The Superconducting Interaction Region Magnet Positioning System for the CESR Phase III Upgrade

Due to the extraordinary sensitivity of beams to misalignments of the superconducting high gradient interaction region magnets for the Phase III upgrade, a beam-based alignment and active positioning scheme has been designed and is being constructed. Using cams and kinematic mounting, the magnetic centers of the four quadrupole magnets will be independently positioned over a radial range of 1 mm with a resolution below 10 m. Beam measurements of the closed orbit will determine where to set the position. In principle realignment can be done while beams are stored. The positioning system must withstand considerable dynamic forces due to the interaction of the CLEO detector solenoid eld with the current in the dipole windings. It is located almost entirely within the CLEO detector and has a special transition from nonmagnetic to magnetic materials so as not to disturb the uniformity of the solenoid eld. It allows for retraction of the CLEO pole from the detector without interference. Work supported by the National Science Foundation On leave from BINP Background In 1998 the CLEO detector will complete another major upgrade to bring its performance up to B factory levels. Taking advantage of the opportunity presented by the re-design of most of the detector, new interaction region focussing and correcting elements were designed to allow the highest possible luminosity [1][2]. To ameliorate the e ects of the long range beam-beam interaction at crossing points near the interaction point, the new magnets are designed to be quite short with high gradients. Misalignment Tolerance Machine performance depends critically on the alignment of the superconducting interaction region quadrupoles. Sensitivity to vertical misalignments is enhanced due to the high gradient, high , and rapid phase advance through the interaction region. The result of misalignments is closed orbit errors, and loss of e ective physical aperture, and vertical dispersion, that will dilute vertical beam size. A 1 mm vertical misalignment of one of the vertically focussing quadrupoles, if uncorrected,