In divertor tokamak plasma, the energetic ion losses of edge plasma are considered to be responsible for the negative radial electric field. In the present paper, a guiding center approximation orbit equation is found by assuming the conservation of three integrals of motion, i.e. the total ion energy E, the magnetic moment # and toroidal angular momentum Pc, and it is used to calculate expediently the ion orbit loss region. The direct ion orbit losses in the initial velocity space near the plasma edge of EAST with SN （single null） divertor configuration are analyzed systematically. The ion loss regions are obtained by solving the guiding center approximation orbit equation of critical ions with the effect of the radial electric field taken into account. Under the influence of plasma current Ip, the type of ions, the toroidal field Bt and the changes of the loss regions are analyzed and calculated accordingly.
This paper explores the patterns of influence of the negative radial electric field on the drift displacement and trajectory of charged particles, for it is essential for further investigation into the transitional mechanism of L-H Mode. In the light of superposition between the poloidal velocity of charged particles and the E × B drift caused by the negative radial electric field, the paper offers a theoretical analysis and value simulations. Under the action of different radial electric fields, results have been obtained in regard to changes in the velocity of charged particles (mainly ions), patterns of changes in drift displacement, regional change of banana particles, and features of transition and change between trajectories of transiting particles and banana particles.
