Slow Muons and Muonium

TL;DR

This paper discusses the high-intensity muon and muonium sources at PSI, highlighting recent developments and future plans to enable advanced precision experiments in fundamental physics.

Contribution

It introduces new high-intensity muon beamlines and a muon cooling technique, significantly enhancing experimental capabilities for fundamental physics research.

Findings

Achieved surface muon rates of up to 10^8 per second.

Developed the HiMB beamline to deliver 10^10 muons per second.

Proposed the muCool phase space cooling method for muons.

Abstract

The Paul Scherrer Institut in Switzerland operates the high intensity proton accelerator facility HIPA. A 590 MeV kinetic energy proton beam of presently up to 2.4 mA is sent to target stations producing pions, muons and neutrons for fundamental and applied physics. The beam power of 1.4 MW provides the world's highest intensities of low momentum muons which can be stopped in low mass targets. Rates of surface muons of up to about $10^8$/s are being provided to various unique precision particle physics experiments. Two feasibility studies are ongoing to considerably improve the available muon beams. The high intensity muon beamline, HiMB, could deliver on the order of $10^{10}$/s surface muons and the stopped muon cooler, muCool, aims at a gain factor of $10^{10}$ in phase space quality while sacrificing only less than 3 orders of magnitude in intensity for low energy $\mu^+$. These beams will allow a new generation of precision physics experiments with stopped muons and muonium atoms.