- 1910: Theodore Wulf notices more radiation at the top of the Eiffel tower than on the ground – later to be identified as muons from cosmic rays.
- 1912: Using Wulf’s electrometers, Victor Hess shows there is a relationship between observed radiation and altitude in a series of ballooning experiments. He found that at 5300 meters altitude, the ionization rate increased approximately fourfold over the rate at ground level.
- 1936: Carl Anderson and Seth Neddermeyer discover the “meson” particle and its properties while studying cosmic rays.
- 1936: Anderson and Hess share a Nobel prize, Hess for his discovery of cosmic radiation and Anderson for discovering the positron.
- 1947: Conversi, Pancini and Piccioni show the discovered particle is actually the muon, and establish the lifetime of 2.2µs for the positive muon.
- 1957: in a paper on parity violation Garmin, Lederman and Weinrich predict muons as a tool for research (“It seems possible that polarised positive and negative muons will become a powerful tool for exploring magnetic fields in nuclei”, in Observations of the Failure of Conservation of Parity and Charge Conjugation in Meson Decays: the Magnetic Moment of the Free Muon by Garmin, Lederman and Weinrich, 1957)
- Early 1970s: applications of µSR to the investigation of materials followed soon after in American, Russian and European laboratories, but the rapid development of µSR as a tool for chemistry and solid state physics research began with the construction of three “meson factories”. Since that time, thriving µSR communities have been developed around the facilities at the Paul Scherrer Institut (Villigen, Switzerland), TRIUMF (Vancouver, Canada), KEK (Tsukuba, Japan; now moved to J-PARC Tokai) and ISIS (Oxford, UK).
- 1987: EC muon facility at ISIS produces the first muons on the original MuSR spectrometer
- 1992: Construction begins on the RIKEN instruments – a set of instruments designed for generating both positive and negative muons, funded by the Japanese government at RAL.
- 1993: EC beamlines upgraded and a new instrument, EMU, is built.
- 1994: First beam on the RIKEN-RAL facility.
- 2005: ISMS created the Yamazaki Prize awarded every three years to any scientist that has demonstrated outstanding, sustained work in µSR with long term impact on scientific and/or technical applications.
- 2014: The ISMS Executive Committee create the Young Scientist Award at the µSR2014 conference in Grindelwald, Switzerlan. This award will be given to 2 young scientists for excellent oral or poster presentations at µSR conferences every 3 years.
During the last several decades µSR has become recognized as an established local probe in condensed matter physics and chemistry.
Three out of four of the world’s muon facilities also provide spallation neutron beams, exploiting the close synergy between µSR and neutron scattering.
Recent technological achievements in the µSR field have included the development of ultra-low background, high-statistics pulsed muon beams and spectrometers, fast timing spectrometers for high applied magnetic fields, and ultra low-energy muon beams for near surface and thin film studies.