Abstract
The development of particle accelerators with ever increasing energies is raising the standards of the structures which could interact with the particle beams. These structures could be subjected to strong shockwaves in accidental scenarios. In order to test materials in such conditions, one of the most promising techniques is the impact with high-power lasers. In view of the setting up of future experimental campaigns within the Petawatt High-Energy Laser for Heavy Ion Experiments (PHELIX), the present work aims at the development of a numerical approach for the simulation of graphite impacted by laser beams. In particular, the focus is on the spallation damage caused by shockwave reflection: a sufficiently intense laser beam could ablate the matter until plasma conditions, hence producing a shockwave which could travel inside the material and reach a free surface. A numerical model to properly describe the spall fragmentation of graphite has been calibrated on the basis of literature-available experimental data. The numerical approach is a ‘two-step’ procedure: the first step is the definition of the laser–matter interaction and the second one concerns the description of the shockwave evolution into matter. The simulations satisfactorily reproduce the dynamic response of graphite impacted by two different laser sources with various intensities, despite the difficulties of characterising a phenomenon which is extremely fast and chaotic.
Highlights
The investigation of the dynamic behaviour of materials is a strongly multi-disciplinary subject which is of paramount importance for several engineering applications
In view of the setting up of future experimental campaigns within the Petawatt High-Energy Laser for Heavy Ion Experiments (PHELIX), the present work aims at the development of a numerical approach for the simulation of graphite impacted by laser beams
The numerical approach is a ‘two-step’ procedure: the first step is the definition of the laser–matter interaction and the second one concerns the description of the shockwave evolution into matter
Summary
The investigation of the dynamic behaviour of materials is a strongly multi-disciplinary subject which is of paramount importance for several engineering applications. The objective is to test several thin specimens of graphite of different grades, MoGr, CrGr, CFC and other innovative materials In view of this challenging experimental campaign, the present work has the aim of investigating the behaviour of graphite impacted by highly energetic laser beams through an extensive use of numerical simulations. The PDV is able to work with a lower return signal, but it is characterised by a lower spatial and temporal resolution For this reason, the interferometry is a very well-suited technique when the tested materials are metals, which generally are reflective and produce flat and solid spallation ejecta, but it might not give the expected results when dealing with brittle and less reflective specimens, e.g., graphite. Due to the complexity of the phenomena involved, the common approach to predict laser–matter interaction is through radiation hydrocode simulations, which according to the characteristics of the laser beam and the properties of the material, define the energy deposition map [30,48,49]
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