Assessment of the risks of laser-induced ionising radiation

With the scientific and technical progress in the development of lasers with ever higher average power, their use and areas of application in industry and medicine have continued to grow in recent years. However, the interaction of high-intensity laser radiation with matter can generate ionising radiation (laser-induced ionising radiation = LIS). 

LIS can be generated in particular when operating ultrashort pulse lasers (USP lasers) with laser systems - the high irradiance required for LIS generation is achieved in very short pulses and by spatial focussing of the laser light. It is therefore necessary to consider the operation of laser systems not only in terms of optical laser protection, but also from the point of view of radiation protection legislation on ionising radiation. 

Potentially LIS-generating laser systems are widely used, for example, in industrial material processing, in the functionalisation and structuring of surfaces, or in drilling, cutting, turning and welding various solid materials. However, they are also used in medicine directly on humans (for example in ophthalmology, dental technology and dermatology). In research, USP lasers are used, for example, in time-resolved spectroscopy, the investigation of atmospheric processes, particle acceleration and the deliberate generation of X-rays. 

This recommendation addresses the questions raised in the consultation and is limited to the unintentional generation of LIS. Laser systems that deliberately used to generate LIS are not considered, as the classification under radiation protection law as a system for the generation of ionising radiation in accordance with Section 5 (2) of the Radiation Protection Act (StrlSchG 2017) is known for these applications.

Of particular practical importance is the licence- and notification-free operation of laser systems. In accordance with Annex 3 Part C Sentence 2 of the Radiation Protection Ordinance (StrlSchV 2018), the current legislation has established a regulation based on the two criteria: irradiance in the focus of the laser beam and localised dose rate by LIS. The SSK has also addressed this issue and included the outcome.