Particle simulation of the initial dynamic damage behaviors of KDP crystals under intense laser irradiation

Abstract

Potassium dihydrogen phosphate (KDP) crystal has been regarded as the solely irreplaceable component in laser-driven inertial confinement fusion (ICF) facilities. Nevertheless, the laser-induced damage on KDP crystal surfaces under highenergy laser irradiation considerably restricts the output power of ICF facilities. The laser damage event on KDP surface is an extremely complex process, among which the non-heat initial energy deposition is regarded as the major absorbed energy source, determining the subsequent thermal damage process and final damage morphology. The initial energy deposition process is a non-heat stage, where the plasmas are generated from ionization processes under intense laser irradiation. However, there is still no available model that can well reproduce the dynamic interaction behaviors between the high-energy laser and plasmas in the initial energy deposition process, resulting in the laser-induced damage mechanisms on KDP crystal surface still not fully revealed. In this work, a Particle-In-Cell (PIC) model is established to investigate the initial dynamic damage behaviors of KDP crystals under intense laser irradiation. On basis of this model, the crater formation process and the particle ejection dynamics involved in the laser damage event are reproduced. The reproduced characteristic parameters of laser damage craters on KDP input and output surfaces, and the obtained particle ejection angles are consistent with the previously reported laser damage morphology, which verifies the effectiveness of the established PIC model. This work could provide theoretical means for investigating the initial energy deposition process and also offer further insights in understanding the laser-induced damage mechanisms of KDP crystal components.