Highlights

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)..

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.

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

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The first happy users inside the XPP endstation of LCLS, Stanford.

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

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FEL Prize Winners 2009 & 2010

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

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Dr. Sven Reiche

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

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First beam screen

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