ACTIVE STABILIZATION OF MECHANICAL QUADRUPOLE VIBRATIONS FOR LINEAR COLLIDERS

To achieve luminosities of some 10(33) cm(-2) s(-1), all linear collid er schemes current y under study require extremely low beam emittances to achieve spot sizes of some 10 nm height and some 100 nm width at t he interaction point. Therefore, high beam position stability is requi red in order to provide central collisions of the opposing bunches. Si nce ground motion amplitudes are likely to be larger than the required tolerances of 85 nm rms for the 500 GeV and 43 nm rms for the 1 TeV S -band linear collider SBLC, some means of active stabilization is nece ssary to damp quadrupole motion to the desired value. Therefore, an in expensive active stabilization system to be installed in the S-band te st accelerator at DESY has been developed and successfully tested. It damps quadrupole motion in the frequency range 2-30 Hz by up to 14 dB, thus leading to rms values of approximately 25 nm even in very noisy environments. Since the system is based on geophone type motion sensor s with an internal noise level corresponding to 1.1 nm at 2 Hz, it is likely that this system allows stabilization below the 10 nm level.