World record: Fastest 3D tomographic images at BESSY II

An HZB team has developed an ingenious precision rotary table at the EDDI beamline at BESSY II and combined it with particularly fast optics.

This enabled them to document the formation of pores in grains of metal during foaming processes at 25 tomographic images per second – a world record.

The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.

Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends on the highest precision: Any tumbling around the rotation axis or even minimal deviations in the rotation speed would prevent the reliable calculation of the 3D tomography. While commercially available solutions costing several hundred thousand euros allow up to 20 tomographic images per second, the Berlin physicists were able to develop a significantly cheaper solution that is even faster. ”My two doctoral students at the Technische Universität Berlin produced the specimen holders themselves on the lathe”, says Garcia-Moreno, who not only enjoys working out solutions to tricky technical problems, but possesses a lot of craftsman skill himself as well. Additional components were produced in the HZB workshop. In addition, Garcia-Moreno and his colleague Dr. Catalina Jimenez had already developed specialized optics for the fast CMOS camera during the preliminary stages of this work that allows even for simultaneous diffraction. This makes it possible to record approximately 2000 projections per second, from which a total of 25 three-dimensional tomographic images can be created.

>Read more on the BESSY II at Helmholtz-Zentrum Berlin (HZB) website

Image: Experimental setup is composed of a fast-rotation stage, an IR heating lamp (temperature up to 800 °C), a BN crucible transparent to X-rays, a 200-μm thick LuAG:Ce scintillator, a white-beam optical system, and a PCO Dimax CMOS camera. The incident (red) and transmitted (green) X-ray beams as well as the light path from the scintillator to the camera (blue) are shown.
Credit: HZB

Insight into catalysis through novel study of X-ray absorption spectroscopy

An international team has made a breakthrough at BESSY II.

For the first time, they succeeded in investigating electronic states of a transition metal in detail and drawing reliable conclusions on their catalytic effect from the data. These results are helpful for the development of future applications of catalytic transition-metal systems. The work has now been published in Chemical Science, the Open Access journal of the Royal Society of Chemistry.

Many important processes in nature depend on catalysts, which are atoms or molecules that facilitate a reaction, but emerge from it themselves unchanged. One example is photosynthesis in plants, which is only possible with the help of a protein complex comprising four manganese atom sites at its centre. Redox reactions, as they are referred to, often play a pivotal role in these types of processes. The reactants are reduced through uptake of electrons, or oxidized through their release. Catalytic redox processes in nature and industry often only succeed thanks to suitable catalysts, where transition metals supply an important function.

>Read more about on the BESSY II at HZB website

Image: Manganese compounds also play a role as catalysts in photosynthesis.
Credit: HZB

Shutdown BESSY II: work has started

As of 30 July 2018, BESSY II will be down for several weeks.

In the summer shutdown, important components in the storage ring tunnel will be replaced and overhauled. The first conversion work for the BESSY VSR project also begins.  Upgrading BESSY II into a variable-pulse-length storage ring (BESSY-VSR) will provide unique experimental conditions for researchers worldwide. The shutdown lasts until 30 September 2018, and user operation will recommence on 30 October 2018.

While the ring is down, the HZB employees will be completely modifying the multipole wavelength shifter, the EDDI beamline and the radiation protection hutches. This space will be needed for installing the cold supply for the superconducting cavities in the storage ring. These are key components in the creation of BESSY VSR. Keeping them cold, however, requires an elaborate infrastructure, which is to be built up in the experimental hall over the next two years.

>Read more on the BESSY II at HZB website.

You can take a detailed look at everything that will be going on during the shutdown in the HZB Science Blog

Picture: The experimental hall of Bessy II.
Credit: HZB / D.Butenschön 

Call for nominations: Innovation Award on Synchrotron Radiation 2018

The Society of Friends of Helmholtz-Zentrum Berlin (HZB) announces the bestowal of the Innovation Award on Synchrotron Radiation*.

The award was established in 2001 for an excellent achievement which has contributed significantly to the further development of techniques, methods or uses of synchrotron radiation. Scientists and engineers from research institutions, universities, and industry within Europe are addressed. The Innovation Award includes a monetary prize of 3000 Euro and will be bestowed at the Users’ Meeting of HZB (BESSY II) in December 2018.

All nominations should be submitted to the Chair of the Society by September 30, 2018. Suggestions of candidates have to be addressed electronically and must include a concise, verifiable description in English of the scientific-technological achievement. The curriculum vitae, the publication list of the candidate(s) and at five most relevant publications have to be submitted. Two references should be named.

Please address nominations to:

Prof. Dr. Mathias Richter
Chair of the Society of Friends of Helmholtz-Zentrum Berlin
Head of Department Radiometry with Synchrotron Radiation, Physikalisch-Technische Bundesanstalt
Faculty of Mathematics and Natural Sciences, Technische Universität Berlin
Email: mathias.richter@ptb.de

*sponsored by SPECS GmbH and BESTEC GmbH, Berlin.

