Study On Electromagnetic Radiation Effects Of Plasma In Fusion Environment

In the large laser targeting device SG-III,the interaction between laser and solid target generates strong electromagnetic pulse radiation(EMP),which can cause electromagnetic interference or even damage to the diagnostic equipment of the system.Therefore,it is necessary to study the mechanism of electromagnetic pulse generated by laser targeting.This article takes the actual project of the Key Laboratory of Electromagnetic Environmental Effects and Information Processing in Hebei Province as the background,and conducts a preliminary study on the target backflow mechanism in the fusion device SG-III target room.Based on this,the electromagnetic pulse radiation characteristics in the target room are simulated.Based on the simulation results,electromagnetic compatibility analysis is conducted on the diagnostic equipment in the target room.The main work is as follows:(1)Study on Target Reflux Mechanism in Vacuum Target Chamber of Fusion Devices.Based on the particle simulation algorithm(PIC)and the finite difference time-domain algorithm(FDTD),the equivalent model of the large-scale laser equipment Shenguang III was established and the physical process of electromagnetic pulse generated by laser shooting was numerically simulated.A detailed study was conducted on the PIC method,including electromagnetic field calculation,particle propulsion,and coupling of charged particles with the field.The electromagnetic field calculation was solved using FDTD.The simulation results indicate that high-energy electrons are generated from the axis of symmetry of the laser incident direction target,and the two wings towards the target gradually expand.Photons are emitted along the direction of electron motion.The electron motion trajectory or reflux trajectory is within the conical range of-π/2 to π/2,flowing back from the axis to the wings.It has been revealed that the target reflux process caused by high-energy electron emission is one of the main mechanisms of electromagnetic pulse radiation generated by laser target interaction,laying a theoretical foundation for rapid simulation of electromagnetic pulse radiation characteristics in vacuum target rooms of fusion devices.(2)Rapid simulation of electromagnetic pulse radiation characteristics in vacuum target chambers of fusion devices.The dipole radiation formed by the reflux current in the plasma generates electromagnetic pulse spectral characteristic peaks that are highly consistent with some spectral characteristic peaks of the actual measured electromagnetic pulse.The dipole radiation model of the reflux current is used as the driving source to simulate the spatial radiation field distribution of the dipole radiation source in the target chamber.Revealed the resonance characteristics and spatiotemporal distribution patterns of the propagation of strong electromagnetic pulses in the target chamber of SG-III,laying the foundation for electromagnetic compatibility analysis of diagnostic equipment.(3)Electromagnetic compatibility analysis of diagnostic equipment in the target room.In the strong and complex electromagnetic environment formed by the interaction between laser and target,some diagnostic equipment in Shenguang III will be subject to varying degrees of interference and damage,leading to data errors or loss,and increasing experimental costs.Based on the theoretical analysis of slot antennas,the spatial radiation field distribution of dipole radiation sources in the target room is used as the radiation source.Taking the most expensive and easily damaged streak camera as an example,the equivalent modeling of the slot structure of the streak camera is carried out.Through simulation analysis,the electromagnetic interference problem of diagnostic equipment in the target room is analyzed,providing basis and suggestions for its protection.