Christian Grünzweig’s research while affiliated with Paul Scherrer Institute and other places

TOMCAT is a tomographic microscopy beamline at the Swiss Light Source (SLS) of the Paul Scherrer Institut (PSI) [1]. For almost two decades, TOMCAT has been offering its cutting-edge tomographic microscopy capabilities to various industries in need of non-destructive, non-invasive, volumetric, and functional material characterization beyond what is currently possible with conventional X-ray tubes [2]. Five years ago, PSI (together with two Swiss institutes and the Canton of Aargau in Switzerland) has co-founded ANAXAM – a technology transfer center that facilitates the use of advanced analytical methods at large-scale facilities such as the SLS for industrial applications. A collaboration between TOMCAT and ANAXAM has leveled up the imaging capabilities that can be offered to industry. One of the main advantages is that ANAXAM has enabled speedy realizations of necessary sample environments that can be used during synchrotron X-ray tomographic microscopy experiments. In this paper, we show examples of successful investigations performed for several industries such as medical technology, pharmaceuticals, marine industry, automotive, and food [3, 4]. In September 2023, TOMCAT paused its operation to allow for the construction of the new SLS 2.0 storage ring [5] in combination with several beamline upgrades [6]. SLS 2.0 is expected to resume operation mid 2025 with a significantly improved machine performance such as smaller source size, improved beam collimation and higher intensity. TOMCAT 2.0 will leverage on the higher brilliance of SLS 2.0 by deploying its upgrade program on two beamlines: (1) I-TOMCAT will be a brand-new instrument based on an insertion device of the latest generation; and (2) S-TOMCAT, the original beamline, will be refurbished with a new high-field superconducting 5T bending magnet. Here we discuss overall possibilities of TOMCAT 2.0 and ANAXAM with respect to industrial applications.

Objective This study aimed to investigate the movement of liquid in the needle region of staked-in-needle pre-filled syringes using neutron imaging and synchrotron X-ray tomography. The objective was to gain insights into the dynamics of liquid presence and understand the factors contributing to needle clogging. Methods Staked-in-needle pre-filled syringes were examined using neutron radiography and synchrotron X-ray phase-contrast computed tomography. Neutron radiography provided a 2D visualization of liquid presence in the needle, while synchrotron X-ray tomography offered high-resolution 3D imaging to study detailed morphological features of the liquid. Results Neutron radiography revealed liquid presence in the needle region for as-received samples and after temperature and pressure cycling. Pressure cycling had a more pronounced effect on liquid formation. Synchrotron X-ray tomography confirmed the presence of liquid and revealed various morphologies, including droplets of different sizes, liquid segments blocking sections of the needle, and a thin layer covering the needle wall. Liquid presence was also observed between the steel needle and the glass barrel. Conclusions The combination of neutron imaging and synchrotron X-ray tomography provided valuable insights into the dynamics of liquid movement in staked-in-needle pre-filled syringes. Temperature and pressure cycling were found to contribute to additional liquid formation, with pressure changes playing a significant role. The detailed morphological analysis enhanced the understanding of microstructural arrangements within the needle. This research contributes to addressing the issue of needle clogging and can guide the development of strategies to improve pre-filled syringe performance.

In the past decade neutron dark-field contrast imaging has developed from a qualitative tool depicting microstructural inhomogeneities in bulk samples on a macroscopic scale of tens to hundreds of micrometers to a quantitative spatial resolved small-angle scattering instrument. While the direct macroscopic image resolution around tens of micrometers remains untouched microscopic structures have become assessable quantitatively from the nanometer to the micrometer range. Although it was found that magnetic structures provide remarkable contrast we could only recently introduce polarized neutron grating interferometric imaging. Here we present a polarized and polarization analyzed dark-field contrast method for spatially resolved small-angle scattering studies of magnetic microstructures. It is demonstrated how a polarization analyzer added to a polarized neutron grating interferometer does not disturb the interferometric measurements but allows to separate and measure spin-flip and non-spin-flip small-angle scattering and thus also the potential for a distinction of nuclear and different magnetic contributions in the analyzed small-angle scattering.

We have recently shown how a polarized beam in Talbot-Lau interferometric imaging can be used to analyze strong magnetic fields through the spin dependent differential phase effect at field gradients. While in that case an adiabatic spin coupling with the sample field is required, here we investigate a nonadiabatic coupling causing a spatial splitting of the neutron spin states with respect to the external magnetic field. This subsequently leads to no phase contrast signal but a loss of interferometer visibility referred to as dark-field contrast. We demonstrate how the implementation of spin analysis to the Talbot-Lau interferometer setup enables one to recover the differential phase induced to a single spin state. Thus, we show that the dark-field contrast is a measure of the quantum mechanical spin split analogous to the Stern-Gerlach experiment without, however, spatial beam separation. In addition, the spin analyzed dark-field contrast imaging introduced here bears the potential to probe polarization dependent small-angle scattering and thus magnetic microstructures.

