Characterization of liquid sheet targets developed for high-repetition-rate laser-plasma experiments

Abstract

Over-dense plasma targets are essential in certain laser-plasma interaction experiments, such as high harmonic generation and particle acceleration. Traditionally, solid targets-often polished mirrors-have been employed due to their excellent surface quality and ease of handling. However, the solid targets are prone to damage with every laser shot, necessitating physical replacement. This limitation has made it challenging to collect extensive experimental data or conduct high-repetition-rate experiments efficiently. To address these challenges, liquid targets have been developed as an alternative. Liquid targets are damage-resistant and self-refreshing, enabling high-repetition-rate experiments. Despite these advantages, managing liquids in a vacuum environment presents significant challenges, including freezing and high vapor pressure, which can degrade the vacuum conditions within the target chamber. Certain liquids, such as silicon oil and propylene carbonate, possess favorable properties, including low vapor pressure and low viscosity, making them suitable for laser-plasma interaction experiments under vacuum conditions without freezing or pressure issues. However, the characteristics of liquid sheet targets created from these liquids has not been investigated so far. In this study, we investigate the formation and properties of liquid sheets using silicon oil and propylene carbonate. Microfluidic nozzles were utilized to produce liquid sheet targets. The resulting liquid sheet exhibited a tree-leaf shape, with a length of 4.4 mm, a width of 1.2 mm, and a thickness of 815 nm at a flow rate of 2.5 ml/min. Our findings highlight the critical role of nozzle surface quality; a smooth, polished nozzle surface, achieved through sanding, was necessary to form a stable liquid sheet. Additionally, we observed that propylene carbonate caused damage to certain O-rings, prompting an evaluation of O-ring durability with different materials. The results confirm that the developed liquid target is suitable for high-repetition-rate laser-plasma interaction experiments. This study underscores the potential of liquid target-based plasma mirrors and high-order harmonic generation technologies to advance ultrafast laser and extreme ultraviolet (EUV) light source research, paving the way for a wide range of future applications. MS/PH Jungho, Ha(하정호), Characterization of liquid sheet targets develope d for high-repetition-rate laser-plasma experiments (고반복률 레이저 -플라즈마 실험을 위한 액체 시트 타겟의 특성 분석). 물리광과학과(Depart ment of physics and photon science). 2025. Advisor: Prof. Kyung Taec Kim 20231089