Research On Solar Polarization Measurement Technology Based On DKDP

There are various activities phenomena in local areas of the solar atmosphere,including sunspots,coronal mass ejections,and flare bursts.These solar activities act on the sun-terrestrial space environment and have a significant impact on the earth's climate,human health,electronic and electrical equipment,radio communications,and aerospace vehicle flight.The magnetic field is the fundamental driving force of solar eruptive activity.The high-precision and rapid measurement of solar magnetic field is helpful to study solar activity and is the main way to realize the early warning of disastrous solar-terrestrial space weather.High-precision real-time solar atmospheric polarization measurement is currently a common method for realizing magnetic field measurement.The rapid change of the solar magnetic field determines the need for high real-time polarization measurement.At present,the traditional solar polarization measurement technology based on Potassium Dideuterium Phosphate(DKDP)crystals and wave plates has a long measurement period and low real-time performance,and cannot be applied to rapidly changing solar active magnetic field detection.In order to solve the above-mentioned problems in solar polarization measurement,this paper proposes a solution idea by changing the modulation method and modulation steps,and conducts in-depth theoretical and application research on the solar polarization measurement technology based on DKDP crystals,and has achieved a series of innovative results.Firstly,the solar polarization measurement technology is researched,the problems of the traditional DKDP polarization measurement method are analyzed,and the 4-step polarization measurement method based on DKDP is proposed.The modulation method of the wave plate is changed,and the real-time performance of polarization measurement is improved by about 20 times.And the feasibility of this method is verified by simulation analysis and polarization measurement error comparison experiment.The measurement accuracy and measurement time of this method are better than the traditional DKDP polarization measurement method.Secondly,the influence of the error of the polarization modulation matrix on the polarization measurement result is analyzed,and the condition number(CN)of the polarization modulation matrix is used as the standard to measure the influence of the polarization modulation matrix on the error transmission.The parameters of the polarization modulation matrix were optimized,and the correctness of the method was verified by simulation analysis.Thirdly,based on the principle of polarized light interference,a method for fast calibration of the birefringent crystal's fast axis angle and phase delay is proposed.The feasibility of this method is verified through experiments,and it is applied to the fast axis and phase delay calibration of the DKDP crystal and wave plate.Calibration accuracy can reach more than 2×10^-3.Fourthly,further study the polarization measurement method based on DKDP.Aiming at the traditional method and the adverse effects of the wave plate on the measurement system in this method,a rapid polarization measurement method based on double DKDP is proposed.The method has no moving parts,and the single measurement time can reach 0.4s,and its feasibility is verified by simulation analysis.In view of the low real-time problem of the current solar polarization measurement technology,this paper has conducted in-depth theoretical and application research to prove that the 4-step polarization measurement method based on DKDP is feasible to improve the real-time performance by changing the modulation method and modulation steps.A double DKDP polarization measurement method using two sets of DKDP crystals as the modulation unit provides a new solution for the future solar polarization real-time detection technology.