A new type of scintillator screen consisting of a ZnS scintillator with a dysprosium neutron converter is explored in a joint effort between Idaho National Laboratory (INL) and Paul Scherrer Institute (PSI). In contrast with a traditional prompt ⁶Li or Gd converters, a dysprosium converter generates a latent image as neutron activated dysprosium produces an isotope which decays with half-lives of 1.26 min and 2.3 h and the decay radiation excites the ZnS scintillator. The activated scintillator screen is physically transported out of the neutron beam and away from radioactive samples into the imaging apparatus and emits photons as the screen decays, which are read by a digital camera. This technology bridges the gap between traditional indirect transfer radiography and modern digital camera-based systems. This paper describes initial development of dysprosium-based scintillator screens and the results of initial tests performed at PSI. Some screen variants exhibit sufficient light output to produce good quality radiographs in a matter of minutes. The basic spatial resolution measured using a Siemens star is approximately 300μm. This work demonstrates for the first time that indirect digital transfer method neutron imaging is a plausible method of imaging highly radioactive sources such as irradiated nuclear fuel.

We demonstrated the use of a neutron grating interferometer setup (nGI) with a significantly improved contrast-to-noise ratio of the operando dark-field (DF) contrast visualization of water in gas diffusion media (GDM). The nGI parameters were optimized in such a way that we could perform DF imaging of a fully operational fuel cell including two GDM layers (anode and cathode side). The DF contrast is sensitive to the size and shape of microstructures and is in principle not influenced by large water clusters present in flow field channels. Thus, DF imaging can be applied to analyze water present in GDM overlapping with channels, which is not possible by attenuation contrast imaging when the cell is placed perpendicular to the beam direction. In GDM regions overlapping with ribs the distinction of hydrophilic and hydrophobic areas is facilitated as well compared to attenuation contrast imaging. Finally, we show that disturbing artefacts introduced by moving water clusters in the channels are considerably reduced by applying a golden ratio phase stepping scan strategy.

The macroscopic properties of advanced engineering and functional materials are highly dependent on their overall grain orientation distribution, size, and morphology. Here we present Laue 3D neutron diffraction tomography providing reconstructions of the grains constituting a coarse-grained polycrystalline material. Reconstructions of the grain morphology of a highly pure Fe cylinder and a Cu cube sample are presented. A total number of 23 and 9 grains from the Fe and Cu samples, respectively, were indexed and reconstructed. Validation of the grain morphological reconstruction is performed by post-mortem EBSD of the Cu specimen.

Within neutron imaging, different methods have been developed with the aim to go beyond the conventional contrast modalities, such as grating interferometry. Existing grating interferometers are sensitive to scattering in a single direction only, and thus investigations of anisotropic scattering structures imply the need for a circular scan of either the sample or the gratings. Here we propose an approach that allows assessment of anisotropic scattering in a single acquisition mode and to broaden the range of the investigation with respect to the probed correlation lengths. This is achieved by a far-field grating interferometer with a tailored 2D-design. The combination of a directional neutron dark-field imaging approach with a scan of the sample to detector distance yields to the characterization of the local 2D real-space correlation functions of a strongly oriented sample analogous to conventional small-angle scattering. Our results usher in quantitative and spatially resolved investigations of anisotropic and strongly oriented systems beyond current capabilities. Acquiring orientation-resolved neutron images currently requires the sample or system to be rotated, precluding single-shot measurement. Here, the authors achieve small-angle scattering information with spatial resolution in a single shot through the inclusion of a circular diffraction grating.

A collaborative project between Idaho National Laboratory (INL) and Paul-Scherrer Institute (PSI) is investigating a new type of scintillation screen that uses ZnS scintillator material with a dysprosium neutron converter instead of traditional prompt converters such as 6 Li. Such a screen exposed to a neutron beam creates a latent image by neutron activation of the dysprosium in the scintillator screen. The activated screen is transported into a camera box allowing the camera to read a digital image from the photons emitted by the activated scintillation screen. Such an imaging system combines modern camera-based system architecture with the approach of traditional indirect transfer method radiography. The results show for the first time that the combination of dysprosium with a scintillation material like ZnS can produce light which is measurable under common camera-based detection conditions and that neutron radiographic images of reasonable quality can be produced. The resolution was poorer than expected at ~ 300 μm, but is on the order of the desired resolution of 100 μm. Potential improvements and additional converter materials may be investigated in the future that could increase the light output and improve spatial resolution.