  This paper outlines the many ways that the initial beam can be made for
particle accelerators. Brief introductions to plasma physics and beam formation
are given. Thermionic and photo emission electron guns, with both DC and Radio
Frequency (RF) acceleration are outlined. Positive ion sources for producing H+
ions and multiply charged heavy ions are covered. Hot cathode filament sources
and cold cathode sources are explored. RF discharge sources (inductively
coupled, microwave and ECR) are discussed, as are laser, vacuum arc, and
electron beam sources. The physical principles of negative ion production are
outlined and different types of negative ion source technologies are described.
Polarised particle sources are mentioned briefly. Source choice is summarised
and the general practicalities of source operation and development are
discussed.
