关键词: 激光烧蚀/
掺杂金属聚合物/
屏蔽特性/
聚甲醛
English Abstract
Numerical investigation on shielding properties of the laser ablation plume of polymer doped metal
Duan Xing-Yue1,Li Xiao-Kang1,
Cheng Mou-Sen1,
Li Gan2
1.Department of Aerospace Science and Engineering, National University of Science and Technology, Changsha 410073, China;
2.National Key Laboratory of Explosion Shock Disaster Prevention and Reduction of Science and Technology of Liberation Army, Nanjing 210007, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant No. 51306203), and the Research Program of National University of Defense Technology (Grant No. JC-14-01-02).Received Date:12 May 2016
Accepted Date:06 July 2016
Published Online:05 October 2016
Abstract:For laser ablation propulsion, the shielding effect of ablation plume on the incident laser is an essential factor affecting the propulsion performance. When the polymer doped metal is utilized as the propellant, the shielding effect would be more significant because the metal dopant is easily ionized. In order to study the shielding effect of ablation plume on the incident laser energy, a laser ablation model with taking into account the plume expansion, ionization and the shielding effect is built in the present work. For the polyoxymethylene doped aluminum particles irradiated by a laser with a fluence of 3-40 J/cm2, the specific impulse of laser ablation is calculated, and the consistency of the numerical results with the experimental data demonstrates the availability of the model. Furthermore, the effects of both the incompletely decomposed polymer chains and the plasma induced by laser ablation on the incident laser are considered. The time variations of electron number density distribution under different laser fluences are calculated based on the laser induced ionization model. Subsequently, the absorption coefficient distributions and the time variations of shielding coefficient under different laser fluences are obtained. The results show that at a low laser fluence (5 J/cm2), the electron number density is small, so the plume shielding effect is dominated by the laser energy absorption of the small polymer chains which are not completely decomposed. While at a high laser fluence (20 J/cm2), small polymer chains are almost completely decomposed into atoms even plasma, hence the shielding effect is dominated by the plasma since the electron number density in the plume increases up to 1020 m-3, and the complicated characteristic in the time variation of shielding coefficient appears. The quantitative analysis results obtained in the present work can be helpful for optimizing the performances of laser ablation propulsion.
Keywords: laser ablation/
polymer doped metal/
shielding properties/
polyoxymethylene
