Intense low energy positron beams

Intense positron beams are under development or being considered at several laboratories. Already today a few accelerator based high intensity, low brightness e⁺ beams exist producing of the order of 10⁸–10⁹ e⁺/s. Several laboratories are aiming at high intensity, high brightness e⁺ beams with intensities greater than 10⁹ e⁺/s and current densities of the order of 10¹³–10¹⁴ e⁺ s^–1 cm^–2. Intense e⁺ beams can be realized in two ways (or in a combination thereof) either through a development of more efficient ⁺ moderators or by increasing the available activity of ⁺ particles. In this review we shall mainly concentrate on the latter approach. In atomic physics the main trust for these developments is to be able to measure differential and high energy cross-sections in e⁺ collisions with atoms and molecules. Within solid state physics high intensity, high brightness e⁺ beams are in demand in areas such as the re-emission e⁺ microscope, two-dimensional angular correlation of annihilation radiation, low energy e⁺ diffraction and other fields. Intense e⁺ beams are also important for the development of positronium beams, as well as exotic experiments such as Bose condensation and Ps liquid studies.