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ISIS Neutron and Muon Source
ISIS Neutron and Muon Source
ISIS Neutron and Muon Source
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ISIS Neutron and Muon Source
Location:Rutherford Appleton Laboratory, United Kingdom
Scientific Purpose:Supports national and international community of around 3000 scientists who use neutrons and muons for research in physics, chemistry, materials science, engineering, biology and more.
Organisation:Owned and operated by the Science and Technology Facilities Council part of United Kingdom Research and Innovation.
Website:isis.stfc.ac.uk
Science with neutrons
Foundations
Neutron scattering
Other applications
Infrastructure
Neutron facilities

The ISIS Neutron and Muon Source is a pulsed neutron and muon source, established 1984 at the Rutherford Appleton Laboratory of the Science and Technology Facilities Council, on the Harwell Science and Innovation Campus in Oxfordshire, United Kingdom. It uses the techniques of muon spectroscopy and neutron scattering to probe the structure and dynamics of condensed matter on a microscopic scale ranging from the subatomic to the macromolecular.

Hundreds of experiments are performed every year at the facility by researchers from around the world, in diverse science areas such as physics, chemistry, materials engineering, earth sciences, biology, and archaeology.[1]

Background physics

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Neutrons are uncharged constituents of atoms and penetrate materials well, deflecting only from the nuclei of atoms. The statistical accumulation of deflected neutrons at different positions beyond the sample can be used to find the structure of a material, and the loss or gain of energy by neutrons can reveal the dynamic behaviour of parts of a sample, for example diffusive processes in solids. At ISIS, the neutrons are created by accelerating "bunches" of protons in a synchrotron, then colliding these with a tungsten target, under a constant cooling load to dissipate the heat from a 160 kW proton beam. The impacts cause neutrons to spall off the tungsten atoms, and the neutrons are channelled through guides, or beamlines, to around 20 instruments, each individually optimised for the study of different types of interactions between the neutron beam and matter. The target station and most of the instruments are set in a large hall. Neutrons are a dangerous form of radiation, so the target and beamlines are heavily shielded with concrete.[citation needed]

ISIS Neutron and Muon Source produces muons by colliding a fraction of the proton beam with a graphite target, producing pions which decay rapidly into muons, delivered in a spin-polarised beam to sample stations.[citation needed]

History

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The source was approved in 1977 for the RAL site on the Harwell campus and recycled components from earlier UK science programmes, including the accelerator hall which had previously been occupied by the Nimrod accelerator. The first beam was produced in 1984, and the facility was formally opened by the then Prime Minister Margaret Thatcher in October 1985.[2][1][3]

The name ISIS is not an acronym: it refers to the Ancient Egyptian goddess and the local name for the River Thames. The name was selected for the official opening of the facility in 1985; prior to this it was known as the SNS, or Spallation Neutron Source. The name was considered appropriate as Isis was a goddess who could restore life to the dead, and ISIS made use of equipment previously constructed for the Nimrod and NINA accelerators.

The second target station was given funding in 2003 by Lord Sainsbury, then science minister, and was completed in 2009, on time and budget, with the opening of 7 instruments. In March 2011, the Science Minister, David Willetts, gave a £21 million investment[4] to build 4 new instruments, which are now[when?] all in their commissioning phase or fully scheduled instruments.[1]

ISIS Neutron and Muon Source was originally expected to have an operational life of 20 years (1985 to 2005), but its continued success led to a process of refurbishment and further investment, intended to advance the facility and extend the life of ISIS through to 2030.[5]

According to its Annual Report from 2017 to 2018, STFC expects the end of the ISIS pulsed neutron source and the associated Second Target Station to be in 2040 and anticipates decommissioning to take 55 years. The cost of radioactive waste disposal could range between £9 million and £16 million.[6]: 51 

Science

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ISIS Neutron and Muon Source is administered and operated by the Science and Technology Facilities Council (previously CCLRC). The Science and Technology Facilities council, or STFC, is part of UK Research and Innovation. Experimental time is open to academic users from funding countries and is applied for through a twice-yearly "call for proposals". Research allocation, or "beam-time", is allotted to applicants via a peer-review process. Users and their parent institutions do not pay for the running costs of the facility, which are as much as £11,000 per instrument per day. Transport and living costs are covered for those associated with UK Universities. Most users stay in Ridgeway House, a hotel near the site, or at Cosener's House, an STFC-run conference centre in Abingdon. Over 600 experiments by 1600 users are completed every year.

