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Low Density Materials for Particle Accelerator Applications
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University of Bath 10W 2.45
University of Bath 10W 2.45
Alexander Lunt
(University of Bath (GB)),
Raymond Veness
(CERN),
Chiara Pasquino
(CERN)
Description
The Low‑Density Materials Workshop for Particle Accelerator Applications will bring together researchers, industry partners and laboratory specialists to examine how lightweight and nanostructured materials can address emerging challenges in accelerator technology. Over two days, the programme will consider community needs in areas such as high‑energy deposition, surface modification, safety and handling, and the growing production capabilities for CNT‑based and other low‑density systems. Sessions will cover thin‑target behaviour, thermal modelling, damage processes, and the latest developments in characterisation and simulation. By drawing together expertise from materials science, accelerator physics and advanced manufacturing, the workshop aims to identify current limitations, highlight promising directions and help shape a coordinated strategy for future research and development.
Held 8–9 June at the University of Bath, the workshop offers a focused setting within one of the UK’s leading centres for engineering and materials research. The event is structured to allow time for technical discussions, collaboration-building and informal exchanges across the community. Bath is easily reached via Bristol or London Heathrow airports, with straightforward onward travel to the city. The programme includes opportunities to explore the campus and the wider surroundings, combining modern research facilities with Bath’s distinctive architecture and landscape.
Hotel Options Near the University of Bath
(All within roughly 1.5 miles of campus)
- Hotel Indigo Bath (HIG) – Modern design inspired by Bath’s Georgian heritage; central location near the station; £100–£180 per night
- The Bird, Bath – Boutique hotel at the bottom of Bathwick Hill; £150–£220 per night
- The Gainsborough Bath Spa – Luxury option with spa access; £180–£260 per night
- No.15 by GuestHouse, Bath – Stylish Georgian townhouse hotel; £130–£180 per night
- Royal Hotel – Classic hotel opposite Bath Spa station; £90–£140 per night
- Apex City of Bath Hotel – Contemporary 4‑star hotel near Green Park; £110–£180 per night
Bus Information (U1, U2, U3)
U1 – City Centre ↔ University of Bath
Frequent service running from early morning to late evening; stops include Bath Abbey, Dorchester Street and Green Park.
U2 – Oldfield Park ↔ University of Bath (term time only)
Useful for those staying in the Oldfield Park area; runs via Bathwick Hill.
U3 – City Centre ↔ University of Bath / Bath Spa University
Connects both universities and is helpful for accommodation located to the west of the city.
Flight Information — Geneva to Bristol / London
To Bristol
- Sun 7 June: GVA 10:50 → BRS 11:35
- Tues 9 June: BRS 13:40 → GVA 16:25
To London Heathrow
- Sun 7 June: GVA 17:25 → LHR 18:10 or GVA 19:00 → LHR 19:45
- Tues 9 June: LHR 20:00 → GVA 22:35
By Train (Heathrow → Bath)
- Heathrow Express from Heathrow T2/3 or T5 → London Paddington (approx. 15 minutes)
- GWR fast service from Paddington → Bath Spa (approx. 1 hour 20 minutes)
Bristol Airport → Bath
- A4 Air Decker (Bath Bus Company) – Direct bus from Bristol Airport to Bath
A £75 conference fee is required for registration and attendance at the conference banquet which will be held on the 8th June at 18.30 at the Architect, Bath. A link to payment can be found here. The conference includes a walking tour of Bath, which will leave from the main doors of Bath Abbey (https://w3w.co/grows.ranged.bind).
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Registration and coffee University of Bath 10W Foyer
University of Bath 10W Foyer
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Introduction and welcome to BathSpeakers: Alexander Lunt (University of Bath (GB)), Raymond Veness (CERN)
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Session 1B:: Applications, state-of-the-art and needs of the communityConvener: Chiara Pasquino (CERN)
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Wire scanners in electron machines
At the Paul Scherrer Institute (PSI), nanotechnology has been successfully employed to develop a new generation of minimally invasive Wire Scanners with sub-micrometer spatial resolution for monitoring the transverse beam size at SwissFEL during lasing operation. The devices consist of a monolithic low-stress Si₃N₄ structure with a C-shaped silicon fork, integrating two perpendicular wires for full transverse beam profile reconstruction. The wires are as small as 2 µm in width and 1 µm in thickness; their length complies with the SwissFEL beam clearance.
