Improving the low-energy muon beam quality of the LEM beamline at PSI: Characterisation of ultra-thin carbon foils

Abstract

The Low-Energy Muon beamline (LEM) at the Paul Scherrer Institute currently stands as the world's only facility providing a continuous beam of low-energy muons with keV energies for conducting muon spin rotation experiments on a nanometer depth scale in heterostructures and near a sample's surface. As such, optimizing the beam quality to reach its full potential is of paramount importance. One of the ongoing efforts is dedicated to improving the already applied technique of single muon tagging through the detection of secondary electrons emerging from an ultra-thin carbon foil. In this work, we present the results from installing a thinner foil with a nominal thickness of 0.5 $\mu gc{m}^{-2}$ and compare its performance to that of the previously installed foil with a nominal thickness of 2.0 $\mu gc{m}^{-2}$. Our findings indicate improved beam quality, characterized by smaller beam spots, reduced energy loss and straggling of the muons, and enhanced tagging efficiency. Additionally, we introduce a method utilizing blue laser irradiation for cleaning the carbon foil, further improving and maintaining its characteristics

References in corpus (6)

• The Mu-MASS (MuoniuM lAser SpectroScopy) experiment
• Intense beam of metastable Muonium
• Geant4 simulation of the PSI LEM beam line: energy loss and muonium formation in thin foils and the impact of unmoderated muons on the $\mu$SR spectrometer
• Measurement of the $2S_{1/2},F$=$0\to 2P_{1/2},F$=$1$ transition in Muonium
• A segmented conical electric lens for optimization of the beam spot of the low-energy muon facility at PSI: a Geant4 simulation analysis
• Small sample measurements at the low energy muon facility of Paul Scherrer Institute

Cited by in corpus (2)

• Monitoring the tagging efficiency of the Low-Energy Muon beamline through background analysis: Insights into the long-term performance of ultrathin carbon foils
• Correcting the Energy-Dependent Asymmetry in Low-Energy $\mu$SR