Search Results (3 total)

The beam-beam effects have been the dominating sources of beam loss and lifetime limitations in the Tevatron proton-antiproton collider [V. Shiltsev , Phys. Rev. ST Accel. Beams 8, 101001 (2005)]. Electron lenses were originally proposed for compensation of electromagnetic long-range and head-on beam-beam interactions of proton and antiproton beams [V. Shiltsev , Phys. Rev. ST Accel. Beams 2, 071001 (1999).]. Results of successful employment of two electron lenses built and installed in the Tevatron are reported by Shiltsev et al. [Phys. Rev. Lett. 99, 244801 (2007); New J. Phys. 10, 043042 (2008)] and by Zhang et al. [X.-L. Zhang , Phys. Rev. ST Accel. Beams 11, 051002 (2008)]. In this paper we present design features of the Tevatron electron lenses (TELs), discuss the generation of electron beams, describe different modes of operation, and outline the technical parameters of various subsystems.

We report the successful application of space-charge forces of a low-energy electron beam for improvement of particle lifetime determined by beam-beam interaction at a high-energy collider. In our experiments, an electron lens, a novel instrument developed for the beam-beam compensation, was set on a 980-GeV proton bunch at the Fermilab Tevatron proton-antiproton collider. The proton-bunch losses due to its interaction with the antiproton beam were reduced by a factor of 2 when the electron lens was operating. We describe the principle of electron lens operation and present experimental results.

In situ atomic force microscopy has been used to investigate step dynamics and surface evolution during the growth of single crystals of canavalin, a protein with a well known structure. Growth occurs by step flow on complex dislocation hillocks, and involves the formation and incorporation of small, mobile molecular clusters. Defects in the form of hollow channels are observed and persist over growth times of several days. The results are used to establish a physical picture of the growth mechanism, and estimate the values of the free energy of the step edge, α, and the kinetic coefficient, β.