This contribution presents dedicated beam tests performed under standard SwissFEL operating conditions. The results are presented in a chronological perspective, highlighting the evolution of the WS design from the first prototype concepts to the final devices capable of reliably operating under both SwissFEL charge schemes. For the first time, the measurements demonstrate WS operation fully compatible with machine protection constraints and with negligible impact on FEL lasing delivery.
A systematic comparison of beam invasiveness is performed against standard wire scanners employing different materials and geometries, including conventional tungsten and aluminum wires as well as more unconventional carbon nanotube (CNT) wires. The results demonstrate a substantial reduction in beam perturbation when using Si₃N₄ nanowires, confirming their suitability for FEL applications and representing a significant step toward truly non-destructive transverse beam diagnostics.
Speaker: Francesca Addesa (PSI) -
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Wire scanners in Hadron machines
Low-density, carbon-based materials are widely used in accelerators for beam-intercepting instruments. Ongoing upgrades to the CERN accelerator complex have exposed the physical limits of these materials to beam damage, which are expected to become increasingly problematic with future upgrades. Novel high strength, lower density 1-D materials such as long-strand Carbon Nanotubes (CNTs) wires have opened new possibilities to extend the reach of these instruments in existing and future accelerators. This presentation will outline recent collaborative developments between the University of Bath and CERN to deliver the simulations and practical understanding required to deliver CNTs wires that meet these needs. In particular, recent modelling has focused on CNT-particle interactions, in terms of inelastic collisions and resulting particle showers, thermal simulations to assess sublimation potential and predictions of CNT wire deformation, which influences the precision of resulting instrumentation.
In terms of practical considerations, a range of thermal treatments and chemical processes are being established to refine commercially available CNTs and those being developed by collaborating research institutions. In order to optimise these processes, a range of advanced characterisation methods and mechanical treatment facilities are also being developed. This includes the production of a novel test rig that can provide both micromechanical assessment and the ability to twist CNTs wires during production and/or testing to improve performance. An overview of a beamtime at Beamline B16 at Diamond Light Source, involving microfocus X-ray diffraction during in-situ loading, will also be outlined, as well as recent results from HRMT experiments. The resulting quantitative insights are essential in delivering CNTs for accelerator physics instrumentation applications, but also have important implications for alternative uses of these promising high specific stiffness wires.
Speaker: Alexander Lunt (University of Bath (GB)) -
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2D low-density materials for screens
Screen-based instruments are deployed throughout the CERN accelerator chain for beam steering, transverse profile measurement, and machine setup. Conventional scintillating and Optical Transition Radiation (OTR) screens act as solid interceptors, but their interaction with high-intensity beams leads to significant beam losses and material degradation, limiting their applicability in high-brightness machines such as the SPS and LHC. A new class of 2D low-density materials , offers the potential to reduce beam-material interaction while preserving the light-emission mechanism exploited for beam imaging. Beam tests of available membranes (e.g. Carbon NanoTubes - CNT and Boron Nitride NanoTubes -BNNT) as candidate imaging screen materials were performed at CERN, mainly at the HiRadMat facility, using 440 GeV/c proton beams combining high intensity with small transverse beam size.
This contribution presents the measurement results including an assessment of the main challenges, including photon yield, surface uniformity, and sublimation effects under intense beam heating. We also discuss completed and ongoing simulations of the material response to charged beams, which underpin future beam-qualification studies at CERN and the continued search for improved screen materials.Speakers: Federico Roncarolo (CERN), Stephane Burger (CERN)
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11:00
Coffee University of Bath 10W Foyer
University of Bath 10W Foyer
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Session 1A: Applications, State-of-the-art and needs of the communityConvener: Thierry Stora (CERN)
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Nanostructured and low-dimensional materials for targets
In the field of particle accelerators, materials are routinely exposed to extreme environments, including high vacuum, intense particle irradiation, and both ultra-low and ultra-high temperatures. These demanding conditions place stringent requirements on structural and functional materials, particularly in fixed target experiments where high-energy, high-intensity proton beams are used to generate secondary particles. Nanostructured and low-dimensional materials (NLDMs), owing to their exceptional mechanical and thermal properties, offer significant potential to address these challenges. In spallation targetry, NLDMs are of interest for both dense, heavy target materials and low-density beam-intercepting components such as beam windows, where enhanced irradiation resistance, reduced stress accumulation, and improved fatigue behavior promise extended operational lifetimes.
