X-ray Emission Hazards from Ultrashort Pulsed Laser Material Processing in an Industrial Setting

Interactions between ultrashort laser pulses with intensities larger than 1013 W/cm2 and solids during material processing can lead to the emission of X-rays with photon energies above 5 keV, causing radiation hazards to operators. A framework for inspecting X-ray emission hazards during laser material processing has yet to be developed. One requirement for conducting radiation protection inspections is using a reference scenario, i.e., laser settings and process parameters that will lead to an almost constant and high level of X-ray emissions. To study the feasibility of setting up a reference scenario in practice, ambient dose rates and photon energies were measured using traceable measurement equipment in an industrial setting at SCHOTT AG. Ultrashort pulsed (USP) lasers with a maximum average power of 220 W provided the opportunity to measure X-ray emissions at laser peak intensities of up to 3.3 × 1015 W/cm2 at pulse durations of ~1 ps. The results indicate that increasing the laser peak intensity is insufficient to generate high dose rates. The investigations were affected by various constraints which prevented measuring high ambient dose rates. In this work, a list of issues which may be encountered when performing measurements at USP-laser machines in industrial settings is identified.

Single-step additive manufacturing of silicon carbide through laser-induced phase separation

Silicon carbide (SiC) tubes are fabricated through femtosecond high-energy ultra-short pulsed laser powder bed fusion (LPBF) additive manufacturing. Widespread implementation of pulsed LPBF of SiC compounds is hampered by a poor understanding of the material–laser interaction for such short processing times and under such extreme thermal regimes, which is due to the complexity of SiC materials. In this investigation, binding and phase separation mechanisms of SiC powders driven by pulsed laser–material interactions are elucidated using numerous state-of-the-art analytical tools as well as theoretical calculations. Partial disintegration of 6H-SiC powders into silicon and carbon during laser sintering is demonstrated to bind SiC powder particles together with no measurable SiO2 phase formation. During femtosecond laser–material interactions, 6H-SiC decomposes into silicon and carbon at high temperatures and localized high pressure state on the process. Decomposition of 6H-SiC is corroborated by density functional theory (DFT) calculations. Furthermore, relatively large (~200 nm–1.5 µm) pockets of 6H-SiC, 3C-SiC, repetitive nanoscale-pattern “nanobreathing” (~2–20 nm) of 6H-SiC and highly oriented pyrolytic graphite spheres are formed. The experimental observations indicate the viability of the synthesis of highly oriented spheroidal pyrolytic graphite and 3C-SiC and 6H-SiC grains, and thin elements of silicon and carbon, using high energy short-pulse laser irradiation.

Preface of the 18th NOLAMP conference

About the conference: The first conference on Nordic Laser Material Processing, NOLAMP was held in Oslo in 1987. Then the laser material processing was a rather new and revolutionary way to manufacture products with high quality and high efficiency. The laser research in the Nordic countries was in its pioneering age and the enthusiasm among researchers for the new possibilities was unrivalled. The intention for creating this conference, which was originally suggested by Dr. Bernt Thorstensen at SI in Oslo, Norway, was to establish a fruitful cooperation among Nordic laser researchers. Also NOLAMP intended to provide a forum for young researchers to present on-going works and to establish contacts in the scientific community as well as in industry. List of Conference date and location, Conference topics, Keynote speakers, Sponsors, Committee members, Editors, Reviewers are available in this pdf.

Squared Focal Intensity Distributions for Applications in Laser Material Processing

Tailored intensity profiles within the focal spot of the laser beam offer great potential for a well-defined control of the interaction process between laser radiation and material, and thus for improving the processing results. The present paper discusses a novel refractive beam-shaping element that provides different squared intensity distributions converted from the Gaussian output beam of the utilized femtosecond (fs) laser. Using the examples of surface structuring of stainless-steel on the micro- and nano-scale, the suitability of the beam-shaping element for fs-laser material processing with a conventional f-Theta lens is demonstrated. In this context, it was shown that the experimental structuring results are in good agreement with beam profile measurements and numerical simulations of the beam-shaping unit. In addition, the experimental results reveal the improvement of laser processing in terms of a significantly reduced processing time during surface nano-structuring and the possibility to control the ablation geometry during the fabrication of micro-channels.