Search Results (4 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.

The inductance of the vacuum chamber of the Proton Storage Ring at Los Alamos National Laboratory was intentionally increased by the introduction of ferrite rings to counteract the longitudinal space-charge effect of the intense beam. The magnetic permeability of the ferrite could be adjusted by introducing current into solenoids wound around the ferrite. Results show that the minimum rf voltage necessary to stabilize the beam against e-p instability may be reduced over that previously measured. The injected bunch length was observed to be longer when the ferrite was heavily biased so that its effect was reduced.

Three-photon transitions induced by a dichromatic CO₂ laser operating on the P(10) and P(20) lines of the 961-cm^-1 band have been observed in a helium plasma. Laser photons interact resonantly with the 4³S and 4³P helium levels, resulting in new spectral lines which flank the 4713-Å, 2³P-4³S He line. The multiple photon transition rates are calculated from a numerical diagonalization of the interaction Hamiltonian and are shown to be in agreement with experimental results.

We have observed several different satellite transitions among HeI excited states. These satellites were induced by large, near-resonant, spatially inhomogeneous electric fields. A simple theory was proposed to explain the line shape of both the satellite and the allowed line based on the rotating-wave approximation. The plasma was contained in a dielectric waveguide and the laser mode pattern inside the guide was calculated and incorporated into the line-shape function. It was shown that excellent agreement between theory and experiment could be obtained over a wide range of experimental parameters. Agreement was very good in regimes where perturbation theory fails. We also observed that at high field strengths the Stark shift of the allowed component was less than the three-level theory predicted. We attribute this error to the fact that we have ignored all of the remaining levels of the HeI system.