At radioactive ion beam facilities such as CERN-ISOLDE, the isotope separation on-line (ISOL) method relies critically on the performance of thick target materials exposed to high-energy proton beams. Radionuclides are produced via spallation, fission, and fragmentation reactions and subsequently released from the target material by heating to ultra-high temperatures (> 2000 °C) under vacuum conditions. The isotope release, however, remains a key limitation of the ISOL method, as only a small fraction of produced isotopes typically escapes the target matrix. As the release is governed by diffusion and effusion processes, which are strongly influenced by the material’s microstructure, application of NLDMs can improve performance.
In this contribution, we explore the potential of NLDMs as advanced target and structural materials for accelerator applications, with a focus on ISOL-based facilities. We discuss how tailored nanostructures can enhance isotope release properties while simultaneously improving microstructural resilience under extreme irradiation and temperature conditions, thereby offering a pathway toward higher yields, improved reliability, and next-generation target performance.
Speaker: Simon Thomas Stegemann (CERN) -
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Development of low density materials for beam strippers
at CERN, the Linac4 accelerator is injecting 160 MeV H− beam into the 4 superposed PS Booster rings. This is achieved by a H− charge-exchange injection chicane system, using 200 µg/cm2 low density material stripping foils, to convert the negative hydrogen ions into protons by stripping off the electrons. In parallel, stripping efficiency measurements, of different foil types, are done with a dedicated stripping foil test stand in the L4 Transfer Line. This paper briefly recalls the design of the stripping foil units and summarises the practical experience on gluing and handling these foils, before reporting on the important results obtained during measurements and operation with beam.
Speaker: Wim Weterings (CERN) -
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Experience with CNTs at ISIS
A feasibility study of a single-wire Scanner profile Monitor (WSM) was conducted for the demonstration ring of a Fixed Field Alternating gradient (FFA) accelerator, together with the Front-End Test Stand (FETS), called FETS-FFA, as a part of the ISIS-II upgrade project. A Carbon Nano Tube (CNT) wire was selected for the FETS-FFA WSM as it is durable against heat damage from low-energy proton beams in the FETS-FFA test ring (3–12 MeV). A bias voltage applied to the measuring wires is required to prevent secondary electrons from returning to the wire due to the stray magnetic fields from the FFA main magnets. This talk presents endurance tests of bias voltages on CNT wires of difference diameters, as well as beam tests conducted on the FETS beam line and the FFA ring at KURNS in Japan.
Speaker: Emi Yamakawa (STFC)
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13:00
Lunch University of Bath 10W Foyer
University of Bath 10W Foyer
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Session 2A: Current and potential capabilities for production and treatmentConvener: Philippe Poulin (University of Bordeaux)
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CNT fibre production - state-of-the-artSpeaker: Matteo Pasquali (Rice University)
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CNT based materials production synthesis
Carbon nanotube macromaterials are promising low-density candidates for accelerator beam instrumentation because they combine low mass, high specific mechanical properties, electrical and thermal transport, and potential resilience under demanding environments. Their performance, however, is governed not only by the intrinsic properties of individual nanotubes, but by the full hierarchy of production: catalyst chemistry, floating-catalyst CVD growth, aerogel formation, drawing, densification, twisting, purification, and post-treatment.
This talk will examine CNT-based material production as a coupled synthesis–structure–property problem. Floating-catalyst CVD routes can produce continuous CNT fibres, yarns, sheets, and aerogels, but the resulting materials are intrinsically heterogeneous, with variations in tube diameter, wall number, crystallinity, bundle packing, porosity, alignment, and residual catalyst content. These features control load transfer, thermal transport, electrical conductivity, dimensional stability, and failure behaviour.
The presentation will discuss how synthesis and processing variables can be linked to the requirements of accelerator-facing applications, where low areal density, reproducibility, thermal robustness, and predictable mechanical response are critical. It will also outline the characterisation methods needed to connect nanoscale tube quality and mesoscale network structure to macroscopic performance, including Raman spectroscopy, electron microscopy, X-ray scattering, thermal analysis, electrical measurements, and mechanical testing. The objective is to identify the production bottlenecks and material descriptors most relevant to future CNT development for accelerator applications.
