International Workshop on Future Linear Colliders 2026

Nov 9, 2026, 8:00 AM → Nov 13, 2026, 6:00 PM Asia/Tokyo

KEK

The International Workshop on Future Linear Colliders 2026 (LCWS2026) continues the established series devoted to the study of the physics, detectors, and accelerator technologies for high-energy electron–positron colliders.

Linear colliders are one of the most compelling options for a next-generation Higgs factory, complementary to circular collider proposals. They offer a unique and flexible path toward higher centre-of-mass energies and luminosities, enabling a long-term exploration of the electroweak scale and beyond. At the same time, many key technologies and physics goals are shared across linear and circular approaches, opening important opportunities for synergy and collaboration within the global community.

Since the last workshop (LCWS2025), significant progress has been made in both linear collider concepts and the broader Higgs factory landscape. LCWS2026 will highlight recent developments and future prospects, with particular emphasis on the long-term vision of linear colliders—including energy and luminosity upgrades—as well as their interplay with circular collider initiatives.

With a comprehensive program of plenary and parallel sessions, the workshop will provide an opportunity to present ongoing work, exchange ideas, and foster collaboration across communities working toward future Higgs factories.

The workshop is scheduled from 9th to 13th of November at KEK. More detailed information will follow.

 

Sponsors

 

 

 

 

 

 

 

LCWS2026_A2_web.pdf

LCWS2026_logo.png

Visa Support Request Form_LCWS2026.xlsx

Mon, November 9

Plenary: Plenary Mon-1

1 Welcome

Speakers: Hiroshi Sakai (KEK), Hiroshi Sakai (Institute for Solid State Physics, University of Tokyo)

2 LOC

Speaker: Takeshi Dohmae

3 KEK's activity

Speaker: Shoji Asai (University of Tokyo (JP))

4 The linear collider study at CERN

Speaker: Alessandra Lombardi (CERN)

5 Status of LEP3

Speaker: Edda Gschwendtner (CERN)

6 Status of FCC-ee

Speaker: Michael Benedikt (CERN)

7 Status of CEPC

Speakers: Jie Gao (IHEP), Jie Gao (Chinese Academy of Sciences (CN))

8 ILC-Japan

Speaker: Masaya Ishino (University of Tokyo (JP))

9 US perspective

Speaker: Cameron Geddes (LBNL)

12:40 PM Lunch

Plenary: Plenary Mon-2

10 IDT status

Speaker: Tatsuya Nakada (EPFL - Ecole Polytechnique Federale Lausanne (CH))

11 View from ICFA

Speaker: Tsuyoshi Nakaya (Kyoto University)

12 Physics overview (title TBD)

Speaker: Hitoshi Murayama (University of California Berkeley (US))

13 A Linear Collider approach to answer the big question

Speaker: Roman Poeschl (Université Paris-Saclay (FR))

3:40 PM Coffee break

Plenary: Plenary Mon-3

14 Upgrade paths: advanced high-gradient RF techniques (C^3) and ERL

Speaker: Emilio Nanni

15 Upgrade paths: plasma wakefield opportunities

Speaker: Marlene Turner (CERN)

16 General discussion - upgrade options

Speakers: Emilio Nanni, Marlene Turner (CERN)

Reception: Reception/Poster session

Tue, November 10

Plenary: Plenary Tue-1

17 ILD status, including an overview of LC detector status (status for all, incl. HALHF)

18 Recent highlights on vertexing/tracking/timing

Speaker: Peter Kluit (Nikhef National institute for subatomic physics (NL))

19 Recent highlights on calorimetry/PID

Speaker: Prof. Wataru Ootani (ICEPP, Univ. of Tokyo)

20 Software development (including key4hep)

Speakers: Frank Gaede, Frank-Dieter Gaede (Deutsches Elektronen-Synchrotron (DE))

10:30 AM Coffee break

Plenary: Plenary Tue-2

21 ITN (ILC Technology Network)

Speaker: Shinichiro Michizono (KEK)

22 LCF@CERN: update on RTML and Main Linac studies

Speaker: Andrea Latina (CERN)

23 LCF@CERN: update on BDS/MDI/x-angle studies

Speaker: Rogelio Tomas Garcia (CERN)

24 LCF@CERN: update on Conventional Facilities and Siting studies

Speaker: Edward Fraser MacTavish (CERN)

12:30 PM Lunch

Beam dynamics; beam delivery systems, main linacs, damping rings

Beyond Colliders Opportunities

25 CERN’s Non-Collider Physics Roadmap

CERN’s scientific program extends well beyond its flagship collider experiments, thanks to early considered flexibility and strategic choices when its diverse and flexible injector chain and accelerator infrastructure were and are conceived. This allows for a broad ecosystem of fixed-target, antimatter, rare-isotope, neutron, neutrino and forward-physics activities, exploited through the Laboratory’s accelerator complex, experimental areas and shared technical infrastructure. Building on these capabilities, following the successful Physics-Beyond-Collider initiative (PBC), CERN has launched the Non-Collider Physics Roadmap (NCPR), covering the period 2027–2046, to establish a coherent long-term framework for the evolution of this diverse program alongside the High-Luminosity LHC and future major accelerator projects.

After a short recap of PBC objectives and results, this presentation will introduce the motivation, scope and process of the NCPR and illustrate how CERN currently prepares and analyses roadmap options and pathways. It will highlight how beams, experimental areas and common infrastructure can support complementary scientific programs over the years to come, provided that their requirements, constraints and opportunities are identified sufficiently early. In line with CERN’s long-term plan, a selection of possible future projects, combined with upgrade and required consolidation activities, will illustrate some of the presently considered roadmap pathways.

Beyond the immediate CERN roadmap, the NCPR may provide an opportunity to further discuss how a diverse scientific ecosystem can be considered collectively. Future opportunities can be assessed in terms of scientific complementarity, maturity, infrastructure requirements, resources, timelines and uniqueness within a given laboratory and the worldwide landscape. Fitting to this conference scope, a future major accelerator facility should therefore be conceived from the outset not solely as an e⁺e⁻ collider, but as a versatile scientific infrastructure capable of supporting a broad and evolving long-term research program.

Speaker: Markus Brugger (CERN)

26 Beam Parameters, Layout and Opportunities for Beyond-Collider Experiments at a Linear Collider Facility

Speaker: Benno List (DESY)

27 CERN’s present and future test-beam capabilities

Test beams are essential for developing and validating detector technologies for future colliders. The CERN PS East Area and SPS North Area provide complementary beams of electrons, muons and hadrons, including pions, kaons and protons. The East Area covers the low-momentum range, extending from sub-GeV/c momenta up to 15 GeV/c, while the North Area provides secondary beams up to 360 GeV/c and attenuated primary proton beams at 400 GeV/c. Ion beams are also available in selected beamlines. Adjustable beam intensities, momentum selection and dedicated instrumentation for beam characterisation and particle identification support tests ranging from individual sensors to large detector prototypes. This contribution will review these capabilities and the available experimental infrastructure, with particular attention to detector R&D for future electron–positron colliders. It will present recent improvements, including developments towards lower-momentum beams and high-quality electron beams, discuss planned infrastructure upgrades and provide an outlook on future beam availability.

Speaker: Johannes Bernhard (CERN)

28 Crystal-Based Technologies for Electron–Positron Colliders

Crystals can channel charged particle beams along major crystallographic directions, providing a compact and efficient tool for beam manipulation at high energies. In bent crystals, channeled particles follow the crystal curvature, enabling beam steering over very short distances. While this technique has been extensively investigated for hadron beam collimation and extraction at the CERN SPS and LHC, as well as at FNAL, its application to electron and positron beams is attracting increasing interest in view of future high-energy lepton accelerators.

For future linear colliders, crystal-based technologies may contribute to several key areas, including beam extraction and manipulation, intense photon generation, and positron production. In oriented crystals, coherent interactions can strongly enhance electromagnetic radiation compared with ordinary bremsstrahlung, enabling compact sources of high-energy photons. Crystalline undulators further extend this concept, offering the possibility of generating hard X-rays and gamma rays at sub-ångström wavelengths through the periodic motion of channeled particles.

A particularly promising application is the use of oriented crystals as photon radiators for high-intensity positron sources, a concept originally proposed by Chehab and Variola and later developed by Chehab, Chaikovska and collaborators for CLIC, with important experimental tests carried out at KEK. The enhanced radiation emission can improve positron production while reducing the energy deposition in the conversion target.

