SwissFEL Scientific Highlights

22.08.2016 .

Catching proteins in the act

Some of the fastest processes in our body run their course in proteins activated by light. The protein rhodopsin sees to it that our eyes can rapidly take in their ever-changing surroundings. Free-electron X-ray lasers such as SwissFEL at the Paul Scherrer Institute PSI now make it possible for the first time to catch such processes in flagranti. Free-electron X-ray lasers generate extremely short and intense pulses of X-ray light. Currently there are only two such facilities in operation, worldwide. An international team under the leadership of the PSI has now successfully shown how the ultrafast processes by which proteins do their work can be studied with free-electron X-ray lasers. As a model organism, they used a simple microbe that can convert light into chemical energy. The researchers report their results in the scientific journal Nature Communications. Read the full story



Facility: Biology, SwissFEL
References: Jörg Standfuss; joerg.standfuss@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


15.06.2016 .

First light from the SwissFEL Experimental Laser.

The experimental laser is an important component for performing time resolved optical pump - X-ray probe experiments at SwissFEL. Only a very high reliability and reproducibility guarantees successful experiments. Flexibility in wavelength is achieved by subsequent optical parametric amplification of the laser output. In a synergy between different research groups at PSI, the SwissFEL Experimental Laser 1 is successfully delivered and installed in a temporary Laser lab by Coherent. At the end of 2016 the system will be moved to its final destination in the SWISSFEL building. There the experimental lasers will be part of the new SwissFEL facility, they will be located at the end of the accelerator tunnel on top of experimental stations A and B, in a dedicated laser hutch (LHx). The system consists of 4 next generation diode pumped, intracavity doubled Nd:YLF lasers (REVOLUTION), a Ti:Sapphire oscillator (VITARA) and a regenerative amplifier (Legend USX) in combination with additional amplification stages. After installation in the temporary lab, the oscillator started to mode-lock directly out of the box. The 800 nm laser output at 100 Hz repetition rate after the pulse amplification was measured to > 20 mJ, with a sub 30 fs pulse duration (SPIDER measurement after pulse compression). The main amplifier specs were already successfully demonstrated during the installation. Verification of parameters depending on long term drifts and stabilities that strongly depend on the building environment will be tested after final installation in the SwissFEL building. Due to the pre-installation in the temporary laser lab, it is possible to become acquainted with the system, to setup a full monitoring and diagnostics system and eventually to debug potential problems in the next months before final installation.



Facility: SwissFEL
References: Gregor Knopp, Christian Erny; gregor.knopp@psi.ch; christian.erny@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


6.06.2016 .

Investigating DNA Radiation Damage Using X-Ray Absorption Spectroscopy.

The key to achieving more effective radioprotection and radiotherapy is to understand the exact mechanism of the interaction between radiation and biomolecules, and in particular to obtain the precise structure of the different forms of damage and their relative ratios. Among all biomolecules exposed to radiation, DNA plays an important role because any damage to its molecular structure can affect the whole cell and may lead to chromosomal rearrangements resulting in genomic instability or cell death. The biochemical and spectroscopic methods that are commonly used to study interaction between DNA and different radiation types can identify the possible damage types and their amount but they are not directly sensitive to the lesion structure. In the presented studies the application of X-ray spectroscopy to investigate the molecular structure of the damage caused by UV and proton radiation in DNA was demonstrated. Phosphorus K-edge X-ray absorption spectroscopy was used to study the changes in chemical structure around the phosphorus atoms in the phosphodiester DNA backbone caused by exposure to radiation. The experiment was performed using synchrotron radiation at the Swiss Light Source’s PHOENIX beamline. By combining the experimental results with theoretical calculations, information about the damage types and changes in electronic structure around the phosphorus atoms associated with each type of lesion was obtained, which can help to establish the possible formation mechanisms involved. Moreover, this method provided approximate quantitative information as to which bond in the sugar-phosphate backbone will most likely be broken after irradiation. The results of this work are preparation for future time-resolved experiments on DNA lesion formation at the SwissFEL X-ray free electron laser.

Related publication: Czapla-Masztafiak et al. Investigating DNA Radiation Damage Using X-Ray Absorption Spectroscopy. Biophysical Journal 110 (2016) 1304–1311. doi:10.1016/j.bpj.2016.01.031



Facility: SwissFEL
References: Joanna Czapla-Masztafiak; Joanna.Czapla-Masztafiak@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


14.04.2016 .

Tailoring Novel Superconductivity

The band insulator strontium titanate SrTiO3 (STO), widely used as a substrate for growing oxide films, is a highly fascinating material. Recently, novel physical properties have been observed at the interface between STO and the materials grown on it. For instance the appearance of superconductivity above the temperature of liquid nitrogen, observed in a single monolayer of FeSe (its critical temperature is higher than in any iron-based bulk material) grown on the STO surface, suggests a key-role of the STO substrate. An international group of scientists has teamed up under the lead of researchers at the Paul Scherrer Institute (PSI) and the University of Geneva to investigate why STO is special. The measurements performed on the two-dimensional electron liquid (2DEL) present at the STO surface, revealed that at low carrier density electrons were always accompanied by a quantized dynamic lattice deformation, i.e. a cloud of phonons. Together with the electron, the phonon-cloud formed a new composite quasiparticle called “Fröhlich Polaron”. These “Fröhlich Polarons” were observed to still move in a band-like fashion through the solid, although with an increased effective mass. In addition, they found that by increasing the doping the electrons and phonons interact weaker and over shorter distances, causing the “Fröhlich Polarons” to dissociate. For their studies, the scientists used high-resolution Angle-Resolved Photoemission Spectroscopy (ARPES), a uniquely powerful technique for visualizing the motion of electrons in crystalline solids. These findings, published in Nature Materials, provide a clear microscopic basis for understanding why superconductivity has been observed in different STO based systems and are a crucial step in the search for a tuning knob with which to tailor interface superconductivity.

Related publication: Wang et al. Tailoring the nature and strength of electron–phonon interactions in the SrTiO3(001) 2D electron liquid. Nature Materials (2016). DOI: 10.1038/NMAT4623



Facility: SwissFEL
References: Milan Radovic; milan.radovic@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
Felix Baumberger; felix.baumberger@unige.ch; University of Geneva, CH-1211 Geneva, Switzerland


01.04.2016 .

Hard X-ray Photon Single-Shot Spectrometer of SwissFEL successfully delivered and installed

Not a joke: on 1st of April 2016 the Photon Single-Shot Spectrometer (PSSS) got delivered fully assembled and installed already to the front end of SwissFEL. It will measure the photon spectral information in every single shot for the Aramis beamline not only for the users, but also as a direct feedback to the machine during formation of the lasing process. The working principle of PSSS is shown in figure 1. The SwissFEL-beam will pass through a transmission grating, where we obtain the +1st as well as the -1st diffraction orders. The 0th order (direct beam) will be transmitted through to the experiments, the +1st order will be sent on a bent Si-crystal, which results the spectral information via diffraction. The -1st order will be send to a YAG-screen, where we can measure the intensity pattern of the beam, which will be convolved with the spectrum to result an intensity corrected spectrum of the generated XFEL shot. The PSSS-team acknowledges our production and assembly partners, especially the Heinz Baumgartner AG in Tegerfelden, Switzerland, for the very fruitful and straightforward cooperation on this project. We succeeded to be ready with the project very well in time. The last alignment and measurements are currently ongoing in the tunnel. The spectrometer will be ready to be used with SwissFEL radiation soon.



