Full-Field Micro X-ray Fluorescence (FF-µXRF)
The CXC system in combination with a poly-capillary optics provides a spatially resolved elemental image of the sample. This can for example be used to image biological samples. A water flea (daphnia magna) was imaged at the BAM line at the BESSY synchrotron. The internal organs and overall structure of the insect are clearly visible, because the CXC system allows wet, small, unpolished specimens to be analyzed with trace level sensitivity and high position resolution.
With an X-ray source at a high incident angle, the CXC system enables imaging of samples with large topographic features with minimal shadowing. Thus, in places like the eyes on the statue shown below, the traces left behind by ancient paint can be identified. The iron based pigments show up as traces in this area of the statue, along with a lead based pigment in the middle. A flexible imaging system based on the CXC is capable of measuring many different types of samples, from flat, polished specimens, to rough samples with little to no sample preparation.
Summarizing, the FF-µXRF technique satisfies the requirement of artists and archeologists for imaging and analysis of cultural heritage objects. It allows analysts to quickly identify critical areas and hidden structures, with the advantage that the imaging technology is extremely similar to other cameras commonly used for optical, UV-VIS and NIR imaging. The final result is always an image that contains spatial and spectroscopic information.
Polychromatic SAXSMost Small Angle X-ray Scattering (SAXS) systems require an X-ray source that is monochromatic. Since monochromation is inherently inefficient, these systems require expensive monochromators and high flux X-ray systems. In contrast, with the CXC, no monochromation is required. The resulting X-ray data can be energy filtered or processed to create diffraction patterns or reciprocal space images. As shown in the SAXS images from a sample of silver behenate (AgC22H43O2), monochromatic SAXS will result in the typical ring pattern (right image). Although the rings are larger in the polychromatic case (left image), the CXC enables energy dependent analysis of the diffraction rings, resulting in a faster measurement with more data and high angular resolution.
X-ray Micro-Tomography (µCT)
The movie below shows the X-ray micro-tomography measurement of a lavender flower. The flower was rotated in front of the pnCCD and the X-ray transmission images were taken for different angles to create cross-sections of the flower, which were used to recreate a virtual model without destroying the original object.
Simultaneous X-ray Fluorescence and Diffraction
Because the pnCCD records both the position and energy of each incoming X-ray photon, high speed, high resolution X-ray diffraction experiments are possible in both transmission and traditional forward scattering modes. At every single point in the image, a full diffraction pattern and fluorescence spectrum can be derived. This is done simultaneously, without monochromation, stage scanning or beam focusing, and the measurements take less than one minute to acquire.
In 5D X-ray imaging, the beam is addressed to equally spaced points in an array on the sample and for each point the five dimensions, sample X-position, sample Y-position, camera X-position, camera Y-position, and energy are saved. For each data cube, three summed images are created, one for each axis. These images are then processed to create diffraction and fluorescence data. These data are then assembled into new data cubes, representing fluorescence and diffraction across the sample.
The pnCCD Properties (typical values)
|Physical pixel size||48 µm × 48 µm × 450 µm|
|Number of physical pixels||264 × 264 (69,696) image area
264 × 528 (139,392) in full frame mode
|Active area||12.7 mm × 12.7 mm (161 mm2)
12.7 mm × 25.3 mm (321 mm2) in full frame mode
|Frame rate||up to 1,000 Hz (264 × 264 pixel)|
|Pixel readout rate||up to 70 MegaPixels/s|
|Binning mode||up to 8-fold binning|
|Windowing mode||24 × 264 pixels (smallest window)|
|Readout noise (rms)|| ENC < 3 e-/pixel at 400 Hz
ENC < 4 e-/pixel at 1,000 Hz
|Energy resolution||145 eV for Mn-Kα|
|Sub-pixel spatial resolution||Δx < 15 µm (rms) for 1 keV X-rays|
|Charge handling capacity||up to 400,000 signal electrons per pixel|
|Radiation hardness||up to 1014 photons/cm2 at 10 keV|
- Active sensor area of 12.7 mm × 12.7 mm
- Dimensions of camera head: 120 mm × 212 mm × 80 mm (W × H × D)
- Model options: beryllium window or vacuum solution
Complete electronic system and data acquisition system
- Mountable in 19 inch rack
- High speed parallel data acquisition
- Selectable amplifier bandwidth and analog gain for high dynamic range
Full software package for
- Camera control
- Offline data analysis
High precision X-ray optics (optional)
- Exchangeable poly-capillary optics
- Focusing, defocusing and 1:1 with capillary diameters from 15 µm to 30 µm
The pnCCDs are back illuminated, three-phase CCDs on a fully depleted silicon substrate. Their operation is based on the principle of sideward depletion and on transfer registers formed by pn-junctions. The outstanding characteristics include a homogeneous and thin photon entrance window leading to high quantum efficiency values between 100 eV and 20 keV and an excellent radiation hardness as well as high charge handling capacity.
The CXC system is equipped with a 264 × 264 pixel pnCDD with a physical pixel size of 48 µm × 48 µm and an imaging area of 161 mm2. The on-chip electronics in combination with a fully column-parallel readout enables low noise operation below 3 e-/pixel (ENC), and frame rates of up to 1,000 Hz. Due to the advanced detector design, the internal potential distribution of the pnCCD can be adjusted by the operation voltages depending on the requirements of the individual experiments. Thus, excellent energy resolution (145 eV for Mn-Kα) and high spatial resolution modes (Δx < 15 µm) are available, as well as high charge handling capacity (up to 400,000 e- per pixel), and anti-blooming modes for handling extremely high amounts of signal charges.
Spectroscopic performanceExcellent elemental information between 200 eV and 30 keV with an energy resolution of 145 eV (FWHM) at 5.9 keV (Mn-Kα) and 48 eV at 277 eV (C-K).
Quantum efficiencyHigh quantum efficiency of > 80% in the range of 2 keV to 20 keV due to back-illumination and optimized X-ray entrance window.
Ultra-fast readout and excellent signal-to-noise ratioStandard full frame rate of 1,000 fps, up to 8,000 fps using windowing and binning. Excellent signal-to-noise ratio even at high readout speeds with < 4e- at 1,000 fps.
High dynamic rangeInimitable single photon sensitivity (left image) and high intensity imaging (right image) with 400,000 e- per pixel (corresponding to 103 photons with an energy of 1 keV) at the same time.
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