Low emittance lattices for LEP

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In order to obtain the largest luminosity with LEP2, it is attractive to make the beam emittance as small as possible because the beam-beam effect is not a limitation at the energy of E 90 GeV for the obtained bunch currents. This can be achieved with a high tune lattice. Two possible candidates are lattices with a horizontal phase advance of 108 0 or 135 0 per cell. Both have a vertical phase advance of 60 0 . These lattices were developed during 1994 and the results are presented. Tests to reach high intensity for the 108 0 lattice were performed and the bunch current achieved is compared with expectations. For this lattice the detuning v.s intensity and several optics parameters were measured as well.

Section: High Tune Latticesmentioning

confidence: 99%

Low emittance lattice for LEP

Alexahia

Brandt²,

Cornelis³

et al.

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Algorithms to get a circulating beam

Verdier

Richard

Two algorithms based of trajectory fitting have been used to obtain rapidly a circulating beam in LEP with strong focusing lattices.A new algorithm called "orbit closure" uses the beam positions measured at the first and the second turn. From their difference, it computes two corrector strengths per plane such that the second turn passes at the same place as the first turn at about ten BPM locations. This produces a closed orbit amplitude with an r.m.s. value close to that of the first turn trajectory.A new 'first turn threader' has been tried. It detects places where an oscillation with an r.m.s. amplitude larger than a specified value starts, and computes two corrector strengths to cancel it. By iterating this process, it should be possible to correct by steps the first turn trajectory so that its r.m.s. amplitude is below a specified value.The orbit closure has been applied with success to a very low emittance lattice (135 in the horizontal plane) in LEP.

Nonlinear chromaticity correction with sextupole families [particle accelerator]

Verdier