This contribution reviews recent experimental and technological advances in crystal-based beam manipulation and radiation generation, with particular emphasis on their potential applications to future electron–positron linear colliders.

Speaker: Laura Bandiera (Universita e INFN, Ferrara (IT))

Conventional Systems and MDI

29 The Civil Engineering for a Future Linear Collider at CERN

The Civil Engineering design of a future Linear Collider at CERN requires the integration of accelerator requirements, site constraints, underground infrastructure and long-term upgrade strategies. As part of the Phase 1 preparation plan (2026–2028), implementation studies are being undertaken for both the CLIC and LCF configurations, addressing siting, civil engineering and conventional infrastructure.
The studies investigate two alternative future linear colliders which could serve in the post LHC era. CLIC is proposed as a staged development, initially constructing a 12.1 km tunnel for a 380 GeV machine before extending to 29.6 km for 1.5 TeV. In contrast, the LCF proposes construction of the full 33.5 km tunnel system in a single stage, providing the infrastructure required for its initial 250 GeV configuration and subsequent 550 GeV upgrade. Although the two designs share major civil-engineering components, differences in injection infrastructure, underground services and machine length lead to distinct construction and land use requirements.
A major focus of the ongoing work is the optimisation of the collider layout and placement. Tunnel alignments are being assessed using a sensitivity grid, building on methodology developed for the FCC studies. The analysis considers geological suitability, with particular emphasis on maintaining construction within favourable Molasse rock, alongside land availability and surface constraints.
Another focus is placed on the Interaction Region and Beam Delivery System, following the evolution to a two-detector configuration. Two civil engineering solutions are being assessed: a single large cavern accommodating both detectors, and two separated detector caverns served by independent beamlines and dedicated civil infrastructure. These options present different trade-offs between detector accessibility, radiation shielding as well as structural and magnet stability.
The ongoing studies aim to establish an optimised civil engineering solution for a future Linear Collider at CERN, balancing geological, technical, environmental and construction constraints while maintaining flexibility for future energy upgrades and scientific diversification.

Speaker: Edward Fraser MacTavish (CERN)

30 Recent study on the main beam dump

Report on the alternative design for achieving vortex water flow.
This includes simulation results and an update on progress with preparing a small-scale test module.

Speaker: Dr Nobuhiro Terunuma (KEK)

31 Precision Luminometry updates for ILC, FCC-ee

We present updates to previous years work on luminometry at ILC and FCC-ee at various scenarios, from Z pole to ZH threshold and to ttbar threshold.

Speaker: Brendon Madison (University of Kansas)

32 Adapting the ILD Detector for HALHF

HALHF is a proposed linear e+e- collider, which uses the novel acceleration technology of PWFA to create high-energy collisions necessary for a Higgs factory. The highly asymmetric nature of the collisions at HALHF calls for an asymmetric detector to effectively capture the signal while avoiding background. In this work, the traditionally symmetric ILD detector, originally designed for colliders upto 1TeV center-of-mass energy, is modified to enhance forward coverage and mitigate beam-induced backgrounds, such as incoherent pair productions and Compton scattering. We present the impact of these backgrounds on the detector design and compare the performance of Higgs physics analyses at HALHF to other proposed colliders such as ILC.

Speaker: Shriyansh Ranjan (DESY)

Joint: Higgs/EW and BSM

The recent progress of ITN project at KEK

33 The recent progress of ITN project at KEK

Speaker: Dr Mathieu Omet (KEK)

34 Recent progress of the ITN cryomodule production and preparation of COI facility at KEK

Speaker: Dr Takafumi Hara (KEK)

35 Automated SRF Cavity Vertical Testing Using MicroTCA.4-Based Digital LLRF System

The vertical test (VT) stand at the KEK Superconducting RF Testing Facility (STF) currently uses an analog RF control system. We are in the process of replacing this system with a new digital LLRF system based on the MicroTCA.4 architecture. The digital system also allows for greater flexibility regarding configurability and software automation. It is our goal to automate the VT process to improve measurement repeatability, reliability, and speed. We have implemented an automated identification of multi-cell (3 and 9-cell) cavity passband modes. We also develop a software suite to configure the LLRF system via EPICS. This software is used to automatically measure the quality factor and accelerating gradient of cavities during VT.

Speaker: Eric Viklund (KEK)

36 Status of SRF cavity tuner for the ILC prototype cryomodule being built at KEK

An ILC prototype cryomodule is currently under construction at KEK. It incorporates eight superconducting 1.3 GHz TESLA cavities. Precise setting and maintenance of the resonance frequency of these narrow-band cavities before and during operation require dedicated cavity tuners. The tuner design is based on the LCLS-II tuner. However, the specific requirements of the ILC prototype cryomodule, together with the current market situation, led to an almost complete re-engineering of the tuner. Due to limited resources, comprehensive system-level testing prior to deployment is not feasible. Therefore, dedicated qualification tests of the individual components are being carried out. This contribution reports on the current status of tuner development and production. In addition, two novel test methods for the slow actuator (stepper motor with gearbox) and the fast actuator (piezo actuator) under cryogenic vacuum conditions are presented, together with first measurement results.

Speaker: Dr Mathieu Omet (High Energy Accelerator Research Organization (KEK))

37 Discussion

Speaker: Yasuchika Yamamoto (KEK)

Tracking, Vertexing and Timing

3:30 PM Coffee break

Beam dynamics; beam delivery systems, main linacs, damping rings

Higgs and Electroweak

Joint: Beyond Colliders and BSM

38 Recent news on muon physics

I plan to review the recent updates in the following topics related with muon;
- Dipole Moments
- charged Lepton Flavor Violation
- muon cooling & acceleration
- high-intensity muon beam
- applications

Speaker: Tsutomu Mibe (KEK)

39 Dark-Sector Theory Overview

Speaker: Felix Kahlhöfer (KIT)

40 Dark-sector searches at ILC beam dumps

Light dark-sector particles may be produced in electron and positron beam dumps at the International Linear Collider (ILC). We propose an experimental setup to search for such particles, the Beam-Dump eXperiment at the ILC (ILC-BDX). This talk provides an overview of future dark-sector searches at ILC-BDX, considering several benchmark scenarios, including axion-like particles and sub-GeV dark matter. In particular, we highlight the projected sensitivity and key features of ILC-BDX-type experiments.

Speaker: Daiki Ueda

41 NA64-like Experiments

Speaker: Sergei Gninenko (Millennium Institute for Subatomic Physics at High Energy Frontier (CL))

42 SHiP-like Experiments

Speaker: Maksym Ovchynnikov (CERN)

Joint: Software and AI Applications

The recent progress of ITN project at KEK

43 ITN-EU activities

The ITN-EU collaboration coordinates European activities for the development and industrialization of SRF cavities for the ILC, in close relation with KEK and international partners. The presentation will provide the latest status of the single-cell and 9-cell cavity activities, covering material qualification, fabrication, and surface treatment. The presentation will also outline the next steps and future R&D programme, aimed at improving cavity performance, reducing production costs and strengthening the industrial readiness of European SRF technology.

Speaker: Karl-Martin Schirm

44 Plasma Processing of Elliptical Cavities at INFN LASA

Plasma processing is increasingly recognized as an effective technique for mitigating field emission and restoring the performance of superconducting radiofrequency (SRF) cavities. A collaboration among the Commissariat à l'énergie atomique et aux énergies alternatives (CEA), the European Spallation Source (ESS), the Fermilab (FNAL) and the Istituto Nazionale di Fisica Nucleare (INFN-LASA) is currently working to adapt and optimize this method for the treatment of SRF elliptical cavities.
This contribution summarizes the ongoing efforts at INFN LASA toward implementing plasma processing both in fully assembled cryomodules and in cavities prepared for vertical testing. We present the first experimental results obtained on a ESS medium-beta 704 MHz cavity equipped with different couplers and on a PIP-II low-beta 650 MHz cavity equipped with the Fundamental Power Coupler.

