Abstract
Optics correction is an important issue in the KEKB B-factory. Especially, the correction of beta functions is performed so as to reach near half-integer resonance of the horizontal betatron tune as closely as possible. Consequently, the luminosity can be improved during experiments of the B-meson in ${e}^{+}{e}^{\ensuremath{-}}$ collisions. Therefore, we have developed a correction method of the beta function not only at the designed beam energy, but also at an energy deviated from the nominal value. We present the procedures used to measure the behavior of the beta function, which depends on the momentum deviation, and the results compared with the model optics in the KEKB rings.
Highlights
The KEKB B-factory is an energy-asymmetric doublering collider consisting of an 8 GeV high-energy electron ring (HER) and a 3.5 GeV low-energy positron ring (LER)[1]
In order to achieve a very high luminosity for mass production of B-mesons, KEKB was designed as a lowemittance lattice with a low beta interaction point
To obtain a large dynamic aperture for a long beam lifetime and good injection efficiency, a 2:5 arc cell structure with noninterleaved sextupoles for chromaticity correction was introduced into the KEKB lattice design
Summary
The KEKB B-factory is an energy-asymmetric doublering collider consisting of an 8 GeV high-energy electron ring (HER) and a 3.5 GeV low-energy positron ring (LER). We conduct an 8-hour shutdown for maintenance every two weeks, and perform optics corrections before starting a physics run The optics corrections, such as x-y coupling, dispersions, and beta functions, usually take place at the designed beam energy (on-momentum) [2,3]. We sometimes found that the beam lifetime was shorter in the real machine than we had expected, we optimized the strength of the sextupole magnets to make the dynamic aperture large enough in the model optics. This implies that the momentum dependence of the real optics is different from the model. We describe in detail the measurement method and correction techniques for both the on-momentum and off-momentum optics
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