NASA Scientific and Technical Aerospace Reports

20060002065 Fermi National Accelerator Lab., Batavia, IL, USA, European Organization for Nuclear Research, Geneva,
Switzerland, European Synchrotron Radiation Facility, Grenoble, France
Experiments on LHC Long-Range Beam-Beam Compensation and Crossing Schemes at the CERN SPS in 2004
Zimmermann, F.; Koutchouk, J. P.; Roncarolo, F.; Wenninger, J.; Sen, T.; January 2005; 8 pp.; In English
Report No.(s): DE2005-15017079; No Copyright; Avail.: National Technical Information Service (NTIS)
Experiments with two prototype long-range beam-beam compensators (current-carrying wires) during the 2004 CERN
SPS run explored the efficiency of a proposed long-range beam-beam compensation for the LHC. In addition, the SPS
compensators were also used to ‘simulate’ the effect of different planes of crossing at two LHC interaction points. We present
the experimental results and compare them with computer simulations.
NTIS
Beam Interactions; Crossings; Hadrons; Wire
20060002066 Fermi National Accelerator Lab., Batavia, IL, USA
Betatron Tune Spread Generation and Differential Chromaticity Control by Octupole Families at Tevatron
Ivanov, P. M.; Alexahin, Y.; Annala, J.; Lebedev, V. A.; January 2005; 8 pp.; In English
Report No.(s): DE2005-15017080; FERMILAB-CONF-05-148-AD; No Copyright; Avail.: National Technical Information
Service (NTIS)
Existing Tevatron octupoles have been rearranged into four functional families. Two of these families generate betatron
tune spreads in the vertical and horizontal planes whereas the other two control the differential chromaticity between the
proton and antiproton helices. The calculated effect on the tunes and chromaticity is compared with direct measurements.
Analytical formulas for betatron tune distribution functions are presented.
NTIS
Betatrons; Color; Particle Accelerators
20060002067 Fermi National Accelerator Lab., Batavia, IL, USA
Landau Damping of the Weak Head-Tail Instability at Tevatron
Ivanov, P. M.; Alexahin, Y.; Annala, J.; Lebedev, V. A.; Shiltsev, V.; January 2005; 8 pp.; In English
Report No.(s): DE2005-15017081; FERMILAB-CONF-05-149-AD; No Copyright; Avail.: National Technical Information
Service (NTIS)
Two-step improvement of transverse beam stability has been done at the Tevatron. First, shielding of the laminated
Lambertson magnets significantly reduced the transverse impedance. Second, Landau damping induced by the octupoles
allowed machine operation with zero chromaticity at injection. That has resulted in a dynamic aperture increase and weakening
of long-range beam-beam effects due to smaller chromatic tune modulation. At collisions, the coherent tunes and incoherent
tune continuum are separated due to the head-on collisions. That leads to Landau damping loss at small chromaticities.
Predictions of the analytical Landau damping model are compared with experiments.
NTIS
Landau Damping; Particle Accelerators
20060002068 Fermi National Accelerator Lab., Batavia, IL, USA
Theory and Reality of Beam-Beam Effects at Hadron Colliders
Alexanhin, Y.; January 2005; 10 pp.; In English
Report No.(s): DE2005-15017082; FERMILAB-CONF-05-176-AD; No Copyright; Avail.: National Technical Information
Service (NTIS)
The beam-beam phenomena in hadron colliders are just as rich as in e(sup +)e(sup -) machines: orbit and focusing
perturbations, excitation of nonlinear resonances, coherent tuneshifts. Moreover, the absence of radiation damping and long
duration of a store permit even high-order (and correspondingly weak) resonances to manifest themselves presenting a major
challenge for both theoretical analysis and machine operation. The recent progress in understanding of and coping with the
beam-beam effects at hadron colliders, primarily at the Tevatron, is discussed.
NTIS
Beam Interactions; Hadrons
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