We present a new technique for the characterization of non-Gaussian laser beams which cannot be described by an analytical formula. As a generalization of the beam spot area we apply and refine the definition of so called effective area (A(eff)) [1] in order to avoid using the full-width at half maximum (FWHM) parameter which is inappropriate for non-Gaussian beams. Furthermore, we demonstrate a practical utilization of our technique for a femtosecond soft X-ray free-electron laser. The ablative imprints in poly(methyl methacrylate) - PMMA and amorphous carbon (a-C) are used to characterize the spatial beam profile and to determine the effective area. Two procedures of the effective area determination are presented in this work. An F-scan method, newly developed in this paper, appears to be a good candidate for the spatial beam diagnostics applicable to lasers of various kinds.

Institute of Physics Academy of Sciences of the Czech Republic Prague Czech Republic

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Damage Mechanisms in Polyalkenes Irradiated with Ultrashort XUV/X-Ray Laser Pulses

Comparing single-shot damage thresholds of boron carbide and silicon at the European XFEL

Quantifying electron cascade size in various irradiated materials for free-electron laser applications

Microscopic Kinetics in Poly(Methyl Methacrylate) Exposed to a Single Ultra-Short XUV/X-ray Laser Pulse

Experimental study of EUV mirror radiation damage resistance under long-term free-electron laser exposures below the single-shot damage threshold