European XFEL starts operation of second X-ray light source

Another important milestone achieved in the development of the facility

The second X-ray light source has successfully been taken into operation at European XFEL, the world’s largest X-ray laser located in the Hamburg metropolitan region. The X-ray light source SASE3 successfully produced X-ray laser light flashes in one of the underground tunnels. SASE3 will serve two experiment stations scheduled to begin user operation at the end of the year. Since the start of operation in September 2017, 340 scientists from across the globe have already used the facility for their research. The successful start of operation of the new SASE 3 source will enable the facility to increase the number of users further.

European XFEL Managing Director Prof. Robert Feidenhans’ said: “The construction and commissioning of the new light source are complex processes, for which we and our DESY colleagues have been preparing intensely for these last weeks and months. We are very happy that the commissioning of this second light source SASE 3 has also run so smoothly, and that both sources, SASE1 and SASE3, produce light simultaneously. For this I would like to thank all those involved, in particular the accelerator team from DESY. We continue to be on schedule to start operation at all four experiment stations currently under construction, beginning with the first two instruments in November. The remaining two will start operation at the beginning of 2019. This will increase our current capacity threefold by mid 2019.”

>Read more on the European XFEL website

Image of the first X-ray laser beam in the tunnel from the European XFEL’s SASE3 undulator. SASE3 generates X-rays with a wavelength similar to the width of an atom. Those X-rays will be used to study subjects such as the formation and breaking of chemical bonds and the emergence of special properties such as semiconductivity in materials.

Extreme-ultraviolet vortices from a free-electron laser

Extreme-ultraviolet vortices may be exploited to steer the magnetic properties of nanoparticles, increase the resolution in microscopy, and gain insight into local symmetry and chirality of a material; they might even be used to increase the bandwidth in long-distance space communications. However, in contrast to the generation of vortex beams in the infrared and visible spectral regions, production of intense, extreme-ultraviolet (XUV) and x-ray optical vortices still remains a challenge. Here, we present an in-situ and an ex-situ technique for generating intense, femtosecond, coherent optical vortices with tunable topological charge at a free-electron laser (FEL) in the XUV.

The first method takes advantage of nonlinear harmonic generation in a helical undulator and exploits the fact that such harmonics carry a topological charge of l = n-1, where n is the harmonic number. The experiment was performed at the FERMI FEL. An ultraviolet (250-nm) seed laser was used to energy modulate the electron beam (e-beam) in the first undulator (modulator), as shown in the top panel of Figure 1. The e-beam was then sent through a dispersive section (a four-dipole-magnet chicane), where the energy modulation was transformed into a current-density modulation (bunching) with Fourier components spanning many harmonics of the seed laser frequency. Such a bunched e-beam entered the helical radiator tuned to a fundamental wavelength of 31.2 nm (i.e., the 8th harmonic of the seed), producing coherent light in the XUV. The FEL was operated in the high-gain regime, close to the saturation point. Under these conditions, the interaction between the radiation at the fundamental FEL wavelength and the e-beam induced bunching at the second harmonic (15.6 nm), resulting in emission of coherent XUV vortices carrying unit topological charge (l = 1) at intensities on the order of 10−3 of the fundamental FEL emission; see bottom panel in Figure 1.

>Read more on the FERMI website

Image:
Top: The scheme to generate optical vortices at harmonics (in the present case at the 2nd harmonic) of the fundamental FEL wavelength. The optical vortex is separated from the fundamental FEL emission using a Zr filter.
Bottom: Intensity profile of the generated optical vortex with a topological charge of l =1 (left), and interference with a Gaussian beam revealing the twisted nature of the vortex (right).

 

Record number of participants at User Meeting

Celebrating a year of glorious firsts and outlining future developments

“Welcome to the first European XFEL user meeting with actual users!” said Martin Meedom Nielsen, head of the European XFEL council as he opened the three day event on 24 January in front of a packed lecture hall on the DESY campus in Hamburg. With 1200 registered participants from ca. 100 institutions from 30 countries, this year’s joint European XFEL and DESY photon science users’ meeting, the first since operation began, was the biggest yet.

