Developments in beam-based alignment and steering of the Next Linear Collider main linac

The Next Linear Collider main linacs are 13 km linear accelerators which each contain approximately 750 hybrid iron/permanent-magnet quadrupoles in a FODO array. The small amount of vertical emittance dilution permitted in the main linacs implies a tight tolerance on the RMS distance between the beam and the centers of the quads. We describe two methods for measuring the offsets between the quads and their integrated beam position monitors, and three algorithms for steering the main linac to minimize the emittance dilution. Simulation studies of the alignment and steering algorithms are presented.