Synchrotron Light Source ANKA Research Articles

Field quality of 1.5 m long conduction cooled superconducting undulator coils with 20 mm period length

The Institute for Beam Physics and Technology (IBPT) at the Karlsruhe Institute of Technology (KIT) and the industrial partner Babcock Noell GmbH (BNG) are collaborating since 2007 on the development of superconducting undulators both for ANKA and low emittance light sources. The first full length device with 15 mm period length has been successfully tested in the ANKA storage ring for one year. The next superconducting undulator has 20 mm period length (SCU20) and is also planned to be installed in the accelerator test facility and synchrotron light source ANKA. The SCU20 1.5 m long coils have been characterized in a conduction cooled horizontal test facility developed at KIT IBPT. Here we present the local magnetic field and field integral measurements, as well as their analysis including the expected photon spectrum.

Frequency-Comb Spectrum of Periodic-Patterned Signals.

Using arbitrary periodic pulse patterns we show the enhancement of specific frequencies in a frequency comb. The envelope of a regular frequency comb originates from equally spaced, identical pulses and mimics the single pulse spectrum. We investigated spectra originating from the periodic emission of pulse trains with gaps and individual pulse heights, which are commonly observed, for example, at high-repetition-rate free electron lasers, high power lasers, and synchrotrons. The ANKA synchrotron light source was filled with defined patterns of short electron bunches generating coherent synchrotron radiation in the terahertz range. We resolved the intensities of the frequency comb around 0.258THz using the heterodyne mixing spectroscopy with a resolution of down to 1Hz and provide a comprehensive theoretical description. Adjusting the electron's revolution frequency, a gapless spectrum can be recorded, improving the resolution by up to 7 and 5 orders of magnitude compared to FTIR and recent heterodyne measurements, respectively. The results imply avenues to optimize and increase the signal-to-noise ratio of specific frequencies in the emitted synchrotron radiation spectrum to enable novel ultrahigh resolution spectroscopy and metrology applications from the terahertz to the x-ray region.

A PCIe DMA Architecture for Multi-Gigabyte Per Second Data Transmission

We developed a direct memory access (DMA) engine compatible with the Xilinx PCI Express (PCIe) core to provide a high-performance and low-occupancy alternative to commercial solutions. In order to maximize the PCIe throughput while minimizing the FPGA resources utilization, the DMA engine adopts a novel strategy where the DMA address list is stored inside the FPGA and not in the central memory of the host CPU. The FPGA design package is complemented with simple register access to control the DMA engine by a Linux driver. The design is compatible with Xilinx FPGA Families 6 and 7, and operates with the Xilinx PCIe endpoint Generation 1 and 2 with all lane configurations (x1, x2, x4, x8). A multi-engine architecture is also presented, where two x8 lanes cores are used in parallel together with a PCIe bridge, to exploit fully the capabilities of a PCIe Gen2 x16 lanes link. A data throughput of 3461 MBytes/s has been achieved with a single PCIe Gen2 x8 lanes endpoint. If the dual-engine architecture is used, the throughput is increased up to 6920 MBytes/s. The presented DMA is currently used in several experiments at the ANKA synchrotron light source.

Imaging methods and their application at the ANKA synchrotron light source

The imaging methods used at the ANKA Synchrotron Light Source (Institute for Synchrotron Radiation, Karlsruhe Institute of Technology) are briefly reviewed. Examples of recent applications of the phase-contrast imaging method using a grating interferometer and fast radiography with optic flow data analysis to study static and moving biological objects are presented.

Investigation of crystallographic and detection properties of CdTe at the ANKA synchrotron light source

The crystallographic properties of a semiconducting CdTe pixelated sensor were investigated at the ANKA synchrotron facility (KIT, Karlsruhe) by means of back reflection white beam topography and high resolution X-ray diffraction. From the results, several orientation contrast features were identified that could be assigned to small angle grain boundaries of 0.01°. Those structures are disseminated in the whole area of the investigated crystal and form a mosaic structure network of tiled and twisted blocks. The topographic mapping of the sensor was correlated with its X-ray response map. The comparison demonstrates the presence of similar features, proving that the structural quality of the sensor material influences the charge carrier transport and consequently the detector performances.

