(1) Possibility of using an LHC access shaft to house a 100m atom interferometer targeting the 1 to 10^-2 Hz range
(2) K. Oide's GW detection by resonant betatron oscillations, for the 10 kHz range
(3) S. Rao's GW detection by a change in revolution period, but "using low-energy" coasting ion beam without RF - sensitivity down to 10^-5 Hz?
(4) S. Elllis' suggestion for heterodyne detection using SC RF, up to ~ 10^7 Hz?
(5) GW generated by the beam; orbital frequency, ~ 10^4 Hz for LHC, and the orbital frequency multiplied by the number of circulating bunches used - combined with high-frequency detector concept