Major scientific research equipment "high-speed high-precision laser Thomson scattering instrument" made

[ Instrument Network Instrument Development ] Recently, the Chinese Academy of Sciences Aerospace Information Research Institute and the University of Science and Technology of China jointly developed a high-speed high-precision laser Thomson scattering instrument.

In May 2019, the research team carried out experiments in a "Keoda One Ring" magnetic confinement fusion plasma device, based on a laser pulse with a repetition rate of 200 Hz and a single pulse energy of 5 joules, achieving electronic temperature measurement accuracy of less than 5 electron volts, electron The temperature security warning interval is 5 milliseconds, and the warning time obtained is half of that of the international similar system, and the index is doubled.

During the working process of the magnetic confinement fusion reaction device, the divertor will be subjected to huge energy release, and the plasma electron temperature needs early warning and real-time feedback control to achieve off-target to avoid catastrophic consequences of the plasma damage device wall. Thomson scattering measurement based on high-frequency high-energy laser is the only reliable measurement method for accurately measuring plasma electron temperature. The working frequency of laser determines the sampling time interval of temperature warning. The smaller the interval, the more timely the system warning, the higher the safety factor of device operation. . Limited by the laser energy and frequency level, China's previous plasma temperature diagnosis uses tens of hertz of low-frequency lasers, the sampling interval is wide, and it is impossible to timely warn in case of emergency, resulting in huge risk of device operation. Although multiple low-frequency laser combining techniques can meet the warning time interval requirements, the method is low in reliability. At present, Europe, Japan, etc. have mastered the high-energy laser technology of 100 Hz working frequency, and the warning time interval reaches 10 milliseconds, but the interval is still long.

Since 2015, Air and Space Information Institute has cooperated with the Institute of Optoelectronic Technology of the Chinese Academy of Sciences and Tongji University to realize high energy and high beam quality laser transmission and amplification, laser phase conjugate wavefront distortion correction, and large diameter/large size laser amplification module. Key technologies such as high-power pulsed laser driving power supply, and in April 2017, the first high-frequency high-energy laser index with a repetition frequency of 200 Hz, a pulse energy of 5 joules, a pulse width of 6.6 nanoseconds, and a beam quality of 1.7 times the diffraction limit was released for the first time in the world. The power level of our nanosecond pulse width laser is increased by one order of magnitude.

The research team also developed a basic and complete process, and the core components/components were localized to form the whole machine engineering manufacturing capability. Recently, with the 200 Hz/5 Joule laser as the light source, China University of Science and Technology solved the problems of high-power laser transmission system comprehensive noise reduction, optical precision focusing, low-light signal detection and extraction, and developed the highest precision laser Thomson scattering detection in China. The system provides the basis for the high-precision measurement of the future magnetic confinement fusion energy device in China.

The research was supported by the National Major Scientific Research Equipment Development Project “Development of High Power Nanosecond Lasers and Precision Detection Instruments”. The research team will follow up with higher power, higher frequency laser development and higher precision diagnostic experiments.

(Original title: made by high-speed high-precision laser Thomson scattering instrument)