The Development And Application Of The Electromagnetic Pulse Diagnosis System On Shenguang-? Laser Facility

High power laser shooting solid targets can generate extremely significant electromagnetic radiations in inertial confinement fusion(ICF).The intensity of Electromagnetic pulse(EMP)is very large and it has a wide frequency band,which will cause interference and damage on some key electronic components.Since Shenguang-?(SG-?)is the foremost laser facility for ICF and some physical researches at extreme conditions in China,there lacks systematical investigations into the EMP generation at SG-?and its intrinsic natures.Therefore,it is significant to figure out the intensity and distribution of EMPs,which is expected to be not only helpful to understand the physical processes in laser interacting with plasma,and it also offers crucial information for EMP shielding design.Based on previous results,we designed five types of antennas that had high gain,low loss and high sensitivity for measuring EMP radiations,and we also designed different sizes for EMP measurement that can cater to different frequency bands.According to the discrepancies between the working principle of antennas that are used for collecting electric field signal and magnetic field signal,two data processing methods were conceived for signal transformation.We assembled and installed two EMP diagnostic systems at the SG-? prototype and SG-? laser chambers,and the acquisition of leaking EMP signals inside and outside the laser chambers were also investigated.We systematically compared the experimental results of the strong laser and different targets coupled radiation electromagnetic pulse,the conclusion was as follows:(1)Remarkable differences in EMP frequency spectra of the hohlraum and flat targets.The intensity of EMP generation on hohlraum is much larger.(2)Owing to various antenna polarizations,EMP signal strength obtained from the same B-dot differs.(3)The EMP signals varied with the different antennas,because antenna main parameters such as gain,directivity and receiving frequency range changed for different antennas.(4)The intensity and waveform were distinctive due to the differences in the target structure and gas filling situation.This paper also explored the radiation characteristics and mechanism of EMP,through the experiments discovered the extra pre-pulse injection process will make EMP intensity higher and the strength of EMP had a same variation trend as total fraction of scattered light.Finally,we developed a model regarding the laser facility to qualitatively simulate the distribution of EMP in the chamber.The study is expected to offer important reference value for the electromagnetic interference evaluation and electromagnetic radiation shielding design for SG-? lasers,which is also of great significance for deeply understanding the EMP characteristics.