Lund, Sweden
Lund, Sweden

Time filter

Source Type

Pietzsch A.,Helmholtz Center Berlin | Hennies F.,MAX IV Laboratory | Miedema P.S.,Helmholtz Center Berlin | Kennedy B.,Helmholtz Center Berlin | And 5 more authors.
Physical Review Letters | Year: 2015

Liquid water molecules interact strongly with each other, forming a fluctuating hydrogen bond network and thereby giving rise to the anomalous phase diagram of liquid water. Consequently, symmetric and asymmetric water molecules have been found in the picosecond time average with IR and optical Raman spectroscopy. With subnatural linewidth resonant inelastic x-ray scattering (RIXS) at vibrational resolution, we take sub-femtosecond snapshots of the electronic and structural properties of water molecules in the hydrogen bond network. We derive a strong dominance of nonsymmetric molecules in liquid water in contrast to the gas phase on the sub-femtosecond timescale of RIXS and determine the fraction of highly asymmetrically distorted molecules. © 2015 American Physical Society.

Falk T.J.,MAX IV Laboratory
Synchrotron Radiation News | Year: 2014

The MAX IV Laboratory is a Swedish national laboratory hosted by Lund University, which provides X-rays over a wider range of energies for researchers from academia and industry as well as doing research and development in accelerator and nuclear physics. It operates the MAX I, II, and III storage rings in the present MAX-lab building and is building the new MAX IV facility on the outskirts of Lund, which will eventually replace the existing MAX-lab when it goes into operation in June 2016 (Figure 1). In this article, we will try to provide you with an update on the current activities with a strong focus on the exciting developments of the MAX IV project. © 2014 Copyright Taylor and Francis Group, LLC.

Einfeld D.,Max IV Laboratory
Synchrotron Radiation News | Year: 2014

One of the most important factors for synchrotron radiation research is the brilliance, typically defined as photon flux emitted into a unit solid angle from a unit source size within a defined relative bandwidth. The product of rms solid angle and source size yields the beam emittance. To reach high brilliance, both the horizontal and vertical beam emittance must be small and the stored beam current high. Even at zero emittance, radiative diffraction effects produce a finite volume of phase space of the radiation [1], with the effective photon beam emittance given by: (Figure presented.)where λ is the X-ray-wavelength and Eγ is the photon beam energy. In recent years, the user community has become increasingly interested in the transverse coherence properties of the X-ray beam. By using the half-Airy disk criterion [2], the coherent fraction of the emitted coherent light is given in Eq. (2), where εitot is the total emittance, including the contribution of the electron beam and the undulator radiation. ©, Copyright Taylor & Francis.

Schroder B.,MAX IV Laboratory
EPJ Web of Conferences | Year: 2014

The upgraded tagged photon facility at the MAX IV Laboratory is presented. The pulsed electron beam from a linac system is stretched in the MAX I ring and the electron beam hits a thin aluminium foil in which bremsstrahlung is produced. One of two available magnetic spectrometers is used to determine the energy of the post-bremsstrahlung electrons. The tagged photon ranges from 10 to 180 MeV with an energy resolution of about 300 keV. Rates as high as 4x10 6 photons s-1 MeV-1 have been used. The experimental area and facilities are described as well as examples of ongoing experiments. © Owned by the authors, published by EDP Sciences, 2014.

Klementiev K.,MAX IV Laboratory | Chernikov R.,German Electron Synchrotron
Journal of Physics: Conference Series | Year: 2016

We present a new implementation of the XAFSmass program that calculates the optimal mass of XAFS samples. It has several improvements as compared to the old Windows based program XAFSmass: 1) it is truly platform independent, as provided by Python language, 2) it has an improved parser of chemical formulas that enables parentheses and nested inclusion-to-matrix weight percentages. The program calculates the absorption edge height given the total optical thickness, operates with differently determined sample amounts (mass, pressure, density or sample area) depending on the aggregate state of the sample and solves the inverse problem of finding the elemental composition given the experimental absorption edge jump and the chemical formula.

Afzali-Far B.,MAX IV Laboratory | Lidstrom P.,Lund University | Robertsson A.,Lund University
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2016

3-DOF Gantry Tau is a type of parallel robot, consisting of six struts configured in three clusters, which provides three translational DOFs. It has increasing industrial use in applications where large workspace and high stiffness are required. In fact, the concept of dynamic isotropy, where all the natural frequencies of a system are equal, can be employed in order to effectively optimize the geometry of robots. However, no study on dynamic isotropy of Gantry Tau robots has yet been reported in the literature. In this paper, the problem of dynamic isotropy in 3-DOF Gantry Tau robots is analytically addressed. Firstly, the kinematics is established based on a general approach with 36 geometric variables. Jacobian and stiffness matrices are also investigated where the struts are considered to be axially flexible. Subsequently, analytical solutions to obtain both a decoupled stiffness matrix and a complete dynamic isotropy are presented. Finally, as an example, dynamically isotropic geometries of a Gantry Tau robot are calculated, for a reference platform, using the developed analytical method. © 2016 IEEE.

