Abstract
The phase 1 LHC interaction region (IR) upgrade aims at increasing the machine luminosity essentially by reducing the beam size at the interaction point. This requires a total redesign of the full IR. A large set of options has been proposed with conceptually different designs. This paper reports on a general approach for the compensation of the multipolar errors of the IR magnets in the design phase. The goal is to use the same correction approach for the different designs. The correction algorithm is based on the minimization of the differences between the IR transfer map with errors and the design IR transfer map. Its performance is tested using the dynamic aperture as a figure of merit. The relation between map coefficients and resonance terms is also given as a way to target particular resonances by selecting the right map coefficients. The dynamic aperture is studied versus magnet aperture using recently established relations between magnetic errors and magnet aperture.
Highlights
The design of the interaction region (IR) of a circular collider is one of the most critical issues for the machine performance
This is the case of the nominal Large Hadron Collider (LHC) ring, for which corrector magnets are located in the Q1, Q2, and Q3 quadrupoles, the latter including nonlinear corrector elements
It is worthwhile stressing that, even though the random errors are Gaussian distributed with zero mean and sigma given by the values in Table I rescaled to the appropriate value of the magnet aperture, the limited statistics used to draw the values for a single realization implies that in reality nonzero systematic errors are included in the simulations
Summary
The design of the interaction region (IR) of a circular collider is one of the most critical issues for the machine performance. It might be advisable to use a method that should take into account all possible sources of nonlinearities within the IR, such as the field quality of the separation dipoles and collective beam effects like the long-range beam-beam interactions For these reasons a more general correction algorithm should be envisaged, allowing a direct and straightforward application to any of the upgrade options or, more generally, to any section of an accelerator. The essential details about the nonlinear effects of the elements comprised in the section of the machine under consideration are retained in the nonlinear transfer map over one turn For this reason the one-turn transfer map was proposed as an early indicator of single-particle instability with a reasonable correlation with the dynamic aperture [10,11,12]. An illustrative first-order relation between achromatic map coefficients and resonance terms is given
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