Speaker: James Elliott (University of Cambridge) -
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Thermal properties of large-scale CNT fiber structuresSpeaker: Yoku Inoue (Shizuoka University)
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15:00
Coffee University of Bath 10W Foyer
University of Bath 10W Foyer
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Session 2B: Current and potential capabilities for production and treatmentConvener: Alexander Lunt (University of Bath (GB))
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CNT macromaterials: challenges in testing and properties
Interconnected networks of carbon nanotubes (CNT) synthesized by the direct Floating Catalyst CVD process (FCCVD) are the key structural components in macroscopic yarns and sheets. These macromaterials demonstrate high mechanical and electrical properties relevant to a wide range of applications.
Mechanical testing of CNT macromaterials usually involves dedicated equipment, such as micro- testing machines and stations for in situ experiments. The examples include tensile tests combined with in situ Raman spectroscopy, SAXS/WAXS, thermal treatments. Not all these options have been explored so far. Whereas for CNT fibres and sheets there is a significant amount of mechanical data in the literature, testing of individual CNT bundles (i.e., building blocks of the nanoscale network) yet remains a challenge because of their length, intrinsic entanglement at the aerogel-state, the lack and/or technical complexity of testing methods. Besides, FCCVD produces inherently polydisperse samples in terms of the CNT diameter and number of layers, leading to the coexistence of predominantly round, elliptical and radially collapsed CNTs in the bundles. Transversal TEM analysis of FIB-milled macroscopic fibres demonstrates the importance of CNT bundling and packing efficiency.
The work will highlight the development of nanomechanical tests of individualized CNT bundles coupled with in situ TEM and/or Raman spectroscopy and its potential applicability in the analysis of advanced materials (bundles, fibres, sheets). The feasibility of complex experimental evaluation of their structure and performance will be discussed along with the types of defects that may be generated under the beam-exposure. Such evaluation could serve as a guideline for the choice of the high-performance material in the future.
Speaker: Dr Anastasiia Mikhalchan -
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Å‑Scale Pore Generation in Functionalised Suspended Graphene
Generating pores in graphene by decoupled nucleation and expansion is desired to achieve a fine control over the porosity and is desired to advance several applications. In situ studies of pore formation are particularly valuable, as they enable direct observation of the process while simultaneously allowing measurement of the associated properties within the same experimental setup.1
Herein, we present a nucleation-decoupled and site-specific pore engineering strategy based on the controlled epoxidation of graphene, where epoxy groups are grafted on graphene surface.2 The high-density (~10¹² cm⁻²) nanoscale epoxy clusters on highly oriented pyrolytic graphite (HOPG) were observed by low-temperature scanning tunneling microscopy (LTSTM). It reveals that these epoxy clusters act as stable pore precursors, exhibiting no carbon vacancy formation in the absence of external energy input. Upon introducing an energy stimulus via electron beam irradiation, the epoxy clusters are transformed into vacancy defects. Real-time evolution of this process was captured using aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM) under an 80 keV electron beam with the maximum transferable energy (15.6 eV). A mathematical model describing the conversion of epoxy clusters to pores was developed, enabling extraction of the displacement energy (Ed) for carbon removal. Using the Seitz–Koehler formalism3 for relativistic electron–nucleus scattering, cross-sectional analysis yielded an average displacement energy of ~1.3 eV for functionalized carbon atoms within epoxy clusters, indicating significantly lower energy requirement compared to knockout energy of pristine graphene (~20 eV).4 This strategy enables pore formation to be confined strictly to the epoxidized regions, i.e., the clusters, thereby achieving precise site-specific pore generation. Additionally, it constrains pore growth, with the maximum pore size inherently limited by the dimensions of the epoxy cluster.
Speaker: Shiqi Huang (University of Bath) -
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Nonlinear photocurrent generation in 2D materials: beyond hydrodynamics
Two-dimensional materials offer a versatile platform for nonlinear optoelectronics, where light can generate electrical currents and optical signals that are strongly tunable, symmetry-sensitive, and intrinsically linked to the microscopic dynamics of electrons. In contrast to conventional photodetection, nonlinear photocurrent generation can provide direct access to electronic structure, collective motion, nonequilibrium carrier dynamics, and energy flow in quantum materials.
