离子束抛光去除函数计算与抛光实验

由于传统的离子抛光工艺采用的确定去除函数的方法操作复杂且成本很高,本文提出了利用法拉第杯对离子束流空间分布进行测量、标定的方法,并计算得到不同离子源工作参数对应的去除函数。首先,基于离子束抛光材料去除原理,研究了离子束抛光过程中束流分布与能量对去除函数的影响,并提出简化的离子束抛光去除函数模型。然后,设计实验并得出离子束流空间分布与去除函数相关参数间的关系,计算得到了不同离子源工作参数产生的离子束流对应的去除函数。对硅和融石英玻璃的相关实验表明:利用法拉第杯扫描结果计算相同材料的去除函数的单位时间体积去除率与实际测量值误差小于2%。结合抛光实验,对Φ800mm碳化硅表面硅改性层平面镜进行抛光,得到的初始面形误差均方根(RMS)值为57.886nm,两次抛光后RMS值为11.837nm,收敛率达到4.89,满足精密光学加工对去除函数的确定性及精度的要求,并大大提升了确定去除函数的效率。

Calculation of removal function of ion beam figuring and polishing experiment

As the method to get the removal function by traditional Ion Beam Figuring (IBF) has complicated operation and higher costs, this paper proposes a new method to calculate the removal function. The method uses the Faraday cup scan to measure and calibrate the temporal distribution of ion beams and to obtain the different working parameters of ion sources which corresponds to removal functions. Firstly, the material removal theory of IBF was studied based on the Sigmund sputtering theory, and the influence of ion beam distribution on the removal function was researched. A simplified IBF removal function model was proposed. Then, an experiment was conducted to obtain the relationship between the temporal distribution of ion beam and the related parameter of removal function, and the different removal functions of various working parameters were calculated with the combination of the basic removal experiment and Faraday cup scan results. Experiments were performed on silicon and fused silica, and the experimental results show that the peak value of the removal function for the same material is proportional to the that of the scan result. A mirror with a Φ800 mm silicon flat modification layer was polished, obtained the Root Mean Square(RMS) of surface error is 57.866 nm. After polishing for two times, the RMS is 11.837 nm, and the convergence rate is up to 4.89. These results meet the requirements of optical fabrication for polishing accuracy and improve the determining efficiency for removal functions.