A large number of support staff operate the facility, aid users, and carry out research. The control room is staffed 24 hours a day, every day of the year. Instrument scientists oversee the running of each instrument and liaise with users, and other divisions provide sample environment, data analysis and computing expertise, maintain the accelerator, and run education programmes. ISIS is also one of the few neutron facilities to have a significant detector group that researches and develops new techniques for collecting data.

Among the important and pioneering work carried out was the discovery of the structure of high-temperature superconductors and the solid phase of buckminsterfullerene. Other recent developments can be found here.

Construction for a second target station (TS2) started in 2003, and the first neutrons were delivered to the target on December 14, 2007.[7] TS2 uses low-energy neutrons to study soft condensed matter, biological systems, advanced composites and nanomaterials.

The synchrotron itself hosted the International Muon Ionization Cooling Experiment (MICE) for parasitic running[8] from 2008 to 2018. MICE replaced the earlier HEP Test Beam.[9]

Neutron and muon instruments

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The instruments currently at ISIS Neutron and Muon Source are:[10]

Target Station 1

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ISIS Neutron and Muon Source experimental hall Target Station 1
  • Alf is a crystal alignment facility.
  • Crisp is a neutron reflectometer designed for high-resolution studies of a wide range of interfacial phenomena.
  • Engin-X is a neutron diffractometer optimised for the measurement of strain, and thus stress, deep within a crystalline material.
  • Gem is a neutron diffractometer that can perform high-intensity, high-resolution experiments to study the structure of disordered materials and crystalline powders.
  • Hrpd is a neutron diffractometer which is one of the highest-resolution neutron powder diffractometers of its type in the world.
  • Ines is a neutron powder diffractometer, built and managed by the Italian National Research Council (CNR) within the cooperation agreement with STFC.
  • Iris is a neutron spectrometer, designed for quasi-elastic and low-energy high-resolution inelastic spectroscopy.
  • LOQ is a small-angle neutron scattering instrument used to investigate the shape and size of large molecules, small particles, or porous materials with dimensions typically in the range of 1–100 nm.
  • Maps is a neutron spectrometer, primarily designed to tackle magnetic and structural excitations in single crystals.
  • MARI is a neutron spectrometer, ideal for the study of phonon densities of states in crystalline and disordered systems, and crystal field excitations in magnetic materials.
  • Merlin is a neutron spectrometer with a high-count-rate, medium-energy-resolution, direct-geometry chopper spectrometer.
  • Osiris can be used as a neutron spectrometer or diffractometer. It is optimised for very low-energy studies and long-wavelength diffraction.
  • Pearl is a neutron diffractometer dedicated to high-pressure powder diffraction.
  • Polaris is a neutron diffractometer optimised for the rapid characterisation of structures, the study of small amounts of materials, the collection of data sets in rapid time, and the studies of materials under non-ambient conditions.
  • Rotax is used for detector and equipment tests.
Another view of ISIS Neutron and Muon Source experimental hall Target Station 1
  • SANDALS is a neutron diffractometer especially built for investigating the structure of liquids and amorphous materials.
  • SURF is a neutron reflectometer and one of the leading instruments in the world for liquid interface research.
  • SXD is a neutron diffractometer which is powerful in applications involving surveys of reciprocal space, such as phase transitions and incommensurate structures, and also in applications where sample orientation may be restricted.
  • Tosca is a neutron spectrometer optimised for the study of molecular vibrations in the solid state.
  • Vesuvio is a neutron spectrometer which uses the high intensity of neutrons in the eV energy range (epi-thermal neutrons) to mass-separate the spectra into a collection of nuclear momentum distributions.
  • EMU is a μSR spectrometer, optimised for zero-field and longitudinal-field measurements.
  • MuSR is a μSR spectrometer which can be rotated through 90 degrees to enable both longitudinal and transverse measurements to be made.
  • HIFI is a high-field muon instrument that provides applied longitudinal fields up to 5T.
  • Argus is a muon spectrometer for condensed matter and molecular studies.
  • CHRONUS is a muon instrument on the Japanese-owned RIKEN-RAL Muon Facility.
ISIS Neutron and Muon Source Target Station 2
ISIS Neutron and Muon Source's second target station.