In this talk, I will present a broad, non-technical overview of nonlinear optical and optoelectronic phenomena in two-dimensional systems, with emphasis on their physical principles and potential device relevance. I will first highlight selected examples of nonlinear optics in graphene and related materials, including electrically tunable harmonic generation and ultrafast optical control. I will then introduce two central mechanisms of photocurrent generation: shift current, associated with real-space charge displacement during optical excitation, and injection current, arising from the asymmetric population of photoexcited carriers. These mechanisms illustrate how material symmetry and band geometry can convert light directly into directed electrical motion.
The second part of the talk will focus on emerging regimes beyond standard single-particle descriptions. I will discuss hydrodynamic and plasmon-assisted photodetection, where collective electron motion can enhance and shape the nonlinear electrical response, as well as light-induced thermoelectric effects, where optical heating and nonequilibrium energy relaxation generate photocurrents. Together, these examples show that nonlinear photocurrent measurements are not only relevant for ultrafast and tunable photodetectors, but also provide a sensitive probe of collective, geometric, and thermal electronic processes in low-dimensional materials.
The talk aims to provide an accessible perspective on nonlinear photocurrent generation as a bridge between fundamental condensed matter physics and future optoelectronic and photodetection technologies based on two-dimensional quantum materials.
Speaker: Habib Rostami (University of Bath)
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17:30
Tour of Bath Bath Abbey Main Doors
Bath Abbey Main Doors
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18:30
Conference Banquet The Architect, Bath
The Architect, Bath
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Coffee University of Bath 10W Foyer
University of Bath 10W Foyer
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Session 3A: Simulation and CharacterisationConvener: Dr Stefano Sgobba (CERN)
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PEPR DIADEM: DIscovery Acceleration for the Deployment of Emerging Materials
Fostering rapid research and the market entry of more efficient and sustainable materials derived from non-critical and non-toxic resources represents a major challenge. In this context, the French nationwide program PEPR DIADEM (DIscovery Acceleration for the Deployment of Emerging Materials), launched in 2022, aims to accelerate the entire innovation chain “from concept to fruition” through the integration of artificial intelligence (AI) and advanced experimental approaches.
Addressing societal challenges in energy, transportation, digital technologies, and healthcare requires the rapid discovery of new materials, ranging from metallic alloys to functional nanostructures. In line with the ambitious timelines of the European Green Deal, this calls for a paradigm shift toward automated, data-driven, and high-throughput research methodologies.
Led by CNRS and CEA in collaboration with seven major academic partners, and supported by France 2030 with an €85M budget, PEPR DIADEM is structured around the DIADEM Discovery Hub. This distributed infrastructure integrates four coordinated platforms across France, combining high-throughput and combinatorial synthesis, automated shaping—including additive manufacturing—advanced multi-modal characterization, and multiscale simulation. These capabilities are complemented by digital tools for data management, data mining, and AI-driven analysis, enabling seamless interaction between experiments and simulations.
Nineteen targeted projects underpin the development of this unique infrastructure, complemented by open calls that engage a broad national community of approximately 4,000 researchers and engineers. Strong interactions with existing research infrastructures, along with co-funding from industry and international partners, further reinforce the program’s impact.
PEPR DIADEM also leverages major facilities such as the SOLEIL and ESRF synchrotrons for high-throughput and operando characterization under realistic conditions. In parallel, dedicated training initiatives and international collaborations support the emergence of a new generation of researchers at the interface of materials science and AI.
By orchestrating the convergence of automation, artificial intelligence, and large-scale research infrastructures, DIADEM aims to reduce materials discovery timelines from decades to just a few years, paving the way for more sustainable and efficient innovation in materials science.
Speaker: Fernando Lomello -
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Advanced microscopy and characterisation techniques at CERN
The microscopy team at CERN supports the community by providing advanced material characterization, including topographical imaging, morphology analysis, phase identification, and chemical characterization using Scanning Electron Microscopy (SEM), Focused Ion Beam (FIB)-SEM, and X-ray Diffraction (XRD).
A wide range of materials is investigated, with emphasis on metals and alloys, as well as ceramics, composites, and thin films. Building on previous work, recent efforts have focused on carbon nanotubes (CNTs), with particular attention to impurity evaluation and distribution, including nanometric residual catalyst particles, and to the analysis of the core structure of CNT yarns as a function of their nominal diameter. In parallel, new cross-section preparation methodologies have been explored using a recently installed Laser-FIB system. This approach could enable faster material removal and improved access to the internal structure of CNT yarns.
Selected examples will demonstrate how these techniques are applied to extract maximum information from materials associated with beam instrumentation devices, highlighting recent progress in CNT characterization and sample preparation strategies.
