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For the first time laser-induced breakdown spectrometry, with laser pulse repetition frequencies of up to 1 kHz, with single pulse evaluation is realized for scanning microanalysis of macroscopic samples. The tightly focused beam of a diode-pumped Q-switched Nd : YAG-laser is scanned with a step size of 20 µm across a sample surface. The emission spectrum of each laser-induced plasma generated by a single laser pulse of 2 mJ energy is guided to a spectrometer of the Paschen-Runge type to detect the line radiation of up to 24 elements simultaneously covering a spectral range from the vacuum ultraviolet to the near infrared. The time resolved spectral signals linked to the respective detector channel are processed to generate maps of the spatial distribution of elements in the sample surface. In a measuring field of typically 1 × 1 cm 2 250 000 measurements are performed within 11 min. The spatial resolution achieved, in terms of the diameter of the crater produced by a single laser pulse in steel samples, is better than 15 µm. The experimental system is applied to investigate inclusions in steel samples. These inclusions influence the quality of steel grades for the production of spring steel, thin sheets and wires. They consist of oxides, nitrides or sulfides. Correlating the maps of different elements allows us to identify the type of inclusion, this is demonstrated for aluminium oxide, aluminium nitride and manganese sulfide.

Spatially resolved information about the distribution and chemical composition of inclusions in steel are gained by scanning methods, such as scanning electron microscopy with energy dispersive X-ray spectroscopy, electron probe microanalysis or capillary-X-ray flourescence. Scanning laser-induced breakdown spectroscopy (LIBS) offers distinct advantages in contrast to these conventional methods. Sample polishing or high vacuum conditions are not necessary, a simple grinding of the sample is sufficient for the preparation. Analysing times can be reduced significantly. At Fraunhofer ILT a measuring system was developed enabling for the first time high-speed scanning LIBS with measuring frequencies of up to 1000 Hz. Sample surfaces with dimensions up to 110×45 mm2 can be analyzed. Light elements such as C, N, O, P, and S are detected, which is demonstrated by the identification of nonmetallic inclusions in steel. Principle, features and results of high-speed scanning LIBS with a spatial resolution<20 μm are presented.

We report the successful implementation of Gires-Toumois (GTI) and chirped mirrors in a diode-pumped, Kerr-lens modelocked (KLM) Cr:LiSGaF laser.The laser delivered 30mW of79fs, nearly transform limited pulses at 855nmand 90MHz repetition rate.The mirror-dispersion controlled cavity is compared to our prism setup and pulse width limitations in diode pumped Cr:LiSGaF I Cr:LiSAF lasers are identified.Mode matching calculations 'of pump beam and cavity mode are presented to optimise low threshold, highly efficient fsoperation.Following this analysis a compact prismiess design of roughly shoe box size is suggested, which incorporates an additional high n2 element to enhance stability.

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