Controls in Use at CESR for Adjusting Horizontal to Vertical Coupling
Machine alignment errors can cause coupled transverse motion that may adversely affect the operation of particle accelerators in many ways. This situation can occur in any circular accelerator during injection and produce unnecessary transverse motion and emittance blowup, or in colliding beam storage rings and reduce the luminosity. Skew quadrupoles, SQ, have been recognized as elements for decoupling the horizontal and vertical motion, but the proper adjustment of these SQ's is difficult since each SQ affects several independant coupling parameters. At CESR (Cornell Electron Storage Ring), an electronpositron colliding beam facility, a group of control functions has been created to allow for ease of coupling adjustments. Since CESR operates with a small natural vertical to horizontal emittance ratio, these control functions are important for limiting vertical enlargement which reduces the colliding beam luminosity. The basic theory for these controls is presented along with data to demonstrate their effectiveness.