INFN/LNF, Frascati (Roma)
The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive 500 nm FEL experiments in SASE, Seeding and Single Spike configurations. The present stage of the commissioning foresees a detailed analysis of the beam matching with the linac in order to confirm the theoretically prediction of emittance compensation based on the “invariant envelope” matching and the characterisation of the spontaneous and stimulated radiation in the SPARC undulators. In this talk we report the experimental results obtained so far. The future energy upgrade of the SPARC facility to produce UV radiation and its possible applications will be also discussed.
FYSIKUM, AlbaNova, Stockholm University, Stockholm
Uppsala University, Uppsala
Uni HH, Hamburg
DELTA, Dortmund
DESY, Hamburg
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
We present results from the new electron bunch diagnostic tool, Optical Replica Synthesizer [1] (ORS), installed at FLASH. The ORS produces an optical replica of the electron bunch profile, which is analyzed with a Grenouille, a device based on the Frequency Resolved Optical Gating (FROG) technique. This optical replica is generated by inducing a microbunching in the electron bunch and letting it pass through an undulator, called a radiator. The radiator emits coherently at the wavelength of microbunching, 772 nm. In order to create the microbunching a laser pulse is spatially and temporally overlapped with the electron bunch in another undulator, placed before the radiator. This introduces an electron energy modulation which is transformed into a density modulation in a chicane before the microbunched electron bunch is sent into the radiator. We observed an optical replica pulse of approximately 5 microJ corresponding to an electron bunch-spike of about 150 fs FWHM when the accelerators were set at optimal FEL conditions. We also showed that the ORS can run parasitically while maintaining SASE by steering the electron beam around the outcoupling mirror for the radiation.
[1] E. Saldin, E. Schneidmiller, M. Yurkov, “A simple method for the determination of the structure of ultrashort relativistic electron bunches,” Nucl. Inst. and Methods A 539 (2005) 499.
Kyoto IAE, Kyoto
UVSOR, Okazaki
A new type of undulator which consists of high-temperature superconductor bulk magnets in the staggered array configuration inside a solenoid is being developed, aimed at short period, high undulator field and controllability by the solenoid current.[1] In order to develop a numerical model, the field calculations were performed and comparisons were made with prototype measurements at the liquid nitrogen temperature. The field in the bulk magnet was modeled by loop currents of which amounts were determined by the critical current density which follow Bean model.[2] In the unsaturated condition, which is decided by the critical current density and the dimension of the bulk magnets, the field distributions and the dependence on the solenoid field were reproduced well. We then estimated the unsaturated performance at the liquid helium temperature, where increment of the critical current density is known [3] and significant improvement of the undulator performance is expected accordingly. In the conference, the experimental results, the detail of modeling and numerical results will be shown and also the performance estimation will be discussed.
[1] T. Kii, et al. FEL 2006, THPPH035 (2006),
R. Kinjo, et al., FEL 2008, THAAU03 (2008)
[2] C.P. Bean, Phys. Rev. Lett. 8, 250 (1962)
[3] M. Morita, et al. NIPPON STEEL TECHNICAL REPORT No. 93 (2006)
DESY, Hamburg
We formulate a complete theory of Edge Radiation based on a novel method relying on Fourier Optics techniques. Special attention is paid in discussing the validity of approximations upon which the theory is built. Our study makes consistent use of both similarity techniques and comparisons with numerical results from simulation. We discuss both near and far zone. Physical understanding of many asymptotes is discussed. As an example of application we discuss the case of Transition Undulator Radiation, which can be conveniently treated with our formalism. This work forms the theoretical basis for understanding the impact of Edge radiation on XFEL setups, which is discussed in another contribution to this conference.
Uni HH, Hamburg
DESY, Hamburg
PSI, Villigen
DELTA, Dortmund
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
Starting from next year, the technical feasibility of a direct seeding scheme at 30 and 13nm will be studied at the free-electron laser FLASH at DESY. During a major shutdown in order to upgrade the SASE-FEL facility, it is planned to install a HHG source, a new chain of 10 m variable gap undulators and a dedicated commissioning beamline for photon diagnostics and pilot time-resolved pump-probe experiments. Besides demonstrating successful seeding at short wavelength, the project aims for time resolution in the 10 fs range to study ultrafast processes by combining the naturally synchronized FEL and seed laser pulses. After the extraction of the radiation in a magnetic chicane, a short branch will accommodate intensity and beam monitors and a spectrometer. The intensity monitor detects scattered photons from a gold mesh on a shot-to-shot basis using micro-channel plates and XUV diodes. It is designed to detect photons several orders of magnitude apart in flux, i.e. spanning the wide range from the spontaneous emission up to the seeded FEL radiation at gigawatt power level. Simulations of this device are presented as well as test and calibration measurements carried out at FLASH.