Search

Full polarization imaging can obtain more information about target, which has a broad application prospect in the target detection, researches of atmospheric characteristics, and medical diagnosis. This paper develops an imaging system of polarized skylight pattern of full polarization for obtaining the information about full polarization rapidly. Meanwhile, aiming at the problem that the error of the light intensity image obtained by the system due to the different “behavior” of the system transmission matrix is brought into the solution of the target Stokes vector, this paper analyzes the condition number and determinant of the system transmission matrix. Firstly, an objective function is established by combining the three sets of condition numbers and the determinant. Therefore, the problem of solving the optimal transmission matrix is transformed into a multi-condition extremal problem. And then the objective function is minimized to determine the optimal angle of the transmission matrix when the 1 norm condition number, 2 norm condition number and ∞ norm condition number reach the minimum value and the determinant reaches the maximum value. In addition, in order to improve the measurement accuracy, the delay components of quarter wave plate, extinction ratio of polarizer, and the transmission matrix of the system are calibrated. Optimization contrast experiment and outfield experiment are performed. The entropy, mean, and standard deviation are used to quantify the optimized results of the angle of polarization, degree of polarization, and degree of linear polarization. ∆Aop is defined as the difference in absolute value of angle of polarization between the two sides of the symmetry axis to verify the optimization performance of angle of polarization. Experimental results show that the polarization angle error after optimization is reduced by more than 10% compared with that before optimization; the error of the band of maximum polarization and the error of the neutral zone in the degree of polarization and linear polarization also decline to different degrees compared with before optimization. On this basis, an experiment on measuring external field full polarization information is carried out. The results show that the system meets the design requirements and can effectively obtain the sky full polarization information.

Recently, helicon plasma sources have aroused the great interest particularly in plasma-material interaction under fusion conditions. In this paper, the helicon wave antenna in helicon physics prototype experiment (HPPX) is optimized. To reveal the effect of the radial density configuration on wave field and energy flow, Maxwell's equations for a radially nonuniform plasma with standard cold-plasma dielectric tensor are solved. Helicon wave coupling and power deposition are studied under different types of antennas, different antenna lengths and driving frequencies by using HELIC. Through the numerical simulation, the optimal antenna structure and size are obtained, that is, half helix antenna, which works at 13.56 MHz and has a length of 0.4 m, can generate nonaxisymmetric radio frequency energy coupling to excite higher electron density.The influences of different static magnetic fields and axis plasma densities on power deposition are also analyzed. It is found that the absorbed power of the plasma to the helicon wave has different peak power points in a multiple static magnetic field and axial plasma densities, and the overall coupling trend increases with static magnetic field increasing, but decreases with axis plasma density increasing. According to the simulation results, the ionization mechanism of helicon plasma is discussed. In order to further study the coupling of helicon wave with plasma in HPPX, the induced electromagnetic field and current density distribution are given when the plasma discharges. Under parabolic density distribution, the field intensity of the induced electric field at the edge is large, while neither the induced magnetic field nor current density changes much along the radial direction, the energy is distributed evenly in the whole plasma. Under the Gaussian density distribution, the induced electric field intensity is higher at the edge, while the induced magnetic field and current density in the center are much higher than at the edge. In this paper studied are the structure and size of helicon wave antenna, the influences of static magnetic field and axial plasma density on plasma power deposition and the distribution of induced electromagnetic field and current density during plasma discharge under different density distributions. This work will provide important theoretical basis for helicon wave antena design and relevant physical experiments on HPPX.