Edge plasma density reconstruction for fast monoenergetic lithium beam probing

Two different electron density reconstruction methods for 8‐keV neutral lithium beam probing have been developed for the Compact Helical System (CHS). Density dependences on emission and ionization processes are included by using effective rate coefficients obtained from the collisional radiative model. Since the two methods differ in the way the local beam density in the plasma is determined, the methods have different applicable electron densities. The beam attenuation is calculated by iteration from the electron density profile in method I. In method II, the beam remainder at the observation point z is determined by integrating the Li i emission intensity from z toward the position of emission tail‐off. At the emission tail‐off, the fast lithium beam is completely attenuated. Selecting an appropriate method enables us to obtain edge electron density profile well inside the last closed flux surface for various ranges of plasma densities (1012–5×1013 cm−3). The electron density profiles reconstructed by ...