Analytical and simulation studies for diode and triode ion beam extraction systems

This work is concerned with ion beam dynamics and compares the emittance to aberration ratios of two-and three-electrode extraction systems. The study is conducted with the aid of Version 7 of SIMION 3D ray-tracing software. The beam dependence on various parameters of the extraction systems is studied and the numerical results lead to qualitative conclusions. Ion beam characteristics using diode and triode extraction systems are investigated with the aid of the computer code SIMION 3 D, Version 7.0. The diode (two electrode extraction system) and triode (three- electrode extraction, acceleration-deceleration system) extraction systems are designed and optimized with different geometric parameters of the electrode system, voltage applied to the extraction electrode, and plasma parameters inside the ion source chamber, as well as by the ion beam space charge. This work attempts to describe the importance of the acceleration-deceleration extraction system. It shows that besides an increase of the beam energy, the ion beam has lower emittance than the two-electrode extraction system. Ion beams of the highest quality are extracted whenever the half-angular divergence is minimum for which the perveance current intensity and the extraction gap have optimum value. Knowing the electron temperature of the plasma is necessary to determine plasma potential and the exact beam energy.