Beam steering using quadrupoles as position monitors

An algorithm to center the beam in the quadrupoles of a transfer line by changing the focusing strength of a quadrupole and observing the resulting position shift on a monitor downstream is proposed. The observed position shift depends linearly on the beam position offset in the quadrupole, and the monitor is not a multiple of pi . The same monitor may thus be used to center the beam in several places of the beam line. The centering accuracy depends on the resolution of the monitor and on the quadrupole current increment which can be set in such a way that the beam profile remains sufficiently peaked to determine its mean position.<>