Facility: SwissFEL
References: Jens Rehanek; jens.rehanek@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


16. March 2016 .

Towards hybrid pixel detectors for energy-dispersive or soft X-ray photon science

JUNGFRAU (adJUstiNg Gain detector FoR the SwissFEL Aramis User station) is a two dimensional hybrid pixel detector for photon science applications at free electron lasers and synchrotron light sources. The JUNGFRAU 0.4 prototype presented here is specifically geared towards low-noise performance and hence soft X-ray detection. With an extremely low noise of less than 30 electrons it enters a field formally reserved for SSD’s and CMOS imagers allowing single photon resolution down to a photon energy of 500eV. Read the full abstract.

Facility: SwissFEL
Reference: Bernd Schmitt; bernd.schmitt@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


09. February 2016 .

Installation progress of the SwissFEL Linac

The installation of the linear accelerator (Linac) progresses very well. This week, the last girder of the so-called “Linac 1” was installed in the SwissFEL tunnel. The entire C-band accelerator consists out of Linac 1, Linac 2, and Linac 3, and a total amount of 104 accelerating structures. Meanwhile, 38 accelerating structures are installed in the SwissFEL tunnel. The assembly work on the remaining Linac modules will take place until end of September of this year. By then it is planned to finish the installation of all Linac modules in the SwissFEL tunnel.

Facility: SwissFEL
Reference: Florian Löhl; florian.loehl@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


25. January 2016 .

Transport of first "completed" Undulator into the SwissFEL Tunnel

On the 25th of January, the first "completed" undulator has been transported to its final position in the SwissFEL tunnel. The 1064 permanent magnets of this undulator where shimmed to the sub-micrometer level and the magnetic profile has been carefully measured for the full gap range. Twelve of such undulators will be installed until October 2016!

Facility: SwissFEL
Reference: Romain Ganter; romain.ganter@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


05. January 2016 .

First ultraprecise mirror for SwissFEL arrived at PSI

Mirrors are key elements to distribute and shape the Xray beam generated by the undulators of the SwissFEL facility. They are essential tools to guide and focus the light according to the specific users requirements and should do this without noticeable effects on the beam quality. A quantitative measure is the quality of the beam wavefront. The wavefront must be conserved by the optical elements in the SwissFEL beamlines within a fraction of the wavelength which can be as short as one Angstrom in the case of the Aramis beamline. There are only a few companies in the world, who are able to fabricate such ultraprecise mirrors. Shortly before Christmas, we received the first mirror for the Aramis beamline. The company JTEC, located in Osaka, was able to fabricate the M-­201 mirror within our tight specifications. Over the central length of 620 mm, the mirror profile deviates by only 3 nm peak to valley (0.5 nm rms) from perfect sphere with a mean radius of 1263 km. To get an impression of this accuracy, suppose we scale the sphere to the radius of the earth and place a human hair with approx. 45 μm diameter across the equator. The resultant bump would then be 3000 times higher than the maximum profile error.

Figure 1 shows a profile scan along the center of the mirror as provided by the supplier. The height is well within the specified maximum profile error of 3 nm (PV). Currently the mirror is in the metrology laboratory for detailed inspection and acceptane measurements of the surface profile (Figure 2).

Facility: SwissFEL
Reference: Rolf Follath; rolf.follath@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


05. November 2015 .

New EU project: Guiding light for the world's brightest light sources

EUCALL will build bridges between major laser and X-ray research centres: For the past half-century, two special kinds of light have changed the landscape of research. Advanced visible-spectrum optical lasers have propelled studies into ultrafast processes, new materials, telecommunications, and many other fields, while intense X-rays produced at synchrotrons have helped image tiny structures and otherwise invisible parts of matter, enabling huge leaps in biochemistry, pharmacology, and materials science. New developments have enhanced the generation of X-rays at optical-laser and accelerator facilities, resulting in the creation of large international research centres. The European Union is now funding a 7 million-euro effort to bring these research centres together through the European Cluster of Advanced Laser Light Sources (EUCALL) project. The project will be managed by European XFEL, an X-ray free-electron laser facility currently under construction in the Hamburg area of Germany.Also involved are five other institutes: DESY, which operates the FLASH and PETRA III X-ray user facilities, in Hamburg, Germany; Elettra, which operates the 2-stage seeded FERMI free-electron laser user facility, in Trieste, Italy; Helmholtz-Zentrum Dresden-Rossendorf, which operates high-power optical-laser facilities and a free-electron laser, in Germany; Lund University, which is building the MAX-IV synchrotron, in Sweden; and Paul Scherrer Institut, which is building the SwissFEL X-ray free-electron laser, in Villigen, Switzerland. Read the full Story

Facility: SwissFEL
Reference: Mirjam van Daalen; mirjam.vandaalen@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


26. October 2015 .

Put in perspective

Researchers from the Paul Scherrer Institute PSI have succeeded in using commercially available camera technology to visualise terahertz light. In doing so, they are enabling a low-cost alternative to the procedure available to date, whilst simultaneously increasing the comparative image resolution by a factor of 25. The special properties of terahertz light make it potentially advantageous for many applications, from safety technology to medical diagnostics. It is also an important tool for research. At PSI, it will be used for the experiments on the X-ray free-electron laser SwissFEL. The terahertz laser developed at PSI is currently the world's most intensive source of terahertz light. Read the full Story

Facility: SwissFEL
Reference: Christoph Hauri; christoph.hauri@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


12. October 2015 .

New methods to generate short and high-power X-ray Free-Electron-Laser pulses

State-of-the-art X-ray Free-Electron-Laser (XFEL) facilities like SwissFEL are able to provide radiation pulses with pulse powers of a few tens of gigawatts and pulse durations of several tens of femtoseconds and shorter. There is, however, a strong demand in research fields such as bioimaging and nonlinear optics to obtain higher radiation powers and shorter pulses than in standard facilities. In this context, we have developed two new methods able to generate terawatt-attosecond XFEL pulses. Both proposals are based on superradiance, a regime with quadratic growth of the radiation power and a shortening of the spike while it slips into unspoiled (good-beam) regions of the bunch. In the first method [1], a multiple-slotted foil defines several unspoiled regions of the beam, which will generate several XFEL pulses in the first section of the undulator beamline. After that, by properly delaying the electrons after certain undulator modules, only the first of the initial XFEL pulses will be amplified by all the other good regions of the electron beam. The separation between the slots in the foil must be uneven to suppress the growth of all unwanted single short XFEL pulses. In the second method [2] we propose to introduce a transverse tilt to the electron bunch. In the first part of the undulator beamline, only the tail of the electron beam will have an aligned trajectory and therefore will radiate significantly. Then, by suitably delaying the electron beam and correcting its trajectory between some undulator modules, the entire electron bunch will contribute to amplify a short XFEL pulse. This second method is more efficient since all the electrons can potentially contribute to the XFEL amplification, and more flexible since by tuning the tilt amplitude one can maximize the XFEL pulse energy or minimize the pulse duration. We have proved the validity of our proposals with numerical simulations for the SwissFEL case – the figure below shows the performance of the first scheme for two different radiation wavelengths. Both methods are simple, compact, and easy to implement in future and existing facilities.