Target Station 2

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  • ChipIR is a chip irradiation instrument dedicated to the irradiation of microelectronics with atmospheric-like neutrons.
  • IMAT is a neutron imaging and diffraction instrument for materials science, materials processing, and engineering.
  • Inter is a high-intensity chemical interfaces reflectometer offering a unique facility for the study of a range of air/liquid, liquid/liquid, air/solid, and liquid/solid interfaces.
  • Larmor is a flexible, small-angle neutron scattering instrument that has been optimised for the development of new neutron scattering techniques which use the Larmor precession of neutrons to encode energy or direction.
  • LET is a neutron spectrometer optimised for the study of dynamics in condensed matter to understand the microscopic origin of material properties.
  • NIMROD is a neutron diffractometer designed to access length scales ranging from the interatomic (< 1 Å) through to the mesoscopic (>300 Å).
  • Offspec is a neutron reflectometer that gives access to nanometre length scales parallel and perpendicular to interfaces.
  • Polref is a neutron reflectometer designed for the study of the magnetic ordering in and between the layers and surfaces of thin-film materials.
  • Sans2d is a small-angle neutron scattering instrument that can be used to examine size, shape, internal structure, and spatial arrangement in nanomaterials, "soft matter", and colloidal systems, including those of biological origin, on length scales of 0.25–300 nm.
  • Wish is a neutron diffractometer designed for powder diffraction at long d-spacing in magnetic and large-unit-cell systems, with the option of enabling single-crystal and polarised-beam experiments.
  • Zoom is a flexible, high-count-rate small-angle scattering instrument.
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The final episode of series 1 of the Sparticle Mystery was filmed on site. The site is also referenced in the book Itch Rocks.[11]

References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

ISIS Neutron and Muon Source

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from Grokipedia
The ISIS and Source is a world-leading pulsed and facility located at the (STFC) Rutherford Appleton Laboratory in , , dedicated to probing the atomic-scale structure and dynamics of materials for applications in physical, chemical, life, and engineering sciences. Operated by the STFC as the UK's national research center for and techniques, it enables non-destructive studies of complex systems, from batteries and to biological molecules and cultural artifacts, supporting 1,673 unique users in 2025 from academia and industry across more than 30 countries. Established in with the production of its first neutrons on of that year, ISIS originated from repurposed infrastructure of the earlier at the Rutherford Appleton and was officially named and opened by in October 1985. Key milestones include energy upgrades from an initial 550 MeV to 800 MeV by 1990, the addition of a second target station in 2008 to expand neutron capabilities with short-pulse beams, and ongoing enhancements like the £93 million Endeavour programme, which is developing new instruments such as Super MuSR and HRPD-X for completion by 2028. These developments have positioned ISIS as one of the world's most powerful pulsed sources, with an average accelerator availability of 87.5% and operations running in cycles totaling around 200 days per year. At its core, ISIS operates an 800 MeV accelerator that delivers intense pulses at 50 Hz onto targets, generating s through nuclear reactions and s via a secondary carbon foil, which are then moderated and directed along beamlines to experimental instruments. The facility features two target stations: the original for long-pulse s and s, and the second for short-pulse s optimized for high-resolution studies. This setup supports a diverse suite of over 30 and instruments, including diffractometers like HRPD for , spectrometers like MAPS for , and imaging tools for engineering applications, allowing researchers to apply for free beamtime through a competitive peer-review process. In 2025, ISIS received 1,402 proposals and delivered 3,879 instrument days, resulting in 559 peer-reviewed publications with significant international collaboration. ISIS's research has profound impacts, addressing global challenges such as through studies on battery degradation and , quantum technologies via investigations of spin liquids, and health innovations like mRNA delivery systems. The facility fosters a vibrant user community of approximately 3,000 scientists yearly, including 37% students, and engages industry partners—reaching 90 companies in 2025—while contributing to with an estimated £0.4 billion in future impacts from prior research. Looking ahead, initiatives like the ISIS-II project are exploring next-generation designs to sustain leadership in and science beyond 2040.

