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).

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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
Ultima modifica il Sabato, 07 Gennaio 2012 18:15