References
[1] E. Prat and S. Reiche, Phys. Rev. Lett. 114, 244801 (2015).
[2] E. Prat, F. Löhl, and S. Reiche, Phys. Rev. ST Accel. Beams 18, 100701 (2015).

Facility: SwissFEL
Reference: Eduard Prat; eduard.prat@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


22. September 2015 .

Laser arrival time measurement and correction for the SwissFEL lasers

To probe ultrafast processes at SwissFEL it is crucial that the pump laser, used at the end stations, arrives in time with the generated X-ray pulses. For fs resolution pump probe experiments a path-length change of few-hundred nanometers already affects the measurement quality. The length of SwissFEL and the total propagation path of the pump laser light to the experiment is in the scale of several hundred meters, which makes this task challenging. The Timing and Synchronization and the SwissFEL laser group are working on developing tools to measure and correct the timing over the machine complex. They report on the Laser Arrival Monitor (LAM) concept for the SwissFEL gun laser, which produces the electron bunch at the start of the linear accelerator [1]. This device is based on high bandwidth electro-optical modulators adapted from telecommunication. They also report on the first results using a spectrally resolved cross-correlator, which enables to measure time of arrival with fs resolution and to correct long term timing drifts of a Terrawatt class Ti:sapphire laser system from the ps level to below 10 fs over 10 hours. The measurements will also help to identify the major sources of drift for passive stabilization. These results are important to enable fs resolution pump-probe experiments at SwissFEL.


Reference
[1] Marta Csatari Divall; Albert Romann; Patrick Mutter; Stephan Hunziker; Christoph P. Hauri, "Laser arrival measurement tools for SwissFEL", Proc. SPIE 9512, Advances in X-ray Free-Electron Lasers Instrumentation III, 95121T (May 12, 2015); oi:10.1117/12.2179016.



Facility: SwissFEL
Reference: Christoph Hauri; christoph.hauri@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


24. August 2015 .

Umbrella MoU Signed by 14 Parties

The Memorandum of Understanding of the Umbrella Collaboration was signed by 14 parties: ALBA, DESY, Diamond Light Source Ltd, Elettra, EMBL Heidelberg, ESRF, European XFEL, HZB, ILL, Instruct Academic Services Ltd, KIT, PSI, STFC and SOLEIL. Umbrella is the pan-European federated identity management system for the users of the large-scale European photon and neutron facilities. This IT platform offers for the first time an EU-wide, unique and persistent ID for a wide, multidisciplinary user community. It was initiated by the IRUVX-PP project and further developed with the support of several EU projects such as PaNdata and CRISP. For more information see the Flyer of the Umbrella Collaboration Download.

Facility: SwissFEL
Reference: Mirjam van Daalen; mirjam.vandaalen@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


17. August 2015 .

Terahertz laser light focused to the extreme

There are limits to how short a flash of light can be – in both time and space. Researchers from the Paul Scherrer Institute (PSI) have now succeeded in reaching these physical limits and producing the smallest possible flash. To do so, they used terahertz light, which is physically related to visible light or radio waves, but differs in its wavelength. In the experiment, a special crystal was illuminated with laser light and thus stimulated to emit terahertz light, which a mirror system subsequently focused to generate a highly concentrated flash. The challenge was to actually produce the terahertz light at a high enough quality for it to be focused. Highly intensive terahertz light is becoming increasingly important as a research tool because it can be used to specifically alter the behaviour of materials and study their properties. Read the full Story

Facility: SwissFEL
Reference: Christoph Hauri; christoph.hauri@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


10. July 2015 .

High-Precision Vertical Linear Translation for Offset Mirrors

The horizontal and vertical offset mirrors are key optical elements for the SwissFEL ARAMIS Beamline. The offset mirrors for example, are used to deflect and steer the x-ray beam into one of the end stations. As the sample position is about 60m from the mirror, very high demands are put on the mirror positioning system in order to deflect the x-ray beam on to the sample with a micro-meter precision. Therefore precise positioning of the mirrors is required, with specifications to move a load of up to 200kg by steps as small as 0.3µm. Not just the positioning must be precise, but also the stability for short term vibrations and long term drifts must be superior. Based on an original design from the Swiss Light Source which was further developed at Petra III at DESY, a third generation high-precision vertical linear stage has been designed at PSI. The fabrication and assembly was made at Högg AG Produktionstechnik in Wattwil, Switzerland. Extensive measurements were performed to ensure the design specifications. The full-range absolute position actuary has been determined to be better than 1.5µm, the uni-directional reproducibility is better than +/-0.2µm. All design specification could be met and were even exceeded in most cases.

Facility: SwissFEL
Reference: Claude Pradervand; claude.pradervand@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


8. June 2015 .

PSI-DESY Collaboration Delivers First Photonics Component for SwissFEL

The gas-based photon beam position and intensity monitor is a device originally developed by Dr. Kai Tiedtke and his team at the Deutsches Elektronen-Synchrotron (DESY) for the non-destructive measurement of an X-ray FEL's beam position and flux. The accurate measurement of these variables is necessary due to the stochastic nature of the self-amplified spontaneous emission (SASE) process which can create jitters in the position and flux of the FEL beam on a shot-to-shot basis. The device has been developed and adapted to fit the SwissFEL parameters in a PSI-DESY collaboration over the course of two years. The gas-based detectors, designated as the Photon Beam Intensity Gas (PBIG) monitor and the Photon Beam Position Gas (PBPG) monitor will be the first components to see the photon beam created by the SwissFEL, and will be the main components that users and operators will use to optimize the operations of the machine and to better understand the data collected. The photon beam positon and intensity monitors detect the position and intensity of the FEL beam by counting the number of ions created in a pre-calibrated gas chamber through the photoionization process, and looking at the differences in a split electrode to find the position of the beam. The device boasts the ability to measure relative flux of the FEL beam to a 1% level or better, the absolute flux of the beam to 10% level or better for photon energies ranging up to 20 keV, and can measure the transverse position of the FEL beam to an accuracy of 10 micrometer. The device arrived at PSI at the end of May, and will be one of the first photonics components to be installed in the new SwissFEL facility.

Facility: SwissFEL
Reference: Pavle Juranic; pavle.juranic@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


19. May 2015 .

Beam Stoppers for SwissFEL

On the 5th of May the two beam stoppers were installed in the SwissFEL tunnel. These two blocks are made out of copper, recycled lead, steel and concrete blocks and weight 60 tons each. These stoppers are placed in front of both Aramis and Athos undulator lines. They will block the electron beam during machine adjustment or diagnostic to avoid uncontrolled beam loss in the undulator magnets. For example, when the electron beam goes through a diagnostic screen it cannot be used anymore for lasing and has to be dumped in the beam stoppers before the undulators.

