Holland, JulianLungu, CristianaWeber, RudolfEmperle, MaxGraf, Thomas2025-05-2720241432-06300947-8396http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-ds-164600https://elib.uni-stuttgart.de/handle/11682/16460https://doi.org/10.18419/opus-16441Ultrafast lasers, with pulse durations below a few picoseconds, are of significant interest to the industry, offering a cutting-edge approach to enhancing manufacturing processes and enabling the fabrication of intricate components with unparalleled accuracy. When processing metals at irradiances exceeding the evaporation threshold of about 10 10 W/cm² these processes can generate ultra-short, soft X-ray pulses with photon energies above 5 keV. This has prompted extensive discussions and regulatory measures on radiation safety. However, the impact of these ultra-short X-ray pulses on molecular pathways in the context of living cells, has not been investigated so far. This paper presents the first molecular characterization of epithelial cell responses to ultra-short soft X-ray pulses, generated during processing of steel with an ultrafast laser. The laser provided pulses of 6.7 ps with a pulse repetition rate of 300 kHz and an average power of 500 W. The irradiance was 1.95 ×10 13 W/cm 2 . Ambient exposure of vitro human cell cultures, followed by imaging of the DNA damage response and fitting of the data to a calibrated model for the absorbed dose, revealed a linear increase in the DNA damage response relative to the exposure dose. This is in line with findings from work using continuous wave soft X-ray sources and suggests that the ultra-short X-ray pulses do not generate additional hazard. This research contributes valuable insights into the biological effects of ultrafast laser processes and their potential implications for user safety.enCC BYinfo:eu-repo/semantics/openAccesshttps://creativecommons.org/licenses/by/4.0/600540570article2025-01-23