Overview and Background

Facility Description

The ISIS Neutron and Muon Source is located at the (STFC) Rutherford Appleton Laboratory on the in , . It is owned and operated by the STFC as part of (UKRI), serving as the UK's national facility for neutron and muon-based materials research. The facility provides non-destructive techniques to probe atomic structures and dynamics in fields ranging from physics to , enabling scientists worldwide to conduct experiments at the atomic scale. At the core of the facility is the ISIS , an 800 MeV proton accelerator that delivers intense pulses of protons at a rate of 50 Hz. These protons strike a target to produce s through , while s are generated via the decay of pions produced in a secondary process. This pulsed beam setup supports a suite of over 30 neutron and muon instruments, allowing time-resolved studies of material properties. Annually, the facility supports approximately 1,673 unique users through 1,402 approved proposals, with beam time allocated through a competitive, peer-reviewed proposal process. Access is free for academic researchers, whose results must be published openly, while industry users can request confidential sessions. The user community includes 37% students and researchers from academia, alongside collaborators from industry—such as the 90 companies hosted each year—and international partners, with 73.3% of journal publications involving international collaboration from over 30 countries.

Fundamental Physics

The ISIS Neutron and Muon Source relies on the spallation process for production, in which high-energy protons accelerated to 800 MeV in the strike a target, dislodging s from the atomic nuclei through nuclear collisions. Each incident proton typically ejects 25–30 fast s in this process, resulting in a yield of approximately 6–8 × 10^{14} s per pulse given the facility's beam of about 2.5 × 10^{13} protons per pulse. These fast s, initially possessing energies comparable to the proton beam, are then moderated—slowed down—to or energies suitable for experiments; light water moderators produce a around 25 meV, while moderators yield a colder peaking below 5 meV. Muon production at ISIS occurs via a secondary interaction where a fraction (2–3%) of the 800 MeV proton beam is directed onto a target, generating charged s through proton-carbon collisions; these pions, with a mean lifetime of 26 ns, subsequently decay into positive and negative muons along with neutrinos. The resulting muons, which inherit polarization from the pion decay, are captured, accelerated, and transported to beamlines for implantation in samples, with delivery energies tunable up to 80 MeV to enable depth-profiling and in condensed matter studies. The pulsed operation of the ISIS accelerator, delivering proton bunches at a 50 Hz repetition rate, underpins the time-of-flight (TOF) technique central to measurements. In TOF, the known start time of each allows determination of individual from their flight times to detectors, providing broad coverage and resolution without the need for mechanical selectors or choppers. This pulsed structure enhances efficiency for dynamic experiments, as the short (∼100 ns) minimizes overlap in arrival times for neutrons spanning thermal to epithermal . The efficiency of neutron production scales approximately with proton as Yn≈k⋅Ep1.8Y_n \approx k \cdot E_p^{1.8}, where YnY_n is the yield, EpE_p is the proton in GeV, and kk is an empirical constant dependent on target material; at ISIS's 0.8 GeV, this scaling underscores the choice of for balancing yield and accelerator feasibility.

Historical Development

Origins and Establishment

The conception of the ISIS Neutron and Muon Source emerged in the 1970s at the Rutherford Appleton Laboratory, driven by the need to replace the aging proton synchrotron, which had operated from 1964 to 1978 but suffered from reliability issues and insufficient neutron flux for advanced materials research. 's closure highlighted the demand for a pulsed capable of delivering higher neutron brightness, leveraging accelerator technology to produce intense, short pulses of neutrons via proton bombardment of a heavy metal target. government approval for the project came in 1977, with construction funded through the Science Research Council (predecessor to the ), utilizing repurposed infrastructure from , including its synchrotron hall and some magnets, to accelerate development and reduce costs. Officially established in 1984, the facility featured a proton accelerator system designed for 800 MeV, comprising a 70 MeV linear accelerator (linac) originally built in the as a Nimrod injector, a rapid-cycling , and a single target station (TS1) using a target to generate neutrons through . The proton beam was first commissioned on December 16, , producing the initial neutrons at an energy of 550 MeV and a repetition rate of 50 Hz, with an initial beam power of approximately 100 kW. The facility was formally opened on October 18, 1985, by Prime Minister , who named it ISIS—standing for Intense Source—a moniker chosen to evoke the Egyptian goddess of magic and the nearby River Isis (the upper Thames), replacing its provisional designation as the Neutron Source. Early operations focused on achieving reliable production for initial experiments in physics and , with the first experiments commencing in at TS1 beamlines. However, challenges included stabilizing the 50 Hz pulsing rate amid synchrotron injection inefficiencies and ensuring target durability, as the uranium targets experienced swelling and degradation under the intense proton , necessitating frequent replacements and material refinements. These hurdles were gradually addressed through incremental upgrades, such as increasing beam energy to 750 MeV by 1987 and to 800 MeV by 1990, laying the groundwork for sustained operations while prioritizing conceptual advancements in spallation-based generation over exhaustive performance metrics.