Facility: SwissFEL
Reference: Romain Ganter; romain.ganter@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


19. March 2015 .

Table-top soft x-ray lasers based on high-order harmonic generation (HHG)

Table-top soft x-ray lasers based on high-order harmonic generation (HHG) deliver routinely linearly polarized light. Many advanced applications including magnetic imaging would profit from a HHG source delivering in addition circular polarized light. In one of our recent work we present now an approach which provides intense soft x-ray radiation of high ellipticity. This source has given us the opportunity to realize the first magnetic dichroism experiment on a nickel sample at 18 nm (67 eV) with a table-top HHG source. So far this type of experiment could only be done at large research facilities, such as synchrotrons and free electron lasers. Compared to those our compact laboratory-size harmonic source offers substantially enhanced temporal resolution (a few fs) and virtually jitter-free pump-probe configurations. Our results achieved together with our French collaborators at LOA were recently published in Nature Communications Nature Communications 6, 7167 (2015)

Facility: SwissFEL
Reference: Christoph Hauri; christoph.hauri@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


17. February 2015 .

Prospective studies for SwissFEL experiments done at the SLS FEMTO station

L. Rettig et al, Phys. Rev. Lett. 114, 067402 – Published 13 February 2015, DOI: PhysRevLett.114.067402
For many years, PSI researchers have been testing experimental methods that will provide insights into novel materials for electronic devices. Using a special trick to make the Swiss Light Source (SLS) at PSI generate light with similar properties to that of PSI's x-ray laser SwissFEL, the researchers were able to demonstrate that the experiments planned for SwissFEL are possible and they are now building an experimental station at SwissFELread the full story)

Facility: SwissFEL
Reference: Christoph Hauri; christoph.hauri@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


13. February 2015 .

Successful start of the series production of the C-band accelerating structures for SwissFEL

A total of 104 C-band accelerating structures will be needed for SwissFEL. Each of these structures is about 2 m long and consists out of 113 copper cells that are manufactured with micrometer precision using ultra-precision diamond machining, which results in mirror-like surfaces. The main components are the couplers at the input and the output of the structure, and the copper disks. For both, couplers and disks, the series production was successfully launched at the end of 2014. Since then the Dutch company VDL and TEL Mechatronics in Trübbach, Switzerland, delivered already many sets of couplers and accelerating disks, respectively.

The copper parts are then further processed at PSI in a special installation in the AMI-workshop. This involves a cleaning of the parts, a heat treatment, and several brazing steps. The individual parts are then combined to a complete structure using a special stacking robot. After this, a brazing of the structure takes place in a big vacuum brazing furnace. The verification of the proper functioning of a completed structure then includes micrometer-precise surveying, vacuum leak tests, and a number of RF measurements in which the field profile and other RF properties are measured.

In the meanwhile, a total of 15 accelerating structures have been brazed at PSI, currently, every week a new structure is completed.

Facility: SwissFEL
Reference: Florian Löhl; florian.löhl@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland


16. January 2015 .

Terahertz wavefront control for extremely bright THz bullet

M. Shalaby and C.P. Hauri “Demonstration of a low-frequency three-dimensional terahertz bullet with extreme brightness.” Nat. Commun. 6:5976 doi: 10.1038/ncomms6976 (2015).

The brightness of a light source defines its applicability to nonlinear phenomena in science. The SwissFEL laser group has now overcome one of the two principal technological hurdles to produce bright pulses in the Terahertz range (0.1-5 THz). Using a present-technology THz generation scheme based on optical rectification in organic crystal we were able to optimize the THz wavefront such that a spatio-temporal confinement of THz energy at its physical limits has become feasible – the least possible three-dimensional light volume of wavelength cubic. The gain of control on the THz wavefront is a technological breakthrough as it allows to reach the highest ever produced single-cycle Terahertz transients (up to 80 MV/cm, 25 Tesla) in a diffraction-limited spot size. While such field strength is of interest for many applications, the THz spot size might be too small for realistic pump-probe investigations. Therefore further developments are required to overcome the second hurdle being the increase of THz pulse energy. The SwissFEL laser team has proposed a novel approach which shall be explored in near future. The combination of both wavefront control and high THz pulse energy will open a new avenue in nonlinear THz optics and will be a unique tool for controlling properties in condensed matter by impulsive excitation.

Facility: SwissFEL
Reference: Christoph Hauri; christoph.hauri@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

Record low emittance for compressed bunches at the SwissFEL Injector Test Facility

The emittance of the electron beam is crucial for Free-Electron Laser (FEL) facilities: it has a strong influence on the lasing performance and on the total length of the accelerator. The emittance of the whole bunch, called projected emittance, is a general indicator of the electron beam quality. However, the key beam parameter for FELs is the slice emittance, i.e. the emittance measured for individual slices along the bunch length. In practice, both slice and projected emittance need to be optimized. A procedure to measure and minimize the projected and slice emittance was developed and implemented at the SwissFEL Injector Test Facility, a 250 MeV accelerator that was in operation between 2010 and 2014 to demonstrate the feasibility of the SwissFEL design. A normalized slice emittance resolution of about 3 nm and a longitudinal resolution of about 13 fs were achieved, with measurement errors estimated to be below 5%. After performing a full optimization, a projected emittance of around 300 nm and a slice emittance below 200 nm were obtained for uncompressed beams with a charge of 200 pC. Moreover, after compressing the bunch from about 4 ps to about 0.5 ps, the emittance of the beam core was preserved. A second bunch compressor available at SwissFEL will compress the electron beam to its final length, e.g. to about 20 fs for a bunch charge of 200 pC. The measured core beam emittances at the SwissFEL Test Facility are consistent with numerical simulations and are well below the tight requirements of SwissFEL. At these bunch charges these slice emittances for both uncompressed and compressed bunches are, to the best of our knowledge, the lowest achieved so far for an electron linear accelerator.

Facility: SwissFEL
Reference: Eduard Prat; eduard.prat@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

A time-dependent order parameter for ultrafast photoinduced phase transitions


Published 3 August 2014 in Nature Materials DOI: 10.1038/nmat4046
The exploration of the interaction of structural and electronic degrees of freedom in strongly correlated electron systems on the femtosecond time scale is an emerging area of research. One goal of these studies is to advance our understanding of the underlying correlations, another to find ways to control the exciting properties of these materials on an ultrafast time scale. So far a general model is lacking that provides a quantitiative description of the correlations between the structural and electronic degrees of freedom. Here we investigate a perovskite-type manganite, a prototypical example of a strongly correlated electron system which exhibits properties such as colossal magnetoresistance and insulator-to-metal transitions that are intrinsically related to symmetry changes of the atomic lattice and to intriguing ordering patterns of the spins, orbitals and charges. The application of an ultrashort optical pulse melts the electronic order and launches a structural phase transition. The long-range electronic and atomic order during the transition is probed directly with time-resolved resonant x-ray diffraction. Although the actual change in crystal symmetry associated with this transition occurs over different time scales characteristic of the many electronic and vibrational coordinates of the system, we find that the dynamics of the phase transformation can be well described using a single time-dependent order parameter that drives the electronic phase transition as well as the coherent motion of the atomic lattice. The striking analogy of this formalism to Landau phae transition theory points to a possibly universal description of complex phase transitions in the time domain.
Facility: SwissFEL
Reference: Paul Beaud; paul.beaud@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

7 Å resolution in protein two-dimensional-crystal X-ray diffraction at Linac Coherent Light Source

