Speaker
Description
The accelerator circumference will remain an unchangeable parameter throughout the entire life of the FCC program. A cautious choice is therefore essential to cover all present and future requirements in terms of beam transfer schemes or bunch spacing and length. The exact circumference becomes particularly important for the FCC-hh, when hadron beams will be supplied by a high-energy booster synchrotron either in the SPS or the LHC tunnel. The numerator and denominator in the rational circumference ratio between the FCC and its injector define the fundamental periodicity of possible beam transfers. The ratio of FCC and LHC for the present baseline circumference is extremely close, but not exactly 17/5. Moving it to precisely that value by shorting the tunnel by 18 m would allow hadron injections to take place every five revolutions, opening the door to, for example, RF manipulations to control the bunch length and alternative beam transfer schemes. This contribution summarizes the impact of the proposed fine tuning of the FCC circumference on RF frequencies, as well as its benefits for more flexibility at beam transfer.
