Beam Dynamics of the Interaction Region Solenoid in a Linear Collider Due to a Crossing Angle∗

Future linear colliders may require a nonzero crossing angle between the two beams at the interaction point. This requirement in turn implies that the beams will pass through the strong interaction region (IR) solenoid with an angle, and thus that the component of the solenoidal field perpendicular to the beam trajectory is nonzero. The interaction of the beam and the solenoidal field in the presence of a crossing angle will cause optical effects not observed for beams passing through the solenoid on-axis; these effects include dispersion, deflection of the beam, and synchrotron radiation effects. For a purely solenoidal field, the optical effects which are relevant to luminosity exactly cancel at the IP when the influence of the solenoid’s fringe field is taken into account. Beam size growth due to synchrotron radiation in the solenoid is proportional to the fifth power of the product of the solenoidal field, the length of the solenoid, and the crossing angle. Examples based on proposed linear collider detector solenoid configurations are presented. Published in Physical Review Special Topics – Accelerators and Beams ∗Work supported by the Department of Energy, Contract DE-AC03-76SF00515. Revised August 2003 Beam Dynamics of the Interaction Region Solenoid in a Linear Collider Due to a Crossing Angle P. Tenenbaum,∗ J. Irwin, and T. O. Raubenheimer Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309 USA Future linear colliders may require a nonzero crossing angle between the two beams at the interaction point. This requirement in turn implies that the beams will pass through the strong interaction region (IR) solenoid with an angle, and thus that the component of the solenoidal field perpendicular to the beam trajectory is nonzero. The interaction of the beam and the solenoidal field in the presence of a crossing angle will cause optical effects not observed for beams passing through the solenoid on-axis; these effects include dispersion, deflection of the beam, and synchrotron radiation effects. For a purely solenoidal field, the optical effects which are relevant to luminosity exactly cancel at the IP when the influence of the solenoid’s fringe field is taken into account. Beam size growth due to synchrotron radiation in the solenoid is proportional to the fifth power of the product of the solenoidal field, the length of the solenoid, and the crossing angle. Examples based on proposed linear collider detector solenoid configurations are presented.