Speaker: Elisa Del Core (INFN Milano - LASA)

45 Analysis of HOM Power Propagation and Absorption in the PERLE String

PERLE (Powerful Energy Recovery Linac for Experiments) is designed to demonstrate multi-turn, high-current operation of an Energy Recovery Linac (ERL). Achieving this demanding operating regime requires effective management of propagating higher-order-mode (HOM) power in order to limit beam instabilities and minimize the associated cryogenic heat load. The PERLE main cryomodule comprises four 5-cell superconducting cavities operating at 801.58 MHz. Each cavity is equipped with two HOM hook couplers, while cold beamline absorbers operating at 40 K are positioned between neighboring cavities, with tapered transitions at both ends of the cavity string. This work presents updated results of the HOM power spectrum of the complete multi-cavity string under the nominal PERLE beam current and filling pattern. The resulting dielectric losses in the cold beamline absorbers are also evaluated. The analysis provides the distribution of HOM power among the different ports of the string and supports the assessment of the HOM damping scheme for high-current operation.

Speaker: Axel Perez Ruiz (Université Paris-Saclay, CNRS/IN2P3, IJCLab)

46 Commissioning of ESS superconducting linac in preparation for beam on target

In this talk will be presented the technical commissioning of ESS superconducting linac, challenges and outcomes are presented

Speaker: Dr Cecilia Maiano (European Spallation Source)

47 Discussion

Speaker: Yasuchika Yamamoto (KEK)

Wed, November 11

Plenary: Plenary Wed-1

48 AI and physics (title TBD)

Speaker: Koji Hashimoto

Sustainability

49 Towards Standardized Sustainability Assessment of Accelerator Research Infrastructures

Accelerator-based research infrastructures are among the most scientifically productive facilities worldwide, but their operation is also associated with significant energy demands, resource consumption, and environmental impacts. As future accelerator facilities pursue increasingly ambitious scientific and technical goals, the need for transparent and quantitative approaches to sustainability assessment is becoming increasingly important.
This contribution presents a framework for the standardized assessment of sustainability in accelerator research infrastructures, developed within the context of the European project Research Facility 2.0 (RF2.0). The framework focuses on environmental sustainability while maintaining links to operational and scientific performance. It organizes sustainability assessment into the domains of resources, energy, and greenhouse-gas emissions, and introduces a set of quantifiable indicators that enable systematic evaluation of facilities, technical systems, and alternative design solutions. A distinctive feature of the methodology is the incorporation of scientific output and operational time as normalization parameters, thereby connecting sustainability performance directly to the mission of research infrastructures. The framework further supports aggregation into composite sustainability scores while preserving transparency and traceability of individual indicators. The presentation will summarize the rationale behind the proposed metrics, their mathematical structure, and their application to accelerator technologies and infrastructure-level assessments.
In addition, selected insights from international sustainability studies involving research infrastructures and accelerator facilities will be discussed, highlighting common priorities, opportunities for energy efficiency improvements, and emerging approaches for integrating sustainability considerations into future facility planning and operation.

Speaker: Falastine Abusaif (KIT)

50 Environmental Impact and Considerations for Future Accelerators: 2nd LDG Mandate

Speaker: Caterina Bloise (INFN e Laboratori Nazionali di Frascati (IT))

51 IHEP Activities on Sustainability

The Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, is actively developing sustainable technologies for future particle accelerators, with the goal of reducing energy consumption and improving overall energy efficiency. Our activities cover a broad range of accelerator technologies, including superconducting radio-frequency (SRF) cavities, permanent-magnet systems, high-efficiency RF power sources, energy-recovery power supplies, and energy-recovery RF loads.

For SRF accelerators, we are investigating technologies to improve cryogenic efficiency and reduce the overall power consumption of accelerator facilities. Permanent magnets are being developed as an alternative to conventional electromagnets, offering significant potential for reducing power consumption and simplifying accelerator operation. High-efficiency klystrons and other RF power sources are being developed to achieve higher wall-plug efficiency, with energy-recovery technologies further improving RF system efficiency.

In addition, IHEP is exploring heat-recovery technologies to reuse waste heat generated by accelerator facilities, including the recovery and utilization of hot water. Energy-recovery power supplies and energy-recovery RF loads are also being studied to recover otherwise wasted electrical and RF energy.

These efforts aim to establish an integrated approach to sustainable accelerator design and operation, contributing to the development of greener, more energy-efficient, and economically sustainable future large-scale accelerator facilities.

Speaker: Zusheng Zhou (IHEP)

52 Sustainability presentation from Japan

11:10 AM Coffee break

Industry and Applications

53 Beyond a Single Project: Connecting ILC and Frontier Science Projects to Drive Industrial Innovation in Tohoku, Japan

Tohoku, northeastern Japan, is home to several major science and technology initiatives, including the International Linear Collider (ILC), NanoTerasu, the ITER Broader Approach (BA) activities, and the Fukushima Innovation Coast Framework. These projects provide local companies with opportunities to acquire advanced technologies, knowledge, and connections with researchers and research institutions.

However, participation in frontier science projects does not automatically lead to new products, new markets, or sustained business growth. Based on a survey of 47 companies in the Tohoku region, we identified two critical gaps in the process of translating frontier science into industrial value: (1) the acquisition and strengthening of R&D capabilities, and (2) the development of market creation and commercialization capabilities.

This suggests that the key challenge is not simply attracting individual frontier science projects, but creating connections among projects, companies, universities, research institutions, startups, and talent across the region.

The Tohoku Economic Federation is therefore exploring a regional innovation system in which ILC and other frontier science projects reinforce one another, while supporting the upgrading of regional companies, the concentration of R&D functions, and the circulation of highly skilled talent.

This presentation will introduce the Tohoku approach and discuss how regional coordination can help transform frontier science investments into sustained industrial innovation, business growth, and international collaboration.

Speaker: Eisaku Nishiyama (Tohoku ILC Promotion Council)

54 FULLCRYO is poised to deliver solid industrial equipment support for the construction of CEPC.

As CEPC-SppC Industrial Promotion Consortium, CIPC is an
industrial collaborative organization established for the CEPC
project, with nearly 100 member entities. The consortium aims to
jointly tackle key technologies and promote the industrialization
of research achievements, facilitating the high-quality
development of China’s industrial manufacturing, technology
R&D and engineering systems. This report outlines the founding
background, development vision and organizational structure of
CIPC, and presents the latest progress made by its member units
in booster, collider ring, MDI, civil engineering,
superconductivity, cryogenics, vacuum and other fields, so as to
comprehensively demonstrate the current status of CIPC.
Driven by the global fusion industry, China’s industrial
manufacturing and engineering capabilities have advanced
rapidly, which will provide strong support for the industrial
supporting construction of CEPC. Especially in the cryogenic
field, FULLCRYO from China stands as a pioneering enterprise,
has specialized in 20K-2K large-scale cryogenic equipment and
technical services. It has delivered more than 40 sets of large￾scale hydrogen-helium cryogenic equipment, covering 40 L/h, 70
L/h and refrigerators with power ratings of 400 W, 500 W, 850 W,
1 kW, 2 kW, 4 kW and 18 kW. The products have been deployed
in major scientific facilities and hydrogen energy projects, and
can meet the development demands of cutting-edge high-end
sectors including controlled thermonuclear fusion, particle
accelerators, hydrogen energy, semiconductors and quantum
technology.

Speaker: Jinlin Gao (Beijing Sinoscience Fullcryo Technology Co.,Ltd)

55 TBC

Speaker: Ronald Agustsson

56 Spanish Industry for Big Science: Capabilities, Collaboration and Success Stories

Future accelerators are major scientific and also industrial challenges. Turning ambitious concepts into reliable machines requires companies capable of designing, manufacturing, integrating and validating highly complex, often one-of-a-kind systems.

Over the last decades, Spain has developed a mature and highly specialised Big Science industrial ecosystem, with proven experience in some of the world's most demanding scientific facilities.

This talk will present some representative examples of these capabilities and, above all, an invitation to the international accelerator community to share their technological challenges: Spanish industry are experts in co-creation and eager to collaborate, transforming demanding specifications into working hardware.

Also, the talk will introduce INEUSTAR (the Spanish Science Industry Association) as a gateway to the Spanish Science Industry, helping research organisations and international partners identify the right industrial capabilities for their technological needs.

Speaker: Dr Leonor Mendoza (INEUSTAR / INDUCIENCIA)

57 AAA: Summary of its activities

58 KYOCERA: ceramic-to-metal brazing technology for accelerators

59 Recent activities of MHI-MS in Accelerator Technologies

Mitsubishi Heavy Industries Machinery Systems, Ltd. (MHI-MS) has extensive experience in the design and fabrication of accelerator components for major scientific facilities in Japan and worldwide. This presentation will highlight recent activities of MHI-MS, with a focus on superconducting and normal-conducting accelerator components, including RF cavities, accelerating structures, and related systems. Manufacturing capabilities, project achievements, and future prospects will also be presented.

