Speaker
Description
The first horizontal-geometry liquid neutron reflectometer (LNR) of China is now being constructed in China Spallation Neutron Source (CSNS), which is designed to complement the existing vertical-geometry reflectometer and address the urgent demand for in-situ characterization of gas-liquid, liquid-liquid, and solid-liquid interface structures in colloid chemistry, biomedicine, advanced energy, friction, corrosion, and other research fields.
The physical design of this instrument has been fixed since May 2026 and is currently in the engineering design phase. Its crucial design specifications are as follows: the momentum transfer (q) coverage ranges from 0.04 to 6 nm⁻¹, the minimum measurable reflectivity is approximately 10⁻⁶, the resolution (Δq/q) ranges from 2% to 10%, and the neutron flux at the sample position is approximately 3×10⁷ n/cm²/s (@300 kW). The key engineering solutions are outlined below:
An optimized neutron guide system is adopted to pursue high neutron flux. In the vertical plane, a downward-tilting straight neutron guide with a natural dip angle of 1.3° is employed, while in the horizontal plane, an elliptical focusing neutron guide with an exit aperture of 50.5×30 mm is configured. This design improves the neutron flux at the sample position while maintaining the uniformity of the neutron beam.
A flexible incident optical path adjustment function is implemented. The instrument integrates a dual-mode configuration of slits set and mirrors, supporting upper-incident angles ranging from 0.2° to 5.3° and lower-incident angles ranging from -0.18° to -2.7°, thus achieving a wide q-value coverage.
Both reflectometry and grazing incidence small-angle neutron scattering (GISANS) modes are realizabled. The mirrors system can be interchanged with a collimations system, and the detector can be positioned along the beam path between 18 m and 21.5 m from the sample, which enable complete characterization of the three-dimensional structure of thin films.
Advanced spectrometer components will be configurated. A T0 chopper combined with shielding is used to suppress fast neutron background. A six DOF sample stage with dual vibration isolation mechanisms (load capacity: 500 kg, positioning accuracy: 0.01 mm) can meet the requirements of various sample environments. A large vacuum scattering chamber (6×2.5×3 m) can further reduces the background noise. A large-area high-performance ³He-GEM detector (600×1000 mm, position resolution ≤2 mm, detection efficiency ≥70%@6 Å) can enables full realization of all functions in one installation.
At present, detailed engineering designs of the neutron guides, shielding components and scattering chamber are in progress. The developments of sample environment equipments including the Langmuir trough, liquid-liquid/solid-liquid sample cells, and variable-temperature/high-pressure/vacuum devices are also being carried out simultaneously. The completion of this instrument will fill the blank in horizontal-geometry liquid interface neutron reflectometry research in China, and provide a unique in-situ research platform for soft matter, biological interfaces, and energy materials.
Key Words
Neutron reflectometer; Liquid interface; Engineering design; Neutron guide; GISANS; CSNS