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OffSpec

OffSpec is a low-background, time-of-flight neutron reflectometer with spin-echo capabilities for Larmor labelling. It enables nanometre-scale measurements parallel and perpendicular to interfaces, supporting diverse studies in biophysics, biochemistry and materials science.

A disc-shaped sample on the OffSpec instrument at the ISIS Neutron and Muon Source.
Neutron reflectometry
Instrument dashboard

Instrument scientists

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Team member

Mario Campana

Instrument scientist
A white man with glasses and ginger hair and beard

Stephen Hall

Instrument scientist

Technical information

The OffSpec reflectometer is designed to study surfaces and interfaces by analyzing 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)

Instrument highlights

Our facility supports a broad research programme that generates impact on a national and global scale. Browse through some of the recent research conducted using the OffSpec beamline.
Diagram showing red cubosomes and hexosomes interacting with a blue and red lipid bilayer
How do complex lipid nanoparticles interact with lipid membranes?
Diagram showing a bilayer, with green heads at the top and bottom and yellow tails between. The gp41 peptide is shown in purple, embedded in the membrane
Dehydration at the membrane interface drives HIV fusion
Cart​oon schematic that shows different surfactant-lipid bilayer interactions observed in the corneal epithelial cells
Protecting farmers’ eyes from pesticides
ISIS scientist Luke Clifton stands next to reflectometry machinery
Understanding programmed cell death — crucial to the body’s prevention of cancer
A 3D graph, showing a well
Maximising beamtime using applied statistics
​​​Image Credit: Pixabay
Can nanomagnetism be exploited for AI tasks?

Recent publications

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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.

Team member