Abstract
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.
Highlights
Elemental analysis of materials, qualitative and quantitative, is used in a broad range of scientific fields
The fundamental differences compared to the XRF technique are, that the muon momentum can be tuned to implant the muons at controlled depths deep inside the material, and that the created μ-X rays have enough energy to escape the material and being detected
Muon Induced X-ray Emission (MIXE) can be applied to carry out non-destructive elemental analysis deep inside a material, which is not possible by XRF or PIXE
Summary
Qualitative and quantitative, is used in a broad range of scientific fields. The different destructive methods include Auger Electron Spectroscopy [1], Scanning Electron Microscopy/Energy Dispersive X-ray Spectrometry [2], Secondary Ion Mass Spectrometry [3], Inductive Coupled Plasma Atomic Emission Spectroscopy [4] and Inductive Coupled Plasma Mass Spectroscopy [5] With these destructive techniques, one can study trace elements (down to parts per quadrillion (ppq) levels) near the surface of the material, but this comes with the cost that the investigated sample cannot be retained in its original form. Fluorescence (XRF) [7], Proton-induced X-ray Emission (PIXE) [8], Rutherford Backscattering Spectrometry (RBS) [9], Nuclear Reaction Analysis (NRA) [10], Prompt Gamma-ray neutron Activation Analysis (PGAA) [11], Neutron Activation Analysis (NAA) [12], and Neutron Depth Profiling [13] All these non-destructive techniques, with the exception of PGAA and NAA, are able to provide information from near (i.e., up to ∼10 micrometer) the surface of the material only. The aim of the present manuscript is to demonstrate the performance of the MIXE technique using a continuous muon beam
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