Experiments on the beam-beam limit of bunched proton beams

A series of experiments on the beam-beam effect has been performed at the CERN Intersecting Storage Rings colliding a bunched test beam with a strong continuous beam. The beam-beam tune-shift was increased by various means to a maximum value of about 3.5*10/sup -3/ per intersection (for 8 crossings). When the beams were colliding well- centered, the blow-up of the effective height of the test beam was still very slow at this value. However, the blow-up rate increased sharply when the beams were off-centered at the intersections by approximately one standard deviation, and decreased again when the test beam was debunched.