Beam-beam performance as a function of βv* at CESR

The beam-beam tune shift parameter for beams colliding at a single interaction point was measured for several values of the vertical β minimum. The authors report linear tune shift parameter as a function of current for 1cm < Bv* < 10 cm. Electrostatic separators are used to horizontally separate beams at all but one crossing point. The quadrupole lattice is characterized by zero dispersion at the interaction point, horizontal βh* = 1m, and horizontal and vertical tunes of Qh ∼ 8.61 and Qv ∼ 9.64 respectively. The two sets of measurements correspond to operation before and after the single interaction point conversion of CESR. The beam energy is 5.29 GeV. They measured a saturated tune shift parameter (ξv = 2ereLβv*/Iγ) of .021, .032, .045 (±.003) for βv* = 2, 5, and 10 cm respectively (σl = 1.8 cm). After removal of the north interaction region they measure ξv = .011, .026, .0275 for βv* = 1,1.55, and 1.8 cm respectively. (σl = 1.97cm)