Major Expansions and Upgrades

Following its initial operations, the ISIS facility underwent key upgrades in the to enhance its capabilities, including an increase in beam current to 200 μA by , achieving an average beam power of approximately 160 kW. This improvement, driven by accelerator enhancements such as upgraded RF systems and developments, significantly boosted production efficiency via processes. Concurrently, the muon program expanded from its inception, with the first dedicated operational since 1987 using a production target; a major rebuild of the primary in 2008 quadrupled the available flux, enabling broader applications in . The most transformative infrastructural project was the Second Target Station (TS2), approved for funding in 2003 at a total cost of £170 million, with construction spanning 2004 to 2008 and full operations commencing in 2009. Unlike the original Target Station 1, TS2 was designed to deliver short-pulse neutrons optimized for time-of-flight techniques in areas like soft condensed matter, providing up to 20% of the proton beam pulses for higher-resolution studies. In 2011, a further £21 million investment from the government supported the construction of four new instruments on TS2, along with upgrades to detectors and the target reflector system, while extending the facility's projected lifespan from 2005 to 2030. Subsequent optimizations focused on accelerator reliability and , with beam power reaching approximately 200 kW through incremental improvements. In 2023, the £93 million Endeavour programme was approved to develop advanced instruments such as Super MuSR and HRPD-X, with user operations targeted for 2028. Additional enhancements included the commissioning of a decoupled moderator at TS2 in June 2024 to improve resolution on the WISH instrument and the replacement of the TS2 proton beam window in January 2025. Looking ahead, planning documents outline a phased decommissioning of the facility by 2040 to manage from targets, with site restoration costs estimated at £9 million to £16 million.

Research and Applications

Scientific Disciplines

The ISIS Neutron and Muon Source supports research across diverse scientific disciplines by leveraging and beams to probe the atomic and molecular structures, dynamics, and properties of materials in a non-destructive manner. These capabilities enable investigations that are complementary to other techniques, such as diffraction, by providing sensitivity to light elements like and magnetic interactions. In physics and , and muons facilitate the study of structures, magnetic ordering, and quantum phenomena in materials like superconductors and magnets. For instance, reveals lattice dynamics and phase transitions, while muons help characterize spin correlations and electronic properties at the atomic scale. These approaches are crucial for advancing understanding of condensed matter systems and developing next-generation quantum technologies. Chemistry and engineering research at ISIS focuses on molecular-level interactions in functional materials, including catalysts for chemical reactions, battery electrodes for , and polymers for structural applications. Neutrons excel at tracking positions and bond vibrations, which inform the design of more efficient and durable materials for . In and sciences, neutron techniques elucidate the conformations of proteins, the organization of lipid membranes, and the self-assembly in systems. By contrast-matching with labeling, researchers can isolate specific components in complex biological environments, yielding insights into molecular motions and interactions relevant to and . Archaeology and cultural heritage studies benefit from the non-invasive nature of neutron-based analysis to examine the composition and degradation of ancient artifacts, such as metals and ceramics, without causing damage. This allows for the identification of manufacturing techniques and environmental impacts on historical objects, supporting preservation efforts and historical interpretations. Muon applications, including muon spin rotation (μSR), provide specialized probes for magnetism in diverse materials and depth-resolved profiling in semiconductors. In μSR, implanted muons act as sensitive indicators of local magnetic fields and spin dynamics, while low-energy muons enable layer-by-layer analysis of dopant distributions and defects in electronic materials. Access to ISIS beam time is granted through a rigorous peer-review process conducted by Facility Access Panels, comprising international experts who assess proposals on scientific merit, feasibility, and potential impact. This system ensures equitable allocation to a global user community of approximately 3,000 scientists yearly, with 1,673 unique users in 2025 (37% students), resulting in 559 peer-reviewed publications that year, with 73.3% featuring international co-authors.

