The VEPP-4M electron-positron collider

The VEPP-4 electron-positron collider with the maximal beam energy of 6 GeV has been commissioned in 1979. In 1979-1985, a range of high-energy physics experiments with the MD-1 detector has been performed, including ypsilon-meson study and two-photon physics. To increase the collider luminosity, a modernization has been done in 1986-1994.

Principal modifications of the VEPP-4M against the VEPP-4:

• ring symmetrization about an axis passing through the centers of the experimental and the technical straight sections;
• inserts with increased aperture and electrostatic separators installed in the middle of semi-rings to provide 2x2-bunch operation and SR output for users;
• modification of the experimental straight section magnet lattice for operation with the detector KEDR longitudinal magnetic field;
• development of the distributed spectrometer for the system of scattered electrons registration;
• the ROKK-1M facility for gamma-quantum beam production by Compton back-scattering.

The VEPP-4M layout in the PDF format is  here.

Main parameters

At present, the main high-energy physics experiment at the VEPP-4M is precise measurement of the tau-lepton mass at its production threshold. Experiments for accuracy improvement of the measured masses of the psi(2s) and psi(3770) mesons are also continued (the beam energy range is 1840-1900 MeV). In the low energy range (1.5-3.0 GeV), peak luminosity of the collider is 2·10³⁰cm^-2s^-1. Average rate of KEDR data collection is about 300 nb^-1 per week.

Design luminosity at the 6 GeV energy is 4·10³¹cm^-2s^-1 with natural beam size; 7·10³¹см^-2с^-1 with superconducting damping wigglers; 10³²см^-2с^-1 with additional superconducting RF cavity to decrease bunch length and beta-fuction at the interaction point.