Speaker: Nobuyuki Shigeoka (Mitsubishi Heavy Industries Machinery Systems, Ltd.)

1:30 PM Lunch

The recent progress of ITN project at KEK

60 The investigation of the manufacturing methods for 1.3 GHz 9-cell cavity under the International Linear Collider Technology Network(ITN)

As a part of research for the manufacturing methods for SRF cavities used in ILC(International Linear Collider), collaborative research is conducted in the framework of the ITN(ILC Technology Network) which includes the Korea University and KEK. Following our previous study on 1.3 GHz single-cell niobium cavities, we have extended our manufacturing scope to full-scale 1.3 GHz 9-cell cavity for ILC in collaboration between the Korea University and KAT. To validate the tooling, jigs and baseline manufacturing procedures, 1.3 GHz 9-cell cavity has been initially fabricated by using copper material. Room-temperature RF measurements and bead-pull test have been conducted, confirming precise field-flatness tuning and assembly accuracy. Building on these results, we are currently manufacturing the 1.3 GHz 9-cell cavity with niobium material. The cavity fabrication in Korea is scheduled for completion by June 2027, followed by surface treatment and vertical test at KEK in Japan. We present the VT results of 1.3 GHz single-cell cavities, the fabrication results of copper prototype cavity, and the progress of the niobium 1.3 GHz 9-cell cavity fabrication.

Speaker: Dr Junho Han (Kiswire Advanced Technology Co., Ltd.)

61 Progress of High-current Superconducting Cavity Cryomodule at IHEP

Energy recovery linac (ERL) based EUV-FELs are among the most promising candidate technologies for next-generation lithography. The development of a 10-mA high-current injector cryomodule for ERL-FELs has been initiated. The cryomodule consists of three 1.3 GHz 2-cell superconducting cavities, which are designed to accelerate 10 mA electron beam to 10 MeV. The cavities will receive the process of mid-temperature furnace baking, to reach the specification of Q₀ = 3×10¹⁰ at 17.4 MV/m (@ 2.0K). The shape of 1.3 GHz TESLA cavity is reference for these 1.3 GHz 2-cell cavities, which adopt the beam pipe with large aperture. Therefore, all higher-order modes (HOMs) can propagate along the large pipe and be absorbed at ~40K. The dipole-mode impedance is well below the beam breakup (BBU) threshold in the simulation, with this damping scheme. Each cavity is equipped with two fundamental power couplers (FPC), which suppresses the effect of transverse kick on the beam. In addition, the multipacting effect and the mechanical performance of the cavity have been evaluated, and both meet the design requirements. Four 1.3 GHz 2-cell cavities have just been fabricated, which will be subjected to post process and vertical test soon.

Speaker: Rui Ge (IHEP，CAS)

62 Fabrication and Radiofrequency Characterization of 1.3 GHz TESLA-type 9-Cell Copper Prototype Cavities

This study presents the fabrication and room-temperature radiofrequency (RF) characterization of 1.3 GHz TESLA-type 9-cell copper prototype cavities as a preparatory step toward future niobium superconducting RF cavity development. Prior to fabrication, three-dimensional electromagnetic simulations were performed to evaluate the resonant frequency, TM010 passband characteristics, and axial electric-field distribution. Based on the simulation results, three copper prototype cavities were fabricated and examined through helium leak testing and preliminary RF measurements. One cavity, in which all nine passband modes were clearly identified, was selected for detailed RF characterization. Vector network analyzer measurements showed an initial TM010 π-mode resonant frequency of 1.297913 GHz. The axial electric-field distribution was subsequently evaluated using bead-pull measurements, followed by repeated frequency-correction calculations and mechanical tuning. As a result, the field-flatness metric was improved from 35.45% to 95.9%, confirming a substantially more uniform field distribution among the nine cells. These results experimentally validate an integrated workflow consisting of cavity fabrication, room-temperature RF measurement, bead-pull characterization, and mechanical tuning. The established procedure provides a practical basis for the future fabrication and RF evaluation of 1.3 GHz niobium superconducting cavities.

Speaker: Seongjae Choi (Korea University)

63 Research Progress on 1.3 GHz High-Gradient Superconducting Cavity and cryomodule at IHEP

Speaker: Dr MI ZHENGHUI (IHEP)

64 Discussion

Speaker: Yasuchika Yamamoto (KEK)

Beam dynamics; beam delivery systems, main linacs, damping rings

Beyond Colliders Opportunities

Calorimetry + Particle ID

Flavor, Top and QCD

High Gradient RF Techniques

65 Status of the COLD (Cool copper Operation Linac) Project

The ESRF long-term plan for the upgrade of the injection complex foresees a full 6 GeV energy linac option. Given the space limitations of the site, the linac must fit in < 140 m, compactness is a strong design constraint. The most promising candidate to fulfill this goal is the C2 (Cool Copper at 77 K) technology in C-Band (5.712 GHz). The COLD Project intends to demonstrate the readiness of such a technology by accelerating a beam produced by a S-Band RF Gun (2.998 GHz) using C2 structures. The Project officially started in April 2025 and the first civil works of the installation started this summer. The status and goals of the Project will be reported.

Speaker: Alessandro D'Elia (ESRF)

66 Update on C-band activities at LANL

This talk will report on the status of C-band research activities at Los Alamos National Laboratory. This includes commissioning of the Cathodes And Radio-frequency Interactions in Extremes (CARIE) high gradient C-band RF photoinjector test stand and design and fabrication of the high-gradient C-band proton acceleration structures. We are testing functionality of the CARIE test stand by conditioning the high gradient photoinjector capable of producing electric fields at the cathode up to 250 MV/m. The photoinjector is powered by a 50 MW, 5.712 GHz
Canon klystron. The all-copper photoinjector is fabricated and cold-tested and undergoes high gradient testing which is likely to finish this Fall. We have also designed and are fabricating a four-cell high gradient C-band accelerating structure for the LANSCE accelerator booster designed to accelerate beta=0.93 protons to the final energy of 3 GeV. The structure will have to be tested at cryogenic temperatures which requires infrastructure updates at CARIE. Finally, at the C-band Engineering Research Facility (CERF-NM), we recently finished the high
gradient testing of the C-band cavity with nickel-chromium higher order mode absorbers. We are conducting the post-mortem inspection of the cavity to evaluate the effects of high gradient on the nickel-chromium absorbing material. The statuses of the CARIE facility, CERF-NM facility, their high-power operation, and the results of various high gradient tests will be presented.

Speaker: Evgenya Simakov (LANL)

67 High-Power Test Results for Multiple-Sector X-band Accelerating Structures Fabricated Using Different Materials but Based on the Same Design

Multiple-sector X-band accelerating structures were designed and fabricated with four quadrants [Nucl.Instrum.Meth.A 1063 (2024), 169272]. We carried out high-power tests at Nextef2, an X-band high-power test stand in KEK, for two such test cavities fabricated using hard pure-copper and copper-silver with the same electrical design. We report the results of the tests and postmortem investigations, including comparison between the two cavities.

Speaker: Abe Tetsuo (KEK)

4:00 PM Coffee break

Beyond Colliders Opportunities

68 Future Linear Colliders as High-Energy Inverse Compton Photon Sources for Photon Science

Inverse Compton scattering (ICS) is today a well-established route to produce tunable, high-brilliance photon beams for photon science, nuclear physics and fundamental studies. Pushing ICS sources towards higher photon energies requires electron beams in an energy range that only large-scale accelerator facilities can provide. Future linear colliders offer electron beams with energies extending from hundreds of GeV to the TeV scale, opening opportunities beyond their primary role as particle colliders. This activity is developed in natural synergy with analogous studies already carried out and ongoing for circular colliders, in particular the FCC-ee. We explore the use of these beams to generate high-energy photon radiation through inverse Compton scattering. As a benchmark, the LCF380 scenario with 190 GeV electrons is considered, using laser pulses synchronized with the electron bunches to provide the photon target for Compton interactions. The photon spectrum, yield, angular distribution and flux are studied as a function of the electron-beam and laser parameters. The study investigates the potential for producing intense and energetic photon beams, as well as possible configurations with multiple Compton interaction points along the linear accelerator. Finally, the scaling of the concept towards TeV-class linear colliders and its potential applications in photon science, nuclear physics and high-energy photon physics are discussed.

