Feasibility study for compensating the anharmonicities in LEP with additional octupoles

Operating LEP with the 108/90 optics at the end of the 1996 run indicated a limitation of the dynamic aperture due to a combined effect of non-linear resonances and anharmonicities. This note analyses the feasibility of improving the dynamic aperture in LEP by compensating the anharmonicities with additional octupoles. The presented scheme reduces the anharmonicities in LEP by more than 60%, resulting in a sufficiently large dynamic aperture. The scheme places octupoles in all odd IP's with 4 octupoles powered in two pairs per IP.