Micro-XANES, -EXAFS, -fluorescence
Micro-XANES, -EXAFS, -fluorescence, -SAXS, -WAXS, -Raman Scattering
mySpot is a verstile microfocussing station for scanning methods with resolution down to 1.5 µm, providing a combination of methods which can be performed simultaneously at the same sample position. It is especially designed (but not limited to) for the study of hierarchically structured biological samples. Structural information from different scales (XRD - crystalline, SAXS - nanometer, Video-microscope -- micrometer, sample translation - milimeter) can be combined with chemical information (XRF-mapping, EXAFS, XANES) and molecular information (Raman) providing unique insight into the mutual dependencies of different parameters.
The beamline provides focal spot of about 500x50µm, which can be refocused at the sample using capillary optics. Capillary optics is used for two main reasons: 1) the focal spot does not depend on the energy which makes EXAFS and XANES measurements very simple, and 2) the optics is positioned very close to the sample which improves the stability of the focus at the sample.
This makes the focal spot of 1.5 µm in 2D scans possible, as well as very parallel beam for scattering experiments down to 10µm, or volume element of 20µm diameter for 3D XRF mapping.
|Monochromator||Selective Si311, Si111, Multilayer|
|Experiment in vacuum||no|
|Temperature range||180 - 320 K|
|Detector||Ionisation chambers, PIN Diodes, 7-channel Si(Li), 100mm^2 Si-Drift, Mar X-ray CCD for scattering, Renishaw Raman spektrometer, Ocean Optics Raman Spectrometer, CCD (visible light) built in the online microscope|
|Manipulators||Several goniometers and translation stages, to be used depending on the sample size|
|Energy range||6 - 30 keV as excitation for XRF, for spectroscopy 5-25 keV|
|Energy band width Si111||4000 E / dE|
|Energy band width ML||500 E / dE|
|Energy band width Si311||8000 E / dE|
|Raman Options||Parallel with X-ray beam, normal to the sample surface|
|Raman wavelength||532 and 785 nm|
MethodsEXAFS, NEXAFS, myXRF, XRF, WAXS, SAXS
The mySpot beamline is specialized for mapping experiments using different methods. Depending on the required method the focus varies between 1.5 and 100µm. Most methods can be combined. However, the user should take into account that the beam requirements vary for different methods. Example: For XRF mapping with 1.5 µm focus the beam is strongly focused to the sample, providing enough intensity to perform even EXAFS at selected positions. If small angle scattering from the same position is required, this strong focusing is not possible, rendering simultaneous microEXAFS and SAXS with 1.5µm focal spot very complicated.
Following methods are available and can be combined with restrictions:
1) micro-XRF mapping. Detectors available: 7 channel Si(Li) detector with 210mm2 surface or 80mm2 Silicon drift detector. The smaller detector is used for combined scattering/XRF measurements. Resolution depends on the used optics and can be selected between 1.5 and 20µm. Primary beam energy range is 6keV-25keV.
2) 3D XRF-Mapping. 7 channel detector is used, althogh only one channel is assigned to the volume mapping. This allows for the acquisition of the fluorescence signal from different directions and estimation of the inelastic scattering. For this method we use polycapillaries with focal distance of about 3 mm and focal spot od about 15µm.
3) X-Ray scattering. SAXS and WAXS signal can be acquired using a CCD camera positioned downstram from the sample. Maximal scattering angle is 45°, resolution in SAXS regime is 0.1 nm-1 (0.01 Å-1 - d-spacing up to ~ 60 nm). This provides structural information at the crystalline and nanometer scale at the same time.
4) micro-EXAFS and XANES. Capillary optics allows the acquisition of the energy-dependent absorption spectra on selected position at the sample.
5) Visible/NIR Raman scattering. It is possible to acquire Raman spectra in combination with X-ray m3easurements. For this two different Raman systems are available. In-line Renishaw Raman spectrometer (in cooperation with MPIKG Golm) allows for very precise Raman spectra to be acquired, using laser axcitation parallel to the X-ray beam. For the combination with XRF measurements, a smaller, faster (down to 0.1s per spectrum) system can be mounted where the laser excitation is illuminating the sample at the 45° twith respect to the X-ray beam. Both systems provide wavelengths 532 and 785nm.
6) Optical microscope is available for alignment purposes, but the microscopy images can be saved at every measurement coordinate, so that the correlation between the measured data and the microscopy is rather simple.
Different scanning environments for different sample sizes (from several micrometer to 150mm) are available at the beamline. Rotational units are available for both scattering and fluorescence methods.
There is no vacuum environment available at the beamline, but it is possible to mount sample environmets or reactors at the available 1-circle goniometer in the experimental hutch. Different experiments were successfully mounted at the station, including in-situ stretching devices, plasma chambers, laser-levitation sample holders...
Sample cooling for very small samples is available through cryo stram down to -150°C. For larger samples a Linkam cryo-scanning chamber is available, providing temperatures between Liquid Nitrogen and 200°C. Only clean, non-gasing samples are accepted for heating experiments.
Temperature and humidity in experimental hutch are controlled.
For information about complicated measurements please contact the beamline scientist.