Speaker: Illya Drebot

69 Can electrons emit photons of energy larger than their own? Full Inverse Compton Scattering

The newly discovered effect of Full Inverse Compton Scattering has shown several implications to unexpected phenomena, like the achievement of extremely high accelerations with electrons coming to a sudden stop from relativistic velocities, therefore showing potentialities of detecting Unruh radiation, and opening a portal towards quantum gravity, and like the emission of photons with energy larger than that of the emitting electron, in apparent violation of energy conservation. We will discuss these new findings with an eye at the historical development, throughout the last century, in the understanding of QED electron-photon interactions, from the nuclear bomb development to the first studies on cosmic rays, to the development of modern Inverse Compton Scattering advanced sources of X/gamma rays. Full Inverse Compton Scattering can have significant impacts also in other fields like plasma physics, with the capability of trapping electrons (positrons) in magnetic bottles, with the spectral purification of broadband gamma ray photon beams, and with several possibile implications in the field of gamma ray cosmic sources.
https://doi.org/10.1016/j.nima.2024.169964

Speaker: Luca Serafini (INFN - Milan)

70 Towards non-perturbative QED at a linear collider facility with plasma-mirror-boosted lasers

Strong-field quantum electrodynamics (QED) offers a unique window into fundamental physics at extreme electromagnetic fields, where higher-order effects may eventually lead to a breakdown of the perturbative description of QED. The recently launched NP-QED project aims to approach this regime by combining relativistic electron beams with ultra-intense laser pulses, intensified by Doppler-boosted plasma mirrors. Future linear collider facilities, providing electron and positron beams with energies extending into the TeV regime, could substantially extend the accessible strong-field parameter space. A particular focus is placed on combining plasma-mirror-boosted laser pulses with the 190 GeV electron beam of the LCF380 scenario. We discuss the strong-field regime accessible with such a setup and its potential for approaching the fully non-perturbative regime of QED.

Speaker: Ivo Schulthess (Deutsches Elektronen-Synchrotron (DE))

Beyond Standard Model

Electron/Positron Sources

71 Prototype Development of Key Components for a High-Intensity Positron Source

Development of a high-intensity positron source requires reliable components capable of operating under severe beam-loading, thermal, mechanical, and electromagnetic conditions. We are developing prototypes of three key components: a rotating positron production target, an accelerator structure for capturing and accelerating positrons, and a flux concentrator for providing a strong pulsed magnetic field near the target.

The rotating-target prototype has been completed and evaluated through rotation, vacuum, and thermal-load tests. This presentation reports its measured performance, together with the design concepts and fabrication status of the accelerator structure and flux concentrator. The remaining technical challenges and future plans toward improving the our prototype are also discussed.

Speaker: Mr Yu Morikawa (KEK)

72 A seamless Blackbox optimization of ILC E-Driven Positron source

Since the ILC (International Linear Collider) cannot reuse beams, it is necessary to generate a large number of particles. In Electron-driven positron sources, it is important to find efficient generation conditions because the target load becomes large. We simulated the process in which an electron beam is injected into a W-Re target, the generated positrons are captured and accelerated by RF, and then collected within the DR acceptance, and conducted research on more efficient positron generation and capture conditions. The parameters under consideration include various parameters of the positron accelerator. We adopted the Black Box optimization method. We report the current status.

Speaker: Yodai Sasaki

73 Beam Simulation and Parameter Study of the Capture Linac for the ILC E-Driven Positron Source

To achieve high luminosity in the International Linear Collider (ILC), we need a high-current multi-bunch beam. Maximizing the positron capture efficiency (yield) is a key challenge. Positrons go through capture and booster linacs before entering the damping ring. For good transport efficiency later, it is important not only to get many positrons, but also to make the bunch short during the capture stage. In this study, we simulated the beam behavior in the capture section of the ILC electron-driven positron source. This section includes a target, a flux concentrator (FC), a collimator, and solenoid-focused accelerating structures. Previous studies showed that beam loss at the collimator is the biggest issue, and the bunch length is mostly decided around the fourth accelerating structure. Based on this, we investigated how the component layout and magnetic field in the upstream region of the capture linac affect the yield and bunch length. We investigated the parameter dependencies to provide guidelines for efficient beam capture under realistic engineering constraints. In this presentation, we report these simulation results.

Speaker: Masafumi Fukuda (KEK: High energy accelerator research organization)

High Gradient RF Techniques

74 Next Generation Low Level RF Control Automated for Breakdown Studies

The radio frequency (RF) system on a chip (RFSOC) is a next generation low level RF board that integrates both direct RF sampling for data collection with local processing and algorithmic control with an FPGA for high precision RF outputs. The ability to directly sample RF inputs allows for local control of real-time frequency tuning and pulse shaping feedback of the RF output pulse. We use this system to control an S-band (2.856 GHz) klystron connected to a single S-band cavity to perform automatic breakdown statistics and conditioning. Here, we present the conditioning performed by the automatic RFSOC feedback and demonstrate the RFSOC as a compelling candidate for LLRF generation at future collider facilities.

Speaker: Sophia Morton (SLAC, Stanford)

75 Short Pulse Driven Photogun for Bright Beams generation

High gradient radio frequency (rf) driven photoguns are photoemission electron sources that have important applications for accelerator-based instruments, such as light sources and electron microscopy. Numerous efforts have been made to push for even higher field gradient while suppressing rf breakdowns. We propose the Compressed Ultrashort Pulse Injector Demonstrator, a 1.6 cell photogun driven by nanosecond high power rf pulses to achieve high gradients with low breakdown rate. This photogun is powered by ultrashort pulses from a rf pulse compressor and a high power klystron. This presentation focuses on the work of the CUPID photogun for generating bright electron beams to drive x-ray free-electron lasers (FELs) at 40 keV photons or higher. We first show the design of CUPID photogun, followed by its capability of bright beam generation when forming a photoinjector with a superconducting solenoid and downstream linacs. We then show start-to-end simulations of the existing LCLS copper accelerator free-electron laser with CUPID photogun as a drop-in replacement to demonstrate its improvement in delivering hard x-rays at mJ level pulse energy. Finally, we show preliminary high power rf testing of CUPID prototypes and plans for electron beam generation.

Speaker: Emilio Nanni (SLAC National Accelerator Laboratory)

Joint: Higgs/EW and Global Analysis

The recent progress of ITN project at KEK

76 Recent SRF cavity fabrication studies at KEK

This talk introduces SRF cavity fabrication research at KEK over the past five years. The common objective is to reduce the cost of SRF cavities. The first topic is a Nb/Cu cavity in which the cavity body is made of copper and the inside is coated with niobium to induce superconductivity. The inner surface of the accelerating cavity must be smooth, and a seamless cavity is ideal as a base for the coating. We developed the idea of manufacturing a seamless cavity from a single copper tube and successfully prototyped it by hydroforming. At CERN, we applied a niobium coating with a film thickness of about 5 µm by magnetron sputtering. RF performance tests were conducted at KEK, and the accelerating gradient reached 12 MV/m at 4 K and 16 MV/m at 1.85 K. We are currently working on further improvements to improve performance. After hydroforming, the inner surface of the cell becomes rough. We report our efforts to improve the roughness by polishing. The second topic is the manufacture of niobium SRF cavities by cold spray. Cold spray is a lower-temperature solid-state thermal spray process that deposits metal powder using a heated inert gas through a supersonic nozzle. When the material hits at supersonic speed and reaches the critical speed, the particles themselves are plastically deformed to form a film. We proposed a novel manufacturing method to form a thick niobium film on the surface of a mandrel by cold spray using niobium powder, then remove the mandrel to finish a hollow shape. We confirmed the feasibility of the proposed method for a 3 GHz one-cell cavity. We also carried out an RRR measurement of the cold-sprayed niobium specimen and obtained a value of 11. We report on these results. The third topic is the manufacture of a niobium foil cavity. We proposed a new approach to fabricating the cavity body by spinning a 1.5-mm-thick niobium sheet, and we prototyped a 3 GHz one-cell cavity. To improve the cavity's structural strength after spinning, we deposited a copper layer on the outer surface using cold spray. We report on the details of the manufacturing process.