Key Achievements and Impacts

One of the landmark discoveries enabled by research at the ISIS Neutron and Muon Source was the elucidation of the structure and dynamics of (C60), conducted in the 1990s using neutron diffraction and techniques. Similarly, in the 1980s, neutron at ISIS revealed the crucial role of magnetic interactions in high-temperature superconductors, advancing the understanding of materials and contributing to the broader field recognized by the 1987 . In energy research, ISIS studies have provided insights into battery degradation mechanisms, such as the three-phase discharge processes in sodium-ion batteries and the ageing of niobium-based anodes, supporting the development of longer-lasting solutions. and techniques have also examined hydrogen dynamics in storage materials, including cycling in metal hydrides for Toyota's applications, aiding the transition to a . Biological advances from ISIS include neutron scattering investigations into mRNA vaccine delivery, where small-angle neutron scattering on beamlines like Zoom and SANS2D revealed the formation of stable polyethylenimine-saRNA nanoparticles, enhancing efficacy and manufacturability for vaccines in collaboration with and EMBL. Additionally, neutrons have elucidated functions, such as the relay-like electron transfer in , which is key to processes. Industrial applications have been significant, with ISIS collaborating with 90 companies (as of 2025), including principal investigators from sectors like pharmaceuticals and aerospace, leading to innovations such as improved systems by and enhanced inertia for Rolls-Royce aircraft engines used in and models. Over its lifetime, ISIS research has contributed to more than 10,000 peer-reviewed publications by 2019, with approximately 600 new publications annually across disciplines, fostering high-impact science cited thousands of times. In 2025, ISIS scientists received the Royal Society of Chemistry's Dalton Horizon Prize for pioneering hybrid glasses and the Materials Chemistry Horizon Prize for developing ChemDataExtractor, a chemistry-aware AI software for materials discovery. Public engagement efforts at ISIS reached 8,260 participants in 2025 through nearly 50 events, including school programs and work experience for 32 students, inspiring the next generation in STEM.

Instrumentation

Target Station 1

Target Station 1 (TS1) is the original neutron production facility at the Neutron and Source, optimized for delivering long-pulse beams that enable high-resolution studies of crystalline and hard materials. It produces thermal and neutrons through of an 800 MeV proton beam on a tantalum-clad target, moderated to provide neutrons suitable for , , and applications. TS1 supports approximately 25 instruments, focusing on high and precision measurements for fields such as , , and analysis. Key instruments on TS1 include the General Materials Diffractometer (GEM), which performs high-intensity, high-resolution and pair distribution function for studying both crystalline and disordered materials. The High-Resolution (HRPD) offers exceptional resolution for structural refinements in samples, utilizing a long flight path from the 110 K moderator. , a time-of-flight , is tailored for applications, enabling rapid of large samples under applied stress or temperature. For , MARI serves as a direct-geometry chopper spectrometer for inelastic , probing magnetic and lattice dynamics in materials. IRIS and facilitate quasi-elastic and low-energy inelastic studies, particularly for dynamics in hydrogenous systems like polymers and biomolecules. ENGIN-X specializes in strain scanning for measurements in components, while VESUVIO employs deep inelastic to investigate distributions in light elements such as . Additionally, the Italian Neutron Experimental Station (INES) supports non-destructive archaeometric , including phase identification and elemental mapping in artifacts without . The neutron beams from TS1 cover energies from approximately 10 meV to 1 eV, encompassing (below 10 meV) and regimes, with a typical flux of around 10^8 s per cm² per second at sample positions, enabling statistically robust data collection over extended pulse durations. This configuration prioritizes resolution over peak brightness, making it ideal for detailed structural and dynamic investigations in dense, hard materials. A unique aspect of TS1 is its integration with production via a preceding target, allowing hybrid neutron-muon experiments that combine structural insights from neutrons with electronic and magnetic information from muons on the same sample setup.

