Sub-NM Beam Motion Analysis using a Standard BPM with High Resolution Electronics

In the Compact Linear Collider (CLIC) project high luminosity will be achieved by generating and preserving ultra low beam emittances. It will require a mechanical stability of the quadrupole magnets down to the level of 1 nmrms for frequencies above 1 Hz throughout the 24 km of linac structures. Studies are presently being undertaken to stabilize each quadrupole by means of an active feedback system based on motion sensors and piezoelectric actuators. Since it will be very difficult to prove the stability of the magnetic field down to that level of precision, an attempt was made to use a synchrotron electron beam as a sensor. The beam motion was observed with a standard button Beam Position Monitor (BPM) equipped with high resolution electronics. Beam experiments were carried out to qualify such a measurement at CesrTA (Cornell University) and at SLS (PSI, Villingen), where the residual motion of the circulating electron beams was measured in the frequency range of 5 – 700 Hz. This paper describes the results achieved along with the equipment used to measure both the residual beam motion and the mechanical vibration of machine elements.