实时控制过饱和度降温法生长KDP晶体

用变压器型电导仪实现了ＫＤＰ晶体生长过程中溶液的浓度和过饱和度的实时测量与控制，测量精度±０．０３ｇ ＫＤＰ／１００ｇ Ｈ_２Ｏ（±０．１０％相对过饱和度），控制精度与测量精度相当．过饱和度实时控制系统提供了一种方法，可以研究在不同工艺条件生长ＫＤＰ晶体时，过饱和度与晶体生长和性能的关系．用分析纯原料生长ＫＤＰ晶体，发现随着过饱和度的增大，晶体的生长速度加快，晶体的均匀性降低．过饱和度实时控制系统可以使ＫＤＰ晶体在相对恒定的过饱和度下生长，提高了晶体生长的均匀性，抑制了生长层和散射颗粒的产生，有利于提高晶体的光学透过率和光伤阈值．

KDP Crystal Growth by Decreasing Temperature Using Supersaturation-Control System

A real-time cross-correlation between concentration, temperature and electrical conductivity of KDP aqueous solution was determined by using an transformer-type conductivity sensor. This correlation can be expressed by L(T_s,t)=L₀(t)+b₁(t)T_s+b₂(t)T_s². On the base of the correlation, a computer system was made to realize the in-line measurement and control of the supersaturation of the growth solution. The system can control the supersaturation within ±0.04g KDP/100g water (±0.12% relative supersaturation). The system was used to study the relationship between the supersaturation of the growing solution and the properties of the crystals grown from different raw materials. It was found that growth rate rise but the homogeneity of KDP crystal goes down as the supersaturation increases. The system makes KDP crystal growing under a stable supersaturation and the growth band and scattering particles inside the crystals suppressed, so the optical transmittance and laser damage threshold of the crystal improved.