Development of low-coherence high-power laser drivers for inertial confinement fusion

The use of low-coherence light is expected to be one of the effective ways to suppress or even eliminate the laser–plasma instabilities that arise in attempts to achieve inertial confinement fusion.In this paper,a review of low-coherence high-power laser drivers and related key techniques is first presented.Work at typical low-coherence laser facilities,including Gekko XII,PHEBUS,Pharos III,and Kanal-2 is described.The many key techniques that are used in the research and development of low-coherence laser drivers are described and analyzed,including low-coherence source generation,amplification,harmonic conversion,and beam smoothing of low-coherence light.Then,recent progress achieved by our group in research on a broadband low-coherence laser driver is presented.During the development of our low-coherence high-power laser facility,we have proposed and implemented many key techniques for working with low-coherence light,including source generation,efficient amplification and propagation,harmonic conversion,beam smoothing,and precise beam control.Based on a series of technological breakthroughs,a kilojoule low-coherence laser driver named Kunwu with a coherence time of only 300 fs has been built,and the first round of physical experiments has been completed.This high-power laser facility provides not only a demonstration and verification platform for key techniques and system integration of a low-coherence laser driver,but also a new type of experimental platform for research into,for example,high-energy-density physics and,in particular,laser–plasma interactions.

Calibration and verification of streaked optical pyrometer system used for laser-induced shock experiments

Although the streaked optical pyrometer(SOP)system has been widely adopted in shock temperature measurements,its reliability has always been of concern.Here,two calibrated Planckian radiators with different color temperatures were used to calibrate and verify the SOP system by comparing the two calibration standards using both multi-channel and single-channel methods.A high-color-temperature standard lamp and a multi-channel filter were specifically designed for the measurement system.To verify the reliability of the SOP system,the relative deviation between the measured data and the standard value of less than 5%was calibrated out,which demonstrates the reliability of the SOP system.Furthermore,a method to analyze the uncertainty and sensitivity of the SOP system is proposed.A series of laserinduced shock experiments were conducted at the‘Shenguang-Ⅱ’laser facility to verify the reliability of the SOP system for temperature measurements at tens of thousands of kelvin.The measured temperature of the quartz in our experiments agreed fairly well with previous works,which serves as evidence for the reliability of the SOP system.