Speaker
Description
Muon spin rotation, relaxation and resonance (μSR) is a powerful local-probe technique for studying magnetism, superconductivity and spin dynamics in quantum materials. However, conventional continuous-beam μSR spectrometers are intrinsically limited by the requirement that only one muon is present in the sample during the measurement time window. This constrains the usable stopped-muon rate and makes measurements on small, inhomogeneous or spatially patterned samples particularly challenging.
At the Paul Scherrer Institute, we are developing Advanced Muon Spectroscopy (AMS), a new μSR concept based on ultra-thin monolithic silicon-pixel detectors and vertex reconstruction. By tracking both the incoming muon and the decay positron, the stopping position of each muon can be reconstructed and correlated with the time-dependent spin asymmetry. This enables vertex-reconstructed μSR (vx-μSR) spectra, opening the path to measurements on millimetre-scale samples, and providing a route towards substantially higher data-acquisition rates at continuous muon sources.
In this contribution, we present the detector concept, reconstruction strategy and first experimental demonstrations of silicon-pixel-based μSR at PSI. We discuss the requirements imposed by low-energy charged-particle tracking close to the sample, including material budget, multiple scattering, timing, hit-rate capability and integration with μSR sample environments. We also outline ongoing developments towards high-rate, position-resolved and triggerless data acquisition, with the longer-term goal of enabling triggerless pump-probe vx-μSR measurements of transient magnetic and electronic states.
AMS illustrates how technologies and methods developed for vertex detectors can enable qualitatively new capabilities in condensed-matter spectroscopy. It therefore provides a concrete example of cross-fertilisation between high-energy detector instrumentation and applications in quantum materials research.