Abstract-Interference effects in angular streaking with a rotating terahertz field

A. K. Kazansky, A. V. Bozhevolnov, I. P. Sazhina, and N. M. Kabachnik

Phys. Rev. A 93, 013407 – Published 11 January 2016

http://journals.aps.org/pra/abstract/10.1103/PhysRevA.93.013407

A method of angular streaking with a rotating terahertz electric field for photoelectrons produced by femtosecond extreme ultraviolet pulses is suggested and theoretically analyzed. The method can be used for free electron laser (FEL) pulse characterization on a shot-to-shot basis. It is shown that in related measurements an interesting phenomenon appears: formation of very bright and sharp features in the angular resolved electron spectra measured in the plane perpendicular to the collinear beam direction. These features are similar to the conventional caustics in the wave propagation. The caustics are accompanied by a well-developed interference structure. The intensity distribution along the caustic is determined by the envelope of the FEL pulse.

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Abstract-Ultrafast X-ray pulse characterization at free-electron lasers

I. Grguraš, A. R. Maier, C. Behrens, T. Mazza, T. J. Kelly, P. Radcliffe, S. Düsterer, A. K. Kazansky, N. M. Kabachnik, Th. Tschentscher, J. T. Costello, M. Meyer, M. C. Hoffmann, H. Schlarb & A. L. Cavalieri

http://www.nature.com/nphoton/journal/v6/n12/full/nphoton.2012.276.html
The ability to fully characterize ultrashort, ultra-intense X-ray pulses at free-electron lasers (FELs) will be crucial in experiments ranging from single-molecule imaging to extreme-timescale X-ray science. This issue is especially important at current-generation FELs, which are primarily based on self-amplified spontaneous emission and radiate with parameters that fluctuate strongly from pulse to pulse. Using single-cycle terahertz pulses from an optical laser, we have extended the streaking techniques of attosecond metrology to measure the temporal profile of individual FEL pulses with 5 fs full-width at half-maximum accuracy, as well as their arrival on a time base synchronized to the external laser to within 6 fs r.m.s. Optical laser-driven terahertz streaking can be utilized at any X-ray photon energy and is non-invasive, allowing it to be incorporated into any pump–probe experiment, eventually characterizing pulses before and after interaction with most sample environments.