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abstract:
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Quasi-isochronous rings (QIRs) have been considered for electron-positron colliders to obtain large luminosity with a small average beam current. This approach offers the advantage of minimizing vacuum and RF system problems, and multibunch instability effects. In this paper, we review the basic physics of a QIR, the condition for stable single-particle motion, and the dynamic aperture. The collider we discuss is a Phi( Phi ) factory with a single ring and beam energy of 510 MeV. This ring uses a very strong focusing of the electron and positron beams at the interaction point, i.e., a beta function in the millimeter range; and a momentum compaction variable over a large range, of -0.008 to +0.005, to control the bunch length. It has a luminosity of 10(33) cm(-2) s(-1), average current smaller than 1 A, and a perimeter of 32.7 meter. Its transverse chromaticities and second-order momentum compaction are set to zero by utilizing three families of the sextupoles. The QIR dynamic aperture is calculated using a new computer code, KRAKPOT, written explicitly for small rings.
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