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OffSpec
OffSpec is a high-resolution, low-background reflectometer for studying the structure of thin films and buried interfaces with exceptional sensitivity. It supports research on complex multilayer materials, polymers, biological membranes and functional coatings, helping scientists understand nanoscale structures that underpin new technologies for healthcare, energy and advanced manufacturing.
Instrument scientists
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Technical information
The OffSpec reflectometer is designed to study surfaces and interfaces by analysing the reflection of thermal neutrons.
The system under investigation lies in a horizontal plane, with reflection occurring in the vertical plane. A position-sensitive detector enables precise analysis of scattering patterns, allowing for comprehensive off-specular reflectometry. This includes both:
- Specular reflection: measurement of reflectivity under Snell’s condition, as a function of the momentum transfer modulus.
- Non-specular reflection: measurement of diffuse scattering in the vertical plane, as a function of the momentum transfer vector.
Specialised cells are available for reflectance measurements at various interfaces, including liquid-air, liquid-solid, air-solid, and liquid-liquid. OffSpec operates within a neutron wavelength range of 1.5–14 Å and offers incident angles between 0.4° and 4°, covering a broad range of q-values.
Instrument parameters
| Moderator | Coupled Grooved H2/CH4 |
| Detectors | 1 x 300 mm linear scintillator detector 1.2mm pixel size 1 x 3He tube |
| Primary flight path, L1 | 23.7 m |
| Secondary flight path, L2 | 3.2 m (3He tube) or 3.6 m (Linear Scintillator) |
| Resolution | ~2-5% ΔQz/Qz |
| Incident wavelengths | 1.5-14.5 Å |
| Choppers | Counter – rotating disc chopper (10 Hz) |
Recent publications
Instrument reference
All publications and datasets based on experiments using OffSpec should cite that the data is collected by DOI: 10.5286/isis.instrument.4071. Experiment DOIs follow the format 10.5286/ISIS.E.RBXXXXXXX, where XXXXXXX is the 7-digit experiment (RB) number and these can be viewed via the Data Gateway.