Neutral Density Estimate of Edge Plasma with Double Null Configuration on EAST Tokamak

摘要

The neutral density plays an important role in the low to high (L-H)confinement mode transition. In this work, population coefficients of hydrogen's n=3 excited state from hydrogen collisional-radiative (CR) model (from DEGAS 2 data file) are used to calculate the photon emissivity coefficients (PECs) of hydrogen Balmer-a (n=3→2) (H_alpha). The results are compared with the PECs from Atomic Data and Analysis Structure (ADAS) database and fit well. 1.5-D fluid transport code FRANTIC gives magnetic surface-averaged neutral density profile of typical doublenull (DN) plasma of EAST. It is found that the sum of integral D alpha and H_alpha emission intensity calculated via the neutral density agrees with the measurement from the absolutely calibrated multi-channel poloidal photodiode array systems viewing the lower divertor at the last closed flux surface (LCFS). This fact, indicates that the typical magnetic surface-averaged neutral density at LCFS is about 3.5 10~(16)m~(-3).