Dispersive crab crossing: An alternative crossing angle scheme

In order to maximize luminosity, many colliding beam storage ring designed are employing two rings, each carrying many bunches. Since the distance between bunches is small, beam-beam interactions other than the desired one at the interaction point occur unless the beams are quickly separated once outside of the high energy physics detector. One possible interaction region geometry is to have the beams collide at an angle. For luminosity degradation and beam stability reasons, this scheme has been augmented with transverse deflecting RF cavities which generate a correlation between horizontal position and time within the bunch, causing the beams to collide in a head-on fashion in their center of momentum inertial frame. The required transverse impedance, in addition to the development costs, of the transverse deflection cavities make this idea unattractive. In this paper an alternate scheme is proposed which makes use of the already existing accelerating RF cavities in the rings