Karen Appel’s #My1stLight

Karen was a beamline scientist at DESY and is currently a beamline scientist at the European XFEL

My first synchrotron experiment was at beamline L at DORIS at DESY, which at that time just set up the possibility to do micro-focus X-ray fluorescence measurements. The first experiment I was involved in was headed by the group of Prof Schenk at the Institute of Mineralogy of the University of Kiel  and focused on minerals that were formed at high pressures and high temperatures. At that moment, I was a PhD student at the University of Bonn, working on metamorphic rocks and isotope geochemistry of rocks and got involved in the experiment, because I was interested in analytical methods that could be applied to minerals that were formed at high pressures and temperatures. Besides some connections through my earlier studies, my main interest was to learn about this new method of X-ray fluoresence. We investigated the chemical trace element composition (Rare Earth elements) of minerals that were formed during metamorphic processes and commonly show a gradient of the element distribution, which is related to the metamorphic formation process. 

As we were simply providing the samples, we had the chance to have a close look at the instrumentation. Having worked with commercial machines so far, I remember that I was very much impressed by the modular set- up of a beamline and this one-day experience motivated me to apply for a job that was offered from GFZ Potsdam that included a main part in experimental work at beamline L.

Later, as a postdoc, my experiences led me into the van Gogh experiment, where we used the polychromatic mode at beamline L and were able to detect the elemental distributions of a van Gogh painting. Now I am working at the High Energy Density Science instrument at the European XFEL, studying extreme states of matter, allowing me to work as a beamline scientist and also pursue my own scientific interests.

Image (above): Karen and her colleague working at the experimental station at the beamline L of DORIS III.

Credit: DESY

Image: DE: Die Experimentierstation HED (High Energy Density Science) dient der Erforschung von Materie unter extremen Druck- und Temperaturbedingungen oder sehr starken elektromagnetischen Feldern. Zu den wissenschaftlichen Anwendungen gehört die Untersuchung von Zuständen, wie sie im Inneren astrophysikalischer Objekte wie Exoplaneten bestehen, von Phasenzuständen unter extremem Druck, von Plasmen mit hoher Dichte oder von Phasenübergängen komplexer Feststoffe unter dem Einfluss starker Magnetfelder. EN: The HED experiment station will be used to study matter under extreme conditions of pressure, temperature, or electromagnetic fields. Scientific applications will be studies of matter occurring inside astrophysical objects such as exoplanets, of new extreme-pressure phases and solid-density plasmas, and of phase transitions of complex solids in high magnetic fields.

Credit: European XFEL / Jan Hosan

Gerold Rosenbaum’s #My1stLight

From Gerold Rosenbaum – Advanced Photon Source user

A Playful Use of the Last 10 Minutes of a Run Turns Out to be Very Educational

In 1967, after finishing data collection on the DESY XUV beamline on the polarizer/polarization analyzer I had built for my diploma thesis, there were 15 minutes to go before the synchrotron was to be shut down. Since I always wanted to know how good the vacuum had to be for working in the XUV, I suggested to bleed up the 1-m-long sample chamber to 1/10000 atm or 0.08 torr. The playful use of the last 10 minutes of the run turned out to be an impressive demonstration of the superiority of the continuous spectrum of synchrotron radiation over other XUV sources (paired with a high-resolution monochromator). The very low intensity below 800 Å, even though at the peak of the monochromator spectrum, told me clearly where vacuum-UV starts.

Journal reference: R.P. Godwin, “Synchrotron radiation as a light source,” Springer-Verlag Tracts in Modern Physics 51, p.66, 1969.

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When vibrations increase on cooling: Anti-freezing observed

An international team has observed an amazing phenomenon in a nickel oxide material during cooling: Instead of freezing, certain fluctuations actually increase as the temperature drops. Nickel oxide is a model system that is structurally similar to high-temperature superconductors. The experiment, which was carried out at the Advanced Light Source (ALS) in California, shows once again that the behaviour of this class of materials still holds surprises.

In virtually all matter, lower temperatures mean less movement of its microscopic components. The less heat energy is available, the less often atoms change their location or magnetic moments their direction: they freeze. An international team led by scientists from HZB and DESY has now observed for the first time the opposite behaviour in a nickel oxide material closely related to high-temperature superconductors. Fluctuations in this nickelate do not freeze on cooling, but become faster.

Read more on the HZB website

Image: The development of this speckle pattern over time reveals microsocopic fluctuations in the material.

Credit: © 10.1103/PhysRevLett.127.057001

Ultrafast lasers protect a DNA building block from destruction

An international research team led by DESY researcher Francesca Calegari and with the key participation of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) has demonstrated that ultrashort laser pulses can be used to protect one of the DNA building blocks against destruction induced by vacuum ultraviolet (VUV) radiation. The research group unveiled that a second laser flash in the infrared, timed shortly (only a few millionths of billions of a second) after the first VUV flash, prevented the adenine molecule to disintegrate, therefore stabilising it. The group presents their work in the journal Communications Chemistry published by Nature publishing group.

High energy radiation can cause irreparable damage to our own biological molecules – such as DNA – leading to mutations and potentially cell death. Damage is often occurring as a consequence of the molecular ionisation, inducing the fragmentation of the DNA subunits. So far, protection against radiation damage has hardly been achieved, as the photo-induced dissociation process could not be stopped. In their ultra-short-time experiments, Francesca Calegari´s research group and collaborators have discovered that, by taking advantage of mechanisms that take place on extremely fast time scales, it is indeed possible to protect the molecule.

Read more on the DESY website

image: Artist´s impression of the ultrafast stabilisation of adenine against dissociation: When the molecule is ionised by VUV radiation it undergoes dissociation, however, by taking advantage of a charge migration mechanism and by properly timing a second infrared laser pulse it is possible to stabilise it via a second ionisation event.

Credit: U. De Giovannini MPSD

Experimental mini-accelerator achieves record energy

Coupled terahertz device significantly improves electron beam quality

Scientists at DESY have achieved a new world record for an experimental type of miniature particle accelerator: For the first time, a terahertz powered accelerator more than doubled the energy of the injected electrons. At the same time, the setup significantly improved the electron beam quality compared to earlier experiments with the technique, as Dongfang Zhang and his colleagues from the Center for Free-Electron Laser Science (CFEL) at DESY report in the journal Optica. “We have achieved the best beam parameters yet for terahertz accelerators,” said Zhang. “This result represents a critical step forward for the practical implementation of terahertz-powered accelerators,” emphasized Franz Kärtner, who heads the ultrafast optics and X-rays group at DESY.
Terahertz radiation lies between infrared and microwave frequencies in the electromagnetic spectrum and promises a new generation of compact particle accelerators. “The wavelength of terahertz radiation is about a hundred times shorter than the radio waves currently used to accelerate particles,” explained Kärtner. “This means that the components of the accelerator can also be built to be around a hundred times smaller.” The terahertz approach promises lab-sized accelerators that will enable completely new applications for instance as compact X-ray sources for materials science and maybe even for medical imaging. The technology is currently under development.

> Read more on the DESY website

Image: The two-stage miniature accelerator is operated with terahertz radiation (shown here in red). In a first step (left) the electron bunches (shown in blue) are compressed, in a second step (right) they are accelerated. The two individual elements are each about two centimetres wide. Credit: DESY, Gesine Born