Spatial-temporal modulation method of nanosecond laser for the double-cone ignition scheme

Opt Express. 2024 Oct 21;32(22):39483-39496. doi: 10.1364/OE.538941.

Abstract

In order to improve the stability of the pulse, realize the high requirements of the direct drive ignition design for the uniformity of the target irradiation, reduce the interference of laser plasma instability, and improve the laser-target coupling efficiency, a nanosecond laser spatial-temporal modulation of high-power laser driver for double-cone ignition (DCI) research was proposed. Under the premise of satisfying the near-isentropic compression waveform of driving implosion, the time-power curves of all sub-beams in the facility are redistributed to reduce the waveform contrast ratio of each sub-beam. A fewer number of sub-beams are utilized to generate low-power foot pulses, which are focused on the target surface of the initial radius. And the remaining sub-beams are utilized to generate high-power driving main pulses, which are focused on a relatively small target surface. It is shown that the stability of the time-power curve of each sub-beam and the power balance control ability can be effectively improved by redistributing. At the same time, the variable focal spot control can be realized to reduce the influence of cross-beam energy transfer (CBET).