Abstract
In high power laser facility for inertial confinement fusion research, final optics assembly (FOA) plays a critical role in the frequency conversion, beam focusing, color separation, beam sampling and debris shielding. The design and performance of FOA in SG-II Upgrade laser facility are mainly introduced here. Due to the limited space and short focal length, a coaxial aspheric wedged focus lens is designed and applied in the FOA configuration. Then the ghost image analysis, the focus characteristic analysis, the B integral control design and the optomechanical design are carried out in the FOA design phase. In order to ensure the FOA performance, two key technologies are developed including measurement and adjustment technique of the wedged focus lens and the stray light management technique based on ground glass. Experimental results show that the design specifications including laser fluence, frequency conversion efficiency and perforation efficiency of the focus spot have been achieved, which meet the requirements of physical experiments well.
Highlights
For inertial confinement fusion (ICF)[1, 2] and high energy density physics research, a few large high power laser facilities have been built, such as National Ignition Facility (NIF)[3] in the United States, Laser Megajoule (LMJ)[4] in France, and series of Shen-Guang facilities[5,6,7,8,9] in China
According to the designed laser fluence of 3 J/cm2 and 2 mm separation among the focal points of the different harmonics, the wedged focus lens is chosen in the final optics assembly (FOA) to achieve the functions of focusing and color separation[19]
The results show that our debugging method of the optical elements in Section 4, especially for the wedged focus lens, is very effective, which ensures a good focal spot morphology
Summary
For inertial confinement fusion (ICF)[1, 2] and high energy density physics research, a few large high power laser facilities have been built, such as National Ignition Facility (NIF)[3] in the United States, Laser Megajoule (LMJ)[4] in France, and series of Shen-Guang facilities[5,6,7,8,9] in China. The final optics assembly (FOA)[10,11,12,13] is at the end of the whole laser beam line in high power laser driver, which converts the 1ω laser to the 3ω laser and focuses the 3ω laser to the target. It is a key system combining the main laser system with the physical experiments in the target chambers. The safe and stable operation of FOA at 351 nm with high fluence is affected by the laser damage, which is related to materials, manufacturing, design and engineering. Two key technologies developed to improve the FOA performance in the engineering process are reported
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