During the past years material processing, using ultra-short laser pulses, has undergone a considerable development and is used for growing amounts of applications. Researchers of the German government institute Bundesanstalt für Materialforschung und -prüfung (BAM) and Steinbeis-Transferzentrum Technische Beratung und Entwicklung have found that unwanted X-ray radiation in the keV range, can be generated when a critical laser intensity is exceeded.
Measurement results were taken from systems with 10 W up to several 100 W, with pulse durations of below 1 ps at repetition rates of several 100 kHz. X-ray spectra and doses were measured for various planar target materials, covering a wide range of the periodic table from aluminum to tungsten. The maximum dose rate measured at the highest intensity was 163 mSv/h. The radiation safety limit, in Germany, for skin dose is 50 mSv/a for members of the public. Without shielding, the measured radiation doses at this high repetition rate clearly exceeds regulatory limits. Estimations for an adequate radiation shielding are provided in the conclusions of the research under the following link.
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