About EuroFEL
EuroFEL is part of the ESFRI Roadmap since 2006. The preparatory phase of EuroFEL (IRUVX-PP) prepared the establishment of the EuroFEL Consortium to link FEL & SPS facilities in Europe closer together. IRUVX-PP has been funded by the European Commission under FP7 from April 2008 to March 2011.

R&D Highlights

First images of proteins and viruses caught with an X-ray laser

Experiments at LCLS show the scientific potential of X-ray Free Electron Lasers

It has been a dream of researchers for over a decade: image biological materials at high resolution using incredibly intense X-ray laser pulses. Calculations had long predicted that these blasts of X-rays would allow exquisite measurements of the molecular structure of biological objects, from samples too small to be studied by conventional methods. In the usual methods, X-ray images of materials are blurred out because the X-rays degrade the structure. Surprisingly, the proposed way to overcome this “radiation damage” is to use ultra-short pulses a billion times brighter than conventional sources. The pulses are so fast that the image is formed before the effects of the damage are felt.

Now, an international collaboration, led by Professor Henry Chapman of the Center for Free Electron Laser Science (CFEL) at DESY in Hamburg, Germany, has proven this principle at the Linac Coherent Light Source (LCLS, at SLAC National Accelerator Laboratory in California, USA) by forming images of the Photosystem I protein complex and particles of the Mimivirus. The results, published in two papers in Nature, open a way for obtaining the molecular structures of proteins and viruses without the requirement of high-quality crystals. By using single virus particles or nanocrystals of proteins too small to see in an optical microscope, it is possible to streamline structural studies and avoid the years of laborious crystallization trials that are often needed to determine a detailed structure. “These achievements are a culmination of many years of effort that began with prototype experiments at DESY´s FLASH facility, the free-electron laser in Hamburg,” said Professor Henry Chapman. “They were only possible with a large multidisciplinary effort involving physicists, biologists, specialists in optics, plasmas, and detectors. Although the X-ray patterns we obtained from single nanocrystals were exactly as we predicted, just like in text-books, we were surprised and thrilled as to how well the experiments worked.”

The 3D structures of proteins and viruses are conventionally recorded by a method called X-ray crystallography. An X-ray beam shining on the crystal scatters into an arrangement of spots called a diffraction pattern. The measurement of the intensities of these spots as the crystal is rotated through the beam can be interpreted to give the 3D image of the protein or virus. However, the ionizing X-rays destroy the very object under investigation, so large exquisite crystals are needed to get strong patterns before radiation damage sets in. The method often fails because defect-free crystals cannot be grown, despite years of effort. The LCLS X-ray laser produces pulses of X-rays that are a billion times brighter than the conventional synchrotron sources used to date. A single pulse is so intense that any sample placed in its path is vaporized into a plasma that is hotter than the sun. But this destruction only happens after the brief X-ray pulse passes through the object. At only 100 femtoseconds long (1 femtosecond = 10-15 seconds) the X-ray pulse is faster than the time it takes the atoms to move and commence the explosion. The X-ray pattern carries the information about the undamaged object. The pulses are so intense that tiny nanocrystals, or even single virus particles, give strong enough patterns for interpretation, in agreement to calculations made over 10 years ago by Professor Janos Hajdu (Uppsala University) and colleagues.

“These experiments are a breakthrough on our roadmap to single object X-ray diffraction,” said Professor Helmut Dosch, Chairman of the DESY Board of Directors. “We see a glimpse of the world of tomorrow, in which X-ray lasers finally get to grips with non-crystalline matter.”

The studies in Nature demonstrate this concept of “diffraction before destruction” in spectacular style. Each X-ray pulse gives a single view of the object and the formation of a 3D image requires many snapshots of randomly oriented but identical particles. The experiments made use of the CAMP chamber and pnCCD detector system, designed and built by the Max-Planck Advanced Study Group at CFEL, a cooperation of eight Max-Planck Institutes, as well as the recent invention of a gas-focused liquid jet at Arizona State University (ASU). The target objects are fed into the X-ray beam in an aerosol beam (developed at LLNL, Stanford PULSE Institute for Ultrafast Energy Science, and Uppsala University) or a liquid jet (developed at ASU) and 1,800 individual patterns are collected every minute. By the time the next pulse arrives, at a rate of 30 per second, a new particle is delivered to replace the vaporized one before it. The high-speed pnCCD X-ray detectors from the Max Planck Semiconductor laboratory and Max-Planck Advanced Study Group recorded and digitized millions of patterns over the course of several days. Many terabytes of data were collected—the data rate exceeds that of particle physics experiments at the Large Hadron Collider (LHC). These data were analyzed on computer clusters at SLAC and DESY, using parallel programs that determine the orientation of the crystal to build up the 3D diffraction pattern that was a composite of tens of thousands of the best patterns. This composite could then be processed as if collected from a single perfect crystal. Photosystem I is is one of Nature’s most important biological machines: the complex converts sunlight to energy during photosynthesis. The Photosystem I nanocrystals were an ideal sample for the proof-of-principle experiments. The crystals, ranging in size from about 100 nanometers to 2 micrometers were produced by Professor Petra Fromme of Arizona State University. They are a class of membrane-bound proteins, which are extremely fragile and are the hardest to crystallize. Less than 300 membrane-bound protein structures have been determined to date (compared with many tens of thousands of soluble proteins), despite their importance as drug targets. The structure of the Photosystem I complex had been previously determined using large crystals that took 13 years of effort to find crystallization conditions. This allowed a quantitative comparison that proved the accuracy of the method using the much more easily produced nanocrystals, and showed that “diffraction before destruction” is viable even with extremely fragile objects.