B. Pedrini et al, Phil. Trans. R. Soc. B 2014 369, 20130500, published 9 June 2014, DOI:10.1098/rstb.2013.0500

Membrane proteins arranged as two-dimensional (2D) crystals in the lipid environment provide close-to-physiological structural information, which is essential for understanding the molecular mechanisms of protein function. Previously, X-ray diffraction from individual 2D crystals did not represent a suitable investigation tool because of radiation damage. That the recently available ultrashort pulses from X-ray Free Electron Lasers (X-FELs) provide a mean to outrun the damage is now well established for the 3D crystal case. This is now demonstrated also for the 2D crystal case, within the work of an international collaboration led by Matthias Frank from the Lavrence Livermore National Laboratory (CA, USA), to which scientists from PSI had the opportunity to participate and contribute. We report on the measurements performed in May 2013 at the Coherent Diffraction Imaging station of the Linac Coherent Light Source X-FEL, and using bacteriorhodopsin 2D crystals as samples. By merging data from about a dozen single crystal diffraction images, we unambiguously identified the diffraction peaks to a resolution of 7 Å, thus improving the observable resolution with respect to that achievable from a single pattern alone (see example in the Figure). On the one hand, this indicates that further improvements in resolution should be achievable by acquiring a larger dataset. will allow for reliable quantification of peak intensities, and in turn a corresponding increase of resolution. On the other hand, the presented results pave the way to further X-FEL studies on 2D crystals, which may include pump-probe experiments at subpicosecond time resolution.
Facility: SwissFEL
Reference: Bill Pedrini; bill.pedrini@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

Lauch of the SwissFEL in Virtual Reality Model

On the 10.06.2014 the new SwissFEL in Virtual Reality Model was launched. The Model was realized in order to help society understand the importance of PSI's new large research facility SwissFEL, which currently under construction.In 2016 the Swiss X-ray free electron laser will go into operation. The SwissFEL X-ray laser will generate extremely short, intense X-ray pulses. The unique properties of the SwissFEL will enable experiments to be carried out at a very high resolution in both time and space. This new facility will open the door to discoveries, in many areas of current research, which cannot be achieved using existing methods. The SwissFEL in a virtual reality model was realized with the help of the AGORA SNF funding project. SwissFEL in a virtual reality is a video game like device with whom SwissFEL researchers want to attract the general public, and especially groups usually less interested in research (i.e. people fancying videogames, entire families: parents in their thirties, with children between 8 and 15). The virtual model fosters communication of cutting edge research to the general public by explaining and guiding through the concept of Switzerland's new cutting edge research facility through the new Virtual Reality Model in a playful way.
Facility: SwissFEL
Reference: Mirjam van Daalen; mirjam.vandaalen@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

First beam from the SwissFEL electron gun

6.06.2014 The new 3 GHz photocathode gun will provide the electron bunches for SwissFEL and has recently been installed in the SwissFEL injector test facility. There, it replaced the CTF2-gun 5, borrowed from CERN. The new gun is capable now of operation with 100Hz repetition frequency and a higher field on cathode and improved field symmetry. After RF conditioning of about 4 days, the gun reached the nominal acceleration gradient of 100 MV/m at an input power of about 17 MW and pulse-width of 1 microsecond. The gun incorporates the same type of copper cathode plugs, as the CTF2-gun and accelerates the electrons in 3 cells up to a kinetic energy of 6.6 MeV. Each cell has a pick-up for amplitude and phase monitoring. The first measurements of the electron beam on the spectrometer arm confirm the expected kinetic energy. Next weeks of test injector operation will be dedicated to gun commissioning and more detailed beam quality measurements.
Facility: SwissFEL
Reference: Lukas Stingelin; lukas.stingelin@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

Investigating ultrafast magnetization dynamics with a table-top femtosecond XUV laser

The study of ultrafast dynamics initiated by a femtosecond laser pulse is a hot topic. Many questions, such as the angular momentum transfer during the laser-matter interaction are yet unanswered which calls for advanced metrology. In order to investigate ultrafast transient dynamics in magnetic materials we have now implemented a new diagnostic scheme at our extreme UV high-harmonic (HHG) beamline which is based on the Transverse Magneto-Optic Kerr effect (T-MOKE). Thanks to its coherent, multi-color emission our table-top XUV scheme allows synchronous tracking of the magnetization dynamics of multiple elements at femtosecond resolution. This opens exciting opportunities for time-resolved studies particularly in alloys (e.g. permalloy (20% Fe/80% Ni) and more complex materials to gain a deeper understanding of the dynamics occurring at the the onset of the laser-matter interaction. Presently, our scheme allows investigations at the M absorption edge of ferromagnetic materials (40-70 eV) and will be extended to higher photon energies in near future. Our scheme complements the experimental opportunities given at Free Electron Lasers, where element-selective investigations have not been demonstrated so far.
Facility: SwissFEL
Reference: Christoph Hauri; christoph.hauri@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

Large European R&D project holds its third annual meeting on the epn campus in Grenoble/France

Large research infrastructures are built on making the latest in technology for use in scientific experiments available to scientists. This often requires joint R&D efforts, and the CRISP project is bringing together eleven main players from across Europe to address four key technology areas for the big science of tomorrow. CRISP was launched in October 2011; the third annual meeting was the occasion to review the current status of the project, present some of the major accomplishments, and to coordinate the work for the last months of the project.

CRISP - the Cluster of Research Infrastructures for Synergies in Physics (http://www.crisp-fp7.eu) - is a 3-year project partly funded by the European Commission with 12 million Euros from the 7th Framework Programme. CRISP comes in four flavours of technological R&D: particle accelerators; large-scale physics instruments and experiments; detectors and data acquisition technologies; IT and data management systems.

Progress in accelerator technology is essential to provide research infrastructures with the best possible sources of Xrays, ions and neutrons, and to tackle tomorrow's challenges in nuclear and high-energy physics. Joint developments for novel types of large-scale physics experiments and their related instrumentation will also create new scientific opportunities, across many other fields of science. New initiatives and approaches are required to cope with the everincreasing flow of data from large experiments, and a joint effort will establish the technological base for adequate platforms for the processing and storage of, and access to these data.

Within the CRISP project, the eleven participating research entities exchange know-how and combine their complementary expertise, ensuring cost-efficient and coherent development of new technologies. Such synergies are crucial to respond to a rapidly evolving and internationally mobile community of scientists using these large research facilities. As major players in cutting-edge science, they also contribute to the technological progress needed for tackling big societal challenges in health, environment, sustainable energy, transport and communication.

The eleven partners of the CRISP Project are listed on the roadmap of the European Strategy Forum on Research Infrastructures (ESFRI). They are under construction (ELI, ESS, EuroFEL, European XFEL, ILC-HiGrade and SKA), or research infrastructures in operation undergoing an important upgrade (ESRF, GSI-FAIR, ILL, SLHC@CERN and GANIL-SPIRAL2).

