Laser-induced ablation of tantalum in a wide range of pulse durations
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Laser‑induced ablation of tantalum in a wide range of pulse durations Steffen Mittelmann1 · Jannis Oelmann2 · Sebastijan Brezinsek2 · Ding Wu3 · Hongbin Ding3 · Georg Pretzler1 Received: 27 April 2020 / Accepted: 22 July 2020 © The Author(s) 2020
Abstract We present data and analysis of the laser-induced ablation of pure tantalum (Ta, Z = 73 ). We have identified different physical regimes using a wide range of laser pulse durations. A comparison of the influence of strongly varying laser pulse parameters on high-Z materials is presented. The crater depth caused by three different laser systems of pulse duration 𝛥𝜏1 = 5 ns and wavelength 𝜆1 = 1064 nm , 𝛥𝜏2 = 35 ps , 𝜆2 = 355 nm and 𝛥𝜏3 = 8.5 fs , 𝜆3 = 790 nm are analyzed via confocal microscopy as a function of laser fluence and intensity. The minimum laser fluence needed for ablation, called threshold fluence, decreases with shorter pulse duration from 1.10 J/cm2 for the nanosecond laser to 0.17 J/cm2 for the femtosecond laser. Keywords Pulsed laser ablation · High-Z material · Tantalum · Ablation threshold
1 Introduction Short and ultra-short laser pulses are used in a wide spectrum of fields like material processing [1, 2], nano-particle production [3, 4] or in diagnostic applications [5]. Our purpose is to establish a reliable quantitative laser-induced breakdown spectroscopy (LIBS) diagnostic for deuterium retention analysis on inner walls of future fusion reactors as proposed by Huber et al. [6]. The goal is to provide a method that can be applied not only to present-day fusion facilities like EAST Tokamak in Hefei, China or W7-X Stellarator in Greifswald, Germany [7, 8], but also to future fusion devices like ITER [9]. The purpose of this paper is to compare the ablation behaviour of different laser systems that are promising candidates to perform first-wall diagnostic in this devices. In this context, laser–material interaction with laser pulses of different pulse durations must be compared and analyzed
* Steffen Mittelmann [email protected] 1
Institut für Laser‑ und Plasmaphysik, Heinrich-HeineUniversität Düsseldorf, 40225 Düsseldorf, Germany
2
Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, 52425 Jülich, Germany
3
Key Laboratory of Material Modification by Laser, Ion and Electron Beams, Chinese Ministry of Education, School of Physics, Dalian University of Technology, Dalian 116024, China
concerning various effects. Early investigations by Chichkov et al. [10] present theoretical models compared to experimental results to describe a wide range of laser pulse duration interacting with solid surfaces. In general, these models predict a logarithmic dependence of ablation yield with respect to the laser pulse energy. However, for achieving a more detailed picture for the differences in ns-, ps-, and fs-ablation, the underlying individual mechanisms must be identified and discussed. When a ns-laser interacts with matter, it will generate plasma and heat it in the interaction region, leading t
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