Microwave Quadrupoles for Beam Break-up Supression In the NLC Main Linac

This is a preliminary study of the effect of using microwave quads (MQs) instead of rf phase shifting to induce BNS damping in the main linac of the NLC collider. We consider MQs running at X-band, and find that the total length of MQs needed for the NLC is 6% of the total length of the accelerating structures. We show through simulations that, by using MQs instead of phase shifting for BNS damping, the quad alignment tolerances can be relaxed but at the expense of shifting the tight tolerances to the MQs; this can be advantageous if the MQs can be better aligned than the quads. For the design final energy spread in the NLC of 0.3%, the quad tolerances are loosened by a factor of 2-3 when using MQs. These tolerances can be loosened by an additional factor of 1.5, but at the cost of 1.7% in energy overhead. SLAC-PUB-9004 LCC-0073 September, 2001 MICROWAVE QUADRUPOLES FOR BEAM BREAK-UP SUPPRESSION IN THE NLC MAIN LINAC K.L.F. Bane and G. Stupakov Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309