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Decommissioning Research Reactor BER II

Neutron research at BER II

Examples from research

Measurements on the time-of-flight spectrometer NEAT - enlarged view

Measurements on the time-of-flight spectrometer NEAT provide information about the energy of the modes of motion in water. Picture: HZB

2019: Batteries with silicon anodes: neutrons reveal how surface structures reduce capacity

Theoretically, anodes made of silicon could store ten times more lithium ions than the graphite anodes that have been used for so many years now in commercial lithium batteries. Yet, so far, the capacity of silicon anodes drops radically after every charge-discharge cycle. An HZB team has now explained with neutron experiments at BER II in Berlin and at the Institut Laue-Langevin in Grenoble what happens at the surface of the silicon anode during charging and what processes reduce their charging capacity. In their neutron experiments, they observed how a blocking layer forms on the silicon surface during charging, thus preventing the penetration of lithium ions. > to the News

Publication: Energy Storage Materials (2019. Doi: 10.1016/j.ensm.2018.11.032

Schematic representation of the 'stripe order - enlarged view

Sketch of the stripe order: The charge stripes, which are superconducting, are shown in blue. Reprinted with modifications from Physical Review Letters.

2018: Neutron research helps in the development of nondestructive test methods

One of the first signs of material fatigue is the appearance of adjacent areas of very different residual stress inside the bulk of the material. At the neutron source BER II at HZB, a team from the Bundesanstalt für Materialforschung und -prüfung (BAM) analysed the residual stresses of ferromagnetic steel weld seams. Their results are helping to improve nondestructive electromagnetic test methods. > to the News

Publication: Journal of Nondestructive Evaluation, 2018. Doi 10.1007/s10921-018-0522-0

Structure of a crystal having a kesterite structure - enlarged view

The fade-in shows the typical structure of a crystal with kesterite structure, in the background the crystal structure and the elementary cell are indicated. Copyright: HZB

2018: Neutrons scan magnetic fields inside samples

With the help of a newly developed method of neutron tomography, an HB team succeeded for the first time in imaging the paths of magnetic field lines inside materials. This “tensorial neutron tomography” promises new insights into superconductors, battery electrodes and other energy materials. > to the News

Publication: Nature Communications (2018): Doi: 10.1038/s41467-018-06593-4

Swords - enlarged view

The sword can be recognized by the stamp showing a wolf (arrow).

2017: High field magnet at BER II: an insight into hidden order

For thirty years, a certain uranium compound had presented mysteries for researchers. Although the crystal structure is simple, nobody understood exactly what happened when it was cooled below a certain temperature. Apparently, a so-called “hidden order” arises, whose nature was entirely unclear. Now, for the first time, physicists characterised this hidden order and studied it on the microscopic scale. To do so, they used the high field magnets at HZB, which allow neutron experiments under extremely high magnetic fields. > to the News

Publication: Physical Review B (2017). Doi: 10.1103/PhysRevB.96.121117

Time-resolved tomography of a lupine root - enlarged view

Sequential tomography of a lupin root (yellowish green) after deuterated water (D2O) was introduced from below. The rising water front (H2O, dark blue) is displaced by the D2O from below over the course of time. The complete sequence can be viewed as a video. Created by Christian Tötzke © University of Potsdam

2016: Storing energy with silicon thin films

Lithium-ion batteries could theoretically quadruple their capacity if their anodes were made of silicon instead of graphite. An HZB team observed for the first time in detail how lithium ions migrate into silicon. Their work shows that even extremely thin layers of silicon are enough to allow maximum charging with lithium. These insights are helpful for the design of good silicon electrodes. > to the News

Publication: ACSnano (2018). Doi: 10.1021/acsnano.6b02032

An excerpt from the crystal lattice - enlarged view

A section from the crystal lattice of Calcium-chromium oxide showing how the spins are subject to conflicting demands. In this ball-and-stick model, the green and red sticks connecting the atoms (grey and black balls) represent ferromagnetic interactions while the blue sticks represent anti-ferromagnetic interactions. Copyright: HZB

2015: Extraordinary magnetic structure and spin dynamics discovered in the magnetoelectric material LiFePO4

An HZB team decrypted the complex magnetic structure and the underlying spin dynamics in the magnetoelectric substance LiFePO4. Materials in this class are already being used for sensor technology and have great application potential in data storage and spintronics. With experiments conducted at the neutron source BER II of HZB, the researchers identified a new branch in the magnetic excitation spectrum in LiFePO4 and demonstrated a non-collinear magnetic structure. > to the News

Publication: Physical Review B (2015). Doi: 10.1103/PhysRevB.92.024404

2015: Crystalline structure and magnetism – new insight into the fundamentals of solid state physics

A team at HZB studied for the first time how magnetic and geometric arrangements mutually influence each other in crystalline samples with a spinel structure. The group had synthesised a series of mixed crystals of molecular formula Ni1-xCuxCr2O4 in which the element nickel was successively replaced by copper. In neutron scattering experiments at BER II, they discovered how this caused not only the crystal structure to change, but also new magnetic phases to appear. > to the News

Publication: Physical Review B (2015). Doi: 10.1103/PhysRevB.91.024407

Tooth cement - enlarged view

The neutron tomography images (left column) show how liquid becomes distributed in this dental filling, while the X-ray CT images (right column) show the microstructure and pores of the same sample. Analyses of these images reveal under what preparation method the least amount of water becomes trapped in pores.

