Large-sized potassium dihydrogen phosphate (KDP) crystals are an irreplaceable nonlinear optical component in an inertial confinement fusion project. Restricted by the size, previous studies have been aimed mainly at the removal principle and surface roughness of small-sized KDP crystals, with less research on flatness. Due to its low surface damage and high machining efficiency, water dissolution ultraprecision continuous polishing (WDUCP) has become a good technique for processing large-sized KDP crystals. In this technique, the trajectory uniformity of water droplets can directly affect the surface quality, such as flatness and roughness. Specifically, uneven trajectory distribution of water droplets on the surface of KDP crystals derived from the mode of motion obviously affects the surface quality. In this study, the material removal mechanism of WDUCP was introduced. A simulation of the trajectory of water droplets on KDP crystals under different eccentricity modes of motion was then performed. Meanwhile, the coefficient of variation (CV) was utilized to evaluate the trajectory uniformity. Furthermore, to verify the reliability of the simulation, some experimental tests were also conducted by employing a large continuous polisher. The results showed that the CV varied from 0.67 to 2.02 under the certain eccentricity mode of motion and varied from 0.48 to 0.65 under the uncertain eccentricity mode of motion. The CV of uncertain eccentricity is always smaller than that of certain eccentricity. Hence, the uniformity of trajectory was better under uncertain eccentricity. Under the mode of motion of uncertain eccentricity, the initial surface texture of the 100 mm 100 mm 10 mm KDP crystal did achieve uniform planarization. The surface root mean square roughness was reduced to 2.182 nm, and the flatness was reduced to 22.013 μm. Therefore, the feasibility and validity of WDUCP for large-sized KDP crystal were verified.

在惯性约束聚变项目中，大型磷酸二氢钾（KDP）晶体是不可替代的非线性光学组件。受尺寸的限制，先前的研究主要针对小型KDP晶体的去除原理和表面粗糙度，而对平面度的研究较少。由于其低的表面损伤和较高的加工效率，水溶性超精密连续抛光（WDUCP）已成为处理大尺寸KDP晶体的良好技术。在这种技术中，水滴的轨迹均匀性会直接影响表面质量，例如平面度和粗糙度。具体而言，由运动方式引起的KDP晶体表面上的水滴轨迹分布不均明显影响表面质量。在这项研究中，介绍了WDUCP的材料去除机理。然后在不同的偏心运动模式下对KDP晶体上的水滴轨迹进行了模拟。同时，利用变异系数（CV）评估轨迹的均匀性。此外，为了验证模拟的可靠性，还通过使用大型连续抛光机进行了一些实验测试。结果表明，在一定的偏心运动模式下，CV在0.67到2.02之间变化；在不确定的偏心运动模式下，CV在0.48到0.65之间变化。不确定的偏心率的CV总是小于某些偏心率的CV。因此，在不确定的偏心率下，轨迹的均匀性更好。在不确定的偏心运动模式下，100 mm 100 mm 10 mm KDP晶体的初始表面纹理确实实现了均匀的平面化。表面均方根粗糙度降低到2.182 nm，平面度降低到22.013μ微米。因此，验证了WDUCP在大型KDP晶体中的可行性和有效性。