Present and future of high energy accelerators

The field of high energy accelerators has been changing rapidly during the last few years. In proton machines, future developments can be expected to involve superconducting magnet rings as well as storage rings to obtain higher cm energies. In heavy ion machines, the trend is towards developing higher current medium energy machines with higher intensities than the present ones. In the region of medium energy physics (proton machines, Ep less than 1 GeV) a number of circular and linear machines are commencing operation whose main advantage over the old fm cyclotrons is primarily the higher intensity. In high energy electron accelerators, the main trend is at present to use the existing machines as injectors for electron-positron colliding ringsminosity and energy are being increased to satisfy the needs of physics research programs. Some years in the future there are plans for electron--proton colliding rings (PEP) at energies around 70 GeV. In the lower energy range of electron machines there is considerable development of medical accelerators underway as sources of pions, neutrons, or x-rays, the last being the conventional use. The electron storage rings of the physics machines are also in use as sources of synchrotron radiation, for physical and biological research in the far ultraviolet and soft x-ray region. The main developments in the next five years in accelerator construction are in the direction of using superconducting magnets for circular machines and superconducting cavities for linear accelerators. Fixed target machines will be used as injectors for colliding beam storage rings. A number of heavy ion machines will be constructed capable of accelerating all ions up to uranium