Speaker: Prof. Masashi YAMANAKA (KEK)

77 Development of an organic-solvent electropolishing process for mirror finishing of Nb

Speaker: Dr Takeyoshi Goto (KEK)

78 Statistical evaluation of mechanical properties of fine grain niobium sheets.

Tokyo Denkai has supplied over 20000 fine grain (FG) niobium sheets for superconducting cavities for the European XFEL, LCLS-II, LCLS-II HE and SHINE projects. In this study, tensile test data obtained during mass production were statistically evaluated. Tensile strength, 0.2 % proof strength and elongation showed normal distributions. The minimum values estimated as the mean minus three standard deviations were 153 MPa, 48 MPa and 45 %, respectively. According to JIS B 8266, the design-stress strength (allowable stress) of FG niobium was calculated to be 32 MPa based on the 0.2 % proof strength. The differences in tensile strength and 0.2 % proof strength between the rolling and transverse directions were small. On the other hand, elongation showed larger differences, mainly due to the fracture position of the tensile test specimens. In addition, the influence of a change in the final heat-treatment condition was statistically evaluated. The tensile strength and 0.2 % proof strength showed statistically significant changes, but the magnitude of the changes was small compared with the specified values. These results show that statistical evaluation of mass-production data is useful for evaluating the mechanical properties of FG niobium and confirming the validity of manufacturing conditions.

Speaker: Hiroaki Umezawa (Tokyo Denkai Co., Ltd.)

79 Improved mid-T heat treatments for cavity performance and the upgrade of DESY’s B-mapping system

Speaker: Dr Marco Voige (DESY)

80 Discussion

Speaker: Yasuchika Yamamoto (KEK)

Thu, November 12

Plenary: Plenary Thu-1

81 SCRF latest technology and for future

Speakers: Hiroshi Sakai (KEK), Hiroshi Sakai (Institute for Solid State Physics, University of Tokyo)

82 Status of ATF2

Speakers: Angeles Faus-Golfe (Instituto de Fisica Corpuscular (IFIC) CSIC-UV), Angeles Faus-Golfe (IJClab)

83 Progress of Positron source

Speakers: Gudrid Moortgat-Pick (Unknown), Gudrid Moortgat-Pick

84 Ghost Collider (ERL)

Speaker: Kaoru Yokoya

10:30 AM Coffee break

Beyond Standard Model

Electron/Positron Sources

85 Generation of Polarized Positron Beams for Ce+BAF

The generation of polarized positron beams for the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is based on bremsstrahlung radiation and electron-positron pair production by a 90% longitudinally polarized electron beam in a rotating tungsten target. The required electron beam energy and target thickness for generating a 100 nA positron beam with 60% polarization and a normalized emittance of 100 mm·mrad are calculated. To prevent target overheating and damage, the peak energy deposition density (PEDD) is also calculated. The electron beam current, beam spot size on the target, and target rotation speed are determined for a PEDD limit of 35 J/g for the tungsten target. The objective of this study is to work backward from the CEBAF 6D acceptance to determine the required parameters of the primary electron beam and tungsten target for positron production.

Speaker: Andriy Ushakov (Jefferson Lab)

86 Photocathodes, Polarization, and Beyond: Advances in Electron Source Development

GaAs based photocathodes play a crucial role as the primary source of polarized electron beams in various accelerator facilities, including CEBAF at Jefferson National Laboratory and the Electron Ion Collider (EIC) at Brookhaven National Laboratory in the USA. The electron pre-injector at the EIC requires a 1-2 nC bunch with at least 85% spin polarization from a superlattice GaAs photocathode, with longitudinal polarization subsequently rotated to transverse directions using a pair of Wien filters before injecting into the linac. To address the source requirements, we have carried out an extensive study of MOCVD-grown superlattice GaAs/GaAsP structures incorporating a Distributed Bragg Reflector (DBR) underneath. We have incorporated different surface cleaning and activation mechanisms to improve the QE and lifetime of the photocathodes. Besides, 2D protective coatings for polarized electron sources are being explored. In this paper, we will report our advances in electron source development.

Speaker: Jyoti Biswas (Brookhaven National Laboratory)

87 Recent advances in long-lifetime photoelectron sources at Jefferson Lab

Highly spin-polarized electron beams for accelerators are almost universally generated by laser-driven, DC-biased photoelectron sources containing GaAs-based photocathodes. These sources are subject to damage mechanisms causing the gradual destruction of the photocathode surface at a rate at least proportional to the beam current, effectively limiting the achievable average current for a given continuous operating time. As the ongoing development of polarized, high-current electron machines and positron conversion targets is pushing the average current requirements beyond what has been reliably demonstrated, Jefferson Lab is pursuing R&D efforts to greatly increase the lifetime of photoelectron sources. Employing a combination of strategies such as deflecting fields for ions, optimized laser profiles, and photocathode materials with enhanced optical absorption, we hope to achieve a tenfold increase in the available average current. In this talk, I will give an overview of the ongoing activities, recent progress made, and the remaining challenges.

Speaker: Max Bruker (Jefferson Lab)

Higgs and Electroweak

Joint: SRF and High Gradient RF

88 Recent advances in high-Q/high-gradient at Jefferson Lab

Speaker: Dr Pashupati Dhakal (JLAB)

89 Redefining SRF surface roughness that matters for attainable surface magnetic fields

Speaker: Dr Eric Lechner (JLAB)

90 Recent results from Nb3Sn R&D at Fermilab

Speaker: Dr Grigory Eremeev (FNAL)

91 Recent advances in high-Q/high-gradient at Fermilab

Speaker: Dr Daniel Bafia (FNAL)

92 Discussion

Speaker: Yasuchika Yamamoto (KEK)

Upgrade with Advanced Accelerator Technologies

93 Enhancing gamma-gamma collider luminosity through scattering-laser wavelength selection in the presence of prolific electron-positron pair production

A gamma-gamma collider capable of reaching the multi-TeV frontier of particle physics may enable the study of phenomena beyond the Standard Model. Based on compact linear wakefield accelerator technology, such a collider could be realized by Compton scattering multi-TeV lepton beams off moderate-intensity laser pulses close to the collider interaction point, producing the required gamma-photons. It is shown that, for a wide range of scattering-laser wavelengths, gamma-gamma collisions at the interaction point can meet the luminosity requirements for novel particle physics studies, even in the presence of the prolific electron-positron pair production that accompanies the interaction of the scattering laser with the multi-TeV lepton beam. It is shown that an enhancement in gamma-gamma collider luminosity can be achieved for 250 nm and 1.25 nm scattering lasers. These enhanced luminosities need to be compared to that of the electron-positron colliders, which also have a number of important interaction point physics problems. In particular, whether the beamstrahlung, electron-positron pair production, and beam disruption can limit the physics reach of such a collider. It is shown that in the strong beamstrahlung regime the high energy collision luminosity is significantly reduced due to photon emission, making gamma-gamma collider option more attractive. The amount of reduction depends on the beamstrahlung strength, which is controlled by the particle bunch charge, length, emittance, and beta function. The obtained results favor the use of extremely short electron-positron bunches for the future collider design.

Speaker: Stepan Bulanov (Lawrence Berkeley National Laboratory)

94 The ReLiC– Recycling Linear Polarized e+e- Collider

I will present our studies of linear collider e+e- collider recycling both the used particles and the beam energy. After each collision particles are decelerated and cooled in damping rings. Recycling collided particles and their energy opens path to very high luminosity O(1036) cm-2 sec-1. ReLiC will be able to collide highly polarized electrons and positrons. The main challenges of such concept are in computing low energy tail caused by beamstrahlung and limiting emittance blow-out during collisions. Beamstrahlung control requires colliding super-flat beams with size ratio exceeding 1,000. I will present progress with simulations of collision effects as function of the c.m. energy and discuss requirements for damping ring in such collider.

Speaker: Vladimir Litvinenko (Stony Brook Univeristy)

95 Narrow Band γγ Colliders: From Precision Higgs Factories to the 10 TeV Energy Frontier

Photon-photon (γγ) Compton colliders offer compelling, high-efficiency pathways to explore the fundamental building blocks of matter without the technological bottlenecks associated with high-intensity positron sources and plasma-based positron acceleration. Furthermore, γγ Compton colliders operating in a narrow-band energy configuration can offer, in many circumstances, additional advantages for precision measurements and energy-frontier discovery. This presentation outlines the design concepts, advanced accelerator technologies, and physics capabilities of narrow band γγ colliders spanning precision Higgs factories to 10 TeV in the center-of-mass.

