The Future of Electron Synchrotrons

The electron synchrotron has become a highly successful instrument for high-energy physics with the application of alternating gradient focusing. Development toward large orbits and low magnetic fields has brought the problem of radiation loss under control and has stimulated design planning for very high energies. The magnets can be powered at high cycling rates (60 cps) by resonant electrical circuits. The most valuable feature is the long duty cycle available for experiments, of up to 20% of total time. Photons emerge tangentially in sharply collimated beams from targets at the edge of the orbit. Emergent beams of electrons can be ejected with high efficiency, having small energy spread and excellent collimation. Future developments should bring higher beam intensities as well as higher energies. Positrons can be accelerated in the same orbit, with reversed magnetic fields and a suitable source. The AG magnet system should distribute the damping due to synchrotron radiation between radial, vertical and synchronous modes, as in a storage ring. In principle, particles could be injected in each cycle and stored to develop high-intensity circulating beams. With orbits as large as the giant AG proton synchrotrons of the future, electron energies of 50-Gev or higher could be obtained. A large fraction of the orbit would be filled with rf accelerating cavities spaced between the AG magnet units, powered in phase as in a linac. As for all large-orbit machines the major cost would be for buildings, tunnels and services