>Read more about the Friends of Helmholtz-Zentrum Berlin e.V. on the HZB website

Picture: Bessy II at Helmholtz-Zentrum Berlin.

Helmholtz International Fellow Award for N. Mårtensson

The Helmholtz Association has presented the Swedish physicist Nils Mårtensson with a Helmholtz International Fellow Award. 

The synchrotron expert of the University of Uppsala, who heads the nobel comitee for physics, cooperates closely with the HZB-Institute Methods and Instrumentation for Synchrotron Radiation Research. Nils Mårtensson is a professor at Uppsala University. He directed the development of the Swedish synchrotron radiation source Max IV and received a grant from the European Research Council (ERC) in 2013. Mårtensson is a member of the Swedish Academy of Sciences and chairman of the Nobel Committee for Physics. At HZB, he cooperates with Alexander Föhlisch’s team at HZB-Institute Methods and Instrumentation for Synchrotron Radiation Research. Together they run the Uppsala Berlin Joint Laboratory (UBjL) to further develop methods and instruments.

Image: Nils Mårtensson, University of Uppsala, cooperates closely with HZB.

Helmholtz Association supports ATHENA

ATHENA (“Accelerator Technology HElmholtz iNfrAstructure”) is a new research and development platform focusing on accelerator technologies and drawing on the resources of all six Helmholtz accelerator institutions (DESY, Jülich Research Centre, Helmholtz Centre Berlin, Helmholtz Centre Dresden-Rossendorf HZDR, KIT and GSI with the Helmholtz Institute of Jena). The Helmholtz Association has now decided to pay almost 30 million euros towards ATHENA as a strategic development project. “This decision demonstrates the Helmholtz Association’s strong commitment to developing and supplying ground-breaking new accelerator technologies for solving the future challenges faced by society,” says Helmut Dosch, who is the Chairman of DESY’s Board of Directors and also the spokesperson for the Helmholtz Association’s research division Matter.

Together, these centres want to set up two German flagship projects in accelerator research based on innovative plasma-based particle accelerators and ultramodern laser technology: an electron accelerator at DESY in Hamburg and a hadron accelerator at HZDR. At both facilities, a range of different fields of application are to be developed, ranging from a compact free-electron laser, through novel medical uses to new applications in nuclear and particle physics. As soon as they have reached the necessary level of maturity to be put to practical use in a particular area, new compact devices could be built for use in other Helmholtz centres, as well as in universities and hospitals.

>Read more on the Bessy II at HZB website or the DESY website

Support for HZB’s future and call for rapid planning of Bessy III

The Helmholtz-Zentrum Berlin (HZB) has received an evaluation of “excellent” in a review of science programmes undertaken at all Helmholtz Research Centres.

This provides the foundation for future financing of HZB.
Two committees of leading international scientists visited the HZB for a week each at the beginning of this year. They evaluated the HZB’s contributions to the Helmholtz programmes in the research areas of “Matter” and “Energy”. Now the written evaluations are available. The team spirit of all employees involved in the HZB was particularly emphasised.

The report states that the HZB and the Helmholtz Association have made decisions characterised by vision. The right course had been set both in terms of infrastructure and in recruiting people. The HZB can rely on highly competent, committed employees at all levels.

All research programmes of the HZB have received an evaluation of “excellent”. The HZB contributions to the MML programme (From Matter to Materials and Life) focussing on the use of photons are considered to be leading, with all of its participating groups receiving the top marks of “Outstanding” or “Excellent”. The Renewable Energies (RE) and the Future Information Technologies (FIT) programmes, the instrumentation at the BESSY II synchrotron (some of which is unique), and the BER II research reactor were likewise evaluated highly.

>Read more on the Bessy II at HZB website

Image: The review panel of the research field “Matter” visited the HZB on 11th January 2018.
Credit: HZB/J. Bierbaum

 

 

Writing and deleting magnets with lasers

Scientists * have found a way to write and delete magnets in an alloy using a laser beam – a surprising effect.

* at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia in Charlottesville, USA

The reversibility of the process opens up new possibilities in the fields of material processing, optical technology, and data storage.
Researchers of the HZDR, an independent German research laboratory, studied an alloy of iron and aluminum. It is interesting as a prototype material because subtle changes to its atomic arrangement can completely transform its magnetic behavior. “The alloy possesses a highly ordered structure, with layers of iron atoms that are separated by aluminum atomic layers. When a laser beam destroys this order, the iron atoms are brought closer together and begin to behave like magnets,” says HZDR physicist Rantej Bali.