Juanhuix J.,ALBA Synchrotron | Gil-Ortiz F.,ALBA Synchrotron | Cuni G.,ALBA Synchrotron | Colldelram C.,ALBA Synchrotron | And 8 more authors.
Journal of Synchrotron Radiation | Year: 2014

BL13-XALOC is currently the only macromolecular crystallography beamline at the 3 GeV ALBA synchrotron near Barcelona, Spain. The optics design is based on an in-vacuum undulator, a Si(111) channel-cut crystal monochromator and a pair of KB mirrors. It allows three main operation modes: a focused configuration, where both mirrors can focus the beam at the sample position to 52 μm × 5.5 μm FWHM (H × V); a defocused configuration that can match the size of the beam to the dimensions of the crystals or to focus the beam at the detector; and an unfocused configuration, where one or both mirrors are removed from the photon beam path. To achieve a uniform defocused beam, the slope errors of the mirrors were reduced down to 55 nrad RMS by employing a novel method that has been developed at the ALBA high-accuracy metrology laboratory. Thorough commissioning with X-ray beam and user operation has demonstrated an excellent energy and spatial stability of the beamline. The end-station includes a high-accuracy single-axis diffractometer, a removable mini-kappa stage, an automated sample-mounting robot and a photon-counting detector that allows shutterless operation. The positioning tables of the diffractometer and the detector are based on a novel and highly stable design. This equipment, together with the operation flexibility of the beamline, allows a large variety of types of crystals to be tackled, from medium-sized crystals with large unit-cell parameters to microcrystals. Several examples of data collections measured during beamline commissioning are described. The beamline started user operation on 18 July 2012. © 2014 International Union of Crystallography.

Sondhauss P.,Max IV Laboratory
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

MASH stands for "Macros for the Automation of SHadow". It allows to run a set of ray-tracing simulations, for a range of photon energies for example, fully automatically. Undulator gaps, crystal angles etc. are tuned automatically. Important output parameters, such as photon flux, photon irradiance, focal spot size, bandwidth, etc. are then directly provided as function of photon energy. A photon energy scan is probably the most commonly requested one, but any parameter or set of parameters can be scanned through as well. Heat load calculations with finite element analysis providing temperatures, stress and deformations (Comsol) are fully integrated. The deformations can be fed back into the ray-tracing process simply by activating a switch. MASH tries to hide program internals such as file names, calls to pre-processors etc., so that the user (nearly) only needs to provide the optical setup. It comes with a web interface, which allows to run it remotely on a central computation server. Hence, no local installation or licenses are required, just a web browser and access to the local network. Numerous tools are provided to look at the ray-tracing results in the web-browser. The results can be also downloaded for local analysis. All files are human readable text files, that can be easily imported into third-party programs for further processing. All set parameters are stored in a single human-readable file in XML format. © 2014 SPIE.

Schonhense G.,Johannes Gutenberg University Mainz | Medjanik K.,Johannes Gutenberg University Mainz | Medjanik K.,MAX IV Laboratory | Elmers H.-J.,Johannes Gutenberg University Mainz
Journal of Electron Spectroscopy and Related Phenomena | Year: 2015

This article reviews photoemission experiments that simultaneously resolve at least two of the following degrees of freedom: space (real and momentum space), time (intrinsic time scale of a fast experiment or time-of-flight) and spin. In the spatiotemporal domain, imaging of fast processes by PEEM gives direct insight into plasmon dynamics or magnetization processes. In the category real space & spin the novel concept of imaging spin filters is discussed. In the time & spin chapter we address time-of-flight spin detectors and ultrafast spin processes that are accessible by pump-and-probe techniques. A main part of the paper is devoted to the resolution of momentum-space & time. This is implemented in form of the time-of-flight momentum microscope, a very recent development of which the first instrument has been in operation since 2014. In an extended outlook chapter, the potential of new developments and of a novel, highly parallelized delay-line type electron detector will be discussed. The combination of all three degrees of freedom k-space, time & spin is emerging through the combination of the ToF momentum microscope with imaging spin filter. © 2015 Elsevier B.V. All rights reserved.

Klementiev K.,MAX IV Laboratory | Chernikov R.,German Electron Synchrotron
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

We present an open source python based ray tracing tool that offers several useful features in graphical presentation, material properties, advanced calculations of synchrotron sources, implementation of diffractive and refractive elements, complex (also closed) surfaces and multiprocessing. The package has many usage examples which are supplied together with the code and visualized on its web page. We exemplify the present version by modeling (i) a curved crystal analyzer, (ii) a quarter wave plate, (iii) Bragg-Fresnel optics and (iv) multiple reflective and non-sequential optics (polycapillary). The present version implements the use of OpenCL framework that executes calculations on both CPUs and GPUs. Currently, the calculations of an undulator source on a GPU show a gain of about two orders of magnitude in computing time. The development version is successful in modelling the wavefront propagation. Two examples of diffraction on a plane mirror and a plane blazed grating are given for a beam with a finite energy band. © 2014 SPIE.

Loading Max IV Laboratory collaborators
Loading Max IV Laboratory collaborators