Secondary hazards: Particle and X-ray emission

Apart from primary hazards caused by the laser beam, ultrashort pulse lasers also pose secondary nonbeam hazards by gaseous and particulate laser-generated air contaminants or ionizing radiation. Though the emission rates for femtosecond-laser applications are remarkably lower than for conventional laser technologies (such as cutting, welding or cladding), the high respirability of particles can pose health risks, especially if carcinogenic, toxic materials (such as Ni or Cu), or, in medical applications infectious tissues, are processed. For human tissue a clear shift of the mean aerodynamic diameter of the aerosols to smaller diameters compared to conventional lasers is observed. This raises new questions in the field of ultrafine particles. Suitable capture systems near to the processing zone or personal protective equipment (PPE) such as respiratory masks are required to avoid possible health risks. Due to the extremely high pulse intensities, X-rays can be generated if laser radiation interacts with matter. In cases of material processing, X-rays are unintentionally directly generated. The emission rate decisively depends on the laser parameters and the physical properties of the target material. The dose rate the employees are exposed to results from the emission rate and the design of the process zone (open or enclosed) or their distance from the target. Depending on the laser process parameters, investigations reveal that legal TLV for exposure to ionising radiation can be exceeded. This obliges a risk assessment to be carried out for X-rays on the basis of which adequate safety measures have to be applied.