Behaviour of inertial confinement fusion reactor materials under high temperatures and high energy fluxes obtained by medium/high-intensity pulsed lasers

The research reports on the effects of medium/high-intensity laser fluxes on the selected materials with potential applications in inertial fusion technology. The investigated materials are: refractory metals – titanium (Ti) and tungsten (W), as well as ODS, AISI 316L and ASP 30 steels. In the course of this work, two experimental apparatus were also designed and built – chamber with the accompanying equipment for irradiations in vacuum and gas ambiences, and LIBS (Laser Induced Breakdown Spectroscopy) apparatus based on nanosecond laser for surface analysis of the targets. Aside from the laser intensity, ambience strongly affects the level of modification in surface morphology and chemical content. Besides vacuum and helium (He), which are relevant for fusion problematics, air environment was also analysed. In main, damage in vacuum was more prominent than in helium and air due to better laser-target coupling. Focusing on the employment of high laser intensities (10¹⁴–10¹⁵ W∙cm-2 femtosecond laser) in vacuum, which is a realistic situation in the IF reactor, Ti as well as W showed similar morphological behaviour, but due to other superior properties, e.g. affinity to H-isotopes, W is a more desirable material. AISI 316L steel exhibited lower damage/crater depth compared to ODS steel, and due to this fact, it is somewhat more favourable. Also, contrary to ODS steel, AISI 316L showed no presence of oxygen in the irradiated areas. Plasma in front of the target was registered in all ambiences at these laser intensities, emitting in Vis, UV to X ray region. Plasma in He and air it is less volumetrically rich compared to vacuum. Unlike in vacuum (presence of plasma plume), in He and air environment the additional breakdown plasma exists. (author)