Periodic Reporting for period 1 - MuCol (A Design Study for a Muon Collider complex at 10+ TeV center of mass)
Reporting period: 2023-03-01 to 2025-02-28
The MuCol Project has been designed to answer some of the most urgent questions about the feasibility of a Muon Collider at an energy of 10 TeV in the center of mass. The exploration of the potential of such a machine was recommended by the 2020 update of the European Strategy for Particle Physics (ESPPU). The possible location of a future project could be either CERN or Fermilab in the US. In the future other regions might propose themselves, in particular China.
MuCol has been designed to allow the European community of physicists and engineers to build-up and consolidate the know-how necessary to address all the challenges and be in a solid position, when the time will come, to bid for the construction of such a facility. The challenges of the muon collider come mainly from the short lifetime of muons. Very strong electric fields are required to achieve fast acceleration before decay causes prohibitive losses. Very strong magnetic fields are needed to reduce the beam size, initially of several cm, down to the few hundred microns that are necessary to achieve the desired values of luminosity in the center of mass of the collisions. The decay of muons in the collider produces a large background in the detectors that must be minimised and mitigated.
MuCol is organised in 8 workpackages: WP1 is dedicated to the coordination of the project; WP2 to physics and detector; 3 WPs study the layouts of the different parts of the collider complex; and 3 WPs study the main technologies (RadioFrequency, Magnets and cooling cells).
The outcome of MuCol studies will be used to inform the next ESPPU, started in March 2025, to allow the community to prioritise continued R&D on this topic, and eventually recommend building a formal project to construct the muon Collider, either in Europe or in the US, for a first beam around 2050.
The initial input to the 2025 ESPPU was submitted at the end of March 2025, and Mucol will contribute to provide additional information during the ESPPU process and beyond.
MuCol has been designed to allow the European community of physicists and engineers to build-up and consolidate the know-how necessary to address all the challenges and be in a solid position, when the time will come, to bid for the construction of such a facility. The challenges of the muon collider come mainly from the short lifetime of muons. Very strong electric fields are required to achieve fast acceleration before decay causes prohibitive losses. Very strong magnetic fields are needed to reduce the beam size, initially of several cm, down to the few hundred microns that are necessary to achieve the desired values of luminosity in the center of mass of the collisions. The decay of muons in the collider produces a large background in the detectors that must be minimised and mitigated.
MuCol is organised in 8 workpackages: WP1 is dedicated to the coordination of the project; WP2 to physics and detector; 3 WPs study the layouts of the different parts of the collider complex; and 3 WPs study the main technologies (RadioFrequency, Magnets and cooling cells).
The outcome of MuCol studies will be used to inform the next ESPPU, started in March 2025, to allow the community to prioritise continued R&D on this topic, and eventually recommend building a formal project to construct the muon Collider, either in Europe or in the US, for a first beam around 2050.
The initial input to the 2025 ESPPU was submitted at the end of March 2025, and Mucol will contribute to provide additional information during the ESPPU process and beyond.
MuCol focussed on establishing a conceptual design for a Muon Collider complex at 10 TeV and ensure the coherence of all the parameters of the various machines that compose the complex. In fact, two very important milestones achieved by MuCol were the establishment of a list of parameters for the machines from start to the end of the accelerator chain, with the goal of attaining a luminosity of 2 × 10^35 cm^−2 s^−1, and its update one year later taking into account the studies made in the project.
The second major technical achievement of the project has been the establishment of a proposal for hosting the Complex on the CERN site, based on a configuration that re-uses the existing CERN-SPS and CERN-LHC tunnels, minimising the excavation to around 16 km, on a machine that overall will count several accelerators spanning around 50 km of underground facilities. the proposal is in its very early stage, and more work will be needed in the next two years to assess the feasibility of such configuration.
All workpackages have taken important decisions on the technologies to be used (e.g. HTS for magnets), the configurations of the machines and contributed to better define the possible issues and mitigation measures. The Technical annual reports published on Zenodo (Community: MuCol) provide detailed information
The second major technical achievement of the project has been the establishment of a proposal for hosting the Complex on the CERN site, based on a configuration that re-uses the existing CERN-SPS and CERN-LHC tunnels, minimising the excavation to around 16 km, on a machine that overall will count several accelerators spanning around 50 km of underground facilities. the proposal is in its very early stage, and more work will be needed in the next two years to assess the feasibility of such configuration.
All workpackages have taken important decisions on the technologies to be used (e.g. HTS for magnets), the configurations of the machines and contributed to better define the possible issues and mitigation measures. The Technical annual reports published on Zenodo (Community: MuCol) provide detailed information
MuCol achieved several breakthroughs, among others:
• Designed a record-setting 40 T solenoid using HTS, relevant beyond particle physics.
• Doubled transverse and tripled longitudinal beam cooling efficiency, increasing luminosity.
• Developed the first design for a 5 TeV muon accelerator capable of accelerating within 10 ms while maintaining over 50% beam transmission.
• Created a high-luminosity 5 TeV collider ring design, gaining attention during the U.S. Snowmass21 process.
• Boosted European momentum and visibility in the global muon collider effort, with contributions submitted to the 2026 European Strategy update.
• Designed a record-setting 40 T solenoid using HTS, relevant beyond particle physics.
• Doubled transverse and tripled longitudinal beam cooling efficiency, increasing luminosity.
• Developed the first design for a 5 TeV muon accelerator capable of accelerating within 10 ms while maintaining over 50% beam transmission.
• Created a high-luminosity 5 TeV collider ring design, gaining attention during the U.S. Snowmass21 process.
• Boosted European momentum and visibility in the global muon collider effort, with contributions submitted to the 2026 European Strategy update.