For overdense plasma a the

For overdense plasma (a) the meniscus is convex and a considerable number of ions are lost as they hit the extraction electrodes. In the case of intermediate plasma density (b) the beam is better matched to the extraction which makes this shape of plasma meniscus the most attractive regarding the extraction design. Finally, for underdense plasma (c) the meniscus is concave and although the beam is not lost at the extraction region, the space charge of the beam will create significant problems (beam blowup). In order to achieve adequate beam extraction conditions (optimal shape of the plasma meniscus), the plasma properties of the FRAX597 Supplier source including plasma density, plasma potential and ion temperature, have to be taken into consideration when designing the extraction systems. The shape of the plasma meniscus is directly related to the plasma density while plasma potential and ion temperature affect the longitudinal and transversal momentum spread of the extracted ion beam. The maximum current density j in mA/cm2 that can possibly be expected for ion beams accelerated by an electric field is obtained under space-charge limited conditions and follows the Child-Langmuir law (planar plasma meniscus is assumed) [52]:where Q is the charge state of the ion beam, M the ion mass (amu), V the acceleration voltage (kV) and d is the extraction gap in cm.

Ion focusing
The field of ion optics is based on the analogy between geometrical light optics and the motion of charged particles in electromagnetic fields. Electrostatic lenses are widely used in charged particle optics [49]. They are used in focused ion beam systems, where they are more effective than magnetic lenses. The aim is to concentrate as many particles as possible in as small a volume as possible. The optical properties of electrostatic lenses are fixed by the voltage ratios. The focusing of charged particles with an electrostatic field could be obtained by devices that consist of a sequence of the accelerating electrodes with cylindrical symmetry has lens-like properties.

Conclusion
In the present work, different types of ion sources with their applications have discussed and reviewed. In all types of ion sources, the 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, and 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. Ion extraction region has been studied with its principle. Ion beam extraction from different types of ion sources is influenced by many parameters such as geometry, applied extraction voltage, magnetic flux density, space charge of the extracted beam and finally the shape of the plasma boundary. Simulation for the extraction region of the accel–decel extraction systems for a singly charged ion trajectories has been done for different types of emittance diagrams. The ion beam trajectories for different shapes of the plasma meniscus were simulated and optimized. Theory of ion focusing for electrostatic lens systems is given and some examples for the two and three cylinder lens systems are given. This study has been done with the aid of SIMION computer program [56]. Design parameters for the lens system were identified as variable parameters in the presence of space charge. These parameters are the separation between each electrode of the lens, the aperture diameter of the outer electrodes of the lens system, the aperture diameter of the intermediate electrode, the focusing points at different distances for singly charged ion trajectories, the applied voltage to the intermediate electrode of the einzel lens system and also to the second electrode for the two lens system and influence of space charge on beam quality and also study of the influence of the mass for the different elements has been investigated.