NG2 HFBS

Instrument Purpose

To explore the "slow" atomic and molecular motions in condensed matter with sub-micro-electron volt precision, bridging the gap between structural and fast dynamics explored by Neutron Spin Echo and Time of Flight.

The NCNR Advantage

• Exceptional Energy Resolution: By utilizing a near-perfect backscattering geometry (𝜃 ≈ 90°), it achieves an energy resolution of < 1 eV, enabling the detection of molecular reorientations and diffusive motions occurring on nanosecond timescales.
• World-Leading Intensity: The HFBS is one of the highest-intensity instruments of its kind globally. It utilizes a unique Phase-Space Transformation (PST) chopper that provides a 4.2x gain in neutron flux, enabling the measurement of small samples or those with a weaker neutron scattering cross-section.
• Unmatched Dynamic Range: Features a high-speed Doppler-driven monochromator that extends the accessible energy transfer to ±50 μeV, more than that of typical reactor-based backscattering spectrometers.
• Low-Background Vacuum Design: Unlike most similar instruments, the entire scattering chamber operates under vacuum, significantly reducing air scattering and improving the signal-to-noise ratio for delicate biological and soft-matter samples.

Research Domains

• Liquids: Probing the diffusion, rotations and molecular relaxations in simple and glassy liquids.
• Polymers and Polymer Blends: Investigating segmental and chain dynamics as well as rotations and tunneling of side groups.
• Biological Systems: Internal motions of biomolecules along with the dynamics of surrounding hydration water. In membranes, lipid dynamics is probed, including molecular rotation, lateral diffusion, and thickness fluctuations.
• Chemical Physics: Investigating hydrogen storage materials, molecular tunneling, and the diffusion of water in nanoporous minerals (e.g., zeolites, clays).
• Energy Materials: Tracking ion hopping and diffusion mechanisms in solid-state battery conductors. Organic cation dynamics and proton/ion diffusion in perovskites.
• Magnetic Materials: Probing low-energy magnetic excitations.

What You Can Measure

• Quasielastic Neutron Scattering (QENS): Quantifying both diffusive and localized motions, as well as relaxation times.
• Fixed Window Scans (FWS): Identifying " transitions" as a function of temperature in materials (e.g., finding the onset of molecular dynamics and phase transitions).
• Inelastic Tunneling: Observing the quantum rotational tunneling of small molecules like methane or methyl groups.