Speaker: Ana Teresa Perez Fontenla (CERN) -
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Characterization of low-dimensional carbon materials using low-energy electrons
Nanostructured carbon allotropes have a wide range of applications for the integration into functional and hybrid materials as well as essential element in integrated sensors and detectors. Their chemical functionalisation furthermore enhances the spectrum of application. Photoelectron spectroscopy is a material characterisation tool that supports the synthesis of such materials via enabling access to information on composition, electronic properties and the potential presence of impurities, residual catalyst species, or intentionally incorporated dopants as well as functional groups. An example of the characterisation and purification of multi-walled carbon nanotubes (MWCNTs), that had been intentionally doped with Boron for enhanced chemical sensitivity, will be discussed and the verification of the existence of functional groups generated by chemical or plasma treatment will be demonstrated. For applications in particle accelerators, aligned MWCNTs are interesting as electron emitters. In this case, the work function of the emitter material is of relevance and can be characterised by low-energy electron spectroscopy – and example will be presented. Furthermore, the TE-VSC-SCC team at CERN also develops thin amorphous carbon stripper foils and supports the community with specialised electron characterisation techniques. I will demonstrate based on a request of measuring the electron transmittivity of randomly stacked bi-layer graphene for gas electron multiplier detectors, how such experiments can be customised for measurement of material and surface characteristics of low-dimensional materials.
Speaker: Marcel Himmerlich (CERN)
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11:00
Coffee University of Bath 10W Foyer
University of Bath 10W Foyer
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3B: Simulation and CharacterisationConvener: Mariusz Sapinski (Paul Scherrer Institute (CH))
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Multiscale Modelling of CNT Systems for Accelerator Applications
Carbon nanotubes (CNTs) and related low-density materials are attracting growing interest for next-generation particle accelerator and beam instrumentation applications due to their unique combination of low density, high thermal conductivity, mechanical resilience, and radiation tolerance. However, understanding their behaviour under extreme accelerator environments requires bridging multiple length and time scales, from atomistic radiation events to macroscopic engineering response.
This presentation will discuss our developing multiscale modelling framework within the University of Bath–CERN collaboration, focusing on molecular dynamics (MD) simulations of CNT-based systems for accelerator applications. The work proposes a workflow that combines atomistic modelling, statistical thermodynamics, and materials simulation to investigate defect formation, thermal transport, irradiation-induced degradation, and structure–property relationships in CNT architectures and related carbon materials.
The talk will also show how previous molecular simulation work on carbonaceous systems, adsorption, and complex materials is now feeding into a broader predictive framework for CERN-facing applications, including beam diagnostic systems and radiation-resistant low-density materials. Particular emphasis will be placed on the role of MD simulations as a bridge between microscopic mechanisms and engineering-scale behaviour.
Speaker: Dr Carmelo Herdes Moreno -
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Thermomechanics of invasive diagnostic devices: recent developments
Beam-induced damage poses a critical threat to the functionality of diagnostic instruments and the operational safety of accelerator facilities. This contribution presents recent advancements and insights into the thermomechanical modelling of invasive beam diagnostic devices (e.g. SEM grids, wire scanners, and screens) under irradiation conditions. Modelling strategies are outlined along with key simulation capabilities and physical insights. An experimental scenario of high-intensity H⁻ ion beam irradiation on tungsten wires is highlighted, which serves as a direct window into material response and a means to numerically validate models.
Speaker: Ryan Paul Camilleri -
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Safety of engineered carbon nanomaterials: a focus on Graphene Oxide and a Safer-by-design strategy to mitigate its potential impact on Health and the Environment
Carbon nanomaterials, and especially Carbon Nanotubes (CNTs) and Graphene have been among the most studied nanomaterials due to their exceptional combination of physical properties which have led to applications in almost all fields. Unfortunately, in the case of graphene, the large-scale production of good quality samples (low number of layers (less than five, what is called "few-layer graphene", FLG), lateral dimensions exceeding one micrometre, good structural quality) still represents a challenge despite the regular advances described in the literature. A simpler alternative consists in preparing graphite oxide, easy to exfoliate into graphene oxide (GO), for example by simple ultrasonic treatment. GO is hydrophilic and much easier to disperse (solvent, matrix) than FLG, which is very hydrophobic. GO is an electrical insulator, while FLG is a good electronic conductor. When electrical conductivity is one of the desired properties, it is required to reduce GO (decrease its oxygen content) to obtain "reduced GO" (rGO), supposed to be equivalent to FLG, but still presenting many structural defects. As the oxygen content decreases, the electrical conductivity is progressively restored but as a counterpart the stability of the dispersion in a solvent or a matrix decreases.
