Quadrupole Misalignments and Steering in Long Linacs

Abstract

We present a study of orbit jitter and emittance growth in a long linac caused by misalignment of quadrupoles. First, assuming a FODO lattice, we derive analytical formulae for the RMS deviation of the orbit and the emittance growth caused by random uncorrelated misalignments of all quadrupoles. We then consider an alignment algorithm based on minimization of BPM readings with a given BPM resolution and finite mover steps.

Control strategies for the final focus of future linear particle collider

“…The superscript ' þ' refers to the half part of the machine from which positrons arrive (e þ ), and the superscript ' À ' refers to the other half part of the machine from which electrons arrive (e À ). k þ and k À are the dimensionless parameters [20][21][22], taken as unity for simplicity. In this simple approach, the unmodelled dynamics and the technical noise are represented by additional random forces F þ and F À , applied on the girder.…”

Recent studies of dispersion matched steering for the ILC bunch compressor and main linac

“…This solution is "hyper-local," the beam is on axis at the cavities, and in the absence of higher multipole moments in these magnets the emittance is preserved. 3 This is not true if residual ¥ § ¦ is generated by misaligned cavities: one must then either precorrect or post-correct these kicks. Experience shows that linear optics remains adequate to determine the corrections.…”

“…The Low Emittance Transport (LET) problem has been the main focus of the ILC Accelerator Physics (APY) group. Basic steering methods aimed at preserving the r.m.s transverse emittance through a misaligned linac are by now well-developed [2,3,4]. Nevertheless, numerous details still need to be studied in order to meet the challenging goal of limiting the total vertical emittance dilution to a few nanometers in a linac that follows the earth's curvature [5].…”