The increased demanding qualities for positron sources dedicated to e+e- colliders pushed on investigations oriented on new kinds of e+ sources. The different kinds of positron sources polarized and no polarized are considered. Their main features (intensity, emittance) are described and analysed. Comparison between the different sources is worked out.

The characteristics of the positron beam available in the collision point are greatly depending on the capture device and on the positron accelerator. Different kinds of capture systems are considered and their qualities, compared.

Intense positron sources which are necessary for the colliders require intense incident beams (electrons or photons). The large number of pairs created in the targets leads to important energy deposition and so, thermal heating, which associated to temperature gradients provoke mechanical stresses often destructive. Moreover, the important Coulomb collisions, can affect the atomic structure in crystal targets and the radiation resistance is of concern.

The description of all the aspects of the positron sources (physical processes associated to positron generation, positron capture and transport, target behaviour) will be presented.