The Study Of Energy Loss For Neutral Beam Injection On EAST

The injection power of EAST NBI (Neutral Beam Injection) system was varied between 2 and 4MW. Under this high injection power condition, it is crucial to numerically simulate the related physical process of the injection power loss. It is aimed at providing a reference on NBI experiment and protection of EAST vessel wall basing on different plasma parameters and engineering Design.The basic theory of energy losses with neutral beam injection is summarized,The methods in the simulation of the neutral beam injection is descriped. Focusing on the certain injection angle, the simulation code ONETWO/NUBEAM operating on toroidal symmetric magnetic equilibrium is adopted to predict the percentage of shinethrough loss, charge-exchange loss and bad orbit loss in EAST with variable beam energy and plasma parameters. Otherwise, the simulating input plasma parameters forms is tested through curve fitting measured shinethrough in DIII-D.considering the environment with different beam energy and plasma parameters, the simulating results show that the shinethrough loss is the major way for energy losses in certain range of parameters. The result comparison between the numerical simulation and empirical formula shows that the percentage of shinethrough under normal injection mode is about 20 percent. As the Analytical theory shown, the simulating shinethrough percentage also decreases exponentially with plasma density, and increases linearly with beam energy. Taking shinethrough percentage 20% as the restraint condition for instance, the linear dependence between beam energy and plasma density was obtain by means of data analysis, which could make a proposal of beam energy for NBI experiment efficiently.The governing formula was derived analytically for beam power profile. According to the calculated shinethrough percentage, the distribution of power density on the wall of injection window and the centerpost of EAST were calculated carefully, which gave the wall protected areas where the power density was larger than 1MW/m2. Taking the power density distribution on the centerpost as the inward heat flux boundary condition, the heat transfer transient modelling in a solid, carried out using finite element method, predicted the surface temperature rise of Copper and Molybdenum target, which could provide a simple Thermal Analysis for the wall protection..