Research On Laser Beam Pointting Control Technology Of ICF Target

Inertial confinement fusion(ICF)laser facility need guide hundreds of high-energy pulsed laser beam and focus the laser to the target precision. This laser facility usually use continuous analog laser (hereinafter referred to as the simulation laser) which strictly coaxial with the main optical path laser (hereinafter referred to as the main laser) for optical alignment, guide and focus adjustment. And achieve closed-loop control of laser pointing by use of electric optical devices the far-field detectors in light path. Target laser pointing accuracy is one of the important indicators of accurate targeting, coaxiality between the main laser and the simulation laser and adjustment quantity of laser beam pointing are two main sources of error. For these two sources of error, this paper first presents a method of calibrate the coaxiality between the main laser and the simulation laser at the target point and a control laser beam pointing method using deformable mirrors, and carried out corresponding theoretical analysis and experimental verification. Research results in this paper solve the two problems that the coaxiality is not high between the main laser and the simulation laser from the main hall of laser and the larger adjustment quantity of laser beam pointing by control through electric reflection frames, then improve the laser pointing accuracy.This paper reviewed the research and development status of the current international and domestic inertial confinement fusion large laser system, laser pointing control system in large laser facility and the development of the important adaptive optics elements.Established a simplified optical model of ICF target area optical system by combined with ray tracing theory and mathematical simulation. By simulating light propagation in the target to find out the variation of laser pointing. Achieved the beam pointing control calculation of target area optical system and provided theoretical support for the pointing control.Using the simulation calculation of ICF target area optical system simplified optical model, analysis the calibration method at the target point of coaxiality which between the main laser and the simulation laser. In order to eliminate the impact of calibration accuracy that stray light projected onto the CCD surface during calibration, we combined with the actual targeting optical system design, given three far-field coaxial calibration methods of two laser beams with placement of the filter positions, and compared advantages and disadvantages of different methods.Based on two common methods use of deformable mirror to achieve wave-front reconstruction, respectively, for pointing control requirements of laser beams with and without wave-front distortion, theoretical derivation of the laser pointing control method using deformable mirror and discussed the optimized design to achieve precise control of the rotation angle.Finally, we designed a set of experimental equipment. Laser coaxial calibration and rotation angle control schemes validated by experiments in the laboratory and analyzed the experimental results. The feasibility of these two methods is well proved.