Quadrupole Centering and Beam Steering in the Next Linear Collider Main Linacs

Accurate measurement of quadrupole-to-BPM center offsets and use of this information in an auto-steering algorithm are two essential components of emittance preservation in the Next Linear Collider main linac. The authors present the results of an analytic/simulation study of possible statistical and systematic limitations on the measurement of quad-BPM center offsets. These results are incorporated in a simulation study of a potential main linac steering algorithm which relies entirely on remote-controlled magnet and RF-structure positioning devices to minimize emittance dilution. The effects of ground motion during the alignment process are also considered.