Global-Beta Measurement and Correction at the KEKB Rings

The global-beta correction is one of the optics corrections such as dispersion and xy-coupling corrections to realize a model lattice [1]. In the KEKB B-Factory, it is performed to regularize the ring optics for achieving high luminosity. The global-beta function is measured by re-constructing responses of orbits generated by 6 different steering magnets per plane. The correction of the beta function and the phase advance is performed by using the fudge factors of power supplies of quadrupole magnets. This correction scheme has been successfully. In the typical case, the rms of the beta function beat and the betatron tune difference are corrected within 5% and 0.0005, respectively. In the luminosity run, we can operate the low energy ring(LER) with the horizontal betatron tune very close to half-integer(45.5050). In this paper, we will report in detail the measurement and correction techniques and its performance in the KEKB operation.