Assessment of chemical species of lead accumulated in tidemarks of human articular cartilage by X-ray absorption near-edge structure analysis

A highly specific accumulation of the toxic element lead was recently measured in the transition zone between non-calcified and calcified normal human articular cartilage. This transition zone, the so-called `tidemark', is considered to be an active calcification front of great clinical importance. However, little is known about the mechanisms of accumulation and the chemical form of Pb in calcified cartilage and bone. Using spatially resolved X-ray absorption near-edge structure analysis (µ-XANES) at the Pb L(3)-edge, the chemical state of Pb in the osteochondral region was investigated. The feasibility of the µ-XANES set-up at the SUL-X beamline (ANKA synchrotron light source) was tested and confirmed by comparing XANES spectra of bulk Pb-reference compounds recorded at both the XAS and the SUL-X beamline at ANKA. The µ-XANES set-up was then used to investigate the tidemark region of human bone (two patella samples and one femoral head sample). The spectra recorded at the tidemark and at the trabecular bone were found to be highly correlated with the spectra of synthetic Pb-doped carbonated hydroxyapatite, suggesting that in both of these very different tissues Pb is incorporated into the hydroxyapatite structure.

A New Superconducting Undulator for the ANKA Synchrotron Light Source

Superconducting insertion devices (IDs) are very attractive for synchrotron light sources since they allow increasing the flux and/or the photon energy with respect to permanent magnet IDs. Babcock Noell GmbH (BNG) is completing the fabrication of a 1.5 m long unit for ANKA at the Research Center in Karlsruhe (FZK). The period length of the device is 15 mm for a total of 100.5 full periods plus an additional matching period at each end. The key specifications of the system are: a K-value higher than 2, the capability of withstanding a 4 W beam heat load and a phase error smaller than 3.5 degrees. The magnet is in the final stages of the winding process and will be soon tested at CERN in liquid helium in vertical configuration. This paper describes the main features of the system, the results of the prototyping phase and details of manufacturing process.

Dislocation generation related to micro-cracks in Si wafers: High temperature in situ study with white beam X-ray topography

The generation and propagation of dislocations in Si at high temperature is observed in situ with white beam X-ray topography. For the heating experiments a double ellipsoidal mirror furnace was installed at the Topo–Tomo beamline of the ANKA synchrotron light source, Research Centre Karlsruhe, Germany. Details of the experimental set-up and the first results on the occurrence of dislocations are presented. Artificial damage was generated in commercial (1 0 0) Si wafers using a nanoindenter with various loads. The applied forces for each set of indents were varied from 100 to 500 mN, respectively. After heating to approx. 790 °C large area transmission topographs were taken every 30 min which were then compared to room temperature topographs before and after heating. At the outset straight 60°-dislocations with b = a/2〈1 1 0〉 originate from the 500 mN indents into the direction of the strongest temperature gradient. After 60 min at constant temperature an increase in the length and number of the dislocations in other directions is also observed. As a result of the continual thermal stressing dislocations develop from the 100 mN indents too.

Studies of LSO:Tb radio-luminescence properties using white beam hard X-ray synchrotron irradiation

A radio-luminescence set-up was installed at the synchrotron light source ANKA to characterise scintillators under the high X-ray photon flux density of white beam synchrotron radiation. The system allows for investigating the radio-luminescence spectrum of the material under study as well as analysing in situ changes of its scintillation behaviour (e.g. under heat load and/or intensive ionising radiation). In this work we applied the radio-luminescence set-up for investigating the radiation damage effects on the luminescence properties of a new kind of thin single crystal scintillator for high resolution X-ray imaging based on a layer of modified Lu2SiO5 grown by liquid phase epitaxy on a dedicated substrate within the framework of an EC project (SCINTAX).1