The ultimate application of the “diffraction before destruction” technique is to record patterns from single molecules, without the need for any crystallization at all. This goal requires further development to focus the X-ray pulses to smaller spots, giving even higher intensities. This didn’t stop the ambitions of the collaboration to carry out yet another spectacular proof of principle experiment on imaging single copies of the giant Mimivirus, the world’s largest known virus, which infects amoebas. The experiments show the feasibility of eschewing crystallinity altogether, which gives rise to continuous diffraction patterns instead of ones consisting of spots. Thousand of patterns of single viruses were recorded, and single images were reconstructed. This new way of imaging avoids having to freeze, slice, or chemically label the structure, and could be extended to whole living cells.

The collaboration conducting the pioneering experiment was made up of 85 members from CFEL at DESY, Arizona State University, the Max Planck Institute for Medical Research and the Max Planck advanced study group at CFEL, Uppsala University, SLAC, Stanford PULSE Institute, Lawrence Livermore National Laboratory, and Lawrence Berkeley National Laboratory. The techniques demonstrated by the collaboration will continue to be developed to higher resolution. The LCLS now provides wavelengths of X-rays short enough to resolve interatomic spacings. Like flash photography, the short X-ray pulses mean that fast molecular processes in proteins can be frozen in time, so reactions can be filmed and the function of biological macromolecules determined. The research shows the enormous potential of X-ray free-electron lasers, and spurs the development of new facilities such as the European XFEL in Hamburg.

Source: DESY / PR / Thomas Zoufal
Content: DESY Website
Date Issued: 2 February 2011


PSI scientists perform the worlds first hard X-FEL user experiment at SLAC

In October 2010, the commissioning phase of the X-Ray Pump-Probe experimental station at the Stanford LCLS source was finished. The very first user experiment in the hard x-ray range was carried out by a group of scientists from SLAC, the European XFEL and PSI under the lead of Christian David (PSI).

The experiment was dedicated to measuring the unique wave front properties of the LCLS using a hard x-ray grating interferometer. The extreme angular sensitivity and high efficiency made it possible to identify the effects of beam line components such as mirrors, monochromator crystals and focusing lenses. As the interferometer is capable of recording the wave front of a single laser pulse, it also provided insight into the effects of the accelerator and undulator settings on the LCLS wave front on a shot-to-shot basis. The technique is expected to develop into a useful diagnostics tool also for the European X-FEL and SwissFEL.

Part of the experimental run was dedicated to the testing of novel diffractive lenses developed in the Laboratory for Micro- and Nanotechnology of PSI. The focusing devices were made of diamond to survive the full radiation load of LCLS, and to provide a focal spot in the 100nm range. More information on these experiments can be found in the SLAC newsletter of October 22nd (see SLAC today)

Source: PSI / SwissFEL/ Mirjam van Daalen
Content: PSI Website
Date Issued: 22 October 2010
Pictures: PSI/SLAC

FLASH opens the view through the water window

Plot for the experts: The spectrum of a flash at FLASH with 4,12 nanometres wavelength.
The Free Electron Laser FLASH at DESY in Hamburg has set a new record: this weekend, the FLASH accelerator team operated the FEL with an electron energy of 1.25 Giga electronvolts, thus reaching a wavelength of 4.12 nanometres. For the first time FLASH has generated laser light in the so-called water window using the fundamental wavelength – so far this was only reached with laser harmonics. The flashes with the short wavelengths had an average energy of 70 and a peak energy of 130 micro joules.

“Congratulations to the FLASH team for their outstanding work,” said DESY accelerator director Reinhard Brinkmann. “By optimisation of the accelerator, they increased the electron energy by another 50 MeV and – reaching the water window – created brilliant conditions for FLASH scientists.”

