Three-dimensional reconstruction of the emission field of the inductively coupled plasma jet

Three-dimensional plasma diagnosis is crucial for understanding the distribution of the physical parameters of inhomogeneous plasma. Optical emission spectroscopy (OES) can obtain the electron temperature and density by spectrum lines. The premise of the 3D diagnosis by OES is to obtain the 3D emission field of plasma at different wavelengths. In this paper, we studied how to reconstruct the 3D emission field of the inductively coupled plasma (ICP) jet. The purpose of this work is to provide an imaging basis for the future 3D diagnosis of plasma. Volume tomography can directly reconstruct the 3D emission field by two-dimensional images from multiple perspectives, so it is used to reconstruct the 3D emission field of the ICP jet. During the reconstruction, the Monte Carlo method is used to calculate the weight coefficient. In order to solve the ill-posed linear equations involving a large-size weight matrix fast, we first compared the performance of three inversion algorithms in terms of different aspects and then proposed the multiscale calculation method to reduce the size of the weight matrix. We eventually established a 3D reconstruction system to obtain the 3D emission field of the ICP jets at different powers with 5 mm spatial resolution, based upon which we demonstrated the non-uniform structure of the ICP jet. The re-projection error of the ICP jet reconstructed verifies the high reconstruction accuracy of the proposed method.