Accelerators for the twenty-first century: a review

The development of the synchrotron, and later the storage ring, was based upon the electrical technology at the turn of this century, aided by the microwave radar techniques of World War II. This method of acceleration seems to have reached its limit. Even superconductivity is not likely to lead to devices that will satisfy physics needs into the twenty-first century. Unless a new principle for accelerating elementary particles is discovered soon, it is difficult to imagine that high-energy physics will continue to reach out to higher energies and luminosities.