Transverse Beam Tails and Aperture in the 1998 102/90 physics optics

In the 90/60 optics, horizontal tail measurements were compatible with gaussian beams up to the maximum stable emittance [1–3]. In other cases, including the 102/90 lattice tested at the end of 1997, a significant broadening of the tails was observed for large emittances. The 102/90 optics of this year uses a different sextupole scheme with reduced anharmonicity [4]. The tail measurements performed in the horizontal plane as function of damping partition are now compatible with nearly gaussian beams up to rather large emittances. The beam was stable (lifetime over 1 hour) for emittances up to about 150 nm which suggests that the dynamic aperture was at least 5:5 p 150 nm = 2:1 p m. Some dependence on the tails for high emittance as function of a trim in anharmonicity was observed.