Test of an Electromagnetic Shimming Concept for Superconducting Undulators

Accurate magnetic field measurements are a prerequisite for the characterization and optimization of undulators. At the synchrotron light source ANKA there is an ongoing R&D program for superconducting insertion devices. Within this program a test stand for precise magnetic field measurements of superconductive coils was designed, built and installed at the Research Center Karlsruhe. Comprehensive magnetic measurements are performed to confirm the magnet design and to detect or correct field imperfections resulting from the manufacturing process. The magnetic field is measured along a fixed direction by Hall probes with a positioning precision of 3 mum. A NbTi undulator prototype with local correction coils was built to verify the performance of the superconductor and the shimming concept. In this contribution we describe the measuring test station and preliminary tests results including the efficiency of the shimming concept.

The micro-imaging station of the TopoTomo beamline at the ANKA synchrotron light source

The TopoTomo bending magnet beamline at the ANKA synchrotron facility in Karlsruhe (Germany) operates in the hard X-ray regime (above 6keV). Recently, an X-ray micro-imaging station has been installed at TopoTomo. For typical imaging applications, a filtered white beam or from 2009 on a double-multilayer monochromator is used. In order to optimize the field of view and the resolution of the available indirect pixel detectors, different optical systems have been installed, adapted, respectively, to a large field of view (macroscope) and to high spatial resolution (microscope). They can be combined with different camera systems, ranging from 14-bit dynamic range CCDs to fast CMOS cameras. The spatial resolution can be brought substantially beyond the micrometer limit by using a Bragg magnifier. Due to the moderate flux of the beamline compared to insertion-device beamlines on third generation light sources, special emphasis has been put on the efficiency of the detectors via a dedicated scintillator concept. The layout of the beamline optics makes optimal use of the coherence properties. Thus, absorption contrast, phase-contrast and analyzer-based imaging can be applied. Additionally, white beam synchrotron topography is performed, using digital indirect X-ray pixel detectors as well as X-ray film.

White beam synchrotron topography using a high resolution digital X-ray imaging detector

X-ray topography is a well known imaging technique to characterise strain and extended defects in single crystals. Topographs are typically collected on X-ray films. On the one hand such photographic films show a limited dynamic range and the production of films will be discontinued step by step in the near future. On the other hand new imaging detectors improved for X-ray tomography become more and more attractive even for topography because of increasing resolution, dynamic range, speed and active area. In this paper we report about the upgrade of the TOPO–TOMO beamline at the synchrotron light source ANKA, Research Centre Karlsruhe, with a high resolution digital camera for the topography use.

Generation of x-ray radiation in a storage ring by a superconductive cold-bore in-vacuum undulator

The first beam measurements with a cold-bore superconducting in-vacuum undulator in a storage ring are reported. Undulators are x-ray generators in light sources. The physical limitations of these devices limit the intensity and the brilliance of the x-ray beam. At present the undulators are made from permanent magnets. It was shown in earlier papers that at low electron beam intensities superconductive wires in the vacuum beam pipe can overcome the limitations inherent to permanent magnet undulators. It was argued that the use of these novel devices in light sources with high beam currents may be limited by the extreme anomalous skin effect regime in Cu at 4.2 K, which has so far undergone very little investigation, and the power deposited by the infrared part of the synchrotron radiation. The purpose of this paper is to present measurements of these effects at the synchrotron light source ANKA with stored currents up to 200 mA.

The experimental station for white beam X-ray topography at the synchrotron light source ANKA, Karlsruhe

At the recently constructed synchrotron radiation facility ANKA at Karlsruhe, Germany, two end stations for X-ray fluorescence and X-ray topography, respectively, are integrated into one beamline offering white light as well as band pass operation. This contribution is focussed on the design, characteristics and performance parameters of this beamline with special reference to experiments in X-ray topography. Results of characterization measurements of the horizontal and vertical beam profile, the source dimension and of components of the experimental stations are presented.