InternalMaterials Imaging and Dynamics (MID): Structure determination of nanodevices and dynamics at the nanoscale
This instrument aims at the investigation of nanostructured materials and of dynamics on the nanoscale. Scientific areas of application are material sciences, nanomaterials and dynamics of condensed matter.
Experiments utilize scattering of coherent X-rays and detection of the coherent diffraction pattern. In coherent diffraction imaging (CDI) experiments 2D and 3D structures of condensed-matter samples will be investigated with resolution reaching into the 10 nm regime. Possible sample systems are nanocrystals, nanostructures on or buried under surfaces or crystallites of a compound sample. Using X-ray photon correlation spectroscopy (PCS) in addition the equilibrium and non-equilibrium dynamics of condensed-matter can be investigated. In these experiments, often carried out with disordered solids or liquids or using soft matter, the temporal fluctuation of structural parameters (e.g. distance of nearest neighbours) is investigated.
Reports
MID Workshop 2009
The first MID workshop took place in Grenoble from 28 to 29 October 2009. Visit the workshop page for more information including the slides of the given presentations.
Mailing list
To subscribe to the mailing list of this experiment station, please use the form at information for the scientific community.
Instrument design
Initial design, TDR-2006 & startup configuration:
- The MID instrument has been created by merging the instruments CXI-1 and PCS-1 described in the TDR-2006. The driving idea was that the sample environment of both instruments is rather similar, but the requirements to detection (angular resolution and q-range) are very different.
- Mounting of samples typically requires a diffractometer to orient and manipulate samples.
- Coherent diffraction patterns need to be collected in forward direction and also near Bragg-diffraction spots using 2D detection systems.
- Photon correlation spectroscopy will use long distance to the sample (∼20 m) to increase the angular resolution (∼10 µrad).
- Both techniques are very sensitive to the size of the focal spot on the sample. For the CDI experiments the illuminated sample area contributes to the scattering and influences therefore the signal-to-background ratio. In PCS experiment the size of the beam spot size or the sample feature (whatever is smaller) determines the typical speckle size at the detector.
- Experiments are likely to use one sample for several illuminations and therefore could require X-ray flux adjustment to prevent sample damage.
- X-ray beam will be focused to focal spots of ∼100 nm, 1 µm and 10 µm.
- The wavefront of the focused X-ray pulse shall be flat or at least known.
- Both techniques require the usage of a monochromator (ΔE/E ∼ 10-4) in order to tailor the longitudinal correlation length such that coherent diffraction is observable even at large q.
- The X-ray beam requires pulse-by-pulse diagnostics of intensity, position, (spot size). Regular measurement of X-ray wavefront and pulse arrival is wishful. Part of this task might be achieved using a specially designed beam stop, other requires intersection of the beam.
- Experiments can be done at air, but vacuum environment might be beneficial for various reasons. Special sample preparation methods are envisaged.
- Methods to visualize the sample (morphology, etc.) might provide insight to sample damage.
- Detection will be achieved by use of the newly developed 2D pixel detectors. In the moment the HPAD detector with a pixel size of (200 µm)2 is foreseen for this instrument. Detector distance can vary for the CDI experiments from 0.5 to 2.0 m and for the PCS experiments it is ∼20 m. The detector has a central hole for the direct beam. Number of pixels is 1 million. For the PCS experiments use of a hole mask might reduce the apparent pixel size and therefore increase the speckle visibility.
- Diffractometer and detection should further foresee the possibility to use spontaneous undulator radiation in the 20–100 keV range for carrying out material science related diffraction experiments, e.g. investigating the structure of hard materials at/below the grain level (sub-µm resolution) and with temporal resolution.
- Construction of one X-ray hutch is foreseen for the final beam delivery, the sample environment and the CDI setup. A long tube shall transport the forward diffracted beam to the detector for PCS experiments. In addition a control hutch will be built for operation of the instrument.
Beamline design considerations
- Instrument is located at SASE 1 beamline (designed for fixed energy operation at 12.4 keV, providing horizontal linear polarization).
- Instrument is ∼1000 m from source point.
- Beamline will be designed for optimized transport of coherent X-ray beam.
- Beamline will feature a monochromator allowing a resolution of 10-5–10-4 thereby raising the longitudinal coherence length.
- Additional capability of transporting spontaneous undulator radiation in the range 20–100 keV.