The third Annual Meeting was jointly hosted from 2 to 4 June 2014 by the ESRF and the ILL. It took place on the epn campus in Grenoble, and attracted more than 100 participants. The meeting started with parallel topic meetings on Monday morning, before the opening of the plenary meeting at 14h, featuring three keynote lectures. John Womersley, the current chair of the European Strategy Forum on Research Infrastructures (ESFRI), explained the role of ESFRI and its priorities within the new framework program Horizon 2020; Alex C. Mueller presented the current status and perspectives for the SPIRAL2 and FAIR facilities; and Lyn Evans, the project leader of the Large Hadron Collider, offered fascinating insights from the design and the construction of the LHC to the discovery of the Higgs boson. Following short status reports from the eleven participating research infrastructures, the meeting continued with a poster session and a buffet dinner in the recently inaugurated Science Building. The Tuesday session started with five highlight talks from the CRISP project, covering subjects from accelerator components diagnostics to federated identity management. These were followed by the status reports from the four topic leaders, and a guided tour to the ESRF and ILL facilities. The meeting left ample time for exchange of ideas, and lively discussions continued during the dinner which took place in the Chateau de la Commanderie in Eybens.
Facility: CRISP 3rd annual Meeting
Reference: Mirjam van Daalen; mirjam.vandaalen@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

Coherent femtosecond radiation up to 300 eV

State of the art table-top high-order harmonic (HHG) sources driven by an intense femtosecond are routinely used to produce coherent soft x-ray pulses up to a photon energy of 100 eV. It is clear that many applications would benefit from higher photon energies, such as seeding a free electron laser, imaging of biological tissue in the water window (285 eV-530 eV) or the investigation of ultrafast magnetization dynamics in transition metals and rare earth elements with absorption edges in the range >100 eV. Motivated by such applications, the SwissFEL laser group has now extended the maximum photon energy from a table-top laser-driven source from 100 eV up to 300 eV (4 nm), by altering the driving laser wavelength from 0.8 Am to 1.9 Am. This significant shift in the cut-off energy becomes possible since the maximum achievable HHG photon energy scales with the square of the driving laser wavelength (see Figure). Even though the present photon flux is still quite low, this development is considered a first important step towards seeding the future soft x-ray branch at SwissFEL. Seeding an FEL helps to improve its temporal coherence and would provide an excellent scheme for x-ray pump and laser probe at intrincially low temporal jitter. Our future developments aim therefore at improving the HHG photon flux by exploring novel phase-matching schemes. Our present HHG source will also provide an excellent test bed for some pre-trigger experiments later on performed at the SwissFEL soft x-ray beamline.
Facility: SwissFEL
Reference: Christoph Hauri; christoph.hauri@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

RF-Gun

The workshop of the PSI engineering department (AMI) recently completed the manufacturing of the high brightness electron source that will drive SwissFEL. The first characterization of the 2.5 cells RF photo cathode is in excellent agreement with the design values without applying a post-manufacturing tuning. This confirms the quality of design [1], engineering and manufacturing process performed at PSI [1]. After completing the fine characterization of the cavity and the calibration of the pick-ups, in April 2014, the RF-gun will be integrated into the SwissFEL Injector Test Facility, where the gun performances will be tested at high power and with electron beam.

[1] J.-Y.- Raguin et al, Proceedings of LINAC2012, Tel-Aviv, Israel
Facility: SwissFEL
Reference: Hans Rudolf Fitze; hansruedi.fitze@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

First lasing in SwissFEL test facility

On the 15th of January 2014, first lasing was achieved in the SwissFEL injector test facility. This is a great success on the way towards SwissFEL, the future hard x-ray free-electron laser that is currently under construction at PSI. It proves the successful functioning of many key components together in a larger system as required for SwissFEL. Furthermore, this is the very first operation of a free-electron laser in Switzerland. Since 2010, PSI has been operating a test facility to study and optimize the electron source for SwissFEL. Over the last years, the test facility was advanced to one of the most brilliant electron sources in the world, and during the last shutdown end of 2013, a first undulator - a highly precise periodic array of magnets - was installed in the facility. This innovative type of undulator is an in-vacuum design with a very small period length of only 15 mm, that was specifically developed for SwissFEL. During the very first beam time after the installation of the undulator, the electron beam could be successfully tuned to pass the undulator with low losses - this is very important to prevent radiation damage to the sensitive 1060 permanent magnets of the undulator. The electrons generate spontaneous radiation when passing the undulator, and this radiation was detected with scintillator screen monitors. In a next step, the electron beam was strongly compressed in a bunch compressor chicane to generate a very large charge density, which is required for the FEL process. This initiated the free-electron lasing process, leading to an exponential increase of the emitted radiation along the undulator. An electron beam with an energy of 220 MeV and a bunch charge of 200 pC was used in that process, and first lasing was detected at a wavelength of around 80 nm. By adjusting the gap of the undulator, the wavelength of the emitted laser light could be tuned over one octave from around 45 to 90 nm
Facility: SwissFEL
Reference: Hans Braun; hans.braun@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

Installation of SwissFEL Undulator Prototype in the Injector Test facility

On December 5th, the 17 tons SwissFEL undulator prototype (In-vacuum Undulator U15) has been successfully moved from the Undulator lab (SLS) to the SwissFEL Injector Test Facility (SITF). The commissioning of the U15 prototype with electron beam is an important step to validate the U15 design and also to detect possible improvements before full series production. At first, the alignment procedure of the U15 segment with the electron beam will be tested. Later, twelve such U15 segments will have to be precisely aligned on a straight line in SwissFEL. Another important step at SITF, will be the detection of free electron laser amplification at 70 nm. Indeed, simulations have shown that with the electron beam parameters within reach at SITF, it should be possible to see the beginning of the SASE (self-amplified spontaneous emission) amplification.
Facility: SwissFEL
Reference: Romain Ganter; romain.ganter@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

New device tested for SwissFEL: Photon Arrival and Length Monitor (PALM).

The accurate measurement of the time between a pump laser pulse and a FEL probe pulse is vital to the success of the future SwissFEL facility, which plans to use pump-probe science as a cornerstone of its activities. This measurement, along with the measurement of the time-profile of the FEL pulse, is the goal of the new device designed and tested by the Photonics group at SwissFEL called the Photon Arrival and Length Monitor (PALM). Using a technique called THz-streaking, the device looks at electrons photoionized by FEL radiation and accelerated by an oscillating THz field generated by a laser to determine when during the field's oscillation the electron was generated from a gas. The accuracy of this type of experiment in laboratory environments has been measured to several femtoseconds, and the group at SwissFEL photonics intends to replicate this feat. The first experiments have been conducted at the Aramis laser hutch in WLHA, using an high-harmonic generation (HHG) laser source to simulate the FEL beam, and have shown the viability of the design, measuring an arrival time accuracy between a HHG laser and THz beam to 8 fs RMS. The preliminary experiments looked at electrons with kinetic energies between 22 and 45 eV, and noted a maximum streak, or gain in their energy as a function of the delay between the HHG and THz beams, of about 2 eV.
The future developments for the PALM lay in optimizing the device to be able to cope with large jitters between the FEL pulse and the pump laser pulse, as well as the integration of the PALM with other methods that may, eventually, yield sub-femtosecond accuracy in both arrival time and pulse length measurements.
Facility: SwissFEL
Reference: Pavle Juranic; pavle.juranic@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

52 MV/m in C-band structure

This summer, the first 2 m long C-band accelerating structure for SwissFEL was installed in the high power test stand at PSI. The goal was to verify that the accelerating structure can handle the high accelerating fields of around 28 MV/m that are needed for SwissFEL. At such high accelerating fields, sporadic break-downs are unavoidable, and a second goal was to confirm that the number of break downs is at a level that is acceptable for SwissFEL. For this first accelerating structure, both of these investigations led to excellent results. An accelerating gradient of up to 52 MV/m - almost twice the nominal field - was reached, and this gradient was not limited by the structure itself but by the available radiation shielding. At the nominal accelerating field, the measured break-down rate was significantly lower than what is required for SwissFEL. Currently, a second accelerating structure is installed in the test stand, and preparations are ongoing to setup a complete accelerating module consisting out of four structures.
Facility: SwissFEL
Reference: Florian Löhl; florian.loehl@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

