Study On Rapid Growth Technology And Properties Of High Deuterium DKDP Crystal

With the continuous improvement and upgrading of Inertial Confinement Fusion（ICF）devices,the standards for the quality and size of the required crystal optical components are also continuously improved.To meet the application capacity requirements of the ICF engineering for nonlinear optical crystal materials,it is very important to grow large-size DKDP crystals with excellent optical quality and improve crystal utilization,based on higher standards and faster speeds.In this paper,the rapid growth technology of DKDP crystal is briefly introduced.Growth devices improvements,solution preparation and transfer,and crystal growth method are described.The properties of the DKDP crystals grown by the plate-seed directional rapid growth method and the point-seed rapid growth method were compared and analyzed;the optical quality and performance of the large-diameter,high-deuterium DKDP crystals were studied.The main research contents of this paper include:（a）The self-designed new crystal carrier was used for the growth of DKDP crystals.By reinforcing the transparent baffle made of acrylic material around the crystal plate of the crystal carrier,the plate-seed is fixed in the crystal carrier.In this way,the size and aspect ratio of the crystal could be controlled artificially and the area of the pyramidal sector could be greatly improved.And then,the pyramid-prism boundary could be avoided in the process of cutting,which could effectively improve the utilization rate of the crystal.（b）A new type of magnetic fluid sealing device was used to prevent the crystal growth solution from contacting with the outside air,so as to improve the sealing effect of the growth tank and effectively prevented the reduction of deuteration rate.（c）The optical uniformity of the DKDP crystal successfully grown by the plate-seed directional rapid growth method was compared with that of the point-seed rapid growth method,and the influence of these two different growth methods on the pyramid-prism boundary of the crystal was studied.The uniformity test results showed that there was no pyramid-prism boundary in the sample taken from the directional rapid growth of DKDP crystals,but there was clear pyramid-prism boundary in the point-seed rapid growth crystal.The RMS of the directional rapid growth crystal was 1.45×10^-8,and the RMS of the point-seed rapid growth crystal was 4.92×10^-8,both of which meet the requirements of the ICF project for the RMS of optical crystal materials to be less than 1×10^-6.The deuteration rate of the crystal grown by the plate-seed directional rapid growth method was 90.27%,and the deuteration rate of the DKDP crystal grown by the point-seed crystal rapid growth method was 90.03%.The data of extinction ratio of DKDP crystals grown in two different ways were not very different.In the wavelength range of 200 nm–2000 nm,the pyramidal sector and the prismatic sector of the 90.27%DKDP crystal sample maintained well transmittance.At the wavelength of 1064nm,the transmittance of the crystal pyramidal sector was 89.71%,and the transmittance of the prismatic sector was 88.94%.The transmittance curves of the DKDP crystal cone regions of the two different growth methods were the same.（d）Through the upgrade and optimization of the original growth equipment,a large-diameter,high-deuterium DKDP crystal was successfully grown by the point-seed rapid growth method.The crystal size was 380 mm×430 mm×280 mm,the deuteration rate was 99.38%,and the weight was 50.1 kg,which was the largest high deuterium DKDP crystal reported in China at present.In the wavelength range of 200 nm–2000 nm,the transmittance of high deuterium 99.38%DKDP crystal was about 93.88%.By comparing the transmittance curves of DKDP crystals with different deuterium contents,it was found that the higher the deuteration rate,the greater the corresponding transmittance spectrum range,and the greater the infrared absorption cut-off edge.The extinction ratio data of the high-deuterium DKDP crystals were generally better,and the distribution of deuterium content in the crystals was relatively uniform.The optical uniformity of the pyramidal sector sample was good,and the overall optical quality was high.The RMS was 1.51×10^-8,which meets the requirements of the ICF project for the RMS of optical crystal materials to be less than 1×10^-6.The LIDT of 99.38%DKDP crystal was 24.7 J/cm²（1064 nm,3 ns）,indicating that the crystal has good anti-laser performance and high crystal quality.