Target Station 2

Target Station 2 (TS2) at the is optimized for the production of cold s with short pulse durations, enabling high-resolution studies of dynamics in complex materials. Operating at a repetition rate of 10 Hz, it delivers protons at 800 MeV and 60 μA to a target, resulting in a power dissipation of 48 kW and pulses from moderators with widths of 30–50 μs, which can be shaped down to approximately 10 μs using disk chopper systems for enhanced time-resolved measurements. The station supports around 11 instruments, with a typical on the order of 10^7 n/cm²/s, particularly suited for probing slow dynamics in systems such as , polymers, and liquids. First operational in 2008, TS2 expanded the facility's capacity for condensed matter research by providing brighter beams of long-wavelength s compared to the higher-repetition-rate Target Station 1. Key instruments on TS2 include several specialized for diffraction, scattering, and imaging techniques. The Wide-angle and Inelastic Neutron spectrometer (WISH) offers high-resolution powder diffraction for crystallographic studies of magnetic and structural properties in materials. NIMROD, the Near and InterMediate Range Order Diffractometer, enables wide-angle diffraction over lengths from atomic to nanometer scales, ideal for disordered materials like glasses and liquids. The LET direct-geometry chopper spectrometer uses counter-rotating disk choppers to monochromate the beam, achieving energy resolutions from 20 μeV to 500 μeV for quasi-elastic and inelastic scattering in magnetic and structural dynamics. IMAT, the Imaging and Materials Testing beamline, combines neutron imaging with diffraction tomography for non-destructive analysis of engineering components and cultural artifacts. Small-angle neutron scattering (SANS) instruments on TS2, such as SANS2d and LARMOR, facilitate investigations into biological macromolecules, self-assembly in polymers, and soft condensed matter structures, with LARMOR additionally supporting spin-echo and precession techniques for dynamics over broad length and time scales. ZOOM provides time-of-flight strain mapping for engineering applications in residual stress analysis. Reflectometry instruments like OFFSPEC, added in 2011, enable high-throughput studies of interfaces in liquid systems, including air/liquid and liquid/liquid boundaries relevant to surfactants and biomolecules. The disk chopper systems, exemplified by those on LET and other spectrometers, allow precise pulse shaping to balance flux and resolution, making TS2 particularly effective for time-resolved experiments in soft matter and nanomaterials research.

Muon-Specific Beamlines

The muon-specific beamlines at the ISIS Neutron and Muon Source are dedicated facilities located at Target Station 1 (TS1), where polarized muons are produced via the decay of pions generated by the interaction of the 800 MeV proton beam with a target. These beamlines deliver muons to spectrometers for condensed , distinct from neutron instrumentation, with a total flux of approximately 4×1084 \times 10^{8} muons per second. Positive muons, which serve as magnetic probes and proton analogs, have a decay lifetime of 2.2 µs and are highly spin-polarized (>99%). The primary technique enabled by these beamlines is muon spin relaxation (μSR), which measures local magnetic fields and dynamics in materials without interference from nuclear magnetism, using surface muons with momentum of about 28 MeV/c (kinetic energy ~3.8 MeV). This allows implantation depths up to ~160 mg/cm², suitable for probing thin films and bulk samples. Applications focus on quantum materials, including skyrmions and frustrated magnets, semiconductors for charge transport, and catalysis via hydrogen site studies, representing ~10% of ISIS experiments. Key beamlines include MuSR, a general-purpose spectrometer for and via spin relaxation, equipped with 64 detectors, rotatable for longitudinal and transverse fields up to 3000 G, and temperatures from 40 mK to 1000 K. EMU specializes in surface muon experiments for thin films, featuring 96 detectors, longitudinal fields up to 5000 G, and an extended temperature range of 50 mK to 1500 K for zero- and low-field μSR. HiFi, a high-intensity forward instrument, supports applied longitudinal fields to 5 T with a superconducting split-pair , enabling RF decoupling and studies of fluctuations, correlations, and phase diagrams in across temperatures from 30 mK to 1500 K.

