Reformulation of the Action and Phase Jump Method to Obtain Magnetic Errors in the LHC IRs

One of the major problems when doing the commissioning of an accelerator is to identify and correct the linear components of magnetic errors. The Action and Phase Jump Technique is one of the available methods to perform this task. For this method to work, it is necessary to have one BPM measurement at the IR, the region where the magnetic error is evaluated. In some cases, this BPM measurement become the biggest source of uncertainty when the action and phase jump technique is used. In this paper, a new formulation based on this method is presented. This new formulation doesn't make any use of BPM measurements at the IR, thereby allowing more robust error estimations. Quadrupole errors in the LHC lattice are estimated with this new formulation, using both, simulated data and LHC experimental data. A comparison with the previous formulation is included. The results on simulated data show that the reformulation leads to a reduction in the uncertainty, while for the experimental case, the reduction is not so clear. Explanations for this behavior and possible remedies will also be discussed.