The High Intensity Muon Beam (HIMB) Project

PSI currently leads the world at the intensity frontier, with its high-intensity proton accelerator complex with muon fluxes of up to several 108 particles per second. These beamlines are used extensively by the national and international user communities of the Laboratory of Particle Physics and the Laboratory for Muon Spin Spectroscopy for fundamental research in particle and solid-state physics, chemistry and materials science. Within the HIMB project we aim at increasing the available muon rates by a factor 100. This will be accomplished by completely upgrading one of the existing target stations and optimizing it for the extraction of low-energy muons. Normal-conducting, radiation-hard solenoids will capture a large fraction of the emitted muons, which will be transported through a high-efficiency beamline based on large-aperture solenoids and dipoles to the experimental areas.

On the particle physics side, experiments searching for rare muon decays challenge our current knowledge, e.g., by searching for the charged lepton-flavour violating (cLFV) decays of the muon. A new generation of experiments is in planning worldwide and the field has been endorsed as a key area of investigation by the national road-maps on particle physics of the major nations involved. The sensitivities aimed for in these new experiments require stopped muon beams with intensities of O(1010) muons per second. Two such international collaborations, MEG II and Mu3e, are preparing to undertake these next-generation experiments at PSI at the highest intensities available. In addition, experiments on muonium, muonic atoms, muon EDM or muon cooling will greatly profit from the increased muon rates.

On the materials science side, together with ongoing advances in detector technology the time needed for the magnetic characterization of samples will be reduced by more than a factor of 10, allowing more detailed or expanded studies, including new research directions in nano and quantum technology. Developments in the direction of re-accelerated muon microbeams will additionally offer a level of control to the measurements that is currently unreachable.

HIMB is embedded in the larger IMPACT project that combines two major upgrades of the PSI facilities: HIMB and TATTOOS. The IMPACT project team consisting of people from the PSI divisions NUM (Research with Neutrons and Muons), NES (Nuclear Energy and Safety), BIO (Biology and Chemistry), GFA (Large Research Facilities), and LOG (Logistics) is currently preparing its Conceptual Design Report to be completed by the end of 2021 with the aim of having the project accepted to the 2023 Swiss Roadmap for Research Infrastructures. If accepted, its implementation would occur during the period 2025-2028 with regular user operations starting in 2029.

More information can also be found in our recent talks:

PD Dr. Daniela Kiselev, +41 56 310 30 37,
Dr. Andreas Knecht, +41 56 310 21 13,

Conceptual design of the new TgH target station and subsequent collimators. To save space the muon capture solenoids are integrated into the vacuum chamber.

HIMB Beamline
Picture showing the advantages of a solenoid-based beamline compared to a conventional, quadrupole-based beamline such as μE4.

Image showing the proposed new target, beamlines and area layouts in the experimental hall of PSI. Together with the implementation of the beamlines and new target station, the shielding, experimental areas, access ways, infrastructure etc. will be adjusted as well.