Study On The Control Scheme And Heat Transfer Characteristics Of Conversion Module With Large-aperture Kdp Crystal

In order to get the short wavelength laser,the initial laser must be conversed by KDP crystal in all of Inertial Confinement Fusion(ICF).KDP crystal with large aperture of 330 mm in diameter is used in the final optics assembly(FOA),which is the most important part in ICF prototype for harmonic conversion of laser.There are two kinds of KDP crystals(type-I and type-II)to fulfill the request of frequency conversion.large-aperture KDP crystal has high temperature sensitivity.By controlling the crystal temperature the uniformity of the crystal temperature surface is ensured and the frequency doubling efficiency is guaranteed.According to the characteristics of optical heat transfer of KDP crystal and the structure of frequency doubling module,a simplified heat transfer model was constructed.The study on heat transfer will be transformed into the study of thermal resistance of components in frequency doubling module.In order to simplify the heat transfer analysis,the whole frequency doubling module is divided into two parts: wall and KDP crystal.The heat transfer characteristics of the wall under different waterway condition and water flow rates were analyzed,and the heat transfer resistance of the wall was obtained.For the KDP crystal module,the temperature field and flow field inside the frequency doubling module are studied,and the maximum temperature difference on the surface of the KDP crystal is less than 0.15 C.By studying the steady-state temperature and transient step response of KDP crystal,the heat transfer resistance of KDP crystal module is obtained.The ability of control scheme to stabilize crystal temperature and reduce external interference was explored through experiments.By adjusting the temperature of constant temperature water,the temperature rise rate of crystal can be controlled.The temperature control scheme and the heat transfer effect of the mixed temperature control scheme and constant-air control scheme are studied.The law of crystal temperature change and dynamic response characteristics under different gas flow rates were obtained by experiments.Finally,comparing different temperature control schemes,it is concluded that the mixed temperature control scheme is the best temperature control scheme with the best temperature control effect.