The toolbox for material characterization has never been richer than today. Great progress with all kinds of particles and interaction methods provide access to nearly all properties of an object under study. However, a tomographic analysis of the subsurface region remains still a challenge today. In this regard, the Muon Induced X-ray Emission (MIXE) technique has seen rebirth fueled by the availability of high intensity muon beams. We report here a study conducted at the Paul Scherrer Institute (PSI). It demonstrates that the absence of any beam time-structure leads to low pile-up events and a high signal-to-noise ratio (SNR) with less than one hour acquisition time per sample or data point. This performance creates the perspective to open this technique to a wider audience for the routine investigation of non-destructive and depth-sensitive elemental compositions, for example in rare and precious samples. Using a hetero-structured sample of known elements and thicknesses, we successfully detected the characteristic muonic X-rays, emitted during the capture of a negative muon by an atom, and the gamma-rays resulting from the nuclear capture of the muon, characterizing the capabilities of MIXE at PSI. This sample emphasizes the quality of a continuous beam, and the exceptional SNR at high rates. Such sensitivity will enable totally new statistically intense aspects in the field of MIXE, e.g., elemental 3D-tomography and chemical analysis. Therefore, we are currently advancing our proof-of-concept experiments with the goal of creating a full fledged permanently operated user station to make MIXE available to the wider scientific community as well as industry.
Bibliographical noteFunding Information:
Funding: Our research was funded by the Swiss National Science Foundation, Sinergia project “Deepµ”, Grant: 193691 (https://www.psi.ch/en/smus/muon-induced-x-ray-emission-mixe-project, accessed on 31 January 2022). The germanium detector array was installed and operated by the muX collaboration (https://www.psi.ch/en/ltp/mux accessed on 31 January 2022) funded by FWO-Vlaanderen (Belgium), the Paul Scherrer Institute through the Career Return Programme, the Cluster of Excellence “Precision Physics, Fundamental Interactions, and Structure of Matter” (PRISMA EXC 1098 and PRISMA+ EXC 2118/1) funded by the German Research Foundation (DFG) within the German Excellence Strategy (Project ID 39083149), the German Research Foundation (DFG) under Project WA 4157/1, and the Swiss National Science Foundation through the Marie Heim-Vögtlin Grant no. 164515 and project Grant no. 200021_165569.
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- Continuous muon beam
- Depth-dependent elemental analysis
- Negative muon induced X-ray emission
- Non-destructive technique
- Sandwich sample