Regarding safety issues, we have evidenced the toxicity and genotoxicity of GO both in vitro and in vivo [1, 2], but also the possibility to suppress these adverse effects by thermal reduction [3]. The aim is to find a compromise between the ease of use of GO on the one hand, and its negative impacts on humans and the environment on the other. This strategy, which aims to identify the most suitable experimental conditions allowing a compromise between the absence of (geno)toxicity and the preservation of its ease of use, is part of the "safer by design" approach.[1] L. Evariste, L. Lagier, C. Chary, A. Mottier, S. Cadarsi, E. Pinelli, E. Flahaut, L. Gauthier, F. Mouchet, Toxics, 2022, 10, 588:1-14. "Exposure of the midge larvae (Chironomus riparius) to graphene oxide leads to development alterations"
[2] L. Evariste, F. Mouchet, E. Pinelli, E. Flahaut, L. Gauthier, M. Barret, Sci. Tot. Env., 2023, 857, 1595152022:1-14. "Gut microbiota impairment following graphene oxide exposure is associated to physiological alterations in Xenopus laevis tadpoles"
[3] L. Evariste, L. Lagier, P. Gonzalez, A. Mottier, F. Mouchet, S. Cadarsi, P. Lonchambon, G. Daffe, G. Chimowa, C. Sarrieu, A-M. Galibert, C. Matei Ghimbeu, E. Pinelli, E. Flahaut, L. Gauthier, Nanomaterials, 2019, 9, 584:1-16. "Thermal reduction of Graphene Oxide mitigates it's in vivo genotoxicity toward Xenopus laevis tadpoles"Speaker: Dr Emmanuel Flahaut (University of Tolouse)
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Lunch University of Bath 10W Foyer
University of Bath 10W Foyer
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Session 4: Wrap up, funding strategy and next stepsConvener: Raymond Veness (CERN)
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Carbon Nanotube Forests as a Platform for Ultra-Compact High-Energy Accelerators
The development of next-generation particle accelerators increasingly depends on materials that can withstand extreme fields while enabling new regimes of beam–matter interaction. Within this context, low-density and nanostructured materials, in particular carbon nanotube (CNT) systems, offer a transformative platform for passive components and active acceleration media.
This contribution will present an overview of recent work within the QUASAR Group and its international partners on CNT-based technologies across the full spectrum of accelerator applications, from high-performance electron sources and beam manipulation to ultra-high-gradient acceleration concepts.
A central focus will be on vertically aligned carbon nanotube forests as engineered low-density plasma media capable of supporting surface plasmon–driven wakefields. Recent simulation studies demonstrate that nanostructured CNT channels can sustain accelerating gradients in the TV/m to 100s TV/m regime, far exceeding conventional gaseous plasma approaches. Two complementary mechanisms, leaky surface plasmon excitation and nonlinear bubble wakefields, enable efficient acceleration of both electrons and positrons, with controllable field structure, phase velocity, and energy transfer efficiency. The tunability of CNT forest geometry and effective plasma density (∼10¹⁹–10²³ cm⁻³) is shown to be critical for matching beam or laser drivers and accessing relativistic surface modes .
Beyond acceleration, the talk will highlight the broader role of CNTs in accelerator science, including their application as robust cold electron field emitters for beam cooling systems, where stability and long operational lifetimes have been demonstrated under realistic conditions. These developments underline the versatility of CNT-based materials, combining high thermal resilience, structural tunability, and favourable इलेक्ट्रonic properties.
The results point toward experimentally accessible pathways for compact, high-energy accelerators and radiation sources, while also identifying key material and integration challenges.
Speakers: Carsten Peter Welsch (Cockcroft Institute / University of Liverpool), Dr Bifeng Lei -
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EU and other possible funding pathsSpeaker: Thierry Stora (CERN)
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Workshop wrap-up and actionsSpeaker: Raymond Veness (CERN)
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Coffee University of Bath 10W Foyer
University of Bath 10W Foyer
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Facility Tour Leaving from 10W Foyer
Leaving from 10W Foyer
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