Chen Shaoshan, Li Shengyi, Peng Xiaoqiang, Hu Hao, Tie Guipeng
Appl Opt. 2015 Feb 20;54(6):1478-84. doi: 10.1364/AO.54.001478.
A new nonaqueous and abrasive-free magnetorheological finishing (MRF) method is adopted for processing a KDP crystal. MRF polishing is easy to result in the embedding of carbonyl iron (CI) powders; meanwhile, Fe contamination on the KDP crystal surface will affect the laser induced damage threshold seriously. This paper puts forward an appropriate MRF polishing process to avoid the embedding. Polishing results show that the embedding of CI powders can be avoided by controlling the polishing parameters. Furthermore, on the KDP crystal surface, magnetorheological fluids residua inevitably exist after polishing and in which the Fe contamination cannot be removed completely by initial ultrasonic cleaning. To solve this problem, a kind of ion beam figuring (IBF) polishing is introduced to remove the impurity layer. Then the content of Fe element contamination and the depth of impurity elements are measured by time of flight secondary ion mass spectrometry. The measurement results show that there are no CI powders embedding in the MRF polished surface and no Fe contamination after the IBF polishing process, respectively. That verifies the feasibility of MRF polishing-IBF polishing (cleaning) for processing a KDP crystal.
采用一种新型的非水无磨料磁流变抛光（MRF）方法对磷酸二氢钾（KDP）晶体进行加工。磁流变抛光容易导致羰基铁（CI）粉末嵌入；同时，KDP晶体表面的铁污染会严重影响激光损伤阈值。本文提出了一种合适的磁流变抛光工艺以避免嵌入。抛光结果表明，通过控制抛光参数可以避免CI粉末的嵌入。此外，在KDP晶体表面，抛光后不可避免地存在磁流变液残留物，其中的铁污染不能通过初始超声清洗完全去除。为了解决这个问题，引入了一种离子束修形（IBF）抛光来去除杂质层。然后通过飞行时间二次离子质谱法测量铁元素污染的含量和杂质元素的深度。测量结果表明，磁流变抛光表面没有CI粉末嵌入，离子束修形抛光工艺后也没有铁污染。这验证了磁流变抛光 - 离子束修形抛光（清洗）加工KDP晶体的可行性。
