Fast feedback systems for orbit correction in the TESLA Linear Collider

In the TESLA Linear Collider feedback systems will provide an orbit correction within the bunch train. To limit the reduction in the targeted luminosity of 3.1·10³⁴ cm^-2 s^-1 due to beam separations to less than a few percent, the collisions have to be vertically stabilized within a fraction of the beam spot size of 5 nm. One system, located in the beam delivery system (BDS), is used to correct vertical bunch offsets generated upstream in the main linear accelerator and BDS. The second at the interaction point brings the two beams into collision using the beam-beam deflection method. Both digital feedback systems provide a correction on a bunch-to-bunch basis. Their design is based on classical proportional-integral control. This paper describes the feedback system designs. Results of simulations are presented