SR-FEL Highlights

Coherent Light with Tunable Polarization from Single-Pass Free-Electron Lasers

Tunable polarization over a wide spectral range is a required feature of light sources employed to investigate the properties of local symmetry in matter. In this Letter, we provide the first experimental characterization of the polarization of the harmonic light produced by a free-electron laser and demonstrate a method to obtain free-electron laser harmonics with tunable polarization. 
C. Spezzani et. al, DOI: 10.11033/PhysRevLett.107.084801

Figure on the left:
Nonlinear harmonic emission at 195 nm.
Upper panel: Normalized Stokes’ parameters M=I (triangles, experiments; dashed line, theory) and S=I (circles, experiments; continuous line, theory), as a function of the ratio Bx =By . Lower panel: On-axis intensity (circles, experiments; continuous line, theory), normalized to the intensity recorded when the polarization is linear horizontal, as a function of the ratio Bx =By . Relative errors are estimated to be about 15%. 

Retrieve article

Coherent Light with Tunable Polarization from Single-Pass Free-Electron Lasers
C. Spezzani1, E. Allaria1, M. Coreno2, B. Diviacco1E. Ferrari3,1, G. Geloni4, E. Karantzoulis1, B. Mahieu5,1M. Vento1, and G. De Ninno5,1 
1Sincrotrone Trieste, S.S. 14 km 163.5, Basovizza (Trieste), Italy
2CNR-IMIP, Montelibretti (Rome), Italy
3Trieste University, Italy
4European XFEL GmbH, Hamburg, Germany
5University of Nova Gorica, Slovenia
DOI: 10.1103/PhysRevLett.107.084801 

 

 


Experimental Characterization of Nonlinear Harmonic Generation in Planar and Helical Undulators

We present an experimental characterization of the process of coherent harmonic generation in single-pass free electron lasers. The harmonic radiation is obtained by seeding the electron beam stored in the Elettra storage ring with a Ti:sapphire laser. 
E. Allaria et al., DOI: 10.1103/PhysRevLett.100.174801

Different methods for generating harmonics are compared between them, and a detailed characterization of the emitted light is performed for different polarizations. Our results also contribute to the debate about the possible presence of a coherent on-axis signal in helical undulators. In this respect, we provide an experimental confirmation of recent theoretical studies that predict no coherent on-axis signal.

In the figure:
Measured angular distribution of the second harmonic in the case of CHG (red) and NHG (black) with helical undulators. Measurements are well fitted by theoretical curves (dashed line, CHG case, continuous line, NHG case).

Retrieve article

Experimental Characterization of Nonlinear Harmonic Generation in Planar and Helical Undulators
E. Allaria1, F. Curbis1, M. Coreno2, M. Danailov1, B. Diviacco1, C. Spezzani1, M. Trovó1, and G. De Ninno3,1
1Sincrotrone Trieste, S.S. 14 km 163.5, Trieste, I-34012 Italy
2CNR-IMIP (Rome branch), c/o CNR-INFM TASC National Laboratory, Trieste, I-34012 Italy
3Physics Department, Nova Gorica University, Nova Gorica, SI-5000 Slovenia
DOI: 10.1103/PhysRevLett.100.174801

 


Sub-picosecond coherent VUV source on the Elettra storage ring

Taking advantage of the storage ring free electron laser beamline at Elettra, we have implemented an experimental setup for the generation of sub-picosecond (ps) coherent optical pulses in the VUV range. 
C. Spezzani et al., DOI: 10.1016/j.nima.2008.08.005


The setup is based on the frequency up-conversion of a high-power external signal (provided by a Ti:Sapphire laser) and makes use of a relativistic electron bunch as resonating medium.The produced VUV pulses have peak power in MW range, variable polarization, high shot to shot stability and control of the timing parameters at the ps level. In this paper, we present the first characterization of the temporal and spectral features of the emitted light. The radiation can be exploited for new experiments in the fields of dynamical phenomena, non-linear physics, magnetism and biology.

In the figure:
Open dots are the CHG amplitude as a function of the relative delay between seed and electron bunch, dashed line is the electron bunch temporal profile as measured with the streak camera, the solid line is the squared bunch profile. The quadratic dependence confirms the coherent character of the emission.

Retrieve article

Sub-picosecond coherent VUV source on the Elettra storage ring
C. Spezzani1 , E. Allaria1, G. Cautero1, M. Coreno4, F. Curbis1,3, M.B. Danailov1, A. Demidovich1, B. Diviacco1, E. Karantzoulis1, R.K. Ivanov1, P. Pittana1, L. Romanzin1, R. Sergo1, P. Sigalotti1, S. Tileva1, M. Trovò1, G. De Ninno1,2
1Sincrotrone Trieste, Basovizza, Trieste, Italy
2University of Nova Gorica, Slovenia
3University of Trieste, Italy
4CNR-IMIP (Rome branch), c/o CNR-INFM TASC National Laboratory, Trieste, Italy
DOI: 10.1016/j.nima.2008.08.005

 


Generation of Ultrashort Coherent Vacuum Ultraviolet Pulses Using Electron Storage Rings: A New Bright Light Source for Experiments

We demonstrate for the first time that seeded harmonic generation on electron storage rings can produce coherent optical pulses in the vacuum ultraviolet spectral range.  
G. De Ninno et al., DOI: 10.1103/PhysRevLett.101.053902

The experiment is performed at Elettra, where coherent pulses are generated at 132 nm, with a duration of about 100 fs. The light source has a repetition rate of 1 kHz and adjustable polarization; it is very bright, with a peak power several orders of magnitude above that of spontaneous synchrotron radiation. Owing to high stability, the source is used in a test photoemission electron microscopy experiment. We anticipate that seeded harmonic generation on storage rings can lead to unprecedented developments in time-resolved femtosecond spectroscopy and microscopy. 

In the figure:
Intensity of the UV pulses vs acquisition time. The pulse at the center corresponds to the coherent harmonic signal, while the small peaks at 
±1000 ns correspond to the synchrotron emission of the undulators. The signal was acquired using a photomultiplier (PMT) placed downstream a monochromator. Note that the PMT does not allow to resolve the sub-ps temporal scale on which the coherent pulse evolves. This, in turn, does not permit direct detection and therefore appreciation of the effective amplitude difference between the seeded and the spontaneous signals, their true ratio being a factor about 104 .

 

 

Red trace: the radiator is tuned for circular polarization; black trace: the radiator is tuned for linear polarization.

Retrieve article

Generation of Ultrashort Coherent Vacuum Ultraviolet Pulses Using Electron Storage Rings: A New Bright Light Source for Experiments
G. De Ninno1,2, E. Allaria2, M. Coreno3, F. Curbis2,4, M. B. Danailov2, E. Karantzoulis2, A. Locatelli2, T. O. Menteş2, M. A. Nino2, C. Spezzani2, and M. Trovò2
1Physics Department, Nova Gorica University, Nova Gorica, SI-5000 Slovenia
2Sincrotrone Trieste, S.S. 14 km 163.5, Trieste, I-34012 Italy
3CNR-IMIP (Rome branch), c/o CNR-INFM TASC National Laboratory, Trieste, I-34012 Italy
4Physics Department, Trieste University, Trieste, I-34100 Italy 
DOI: 10.1103/PhysRevLett.101.053902




 
Last Updated on Thursday, 12 January 2012 15:41