Factors enhancing production, extraction and focusing of positive ion beams

In this work, historical review about different kinds of ion sources and their applications are reviewed and discussed. Principle of plasma generation and ion extraction are discussed and investigated. In all types of ion sources, ions are produced by various types of gas discharge including electron collisions with gas particles. The general parameters are a source of electrons, a small region of relatively high gas pressure, an electric field to accelerate the electrons in order to produce an intense gas discharge (plasma) with a relatively high electron and ions density and some mechanism for extracting a collimated parallel high current ion beam. Types of gas discharges and different ionization processes are described. Optimum extraction conditions are reached whenever the plasma meniscus has an optimum curvature for a given current density. Also, different patterns of emittance diagrams for a typical illustration pictures with the aid of SIMION computer program are given. Indeed, theory of ion focusing is given and some examples on electrostatic focusing systems as two and three cylinder lens systems are given. These studies clearly demonstrate the importance of being able to produce, focus and adjust the extraction region in order to ensure high quality, minimum divergence (highly transportable) ion beams. The ion source is evaluated by; the large ion current extracted from it, the large percentage of ions in the beam, the higher degree of ionization inside the atom, the small gas consumptions, and the degree of divergence of the extracted ions must be small.