Meedom Nielsen and European XFEL Managing Director Robert Feidenhans’l started the meeting by summarizing the achievements and developments of the last year and thanking everyone who had contributed to the facility’s success. “It has been a fantastic year,” said Feidenhans’l looking back on his first year as director of the facility, “a tough year and we have worked really hard, but a fantastic year.” “2017 was a year of glorious firsts” said Meedom Nielsen, highlighting especially the facility’s inauguration in September and the beams of laser light that shone across the city to mark the occasion. “Hamburg was shining for European XFEL, and European XFEL was shining back” he said.

>Read more on the European XFEL website

 Photo Credit: European XFEL

 

Superconducting X-Ray laser takes shape in Silicon Valley

The first cryomodule has arrived at SLAC

Linked together and chilled to nearly absolute zero, 37 of these segments will accelerate electrons to almost the speed of light and power an upgrade to the nation’s only X-ray free-electron laser facility.

An area known for high-tech gadgets and innovation will soon be home to an advanced superconducting X-ray laser that stretches 3 miles in length, built by a collaboration of national laboratories. On January 19, the first section of the machine’s new accelerator arrived by truck at SLAC National Accelerator Laboratory in Menlo Park after a cross-country journey that began in Batavia, Illinois, at Fermi National Accelerator Laboratory.

These 40-foot-long sections, called cryomodules, are building blocks for a major upgrade called LCLS-II that will amplify the performance of the lab’s X-ray free-electron laser, the Linac Coherent Light Source (LCLS).

 

>Read more on the Linac Coherent Light Source website

Photo credit: Fermilab / Jefferson Lab

 

 

Behind the scenes at European XFEL

Users and staff give their impressions of the first experiments

In mid-September, fourteen metres under the European XFEL building in north Germany, users started their experiments at the first two instruments to go online: the FXE Femtosecond X-Ray Experiments (FXE) instrument, and the Single Particles, Clusters, and Biomolecules and Serial Femtosecond Crystallography (SPB/SFX) instrument. But what was it like to be among the first users to ever do experiments at the facility, and how did the European XFEL staff members who supported them during their stay experience it all? We asked some for our users and staff for their impressions.

LEAPS initiative launched by European light source facilities

European XFEL founding member of the League of European Accelerator based Photon Sources (LEAPS)

European XFEL joined other European light source facilities and organisations today in Brussels to launch a new collaborative initiative to drive a more efficient, effective and collaborative use of light source technologies. The League of European Accelerator based Photon Sources (LEAPS) brings together 16 research organisations from across Europe, including European XFEL.  The light sources aresuper-microscopes’ that produce exceptionally intense beams of X-rays, ultra-violet and infrared light enabling the exploration of samples in the tiniest of details. LEAPS consists mainly of synchrotron light sources such as DESY’s PETRA III, and free-electron lasers such as the European XFEL.

While European light sources have been working alongside each other for years, the LEAPS members strive for closer collaboration and cooperation. They share a common vision to drive forward the development of common technologies, to strengthen economies and create employment, and to support industries to make better use of available instruments and techniques. Together, they aim to inspire emerging technologies and innovations, and to foster a stronger skills base across Europe.

European XFEL at Hamburg Night of Science 2017

Record number of visitors to the DESY campus

On Saturday, 4 November over 20,000 visitors came to the DESY campus in the west of the city on the occasion of the Hamburg Night of Science and the DESY open day “DESY DAY” to learn more about the research and work done on site. Alongside DESY, European XFEL and other campus partners put on a wide range of activities for the visitors including inspiring lectures, hands-on experiments, educational games and demonstrations. On site at the European XFEL injector and shaft buildings, European XFEL staff presented their facility and research opportunities.

Read more on the European XFEL website

Image: Sparks fly at the Hamburg Night of Science

 

Scientists demonstrate unparalleled phase control of free-electron laser pulses

Double flashes with attosecond precision

Thanks to a smart mirror scientists can control the phase of X-rays from DESY’s free-electron laser FLASH with attosecond precision. The feat enables new investigations of the interactions of light and matter, as the team headed by DESY scientist Tim Laarmann reports in the journal Nature Communications. An attosecond is a billionth of a billionth of a second. The phase indicates at which point in its rapid oscillation a light wave is at a given point in time or space. Phase-sensitive measurements are important to gain insight of light-matter interactions and require phase-controlled pulses. Although phase control is an established technique in optics, the soft X-rays generated by FLASH oscillate a hundred times faster than visible light, requiring a hundred times better precision.