The water window is a wavelength region between 2.3 and 4.4 nanometres. In this wavelength region, water is transparent for light, i.e. it does not absorb FEL light. This opens up the possibility to investigate samples in an aqueous solution. This plays an important role especially for biological samples, because carbon atoms in these samples are highly opaque to the X-ray radiation, while the surrounding water is transparent and therefore not disturbing.

Additional measurements with extremely short wavelengths are scheduled for November. From the beginning of April 2011, the FEL radiation will give users the opportunity to look through the water window.

Source: DESY / PR / Thomas Zoufal
Content: DESY Website
Date Issued: 28 September 2010

The sFLASH seeding test takes up operation

The most valuable good at FLASH is time. FLASH is more or less the universal prototype for X-ray Free Electron Lasers; therefore, many scientists compete for every minute on it. This is not only true for the users who have been served in routine operation since 2005, but also for accelerator physicists and developers who never run out of ideas on how to improve the facility. They keep upgrading FLASH under the critical eyes of the researchers’ world and show what this technology can do. One of these improvements was now sent into the ring of FEL pilot facilities: in a collective research project with the University of Hamburg, a so-called seeding test section installed in during the FLASH upgrade last winter. At a 40-metrelong section between accelerator and SASE undulator magnets, the scientists built in four additional undulators through which the electron beam is threaded. The special feature: simultaneously with the electron bunch, the pulse of an optical laser is shot through this set of undulators. It “seeds” the light into the system which the undulators then amplify to an FEL pulse. Thus, the laser light does not have to come from the synchrotron light that is generated from the electrons at the beginning of the undulator – like in the SASE effect. This means that the FEL pulse becomes much more reproducible. “Based on all kinds of calculations, the seeding will work in the soft X-ray range,“ says Jörg Roßbach, Björn Wiik Professor at the University of Hamburg and head of the research project. “At FLASH, we want to establish this technology in such a way that it can be used in experiments.” Seeding has already been successfully produced at two other research centres; albeit, with wavelengths well over 100 nanometres. The team around Roßbach wants to try out seeding at sFLASH with 38 nanometres at first and then proceed step by step with smaller wavelengths. The injected seeding laser light comes from a container adjacent to the FLASH tunnel. The highly intense 800 nanometre basic wavelength is shot through an inert gas. From there, a small amount is produced with 38 nanometres, which is reflected into the seeding section. At the end of the undulator section, the generated shortwave light is deflected and analysed in a container near the FLASH tunnel. Later, it may even be used for experiments.

The first tests with sFLASH have just started. One of the major problems is clocking. Seeding laser pulse and electron bunch – both incredibly small – must traverse the undulator simultaneously and on the same track. Therefore, in their first tests, the scientists elongated the electron bunch as much as possible and tried to hit it with the laser flash – a time-consuming game. But the effort is worth it. “Seeding has become a kind of holy grail of FEL science. With it, we are able to eliminate two problems of SASE lasing: repeatability of laser pulses and synchronisation of pump probe experiments,” says Roßbach. In these experiments, a state is excited by an optical laser which the Free Electron Laser photographs with a certain time lag. The synchronisation of laser and FEL pulse at this kind of experiments is of course easier when only one laser does both, the excitation and the FEL pulse. As always, starting is the most difficult phase and the experimental time at FLASH is limited. The user period at FLASH is imminent, and a problem with the injector lost valuable time. However, if seeding runs as required, one of these days these experiments may run parallel to the FEL experiments in the large FLASH experimental hall. Roßbach is satisfied with the current achievements: “We have already seen SASE laser light from our magnets. Now we hope for a repeatable seeding signal.” Nobody is able to predict whether this will happen within hours or months – another situation in which the valuable FLASH measuring time plays a key role. In any case, the FEL world is again looking expectantly at FLASH.

Source: DESY / PR / Thomas Zoufal
Content: DESY inFORM
Date Issued: 1 September 2010

Record wavelength at FLASH – First lasing below 4.5 nanometres at DESY´s Free Electron Laser

