Trends in high energy particle accelerators

Particle accelerators of higher and higher energy and intensity are required, as the investigation of subatomic matter needs to be pursued with higher and higher resolving power. To keep pace with this need while keeping physical dimensions and the cost of accelerator installations affordable, ever new ideas and technologies must be devised. After a brief general introduction and a summary of accelerator physics basics, we review the main lines of development of state of the art installations recently built, in construction or on the drafting board. New physics and technology challenges they pose and main topics still open to further research and development are also outlined