We describe the design and experimental result of a LD pumped Nd:YAG laser with 12J energy at repetition rate of 10Hz. The temperature distribution was controlled to less than 2℃ on the surface by means of uniform pump and cooling. The ASE was calculated by energy storage code and fit well with the measurement results which was about 1.72 in average. The beam quality was controlled by means of mechanical design and adjustment and compensation by a home-made deforming mirror. The far field was measured to 3.23 TDL. The stability of energy and pointing were paid great attention and control by means of full absorption and high stability mechanical design. The energy stability was less than1%(RMS) and pointing stability was 73μrad(PtV), which made the laser very comfortable for use.
Adaptive optics is a real-time compensation technique using high speed support system for wavefront errors caused by atmospheric turbulence. However, the randomness and instantaneity of atmospheric changing introduce great difficulties to the design of adaptive optical systems. A large number of complex real-time operations lead to large delay, which is an insurmountable problem. To solve this problem, hardware operation and parallel processing strategy are proposed, and a high-speed adaptive optical control system based on DSP is developed. The hardware counter is used to check the system. The results show that the system can complete a closed loop control in 7.1ms, and improve the controlling bandwidth of the adaptive optical system. Using this system, the wavefront measurement and closed loop experiment are carried out, and obtain the good results.
The shooting accuracy of cluster laser is an important indicator to evaluate the performance of ICF laser devices. By measuring the distribution of the X-ray generated from interaction between the third-harmonic beam and the target, the position information of the third-harmonic beam to the target can be obtained, along with the shooting accuracy. In the beam transmission process, the fundamental, second-harmonic beams and the third-harmonic beams approach to the target at the same time generating spurious X-ray. Based on the radiation fluid, the present paper is to assess the effect of the stray light on the performance of the shooting accuracy. The intensity distribution and power density of the fundamental, second-harmonic and third-harmonic beams at the target position were calculated for the SG-III laser device using SG-99 software. The characteristics of X-ray generated by the different beams radiation are simulated by one-dimensional radiation fluid program MULTI 1D. The results show that the power density of the fundamental, the second-harmonic and third-harmonic beams at the target position are, under the condition of typical shooting precision test (infused fundamental energy of 50J and pulse width is 200ps) 0.28GW / s / cm2 , 0.14GW / s / cm2 , 99GW / s / cm2 , respectively. The X-ray energy intensity radiated from the interaction between the third-harmonic beam and target is 104 times of that from the fundamental, second-harmonic beam. In the current optical system configuration conditions of SG-III laser device, the effects of the fundamental and second-harmonic beams on the target accuracy test can be ignored.