2014: What happens to steel under stress?

Stainless steel is often expected to withstand extreme loads. In order to estimate when the material might succumb to fatigue, it is essential to know when and where applied forces will induce changes in the microstructure. Teams at HZB developed a new neutron imaging method for mapping the crystalline phases and their changes under loads inside the sample with high spatial precision. > to the News

Publication: Advanced Materials (2014) Doi:10.1002/adma.201400192

2011: Surprising insight in the snout of a fossil

Scientists from the Berlin Natural History Museum studied a fossilised “dino skull” using neutron tomography at HZB. They did not have to free the skull from the stone, rather they were able to study it where it was, embedded within.  They shone neutrons through the composite and were able to reconstruct a three-dimensional image, layer by layer. In particular, they were able to distinguish between relatively hard and soft components in the skull. Astonishingly, the researchers found traces of soft cartilage in the snout area. These traces of tissue would have certainly been destroyed of the skill had been dug out mechanically.

Publication: Acta Zoologica 92, 363-371 (2011)

3D-Magnet - enlarged view

Boundaries of magnetic domains can be computer imaged in three dimensions. Copyright:: HZB/Manke, Grothausmann

2010: The Golden Ratio also exists in the quantum world

At BER II, scientists discovered properties of hidden symmetry in solid matter for the first time. The researchers found indicators of the Golden Ratio, well known from art and architecture, in the atomic arrangement of a cobalt-niobate crystal. > to the News

Publication: Science, (2010) Doi: RE1180085/JEC/PHYSICS

Dysprosium titanate crystal - enlarged view

Dysprosium titanate crystal

2008: Three-dimensional imaging – unique insight into magnetic fields

It is now experimentally possible to picture what magnetic fields look like inside solid, opaque materials. To gain this insight, a team shone polarised neutrons through a sample and reconstructed the image from the measured data. > to the News

Publication: Nature Physics (2008) Doi: 10.1038/nphys912

2006: How does cement become strong?

Cement first starts off as a soft and plastic mixture when mixed with water, and hardens into a very solid material over time. The reactions and interactions with the water molecules as it sets are decisive to its quality. Using quasi-elastic neutron scattering at BER II, a team studied a series of different cement mixtures. Based on the measured data, they were able to distinguish between three different processes that play a role in setting: some of the water molecules become chemically bound into the cement while another fraction becomes physically bound, and a third fraction does not become bound at all, but rather remains in the pores and capillaries of the cement.

Source: Journal of Physical Chemistry B (2006); Doi:10.1021/jp062922f

2006: How fast does a tomato drink?

Neutrons can be used to see how fast water rises inside a plant. Japanese scientists demonstrated this on a tomato seedling, which they studied at the neutron source BER II at HZB. They watered the plant with so-called “heavy” water, which stands out very clearly from ordinary water when examined with neutrons. The results could help to increase agricultural yields. Neutrons have a strong advantage over X-rays especially when the goal is to make light elements like hydrogen show up or to penetrate deep into metals. > to the News

2003: Bose–Einstein condensate: magnetic fields create an unusual state of matter

In an experiment at BER II, the magnetic properties of a crystal were used for the first time to create a Bose–Einstein condensate. The crystals used were of the unusual chemical compound TlCuCl3 (thallium-copper-trichloride). The exotic quantum physical material state arose when the crystal was introduced into a strong magnetic field of 14 teslas, and was detected with the help of neutrons. > to the News

Publication: Nature Vol. 423, 1 May 2003, pp. 62-65

Alzheimer-Beta-Amyloid - enlarged view

Publication: Biophysical Journal  (2002) Volume 83, 2610-2616 Silvia Dante, Thomas Hauß, Norbert A. Dencher

2001: Painting studied with neutrons: a surprise awaited behind the “Girl with a Bowl of Fruits”

Titian painted the “Girl with a Bowl of Fruits (Lavinia)” in 16th century Venice. On behalf of the art gallery, the painting was investigated with neutrons at BER II. The way the neutrons excite the pigments in the paint allowed the type of pigments to be identified. The study brought a surprise to light: although he painted the portrait in 1555, Titian had already used Naples Yellow for the girl’s gold-embroidered dress. The first known mention of this pigment in literature is from 1702! This shows how extensive the international network of the mighty market Venice was at the time.