First, we review the conceptual design of the X-ray Free-Electron Laser (XFEL)-based γγ Compton collider (XCC) Higgs factory. Driven by cold copper distributed coupling (C$^3$) accelerator technology, XCC collides 62.8 GeV electron beams with 1 keV XFEL pulses to generate colliding beams of 62.5 GeV photons. The resulting sharply peaked γγ luminosity spectrum produces 75,000 Higgs bosons per 10$^7$ s year, yielding Higgs coupling measurements comparable in precision to $e^+ e^-$ colliders, with an upgrade path to 280 GeV for triple Higgs coupling studies. Issues of beamline layout, the machine-detector interface and backgrounds are addressed.

Extending the narrow-band approach to the 10 TeV frontier, we evaluate a high-geometric-luminosity configuration of a plasma wakefield $e^-e^-$ collider ($L_{e^- e^-}^{geo} =60\times 10^{35} $ cm$^{-2}$ s$^{-1}$) utilizing short-wavelength, 1 keV scattering lasers paired with 5 TeV electron beams. While optical/UV scattering ($\hbar\omega_0=2.5$ eV) leads to severe primary interaction region electromagnetic fields up to $6\times 10^{16}$ V/m that induce heavy beamstrahlung and coherent pair production, the 1 keV laser configuration mitigates these fields by over two orders of magnitude. This yields a clean, highly peaked luminosity spectrum with a partial 1.5% γγ luminosity of $L_{\gamma\gamma}^{1.5\%}=0.33\times 10^{35}$ cm^{-2} s$^{-1}$ and low pileup ($\langle\mu\rangle_{pileup}\approx 3.3$). Together, these designs demonstrate the unique physics and accelerator advantages of X-ray-driven Compton colliders from 125 GeV to 10 TeV.

Speaker: Tim Barklow (SLAC National Accelerator Laboratory (US))

96 Proposal of electron-positron ERL collider

Energy recovery linac, ERL is promising scheme for high-luminosity colliders with reasonable construction costs and power supply. A racetrack-type ERL accelerator is proposed as a compact electron -positron collider at the Z-pole. The circumference is approximately 6 km. It is assumed to be located at the Tsukuba campus of KEK.

Speaker: Miho Shimada (KEK)

12:30 PM Lunch

Calorimetry + Particle ID

Electron/Positron Sources

97 FCC-ee positron source design at 3 GHz

A high-performance positron source is essential for FCC-ee to provide the high-intensity, low-emittance beams required for rapid injection, especially in the Z-pole operation mode. In the FCC-ee Feasibility Study, the reference positron source is based on a 2.86 GeV electron drive beam impinging on a 15 mm tungsten target, followed by an HTS matching device and a 2 GHz travelling-wave RF capture section embedded in a 0.5 T solenoidal channel. A chicane separates electrons from positrons, after which the positron linac, based on the same 2 GHz RF structures as the capture section, is divided into two focusing sections: a solenoid-focused section with a 0.5 T field, followed by a FODO-based section with quadrupole focusing between the RF structures.
This work investigates 3 GHz S-band RF structures as potential alternatives for the FCC-ee positron linacs, motivated by the maturity and broad availability of high-power S-band RF technology. Two 3 GHz configurations are studied in detail. The first, denoted v1, employs five 3 m long travelling-wave structures in the capture section, whereas the second, v2, uses twelve 1.2 m standing-wave structures developed for the P³ experiment. In both configurations, the capture structures are embedded in a solenoidal focusing channel. Following electron–positron separation in a chicane, the positron beam is matched into a quadrupole-focused linac based on large-aperture 3 GHz travelling-wave structures. Its first and second sections contain 16 and 48 structures, respectively. A downstream energy-compression system, comprising a magnetic chicane and four additional travelling-wave structures, together with a matching line, prepares the beam for injection into the damping ring. A 6D DR acceptance approach, benchmarked against direct particle tracking through the damping ring, is incorporated into the fast optimization workflow. Start-to-end simulations are performed using RF-Track, while the princpal machine parameters are optimized with Xopt. By retaining a common downstream layout, the study enables a consistent comparison of the two capture configurations, identifies their principal performance trade-offs and provides the basis for establishing the current 3 GHz baseline design for the FCC-ee positron source.

Speaker: Yuting WANG (IJCLab - IN2P3/CNRS)

98 Status of P3 Experiment

The PSI Positron Production (P3, or P-cubed) experiment is a demonstrator of a positron source and capture system developed within the FCC-ee injector study. Installed at the SwissFEL facility of the Paul Scherrer Institute, the experiment aims to significantly increase the positron yield compared with the current state-of-the-art. The facility combines a conventional pair-production target with an advanced capture system based on high-temperature superconducting solenoids and large-aperture RF cavities to maximize positron collection efficiency. Following the successful installation of the experimental setup, this presentation reports the first e⁺ beam measurements, representing an important milestone for the P-cubed experiment and for the development of high-intensity positron sources for future electron-positron colliders.

Speaker: Simone Giroldi (PSI and EPFL)

99 Positron Source for HALHF and Future Collider Designs

The current polarized source for the HALHF design has been studied and synergies with positron sources for ILC, LC and CLIC will be discussed.

Speaker: Gudrid Moortgat-Pick

Joint: Higgs/EW and BSM

Joint: SRF and High Gradient RF

Upgrade with Advanced Accelerator Technologies

100 HALHF: recent progress and relevance toward 10 TeV

The hybrid, asymmetric, linear Higgs factory (HALHF) is a plasma-based collider concept that combines plasma-wakefield acceleration (PWFA) of electrons and radio-frequency (RF) acceleration of positrons for asymmetric-energy collisions at 250 to 550 GeV. This has the potential to overcome the positron problem in PWFA, and provide a cost-effective collider with a reduced footprint. We report on recent progress in the HALHF project as we move toward a pre-CDR. This includes work on emittance preservation in the multistage plasma accelerator, handling of high heat flux and plasma temperatures, the driver-delivery complex, the beam-delivery system, and more. Finally, we discuss how developments in HALHF can be relevant to a 10-TeV collider design.

Speaker: Carl Andreas Lindstrom

101 Simulating the Luminosity Spectrum at HALHF

HALHF is a proposed hybrid linear collider with highly asymmetric beam energies. WarpX, a Particle-In-Cell (PIC) code capable of self-consistently simulating beam-beam effects, including beamstrahlung, has been used to characterise the luminosity spectrum expected at HALHF for three different baseline designs with centre of mass energies of 250 GeV, 380 GeV and 550 GeV. The resulting luminosity spectra are compared with independent simulations performed using GUINEA-PIG, a dedicated beam-beam interaction simulation code widely used for linear collider studies. We present the luminosity distributions obtained with both simulation approaches and demonstrate good agreement between them.

Speaker: Lucy Bishop (DESY)

102 Plasma-based Linear Colliders: Relevant Experimental Demonstrations at FLASHForward

Plasma-based accelerators can produce accelerating fields several orders of magnitude stronger than those of conventional accelerators. They operate by driving density waves in a plasma using compact particle beams or laser pulses. The resulting strong wakefields are then used to accelerate a trailing electron bunch. The FLASHForward experiment at DESY performs fundamental research on this scheme using FEL-quality bunches from the FLASH linear accelerator. This contribution will summarise recent results from FLASHForward to provide insight into the state of beam-driven plasma accelerator research.

The trailing bunch can be injected internally from the plasma, a promising route to ultra-low emittance. Results from FLASHForward will be presented demonstrating reproducible density down-ramp injection and GV/m acceleration of bunches with collider-relevant quality.

Both matching into plasma-based accelerating stages and collider final-focusing systems require strong focusing fields. Fields of the required magnitude can be produced by passive plasma lenses. Experimental results will be discussed showing that such lenses can preserve FEL-quality transverse slice emittance and produce focusing fields two orders of magnitude stronger than permanent quadrupole magnets.

A novel diagnostic of the driver-to-witness energy-transfer efficiency will also be shown. Exploiting the emitted plasma light, the technique is parasitic and longitudinally resolved.