The scientists have now demonstrated phase control and interferometric autocorrelation at FLASH using pulse pairs created with a smart split-and-delay unit. The successful transfer of a powerful optical method towards short wavelengths paves the way towards utilization of advanced nonlinear methodologies even at partially coherent free-electron lasers that rely on self-amplified spontaneous emission (SASE). Free-electron lasers (FEL) are driven by powerful particle accelerators and produce laser-like light pulses by sending bunches of fast electrons through a magnetic slalom course.

>Read More

Time-resolved measurement of interatomic Coulombic decay

… induced by two-photon double excitation of Ne2

On the 24th of March 2017, Tsukasa Takanashi gained his doctorate from the University of Tohoku (Japan), together with the President’s Award prize (総長賞). The prize is awarded each year to the best PhD students in recognition of their outstanding academic curriculum, and particularly for the excellent results obtained during their studies. Tsukasa carried out his studies under the supervision of Professor Kiyoshi Ueda, a leading figure on the international scene of atomic and molecular physics, and until recently, a member of the FERMI Review Panel. In his thesis, Tsukasa used the light from Free Electron Lasers (FELs) to study the dynamics of highly excited molecular systems; in his home country, he utilized the Japanese FEL SACLA, and he studied the Coulomb explosion of the molecule CH2I2 (diiodomethane). This process is the fragmentation by multiple ionization of a sample, and the successive repulsion of the ions by the positive charge which is generated.

An important part of his work was carried out at FERMI, currently the only FEL source in the world able to provide Tsukasa the wavelength (75.6 nm) and temporal resolution (10-13 s) necessary to study the dynamics of his system: the Ne2 molecule, which consists of two neon atoms bound by their weak van der Waals interaction. The apparent simplicity of this system allows the detailed study of complex phenomena, such as the exchange of energy after electronic excitation, which is basic to all photochemical processes.

>Read more on the FERMI website

Image: Schematic representation of the resonant absorption of two FEL photons by a neon dimer (upper panel) and the ICD relaxation process by ionization (lower panel).

FLASHForward accelerates first electron bunches

The plasma accelerator project FLASHForward achieved an important milestone in January 2017.

For the first time, the facility’s high-power laser accelerated electron bunches in a plasma cell. Later in the operational phase, the laser will control the formation of the plasma at FLASH. The group of scientists around DESY’s Jens Osterhoff used the laser to ignite a plasma, from which electrons were accelerated to energies of around 100 mega-electronvolts within a distance of just a few millimetres. This allows important pre-experiments for the planned beam-driven plasma experiment. As of the second half of this year, the FLASHForward scientists want to use the FLASH electron beam to generate a plasma in a plasma cell in order to further accelerate other electron bunches from the FLASH particle accelerator or electron bunches which are formed in the plasma itself.

“The electron bunches that have now been accelerated by the laser in the plasma cell have in many respects very similar properties to those that we are later hoping to accelerate with the FLASH beam in FLASHForward,” explains the project leader Jens Osterhoff.

>Read More

Picture: The FLASHForward scientists accelerated the first electron bunches in such a plasma cell (photo: DESY/ H. Müller-Elsner).

Precise test of quantum physical tunnel effect at DESY’s X-ray laser FLASH

Partnership at a distance: deep-frozen helium molecules

Helium atoms are loners. Only when you cool them to very low temperatures do they form extremely weakly bonded molecules. Yet even in this state, they are able to maintain an extremely large separation from each other thanks to quantum tunnelling. With the help of DESY’s free-electron laser FLASH, Frankfurt nuclear physicists have been able to confirm that the atoms spend more than 75 percent of their time so far apart from each other that their bond can only be explained by means of quantum tunnelling. The scientists have presented their findings in the US journal “Proceedings of the National Academy of Sciences” (PNAS).

The binding energy of a helium molecule is approximately one billionth of the binding energy of everyday molecules like oxygen or nitrogen. On top of this, the molecule is so huge that small viruses or soot particles could actually pass between the atoms. Physicists explain this in terms of quantum tunnelling. They visualise the bond in a classical molecule as a potential well, in which atoms cannot get further apart from each other than by going to opposite “walls”. However, quantum theory also allows atoms to tunnel inside these walls. “It is as if each of them were to dig a shaft without an exit,” explains Reinhard Dörner, a professor at the Institute of Nuclear Physics at the Goethe University in Frankfurt.

 

>Read more on the FLASH website

Cartoon: “When two loners are forced to share a bed, they move well beyond its edges to get away from each other.”
Credit: Peter Evers