• A. Valishev, G.F. Kuznetsov, V.D. Shiltsev, G. Stancari, X. Zhang
  Fermilab, Batavia
• A.L. Romanov
  BINP SB RAS, Novosibirsk

Tevatron electron lenses have been successfully used to mitigate bunch-to-bunch differences caused by long-range beam-beam interactions. For this purpose the electron beam with uniform transverse density distribution was used. Another planned application of the electron lens is the suppression of tune spread due to head-on beam-beam collisions. For this purpose, the transverse distribution of e-beam must be matched to that of the antiproton beam. In 2009, the gaussian profile electron gun was installed in one of the Tevatron electron lenses. We report on the first experiments with non-linear beam-beam compensation. Discussed topics include measurement and control of the betatron tune spread, importance of the beam alignment and stability, and effect of the electron lens on the proton and antiproton beam lifetime.

• A.L. Romanov, D.E. Berkaev, I. Koop, A.N. Kyrpotin, E. Perevedentsev, Yu. A. Rogovsky, P.Yu. Shatunov, D.B. Shwartz
  BINP SB RAS, Novosibirsk

Lattice correction based on orbit responses to dipole correctors and orbit correction based on orbit responses to field gradient variations in quads were successfully implemented on VEPP-2000 [*] for the flat-beam lattice. The round-beam lattice involves strong coupling of vertical and horizontal motions that require a full-coupling analysis in the orbit response technique. Programs used were modified to treat this task. Also, automation and speed enhancements were done that enable a routine use of this technique at VEPP-2000. New experimental results from VEPP-2000 are presented.

* Yu.M.Shatunov et al. Project of a New Electron-Positron Collider VEPP-2000, in: Proc. 7th European Particle Accelerator Conf. (EPAC 2000), Vienna, Austria, 439-441

• A.L. Romanov
  BINP SB RAS, Novosibirsk
• V.D. Shiltsev, A. Valishev
  Fermilab, Batavia

One of the possible ways to increase luminosity of hadron colliders is the compensation of beam-beam tune-spread with an electron lens (EL). At the same time, EL as an additional nonlinear element in the lattice can increase strength of nonlinear resonances so that its overall effect on the beam lifetime will be negative. Time-consuming numerical simulations are often used to study the effects of the EL. In this report we present a simplified model, which uses analytical formulae derived for certain electron beam profiles. Based on these equations the idealized shapes of the compressed tune spread can be rapidly calculated. Obtained footprints were benchmarked against several reference numerical simulations for the Tevatron in order to evaluate the selected configurations. One of the tested criteria was the so-called "folding" of the compensated footprint, which occurs when particles with different betatron amplitudes have the same tune shift. Also studied were the effects of imperfections, including misalignment of the electron and proton beams, and mismatch of their shapes.