First beam: XUV laser meets Terahertz laser

Two new coherent photon sources, combined on a single laser table, have been built by the SwissFEL laser group and are operated successfully since several weeks by now. While the first type of laser delivers intense radiation in the Terahertz region at around 0.3 THz (i.e. 1 mm wavelength), the second laser source is a table-top, laser-driven XUV source based on high-order harmonic generation. It delivers photon energies up to 120 eV (i.e. 10 nm wavelength) in fully coherent XUV bursts of a few tens of femtosecond or even attosecond duration. The availability of these two complementary laser sources in one common lab opens up new opportunities. Scientifically, it allows for THz pump/XUV probe experiments at extremely short time-scales, such as element-specific investigations of ultrafast magnetization processes in compounds, or to drive coherent Zeeman spin precessions initiated by a strong THz stimulus. On the other hand, the XUV-THz laser assembly offers a realistic test bed for future SwissFEL temporal diagnostic equipment. Even though the photon flux will be orders of magnitude larger at SwissFEL, the lab-scale laser facility is a cheap and efficient way to explore the feasibility of advanced time-arrival schemes, such as the Terahertz streak camera currently developed by Dr. Juranic. Indeed, this timing tool has recently been successfully commissioned and debugged at our HHG/THz beamline and will next be tested on the hard x-ray FEL in Japan. Ongoing developments are aiming to extend the HHG photon energy towards the keV range with the vision to explore ultrafast magnetization dynamics by the T-MOKE technique at the L-absorption edge of magnetic materials like Cobalt. Such experiments could be pre-cursers for investigations at the future SwissFEL soft x-ray beamline where higher photon flux will be available.
Facility: SwissFEL
Reference: Christoph Hauri; christoph.hauri@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

First measurement campaign of the U15

The first measurement campaign of the U15 (the undulator prototype for the SwissFEL project) shows that electron trajectory straightness (measured with a dedicated Hall Probe bench) can be optimized beyond the micrometer level over the full operational range. Such trajectory straightness (about 10 times better than requirements) is attained thanks to an automatized shimming procedure based on individual pole height adjustment. The stability over the operational gap range is achieved thanks to the novel undulator support structure designed at PSI and to the status of the art manufacturing services of the Swiss industrial partner, Max Daetwyler AG.
Facility: SwissFEL
Reference: Romain Ganter; romain.ganter@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

Magnetisation controlled at picosecond intervals

A terahertz laser developed at the Paul Scherrer Institute makes it possible to control a material's magnetisation at a timescale of picoseconds (0.000 000 000 001 seconds). In their experiment, the researchers shone extremely short light pulses from the laser onto a magnetic material, where the magnetic moments – “elementary magnets” – were all aligned in parallel. The light pulse's magnetic field was able to deflect the magnetic moments from their idle state in such a way that they exactly followed the change of the laser's magnetic field with only a minor delay. The terahertz laser used in the experiment is one of the strongest of its kind in the world. One special feature is the fact that it is phase-stable, which enables the exact change in the electrical and magnetic field within the individual pulses to be defined reliably for each laser pulse. As the majority of data is stored magnetically these days, the possibility to quickly change a material's magnetisation is crucial for new, rapid storage systems. The researchers report on their results in the journal Nature Photonics. Read more
Facility: SwissFEL
Reference: Christoph Hauri; christoph.hauri@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

Last high power RF plant of the SwissFEL Injector Test Facility

End of May 2013 the last high power RF plant of the SwissFEL Injector Test facility became operational. The plant consist in a X-band (12 GHz) high power amplifier capable of producing RF pulses up to 50 MW power, feeding a 70 cm long accelerating cavity. This cavity operates at the fourth harmonic of the basic RF system used for accelerating the beam up to 250 MeV. Operated in decelerating mode, the X-band system allows removing the correlated non-linearity of the energy distribution induced by the RF curvature in the acceleration stages. This feature is essential to achieve an efficient compression of the electron bunches without degrading the beam properties. The figure illustrates the effect of the cavity. In the first picture, with X-band system off, the curvature induced by the RF with on crest acceleration is wisible, while in the second the curvature is completely removed by the harmonic system.
Facility: SwissFEL Injector Test Facility
Reference: Marco Pedrozzi; marco.pedrozzi@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

First C-band accelerating structure

In May 2013, the first 2 m long accelerating structure for the linear accelerator of SwissFEL was finalized at PSI. In total, 104 of these accelerating structures will be needed to accelerate the ultra-bright electron beam of SwissFEL to an energy of 5.8 billion electron-volt. By coupling a high-power 5.7 GHz RF pulse into the structure, an accelerating field of around 30 million volts per meter is generated inside of the structure. While the concept is based on a similar technology used at the x-ray free-electron laser SACLA in Japan, an entirely new design was developed at PSI, which will allow SwissFEL to operate with a significantly better power efficiency. Later this month, the structure will be installed in the C-band test stand to evaluate its performance under high power operation.
Facility: SwissFEL
Reference: Florian Löhl; florian.loehl@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

X-ray Laser: A novel tool for structural studies of nano-particles

Development of analysis method for X-ray laser scattering data.

Prominent among the planned applications of X-ray free electron laser facilities, such as the future SwissFEL at the Paul Scherrer Institute, PSI, are structural studies of complex nano-particles, down to the scale of individual bio-molecules. A major challenge for such investigations is the mathematical reconstruction of the particle form from the measured scattering data. The experiment consists of exposing the nano-particles to the X-ray laser pulses and of registering the resulting scattered rays. To guarantee sufficient statistical accuracy, many repeated exposures are required – each one on a different collection of identical, but randomly-oriented particles. Researchers at PSI have now demonstrated an optimized mathematical procedure for treating such data, which yields a dramatically improved single-particle structural resolution. The procedure was successfully tested at the Swiss Light Source synchrotron at PSI, with custom-fabricated, two-dimensional nano-structures. With the inclusion of some additional information, such as the particle symmetry, the method can be extended to real three-dimensional objects. The researchers report their results on-line in the current issue of Nature Communications. Read more
Facility: SwissFEL
Reference: Bill Pedrini; bill.pedrini@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

An intense Terahertz source for SwissFEL

Terahertz radiation (0.1-10 THz), located between the optical and radio frequency range, is suited to explore fundamental physical phenomena and to drive novel applications in condensed matter physics, biology, surface chemistry and others. Ultrashort and intense Terahertz pulses are of particular interest in view of the future hard x-ray free electron laser at PSI, since a series of resonant modes (magnons, phonons, electromagnons) can be coherently excited by THz and tracked by the femtosecond x-ray pulses. A high-field Terahertz transient provide a novel tool to control and investigate collective motions since it can be understood as "cold" stimulus: indeed the photon energy in the THz range is not more than a few meV, and therefore orders of magnitudes lower than the equivalent photon of a conventional laser (e.g. Ti:sapphire laser hʋ=1.6 eV). While the latter heats electronic system significantly, the terahertz driving field excites only the THz sensitive port while leaving other degrees of freedom unexcited. Read more
Facility: SwissFEL
Reference: Christoph Hauri; christoph.hauri@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

Record low emittance at the SwissFEL Injector Test Facility

The SwissFEL injector test facility at PSI is the principal test bed and demonstration plant for the SwissFEL project. Significant progress has been achieved in the past few months, during which the injector settings were systematically optimized for maximum brightness of the electron beam (low emittance at high beam current).


