Electron cooling experiments at LEAR

In 1987, after a longer phase of development this frist cooler to be used in routine operation in a storage ring was built into LEAR. Thereafter cooling experiments with 6, 10, 21 and 50 MeV protons, and later on (1989) also with antiprotons, were successfully performed; the number of stored ions was some 107 to 5x109, typically. In this paper the performance of the experiments is described and the results of all cooling experiments are summarized. First of all the theory of electron cooling is described, whereby, amongst other things, the enhancement of the friction (cooling) force due to the solenoidal magnetic field is explained and whereby a possible difference in the friction force for protons and antiprotons is discussed. Thereafter a description of the LEAR cooler follows, especially of its electronic control system, together with the computer code, as it was used during the experiments. Then the beam control and diagnostic equipment is summarized, which could be used during the cooling experiments to prepare the ion beam and to determine its equilibrium properties and the friction force, respectively. Especially the analysis of the Schottky signals which showed an unusual behaviour in the case of a cold beam is explained in more detail. After describing the optimization of the cooling the presentation of the results of all cooling experiments follows. (orig./HSI)