Recent Developments and Future Prospects

Ongoing Upgrades and Programmes

The Endeavour Programme, launched as part of the (UKRI) strategy, represents a £90 million spanning 2021 to 2028 aimed at enhancing the capabilities of the ISIS Neutron and Muon Source through nine approved projects. This initiative focuses on developing new instruments and upgrading existing ones to meet evolving research demands in and beyond. Key components include the Super MuSR (Multi-Use Spectrometer for High-Rate Observations of Materials), which will deliver enhanced muon flux and time resolution for studying smaller samples in fields like ; the HRPD-X, a next-generation high-resolution set to set global benchmarks in diffraction science with improved resolution and sample throughput; and broader detector upgrades across multiple beamlines to boost sensitivity and data quality. Production of Super MuSR detectors commenced in summer 2025, with both Super MuSR and HRPD-X targeted for user operation by mid-2028. In 2025, several instrument-specific enhancements were completed or advanced, underscoring ongoing efforts to optimize performance. New in-house-built diffraction detectors were installed on the IMAT (Imaging and Materials Analysis) , enabling high-resolution imaging for and materials , with a second tranche planned for 2026. On the (Emu Muon) , a novel decay degrader was designed and installed, improving by up to 50% for experiments on semiconductors and catalysts. Additionally, the secondary spectrometer upgrade, featuring advanced analysers, is scheduled for installation in January 2026 and commissioning in May or June 2026, promising a fivefold increase in productivity for inelastic scattering studies of energy materials. Sustainability initiatives gained momentum in 2025, with the launch of a D₂O () recovery and recycling project led by a dedicated team to reduce environmental impact and operational costs at the facility. This effort complements broader efficiency measures, such as the delivery of 3,879 instrument days during the 2024–2025 cycle, supporting 1,402 submitted proposals and maintaining high uptime despite global challenges. The year also highlighted growing community engagement through awards recognizing scientific excellence. ISIS scientists contributed to two 2025 Royal Society of Chemistry (RSC) Horizon Prizes: David Keen as part of the Dalton Horizon Prize-winning team for advancements in computational materials discovery, and Jacqui Cole's for the Materials Chemistry Horizon Prize on sustainable chemical processes. Furthermore, the inaugural ISIS Springboard Awards were presented in March 2025 to three early-career researchers—Shurui Miao, Jennifer Johnstone-Hack, and William Sharratt—for innovative proposals in and techniques, fostering talent development. User engagement continued to expand, with 1,673 unique users accessing the facility in 2025, including 37% students and 214 new principal investigators, reflecting a 73.3% rate of international collaboration. This activity yielded 559 journal publications involving 3,546 authors and 5.8% industry collaborators, demonstrating the facility's impact across disciplines.

Long-Term Outlook and Collaborations

The ISIS Neutron and Muon Source's operational lifespan has been strategically extended to at least 2030, ensuring continued leadership in neutron and muon through targeted upgrades and enhancements to the existing facility. As part of this long-term planning, the science case for a successor facility, ISIS-II, is being developed in consultation with the user community, with key drafts anticipated in 2025 to justify potential advancements such as increased beam power to support higher scientific throughput. Decommissioning of the current ISIS facility is projected to commence around 2040–2045, following an expected 60-year operational lifetime, with comprehensive efforts focused on managing and site restoration over subsequent decades. In preparation for this transition, ISIS is contributing expertise and hardware to the (ESS), including the design and delivery of instruments such as for and FREIA for reflectometry, to maintain seamless access for and European researchers. ISIS maintains a robust network of international collaborations through formal agreements and memoranda of understanding, fostering joint experiments, instrument development, and training programs. Key partnerships include long-standing ties with India's (via Jawaharlal Nehru Centre for Advanced Scientific Research) for neutron scattering and muon studies since 1983, renewed in 2016; a 2024 agreement with Neutrons Canada for beam time access and research proposals; collaborations with on neutron techniques and the Multipurpose Brazilian Reactor project; a 2025 memorandum with Indonesia's (BRIN) for neutron and muon science; skills development under the Newton Programme with (2018–2020); an extended agreement with Sweden's Research Council until 2029 for user access and instrument enhancements; ongoing partnerships with Japan's , , and JAEA since 1990 for muon facilities and experiments; and a new 2024 strategic partnership with under the International Science Partnerships Fund for advanced capabilities in s, muons, and X-rays. Looking ahead, envisions enhanced capabilities in quantum science—such as studies of and —and research, including low-carbon materials and , even as global and faces capacity constraints by the 2050s due to facility closures and limited new builds. Integration of for is expected to play a pivotal role, improving efficiency in handling large datasets from advanced instrumentation and enabling real-time insights. However, these ambitions are tempered by challenges, including the aging of core requiring sustained investment and intensifying competition from facilities like the and Japan's J-PARC, which could impact user access and resource allocation.

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