The Importance of Particle Accelerators

As initial remark to this opening talk of EPAC2000 it can cursorily be said that particle accelerators are certainly important because the salaries and pension funds of the participants to this Conference depend on the existence, the running and the construction of accelerators. More seriously, it is useful to consider the three main uses of the primary and secondary beams produced by particle accelerators. 1. In a first type of application, beams of particles are employed as probes in the analysis of physical, chemical and biological samples. Particle Induced Xray Emission (PIXE) is a notable example. 2. In a second large family of application, beams of particles are used for the modification of the physical, chemical and biological properties of matter. Sterilisation can be quoted here. 3. The most energetic beams of particles are today the main instruments for research in basic subatomic physics. These particles move close to the velocity of light and one should speak of ‘massificators’. In the next Section some applications belonging to the first two categories are presented. Accelerators of the next generations are the subject of Section 3, devoted to future applications, and of Section 4, where the requests made to accelerator-builders by the present status of subatomic physics are justified.