Particle-in-Cell Investigation on the Influences of Ion Source Parameters on Flow and Expansion Characteristics of Deuterium-Titanium Ions

Abstract

By using a self-programmed cylindrical coordinate 2-D, three velocity components, particle-in-cell (2D3V-PIC) code, the influences of ion source parameters on the flow, and expansion of deuterium-titanium ions in a vacuum device are investigated. The flow and expansion characteristics of deuterium-titanium ions from the ion source to the expansion cup are influenced by plasma generation rate, electron temperature, and kinetic energy of multicomponention, but hardly influenced by ion proportions. Decreasing electron temperature or plasma generation rate will weaken the radial expansion capabilities of ions. Increasing the kinetic energy of a certain component ion will also weaken the radial expansion capabilities of this component ion. But, the influence mechanisms are not the same. Decreasing electron temperature or plasma generation rate will weaken the electric field intensity in the plasma sheath near the ion source wall. This effect will weaken the radial accelerating capabilities of ions. Increasing the kinetic energy of a certain component ion will cause the total velocity of this component ion deflection from radial to axial direction. Compared with Ti2+, the flow and expansion characteristics of D+ are more sensitive to ion source parameters. The ion extraction efficiency of D+ is notably lower than Ti2+. In the steady phase, there is no ion-acceleration in the axial direction. Ion-acceleration occurs only in the radial direction. The two different radial ion-acceleration mechanisms are theoretically analyzed. One is sheath acceleration; ions are radially accelerated by the electric field formed by the sheath near the ion source wall. The other one is expansion acceleration, ions are radially accelerated by the electric field formed by the gradient of electron density in the expansion cup. The theoretical results well verify the simulated results.