Bali and his team prepared a thin film of the alloy on top of transparent magnesia through which a laser beam was shone on the film. When they, together with researchers of the HZB, directed a well-focused laser beam with a pulse of 100 femtoseconds (a femtosecond is a millionth of a billionth of a second) at the alloy, a ferromagnetic area was formed. Shooting laser pulses at the same area again – this time at reduced laser intensity – was then used to delete the magnet.

>Read more on the Bessy II at HZB website

Image: Laser light for writing and erasing information – a strong laser pulse disrupts the arrangement of atoms in an alloy and creates magnetic structures (left). A second, weaker, laser pulse allows the atoms to return to their original lattice sites (right). (Find the entire image here)
Credit: Sander Münster / HZDR

Twin Orbit operation successfully tested at BESSY II

The first “Twin Orbit User Test week” at BESSY II in February 2018 was a big success and can be considered as an important step towards real user operation.

Physicists at Helmholtz-Zentrum Berlin have been able to store two separate electron beams in one storage ring. The twin orbit operation mode can serve users with different needs of the time structure of the photon pulses simultaneously and offers elegant options regarding the future project BESSY VSR.

The Twin Orbit operation mode makes use of non-linear beam dynamics and provides two stable well separated orbits for storing two electron beams in one storage ring. The bunch fill patterns of both orbits can be chosen, to some extent, independently, which allows for fulfilling normally incompatible user needs, simultaneously. For example, one orbit can be used to store a homogenous multi bunch fill to deliver high average brilliance for photon hungry experiments, whereas only one single bunch is stored on the other orbit for timing experiments, providing a much lower pulse repetition rate.

>Read more on the Bessy II at HZB website

Image: A synchrotron source point image of a bending magnet of the Twin Orbit modus. The second orbit closes after three revolution and is winding around the standard orbit at the center. (full image here)
Credit: HZB

Solar–to-hydrogen conversion

Polymeric carbon nitrides exhibit a catalytic effect in sunlight that can be used for the production of hydrogen from solar energy.

However, the efficiency of these metal-free catalysts is extremely low. A team at the Tianjin University in China, in collaboration with a group at the Helmholtz-Zentrum Berlin, has increased the catalytic efficiency of these polymeric carbon nitrides by a factor eleven through a simple process resulting in a larger surface area. The paper was published in the journal Energy & Environmental Science.

One of the major challenges of the energy transition is to supply energy even when the sun is not shining. Hydrogen production by splitting water with the help of sunlight could offer a solution. Hydrogen is a good energy storage medium and can be used in many ways. However, water does not simply split by itself. Catalysts are needed, for instance Platinum, which is rare and expensive. Research teams the world over are looking for more economical alternatives. Now a team headed by Dr. Tristan Petit from the HZB, together with colleagues led by Prof. Bin Zhang from Tianjin University, Tianjin, China, has made important progress using a well-known class of metal-free photocatalysts.

>Read more on Bessy II at HZB website

Image: PCN nanolayers under sunlight can split water.
Credit: Nannan Meng /Tianjin University

40-year controversy in solid-state physics resolved

An international team at BESSY II headed by Prof. Oliver Rader has shown that the puzzling properties of samarium hexaboride do not stem from the material being a topological insulator, as it had been proposed to be.

Theoretical and initial experimental work had previously indicated that this material, which becomes a Kondo insulator at very low temperatures, also possessed the properties of a topological insulator. The team has now published a compelling alternative explanation in Nature Communications, however.

Samarium hexaboride is a dark solid with metallic properties at room temperature. It hosts Samarium, an element having several electrons confined to localized f orbitals in which they interact strongly with one another. The lower the temperature, the more apparent these interactions become. SmB6 becomes what is known as a Kondo insulator, named after Jun Kondo who was first able to explain this quantum effect.

In spite of Kondo-Effect: some conductivity remains

About forty years ago, physicists observed that SmB6 still retained remnant conductivity at temperatures below 4 kelvin, the cause of which had remained unclear until today. After the discovery of the topological-insulator class of materials around 12 years ago, hypotheses grew insistent that SmB6 could be a topological insulator as well as being Kondo insulator, which might explain the conductivity anomaly at a very fundamental level, since this causes particular conductive states at the surface. Initial experiments actually pointed toward this.

>Read more on the Bessy II website

Image: Electrons with differing energies are emitted along various crystal axes in the interior of the sample as well as from the surface. These can be measured with the angular-resolved photoemission station (ARPES) at BESSY II. Left image shows the sample temperature at 25 K, right at only 1 K. The energy distribution of the conducting and valence band electrons can be derived from these data. The surface remains conductive at very low temperature (1 K).
Credit: Helmholtz Zentrum Berlin

Complex tessellations, extraordinary materials

Simple organic molecules form complex materials through self-organisation

An international team of researchers lead by the Technical University of Munich (TUM) has discovered a reaction path that produces exotic layers with semiregular structures. These kinds of materials are interesting because they frequently possess extraordinary properties. In the process, simple organic molecules are converted to larger units which form the complex, semiregular patterns. With experiments at BESSY II at Helmholtz-Zentrum Berlin this could be observed in detail.

