Low emittance lattice for LEP

Abstract

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.

Algorithms to get a circulating beam

“…All the nonlinear elements (sextupoles) are in the arc cells. Low-emittance lattices have been envisaged for LEP as a mean to increase the luminosity at low current [1]. In one of these lattices, which was found to be difficult to operate, the arc FODO cells have an horizontal phase advance of 135 and a vertical phase advance of 60 .…”

“…This led us to an extensive analysis of the problems associated with this lattice in order to understand why it was so difficult. A report on this study is available [2] and some of the results concerning this lattice can be found at this conference [1]. One interesting outcome of this study was that it is not possible to correct both third order resonances and horizontal anharmonicity.…”