Sr of detection. Cooled Be, BeO and HOPG filterss and 90' collimators before the analyzers.
Detector: 40 He detectors (20 spectroscopic and 20 diffraction detectors)
Flux at sample: 5x108 neutrons/cm2-s at 12meV open collimator
Novel State of Matter: Observation of a Quantum Spin Liquid
A novel and rare state of matter known as a quantum spin liquid has been empirically demonstrated in a monocrystal of the compound calcium-chromium oxide by team at HZB. What is remarkable about this discovery is that according to conventional understanding, a quantum spin liquid should not be possible in this material. A theoretical explanation for these observations has now also been developed. This work deepens our knowledge of condensed matter and might also be important for future developments in quantum information. The results have just been published in Nature Physics. Details
NIST Contributes to Discovery of Novel Quantum Spin-Liquid
An international team of researchers including scientists from the National Institute of Standards and Technology (NIST) has found what may be the first known example of a "spin-orbital liquid," a substance in a never-before-seen quantum mechanical state. Details.
For Newly Discovered 'Quantum Spin Liquid', the Beauty Is in Its Simplicity.
A research team including scientists from the National Institute of Standards and Technology (NIST) has confirmed long-standing suspicions among physicists that electrons in a crystalline structure called a kagome (kah-go-may) lattice can form a "spin liquid," a novel quantum state of matter in which the electrons' magnetic orientation remains in a constant state of change. Details.
Neutron scattering experiments clarify mechanism of piezoelectricity in PMN.
Piezoelectrics—materials that can change mechanical stress to electricity and back again—are everywhere in modern life. Computer hard drives. Loud speakers. Medical ultrasound. Sonar. Though piezoelectrics are a widely used technology, there are major gaps in our understanding of how they work. Now researchers at the National Institute of Standards and Technology (NIST) and Canada's Simon Fraser University believe they've learned why one of the main classes of these materials, known as relaxors, behaves in distinctly different ways from the rest and exhibit the largest piezoelectric effect. And the discovery comes in the shape of a butterfly. . Details.