Finally, preliminary experimental results, including plasma acceleration, will be presented on generating twin bunches at the photocathode suitable for plasma wakefield acceleration with tunable delay and bunch shapes.

Speaker: Marcel Hohmann (DESY)

3:30 PM Coffee break

Calorimetry + Particle ID

Electron/Positron Sources

103 Results of Active Plasma Lens and Pulsed Solenoid Studies as Optical Matching Devices at the ILC Polarized Positron Source

The polarized positron source of the International Linear Collider requires efficient optical matching of the highly divergent positron beam produced at the target.
The long ILC bunch train also places strong requirements on the stability and operation of the matching device.
This contribution will summarize studies of two alternative concepts: a pulsed solenoid and an active plasma lens.

A pulsed solenoid was studied using numerical optimization and magnetic-field measurements. A simulation framework coupling COMSOL and
ASTRA was used to optimize the solenoid geometry and study positron capture. The simulations identified a transverse dipole kick as an important limitation of the current design,
while measurements of a prototype showed promising temporal field stability.

As a novel alternative, a downscaled active plasma lens prototype was experimentally studied with a focus on discharge stability and long-term operation.
The measurements showed significant electrode erosion and material deposition, changes in discharge behavior over time
and limitations for repetitive MHz operation. High-speed imaging was used to further investigate the spatial and temporal behavior of the plasma discharge.

The results provide a comparison of both concepts and identify the main challenges for their application at the ILC.

Speaker: Niclas Hamann (Uni Hamburg/DESY Hamburg)

Higgs and Electroweak

Upgrade with Advanced Accelerator Technologies

104 The Linear Ghost Collider - Efficient & High Luminosity LC Upgrade

A 550 GeV centre-of-mass Higgs factory is presented, the Linear Ghost Collider (LGC). Acceleration and deceleration is performed within an SRF linac where the bunches transported are net neutral, termed ghost bunches. Within these, one charge partner accelerates, and the other decelerates. In this way energy is recovered after collision, and all particles recycled. An accompanying plenary talk - Ghost Collider (GC) - introduces this concept. LGC comprises an improved configuration to GC that eliminates turn-around arcs. This enables a large reduction in energy lost to synchrotron radiation, and an increase in luminosity as bunches are degraded less, in comparison to GC. Lacking arcs, LGC can therefore be considered as a luminosity upgrade of a pre-built LC. The key innovation is that within a ghost bunch only the velocities of the charge partners must match, not their energies. Therefore, only one charge partner need be accelerated to collision energy. This allows the linac to be split into stages, with the other charge partners only accelerated to collision energy divided by the number of stages - these are termed drive bunches. Recirculation is only needed for drive, not colliding, bunches. As with GC, collisions are arranged between net neutral bunches, this strategy of charge compensation of beamsstrahlung with small disruption allows the energy recovery and re-use of spent colliding bunches. Two variants of LGC are presented: firstly, a pulsed version analogous to GC realisable with existing SRF technology and capable of $34.6\times 10^{34}$ cm$^{-2}$ s$^{-1}$ @ <100 MW electrical power for RF with disruption parameter 2.25; and secondly, a continuous-wave (CW) version based on expected parameters for thin-film $\textrm{Nb}_3\textrm{Sn}$ on copper SRF technology, capable of $348\times 10^{34}$ cm$^{-2}$ s$^{-1}$ @ 160 MW electrical power for RF with disruption parameter 1.48. We compare these values to established collider proposals, and scale to $380$~GeV and $250$~GeV centre-of-mass energies, showing their attractiveness over a large parameter range.

Speaker: Peter Williams

105 New Concept: Gravity-Aligned Vertical Electron-Positron Linear Collider

A gravity-aligned vertical electron-positron linear collider is proposed as a concept to break the cost-and-scale impasse that confronts conventional horizontal Higgs factories [KEK Preprint 2026-16, arXiv:2607.24179]. The accelerating axis is oriented along the local gravitational field inside a single deep vertical shaft with a depth of ~3 km. Positrons are injected downward from the surface while electrons are accelerated upward from the bottom, the two beams meeting at an interaction point located deep underground. Targeting a staged center-of-mass energy in the Higgs factory range (250 - 500 GeV), this concept assumes high-gradient, high-efficiency, normal-conducting accelerating structures operated at cryogenic temperature together with a two-beam power-delivery scheme. It can be designed to reuse the existing KEK/SuperKEKB accelerator complex in the KEK Tsukuba Campus. We discuss the advantages of the vertical orientation, namely a small surface footprint, intrinsic azimuthal symmetry of the gravity load, deep vibration isolation of the collision point, a natural vertical alignment reference, a cosmically quiet deep interaction point, a unique opportunity and value in social/industrial evaluation, as well as the principal disadvantages and challenges, including the required high accelerating gradient and the construction of a kilometers-deep shaft. This presentation is deliberately concept-level and is intended to motivate technological innovation and feasibility studies.

Speaker: Abe Tetsuo (KEK)

106 Driver guiding and length matching for improved misalignment tolerances plasma accelerators

Plasma wakefield acceleration offers a pathway to compact linacs, but stringent angular tolerances and transverse instabilities pose significant challenges. This paper presents a combined approach of active drive beam guiding and stage betatron length matching to mitigate these effects. Using analytical modelling and PIC simulations based on the HALHF baseline parameters, a reduction of the multi-shot normalised emittance by 3--4 orders of magnitude compared to when no corrections are applied, is shown.

Speaker: Erik Adli (University of Oslo (NO))

107 Monoenergetic, stable, electron beam generation via laser wakefield acceleration

The advent of high-peak-power laser technology [1] has enabled compact charged-particle acceleration with a higher acceleration gradient than conventional RF accelerators. One of the most promising schemes is laser wakefield acceleration of electrons [2], and significant progress has been made in achieving 10 GeV energy [3], a few-fs pulse duration [4], a transverse emittance of <1 mm-mrad [5], etc. However, these record values are not simultaneously achieved (or measured), and the parameter stability is not comparable to that of state-of-the-art linear accelerators.
Recently, we developed two schemes that improve both quality and stability. With these schemes, we demonstrated a high-quality electron beam with an energy of 376±16 MeV, a relative energy spread of 1.5±0.5%, a charge of 25.3±7.4 pC, a divergence of 0.5 mrad, and a pointing stability of 0.41ｘ0.23 $\mu$rad (error bars show standard deviations over multiple shots). With the improved quality, free-electron lasing around 20-50 nm was observed using a 2-m-long undulator with the undulator parameter of $K$=0.4-1.4 [6].
These stable electron beams further improved the system; more recently, we have removed some thermal effects, and electron-beam stability has improved [7].
In addition, we discuss the perspective of LWFA for higher electron energy and more stable electron-beam generation.

Acknowledgement
This work was supported by JST-Mirai Program Grant Number JPMJMI17A1, Japan.

References
[1] D. Strickland and G. Mourou, Opt. Commun. 56, 219 (1985).
[2] T. Tajima and J. M. Dawson, Phys. Rev. Lett. 43, 267 (1979).
[3] C. Aniculaesei et al., Matter Radiat. Extremes 9, 014001 (2024); E. Rockafellow et al., Phys. Plasmas 32, 053102 (2025).
[4] O. Lundh et al., Nat. Phys. 7, 219 (2011).
[5] S. K. Barber et al., Phys. Rev. Lett. 119,104801 (2017).
[6] Z. Jin, M. Kando et al., Phys. Rev. Res. 8, 013207 (2026).
[7] Z. Jin et al., Phys. Rev. Res. (submitted).

Speaker: Masaki Kando (Kansai Instiute for Photon Science, Naitonal Institutes for Quantum Science and Technology)

Banquet

Fri, November 13

Plenary: Plenary Fri-1

108 Summary of physics

109 Summary of Detector & software

110 Summary of Accelerator (basic)

111 Summary of Accelerator (upgrade)

112 Summary of beyond collider

Speaker: Ivo Schulthess (Deutsches Elektronen-Synchrotron (DE))

10:30 AM Coffee break

Plenary

113 Quantum Information and Future Linear Colliders

Speakers: Kun Cheng, Kun Cheng

114 The future of Linear Colliders

Speaker: Jenny List (Deutsches Elektronen-Synchrotron (DE))

115 Next (next) LCWS

116 Farewell

Speakers: Hiroshi Sakai (KEK), Takeshi Dohmae

1:00 PM Lunch

Lab tour

Satellite