Application of soft X-ray tomography on HL-2A

Soft X-ray tomography is an important tool to study various phenomena in fusion plasmas, such as MHD events, sawteeth, and disruption. Central MHD instabilities can be observed with pinhole cameras to record soft X-ray emission from the plasma along 120 chords with high temporal resolution on HL-2A. Tomographic inversion can be obtained by various methods. The main tomography reconstruction techniques applied to soft X-ray tomography on HL-2A were the Cormack method [1] and Bessel expansion [2]. Using Bessel expansion, we can decrease the expansion term and thus reconstruct a fine image near the boundary. However, the precision of the center of the reconstructed image is lower than that by using the Cormack method. The soft X-ray system mainly detects the MHD instabilities of the central plasma, so we choose the Cormack method to reconstruct the internal magnetic structure of the plasma on HL-2A.