The LEP main ring accelerating structure

A total effective voltage of more than 400 MV per turn is produced in the LEP main ring by 128 accelerating units. Each unit consists of a low-loss storage cavity coupled to a five-cell accelerating cavity. By driving the coupled system with its two resonant frequencies, the stored RF energy is made to oscillate between the two cavities in synchronism with the passage of the bunched beam. Since on average the energy spends one half of its time in the low-loss environment a substantial saving in power is obtained. This paper gives the basic theory associated with the design of this coupled-cavity system and reviews the main RF parameters. (orig.)