VEPP-2000 Operation with Round Beams in the Energy Range from 1 to 2 GeV

The idea of round-beam collision was proposed more than twenty years ago for the Novosibirsk Phi-factory design [V.V. Danilov et al., in Proc of the EPAC 1996, Sitges, vol. 2, p. 1149]. It requires equal emittances, equal small fractional tunes, equal beta functions at the IP, no betatron coupling in the collider arcs. Such an approach results in conservation of the longitudinal component of angular momentum. As a consequence, it yields an enhancement of dynamical stability, even with nonlinear effects from the beam-beam force taken into account. The Round Beam Concept (RBC) was realized at the electron-positron collider VEPP-2000 and successfully tested at the energy of 510 MeV [D.E. Berkaev et al., in Proc. of the EPAC 2008, Genoa, p. 956]. Despite the low energy, a high single-bunch luminosity of 1031 cm-2s-1 was achieved together with a maximum tune shift as high as 0.1. At present the work is in progress to increase the energy of the collider to explore the range between 500 MeV and 1 GeV in collision.