A second experimental station, the imaging station, is currently being finalised. In its fully operational state, it will provide an X-ray beam focused down to a 30 nm spot, with a long term goal of 10 nm. The station is operating in vacuum and will have liquid nitrogen sample cooling. The imaging endstation will rely on position monitoring at the nanometer scale using optical interferometry and will provide a single rotation axis for tomographic measurements.
First test experiments in air were conducted in late 2021 and 2022. During spring and summer 2023 the vacuum microscope and the flight tube have been installed and are ready for user experiment at room temperature. The liquid nitrogen cooling will the installed and commissioned in 2024.
Methods
X-ray fluorescence (XFM) mapping
Using the nano-focused beam, information about the local elemental composition of the illuminated area can be extracted by measuring the secondary X-ray fluorescence photons using the energy-dispersive detectors mounted to both sides of the sample. This arrangement is especially advantageous for XRF tomography (3D) measurements.
(Scanning) Coherent diffraction imaging (CDI) – ptychography
The beamline design allows to freely choose the degree of coherence in the probing beam, facilitating coherent diffraction imaging methods. These allow to measure the complex transmission function of the sample, as well as the complex beam profile. Both with a resolution better than the size of the focused beam. Again, 2D, as well as 3D measurements are possible.
Optics and beam size
The NanoMAX imaging station currently offers only Fresnel zone plates (FZP) as beam focusing optics. Various FZPs with different diameters, different outer most zone widths and different designs are present at the beamline. To choose the FZP best fitting for your application, please contact the beamline staff early when writing your proposal / planning your beamtime.
As a well rounded standard FZP, we offer is made from gold, has 72.32 µm diameter and 60 nm outermost zone width. It does create a focal spot with the shape of an Airy disc, where the width of the central spot matches the outermost zone width (see the beam profile measured at the focus position shown in Figure to the right).
The usage of gold FZPs and gold central stops, currently limits the photon energy range from 6 keV to 10 keV.
Detectors
The NanoMAX imaging station offers two types of detectors. Firstly, a large in-vacuum pixel detector (EIGER2 X 4M) in the forward direction for diffraction and coherent imaging methods. Secondly, two in-vacuum Silicon Drift Diode X-ray fluorescence detectors with carbon windows used for elemental mapping.