Controlling the crossing angle in the SSC

The colliding beams in the SSC (Superconducting Super Collider) must cross at a small angle, so that when the bunches pass each other away from the interaction point (IP), they are sufficiently separated to avoid disruptive beam beam forces. However, the crossing angle is so small that the adjacent quadrupoles must be common to both beams. Only after passing through four common quadrupoles on each side of the IP are the beams split by vertical dipoles into separate beamlines. In order to make the closed orbits of the two beams cross at a definite angle at the IP (within a range up to 150 μrad), a series of correction dipoles is placed in the insertions. If these dipoles are excited in such a way as to control the closed orbits alone, the dispersion will be mismatched, reaching values of up to 50 cm in the arcs. This mismatch is due to the closed-orbit displacements in the interaction region quadrupoles, causing them to act as bending magnets. Therefore, the closed orbit and dispersion must be matched simultaneously. Solutions to this problem are presented