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Larmor

Larmor explores an extraordinary range of length scales, from the spacing between atoms to the width of a human hair. By combining conventional neutron scattering with advanced techniques that exploit the fundamental properties of the neutron, it enables researchers to study a diverse range of systems, including foods, battery components, next-generation automotive steels, artificial skin, personal care products, vaccine delivery systems and quantum materials for data storage. These insights are helping to save energy, reduce waste, improve healthcare and create more reliable technologies.

Technical information

Larmor is capable of operating in a number of different measurement configurations. Currently, SANS and SESANS are the primary operating modes. In order to swap between these configurations, it takes of the order of 2 to 3 hours after which the instrument must then be checked and calibrated. As a result, mode switching within an experiment is not encouraged although it is possible. Two v-cavity polariser options are available, allowing access to different wavelength ranges, and an additional MEOP polarised 3He cell can be installed for fully polarised SANS measurement. A supermirror bender is used to analyse the beam for SESANS measurements.

SANS mode

 

Incident wavelengths 0.9 – 13.0 Å or 0.5 – 12.5 Å unpolarised
1.9 – ~10.0 Å polarised with polariser 1
3.0 – 13.0 Å polarised with polariser 2
Momentum transfer, Q 0.0035 – 0.7 Å-1 with the beam centred in the middle of the detector
0.0035 – 1.0 Å-1 with the beam offset at 2° (sample-to-detector preset distance 4m fixed)
Polariser Larmor has a polarised beam option with a supermirror V cavity and a RF gradient spin flipper. Upon request, polarisation analysis with a 3He spin analyser is available from ISIS Polarisation group.
Detector The main SANS detector consists of an array of 80 x 600 mm2-long position-sensitive 3He tubes with an angular coverage of ~4° (vertical) x up to 8° (with horizontal offset), located 4.4 m from the sample.

A high-count rate detector of 38 x 50 mm2 in size is installed for SESANS measurements.

A 1-dimension high-angle detector can be installed for wide-angle diffraction measurements.

Sample Area Sample-to-detector fixed distance: 4m.
Larmor is unique having a large sample area capable of installing a range of different sample environment and associated hardware.
Beam size Defined by sample apertures final collimation. Up to 15 x 15 mm2 is possible, typically an 8 x 8 mm2 is used. Smaller apertures are available, please discuss with an instrument scientist for further information.

SESANS mode

Typically, SANS can measure length scales of the order a few 100 nms. To go to larger length scales can be achieved using a combination of magnetic fields and a polarised neutron beam.

A nice gentle introduction is written by one of our collaborators and regular users, this is focused on food research but covers the technique in detail for new users:
Spin-echo small-angle neutron scattering for multiscale structure analysis of food materials

 

We also work with teams across other institutes to refine and develop this technique along with pictures illustrating what the SESANS setup looks like and a brief introduction:
Data Reproducibility of Spin-Echo Small-Angle Neutron Scattering Instruments

 

Some recent examples include combining SANS and SESANS to look at emulsions:
RipeningofNonaqueousEmulsionsofn‑DecaneinDimethyl SulfoxideObservedbyTime-ResolvedSpin-EchoSmall-Angle NeutronScattering(SESANS)

 

Looking at solubility in solar cells:
Different agglomeration properties of PC61BM and PC71BM in photovoltaic inks – a spin-echo SANS study

 

 

Incident wavelengths 1.9 – ~10.0 Å polarised with polariser 1
3.0 – 13.0 Å polarised with polariser 2
Spin-echo length We can access a range of spin echo lengths by varying the pole shoe angle and magnetic field strength/RF frequency. These are typically

0.5MHz: ~50nm to 6micron (80degrees to 40degrees)
1.0MHz: ~100nm to 12micron (80degrees to 40degrees)
2.0MHz: ~200nm to 24micron (80degrees to 40degrees)
– Higher frequencies of 3MHz can be used however with limitations on bandwidth and should be discussed with the Larmor instrument scientist prior to submitting a proposal

Polariser In SESANS mode Larmor uses a polarised beam with a supermirror V cavity and a RF gradient spin flipper and a supermirror array as the analyser. Note that due to using a polarised neutron beam this method is not compatible with magnetic samples.
Detector A high-count rate detector of 38 x 50 mm2 in size is installed for SESANS measurements.
Sample Area Sample-to-detector fixed distance: 4m.
Larmor is unique having a large sample area capable of installing a range of different sample environment and associated hardware.
Beam size Defined by sample apertures final collimation. Up to 15 x 15 mm2 is possible, typically an 8 x 8 mm2 is used. Smaller apertures are available, please discuss with an instrument scientist for further information.

Related resources

Larmor is part of the SANS instrument suite at ISIS together with: Zoom, SANS2D, Loq.

Sample preparation and sample environment

SANS quartz cells information can be found on the SANS technique page.

Information about the ISIS Soft Matter team can be found on the sample environment page.

Latest publications

Instrument reference

All publications and datasets based on experiments using Larmor should cite that the data is collected by DOI: 10.5286/isis.instrument.5418. 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.