R&D Highlights

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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

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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