An adaptive noise cancelling system used for beam control at the Stanford Linear Accelerator Center

The SLAC Linear Collider now has a total of twenty-four beam-steering feedback loops used to keep the electron and positron beams on their desired trajectories. Seven of these loops measure and control the same beam as it proceeds down the linac through the arcs to the final focus. Ideally each loop should correct only for disturbances that occur between it and the immediate upstream loop. In fact, in the original system each loop corrected for all upstream disturbances. This resulted in undesirable over-correction and ringing. The authors added MIMO (multiple input multiple output) adaptive noise cancellers to separate the signal they wish to correct from disturbances further upstream. This adaptive control improved performance in the 1992 run.<<ETX>>