研究目的
Investigating the x-ray emission during ultrashort pulse laser material processing and discussing the properties of potential shielding materials for radiation protection.
研究成果
The study concludes that ultrashort pulse laser material processing at high repetition rates and peak intensities can generate significant x-ray radiation, necessitating radiation protection measures. The x-ray dose does not monotonously scale with the atomic number of the sample materials, and additional material properties must be considered. A scaling of the x-ray emission to higher peak intensities is possible, with the electron temperature scaling with the peak intensity as I1/3 and the integrated photon flux in the Bremsstrahlung continuum with I1.7 for aluminum-alloy. For x-ray photon energies exceeding 30 keV, shielding made of aluminum and borosilicate glass requires a 30–40 times larger thickness to obtain the same protection level as iron or steel.
研究不足
The study is limited to peak intensities up to 2.6 × 1014 W/cm2 and a repetition rate of 400 kHz. The scaling to higher peak intensities up to 1015 W/cm2 is based on extrapolation and may not account for all potential variables at these higher intensities.
1：Experimental Design and Method Selection:
The experiments were performed using a TRUMPF laser system with a laser wavelength of 1030 nm, a maximum pulse repetition rate of 400 kHz, and a pulse duration of 925 fs. Using a galvanometer scanner head, scan fields with an area of 10 × 10 mm2 were filled by parallel line scans with an interline distance of 20 μm. The laser beam was focused in air by means of an F-Theta lens with a focal length of 56 mm.
2：Sample Selection and Data Sources:
Different target materials were investigated including tungsten, steel (S235JR), aluminum-alloy (AlMgSi
3：5), zirconium, copper, and Gorilla glass. List of Experimental Equipment and Materials:
TRUMPF laser system (TruMicro 5050 femto edition), galvanometer scanner head (hurrySCAN II 14, SCANLAB GmbH), F-Theta lens, active ionization chamber dosimeter (OD-02, STEP GmbH), CdTe spectrometer (X-123CdTe Spectrometer, Amptek Inc.).
4：Experimental Procedures and Operational Workflow:
The samples were irradiated over 5 s with a scan speed of 1000 mm/s. From the accumulated x-ray radiation dose, the dose rate was calculated.
5：Data Analysis Methods:
The spectral dose rates were calculated from measured x-ray spectra by using energy dependent photon-to-dose conversion factors.
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