The spectrum of the record laser pulse peaks at a wavelength of 4.45 nanometres. For the first time, FLASH produced laser light with a wavelength of 4.45 nanometres; thus, DESY’s Free Electron Laser for soft X-ray light considerably beat its previous record of 6.5 nanometres. At the same time, the peak intensity of single light pulses nearly doubled, with 0.3 millijoule. Prior to this, there was a five-month machine upgrade, above all with a significant improvement of the superconducting linear accelerator and the installation of a seeding experiment together with the University of Hamburg.
FLASH, the world’s first X-ray Free Electron Laser is available to the photon science user community for experiments since 2005. Last winter, the facility underwent a major upgrade. The accelerator was equipped with a seventh superconducting accelerator module to increase the maximum electron energy to 1.2 Giga-electronvolts (GeV). Moreover, a special 3.9-GHz module was installed to improve the quality of the accelerated electron bunches. The first tests during the current commissioning showed excellent results: the linear accelerator was operated at 1.207 GeV and the 3.9-GHz module shapes the electron bunches in a way that the intensity of the laser light is higher than ever before.
„It is absolutely impressing, how fast and promising FLASH is operating after such a substantial upgrade. My compliments to the FLASH accelerator team,” congratulates Reinhard Brinkmann, director of the DESY accelerator section. With the now obtainable laser wavelength, experiments with carbon in organic molecules come within reach, and magneto-dynamics experiments with the third-harmonic wavelength benefit from substantially increased intensities.
This success is also an important milestone for the European XFEL on the way to the observation of movements that only take femtoseconds. The accelerator module recently built-in at FLASH is a prototype for the XFEL accelerator, and the properties of the 3.9-GHz module too are decisive for operating the XFEL injector. The third FLASH user period is to start end of August.

Source: DESY / PR / Thomas Zoufal
Content: DESY website
Date Issued: 15 June 2010

Recent seeding result at SPARC

The SPARC [1] test facility provides a new and exciting opportunity to study Free Electron Laser (FEL) dynamics in exotic configurations. The undulator is based on six variable gap modules which may be tuned combining the higher order resonances to realize Free Electron Laser cascades or harmonic cascades [2]. A seeding system has been implemented within the past EUROFEL Design Study project funded by the EC under FP6. In collaboration with CEA (France) a system of chambers for the generation of high harmonics in gas was realized and installed to drive the FEL. This system now provides the possibility to seed the FEL amplifier and the various cascades with the odd harmonics generated in gas (Ar) and with the second harmonic of the Ti:Sa drive laser. The first seeding experiment started this year. For the first time an FEL cascade has been seeded with radiation generated in gas and recently the FEL has been operated in a cascaded configuration operating above saturation. This layout, based on a mechanism which is efficient in the generation of higher order harmonics, allowed to observe a coherent signal at the 6th harmonic of the seed at 67nm, with a beam energy of 176 MeV only. The spectrum of the signal is shown in Fig. 1.

[1] L. Giannessi et al. Nuclear Instruments and Methods in Physics Research A 593 (2008) 132– 136

[2] L. Giannessi, P. Musumeci New Journal of Physics 8 (2006) 294

Fig. 1 SPARC FEL operating above saturation in a cascaded configuration. Spectrum of the third harmonic of the radiator.

Source: SPARC/ Luca Giannessi
Date Issued: 12 June 2010


Upcoming Events

21-23 May 2014
Workshop on "Advanced X-Ray FEL Development
Organized by the Seeding Experts Group of FEls-of-Europe
Venue: DESY, Hamburg, Germany

2-4 June 2014
Laserlab-Europe Foresight Workshop 'Lasers for Life'
Registration deadline: 30th April 2014
Venue: Royal Society, London
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8-13 June 2014
5th Photoinduced Phase Transitions and Cooperative Phenomena (PIPT5) conference
Abstract submission deadline: 31st March 2014
Registration deadline: 31st May 2014
Venue: Bled, Slovenia
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15-20 June 2014
5th International Particle Accelerator Conference IPAC’14
Abstract submission deadline: 4th December 2013
Registration deadline: 14th April 2014
Venue: Dresden, Germany
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07-11 July 2014
SXNS13 Conference on Surface X-ray and Neutron Diffraction
Venue: DESY, Hamburg
Abstract submission: 7th March 2014
Regular registration deadline: 15th May 2014
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25-29 August 2014
FEL 2014
Abstract deadline: 30th May 2014
Registration deadline: 15th August 2014
Venue: Basel, Switzerland
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14-19 September 2014
12th Biennial Conference on High-Resolution X-Ray Diffraction and Imaging (XTOP 2014)
Venue: Grenoble & Villard-de-Lans, France
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15-17 September 2014
Science@FEL 2014 Conference
Venue: PSI, Switzerland
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29 Sept. - 01 Oct. 2014
27th Annual MAX IV Laboratory User Meeting (UM14)
Venue: Lund University, Lund, Sweden
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6-8 October 2014
6th Microbunching Instability Workshop
Organized by the seeding Experts Group of FELs-of-Europe
Venue: Elettra, Trieste, Italy
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9-14 November 2014
AVS 61st conference, dedicated to synchrotrons and FELs
Venue: Baltimore, USA
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