The result of this optimization is a stable working point for uncompressed electron bunches, which ensures beam transport with minimal emittance dilution. Once the influence of the accelerator itself on the beam emittance is kept at a minimum, subtle effects of the laser generating the electrons at the cathode (via the photo-electric effect) become accessible to beam optics measurements. In this way it was possible, for instance, to demonstrate the effect of the laser photon energy (or wavelength) on the beam emittance. During these studies extremely small emittances were measured, in particular for low bunch charges, where the adverse effects of Coulomb repulsion (space charge) are also smallest. But even at the nominal SwissFEL working point of 200 pC charge and with the standard laser wavelength of 260 nm, which ensures high electron yield, record low emittances well below the SwissFEL requirements have been achieved. At these conditions, global (projected) emittances below 0.35 mm mrad are now obtained routinely, with best values around 0.30 mm mrad. The more relevant slice emittance, i.e. the emittance measured for individual slices along the bunch length, which represents a key beam parameter for free-electron lasers, is typically below 0.20 mm mrad, with a record value of 0.18 mm mrad (see image).


These promising results were obtained with still uncompressed electron bunches. To reach the high peak currents necessary to drive a free-electron laser, longitudinal bunch compression is essential. The study of compressed electron bunches at the SwissFEL injector test facility is planned for 2013, when a linearizing harmonic cavity will be installed. The new cavity will allow for a more uniform compression of the bunch in the magnetic chicane (the so-called bunch compressor).
Facility: SwissFEL Injector Test Facility
Reference: Thomas Schietinger; thomas.schietinger@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

New opportunities for coherently exciting magnetic materials

The ability to manipulate matter on ultra-short time scales offers potential breakthroughs in future device technologies as well as a better understanding of fundamental material properties. For this purpose, it is of immense importance to be able to selectively drive excitations of interest. This has recently been demonstrated by team of researchers from PSI, the ETH, Stanford (SLAC) and Berkley with an experiment (performed in July 2012) at the x-ray free electron laser LCLS. They showed that a coherent electromagnon can be excited with a short THz pulse in multiferroic TbMnO3. Electromagnons are hybrid excitations of a magnon and a phonon that couple polarization with magnetism in multiferroic materials. The material was studied by time dependent resonant magnetic soft x-ray diffraction (see figure 1). A detailed analysis of the immense amount of data acquired in the experiment will verify if the excitation is indeed an electromagnon and give a quantitative estimate of the motion of spins involved. This experiment demonstrates that it is now feasible to coherently control magnetic moments. This is due to newly available methods of creating short, intense THz pulses, and to the availability of x-ray free electron lasers that allow us to study such responses of the material in real time.
Facility: LCLS at SLAC in Stanford
Reference: U. Staub; urs.staub@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
S. Johnson; johnsons@ethz.ch; ETH Zürich Institute for Quantum Electronics

Progress at the SwissFEL Injector

From 2011 to 2012 major progress was made at the SwissFEL Injector test facility. The installation of the magnetic bunch compression chicane was completed in July 2011. The following months were dedicated to the consolidation of the S-band RF system, the integration of the longitudinal diagnostics at the bunch compressor and the amelioration of the stability of the photo-cathode laser system.
In early April 2012 beam development studies started again, for the first time with all RF accelerating cavities in operation at the same time. The nominal beam energy of 250 MeV was reached for the first time on April 11. Within a couple of weeks of operation at the SwissFEL nominal charge of 200 pC it was possible to demonstrate transverse beam quality fulfilling the FEL requirements for uncompressed beam thus reaching an important milestone. The smallest measured values for projected and slice emittance at the beam core are 0.37 and 0.25 mm mrad, respectively.
The first compression experiments using the bunch compression chicane resulted in a compression factor of 18 corresponding to a reduction of the rms bunch length from 3.6 to 0.2 ps. To achieve the nominal bunch parameters after compression a harmonic (X-band) RF cavity is foreseen to be installed upstream of the bunch compressor later in 2012. This additional cavity will compensate the electron bunch curvature in longitudinal phase space introduced by the RF non-linearity in the preceding accelerating cavities. This system will be the last key component required to complete the SwissFEL Injector test facility.
Facility: SwissFEL Injector Test Facility
Reference: M. Pedrozzi; marco.pedrozzi@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

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) more information
Facility: LCLS at SLAC in Stanford
Reference: Christian David; christian.david@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

FEL Prize Winners of 2009 and 2010 work together at the SwissFEL Injector

Last years FEL Prize winners Paul Emma and David Dowell, work together with this years FEL prize winner, Sven Reiche at the SwissFEL injector test facility. The FEL Committee awards one prize each year to a person or people whose work has advanced the field of free-electron laser science. Our colleagues from LCLS received the first FEL prize that was given to an operating machine, i.e. LCLS (world's first operating XFEL). Sven Reiche received his prize for more theoretical work on FEL simulation codes. These joint forces of outstanding scientists, with expertise's in different fields, working on the SwissFEL injector, shows once again the high international importance of the SwissFEL project as well as the strong global network SwissFEL is part of.
Facility: SwissFEL Injector Test Facility
Reference: Hans Braun; hans.braun@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

A prestigious FEL award for an outstanding scientist at the Paul Scherrer Institute

At the 32nd International Free Electron Laser Conference in Malmö, Sweden, the Prize Committee decided to award the prestigious 2010 FEL prize to Dr. Sven Reiche for “his outstanding contributions to the advancement of the field of Free-Electron Laser science and technology”.

The FEL simulation code, GENESIS 1.3 developed by Dr. Sven Reiche, is used as design tool world wide, and the anticipated performances of new projects have been very successfully benchmarked with experimental results in the most advanced FEL facilities. He contributed to all major FEL projects, influencing the machine layouts according to user's expectances, as well as anticipating possible operational modes that in the near future could enlarge the experimental perspectives of the X-ray FELs. Today at the Paul Scherrer Institute, Dr. Reiche plays an essential role in the SwissFEL project, leading the FEL line design and coordinating the accelerator beam dynamic activities. Remarkable as well are his contributions to the SwissFEL science case and to the implementation of new schemes for the experimental lines. We congratulate Sven for the prestigious award as recognition of his outstanding career.

The SwissFEL Project Management Team
Reference: S.Reiche; sven.reiche@psi.ch
Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

First beam at the SwissFEL Injector Test Facility

The technical development of the project has reached another milestone: In the SwissFEL injector test facility the first electron beam from the gun has been extracted and accelerated to 5 MeV on the 12th of March 2010. The characterization of the beam, improvements on their quality and the implementation of the diagnostic are the short term goals. We express our thanks all to the groups that worked hard for these achievements, as well as for the installation of the whole facility.
Facility: SwissFEL Injector Test Facility
Reference: M. Pedrozzi; marco.pedrozzi@psi.ch; Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland