Crucial to all the preceding chapters is the assumption that we are able to produce beams and targets of polarized particles and that we are able to analyse the state of polarization of these particles.

In the production of targets and beams we are dealing with stable particles (or at least particles stable on the time scale involved) and the physics involved is basically a mixture of classical and quantum mechanics.

There has been extraordinary progress in the design and construction of polarized proton sources at Argonne and Brookhaven and in the development of highly polarized, radiation-resistant targets of various materials by workers at CERN, Fermilab, HERA, Basel, Virginia, SLAC and Ann Arbor.

Great advances have been made in the resolution of problems involved in the acceleration of polarized protons by groups at Bloomington and at Brookhaven. The electron beams at LEP and at HERA have been successfully polarized and a superb polarized electron source is in use at SLAC.

Also quite remarkable has been the building of secondary and tertiary beams of polarized hyperons at Fermilab. Who would have believed it possible that one can measure the magnetic moment of the Ω–?!

Firstly we shall provide a brief discussion of the physical principles of polarized proton sources and targets and of the problems involved in accelerating beams of polarized protons without loss of polarization.

We also discuss a relatively new development, the attempt to polarize protons and antiprotons via the Stern–Gerlach effect.