Physics with a 15-30 GeV high intensity continuous beam electron accelerator: the ELFE project

In order to understand the inner structure of nucleons and nuclei it is proposed to build on a European basis a new 15-30 GeV electron facility: ELFE (Electron Laboratory for Europe). After an historical introduction and a quick survey of QCD, a physics program for the ELFE project is outlined. It centers on the study of exclusive phenomena and semi-inclusive experiments at high energy and high momentum transfers aiming to use well understood perturbative aspects of QCD dominated by asymptotic freedom to study the non-perturbative aspects dominated by confinement and hadron structure. Four detectors which would cover the needs of the outlined scientific program are described. At the end a status of the project is given. (author)