Only a few basic geometric shapes lend themselves to covering a surface without overlaps or gaps using uniformly shaped tiles: triangles, rectangles and hexagons. Considerably more and significantly more complex regular patterns are possible with two or more tile shapes. These are so-called Archimedean tessellations or tilings.

Materials can also exhibit tiling characteristics. These structures are often associated with very special properties, for example unusual electrical conductivity, special light reflectivity or extreme mechanical strength. But, producing such materials is difficult. It requires large molecular building blocks that are not compatible with traditional manufacturing processes.

 

>Read more on the Bessy II website

Image: The new building block (left, red outline) comprises two modified starting molecules connected to each other by a silver atom (blue). This leads to complex, semiregular tessellations (right, microscope image).
Credit: Klappenberger and Zhang / TUM

Perovskite solar cells: perfection not required!

Experiments at BESSY II reveal why even inhomogeneous perovskite films are highly functional

Metal-organic perovskite layers for solar cells are frequently fabricated using the spin coating technique. If you follow the simplest synthesis pathway and use industry-relevant compact substrates, the perovskite layers laid down by spin coating generally exhibit numerous holes, yet attain astonishingly high levels of efficiency. The reason that these holes do not lead to significant short circuits between the front and back contact and thus high-rate charge carrier recombination has now been discovered by a HZB team headed by Dr.-Ing. Marcus Bär in cooperation with the group headed by Prof. Henry Snaith (Oxford Univ.) at BESSY II.

>Read more on the HZB website.

BER II and BESSY II User Meeting at HZB

More than 600 scientists registered for the 9th annual BER II and BESSY II User Meeting in December.

The Friends of Helmholtz-Zentrum Berlin recognised outstanding work in the field of synchrotron radiation with an Innovation Award, and the best doctoral dissertation with the Ernst-Eckard-Koch prize.

Research with synchrotron radiation was the focus on Wednesday. On Thursday, the „Science Day“, a broad overview on user research was given. The public talk entitled “Interfacing with the brain using organic electronics” found great appeal with the audience: George Malliaras from the University of Cambridge spoke about the potential of organic electronics as brain implants for treating neurological diseases such as epilepsy. New materials and their characterisation at synchrotron sources will play a crucial role in this development. A vendor exhibition by 56 companies on new technical and optical instruments for research was well visited by the scientists.

>Read more on the HZB website.

Image: The Innovation Award of Freundeskreis HZB was given to a team of DESY, Hamburg.
Credit: HZB

Antiferromagnetic dysprosium reveals magnetic switching with less energy

HZB scientists have identified a mechanism with which it may be possible to develop a form of magnetic storage that is faster and more energy-efficient.

They compared how different forms of magnetic ordering in the rare-earth metal named dysprosium react to a short laser pulse. They discovered that the magnetic orientation can be altered much faster and with considerably less energy if the magnetic moments of the individual atoms do not all point in the same direction (ferromagnetism), but instead point are rotated against each other (anti-ferromagnetism). The study was published in Physical Review letters on 6. November 2017 and on the cover of the print edition.

Dysprosium is not only the atomic element with the strongest magnetic moments, but it also possesses another interesting property: its magnetic moments point either all the same direction (ferromagnetism) or are tilted against each other, depending on the temperature. This makes it possible to investigate in the very same sample how differently oriented magnetic moments behave when they are excited by an external energy pulse.

>Read More on the Bessy II (HZB) website

Image: A short laser pulse pertubates magnetic order in dysprosium. This happens much faster if the sample had a antiferromagnetic order (left) compared to ferromagnetic order (right). Credit: HZB

Approved! The EU INFINITE-CELL project

A large EU-sponsored research project on tandem solar cells in which HZB is participating begins in November 2017.

The goal is to combine thin-film semiconductors made of silicon and kesterites into especially cost-effective tandem cells having efficiencies of over 20 per cent. Several large research institutions from Europe, Morocco, the Republic of South Africa, and Belarus will be working on the project, as well as two partners from industry.

“We not only have detailed experience with kesterite thin films, but also a wide spectrum of analytical methods at our disposal to characterise absorber materials very thoroughly”, explains Prof. Susan Schorr. The FUNDACIO INSTITUT DE RECERCA DE L’ENERGIA DE CATALUNYA (IREC), Spain – a long-term collaborating partner of the HZB, is coordinating the entire project. The project begins with a kick-off workshop in Brussels in November 2017.