Self-compensation of the LEP distributed skew gradient

In 1991, the tunes of the LEP were changed from 71/77 to 70/76 with a resulting performance improvement; the required tune difference caused, however, the vertical tune to become a multiple of the machine superperiod, making the machine rather sensitive to imperfections. An alternative solution is described which consists in departing from the equal betatron phase advances in the cells to make possible a cancellation of the betatron coupling over each arc. The tunes become free parameters that are optimized for highest performance and polarization at the Z0 peak (78/78). (author) 4 refs.; 5 figs.; 2 tabs