Testing the accuracy of the LHC impedance model

Published on 5 May 2016

The most important limitations to achieve high luminosities in an accelerator are transverse collective instabilities. These instabilities have been regularly observed during the LHC Run I. In order to study the single-bunch instabilities, Daria Astapovich used the tracking code HEADTAIL and the numerical code NHTVS, using the LHC impedance model. To be able to do predictions for the future operation in the LHC, it is necessary to verify the accuracy of the impedance model. One of the options to do it is to compare the octupole current threshold from simulations and the octupole current in the measurements.

In a CERN Internal Notes article Daria presents the analysis of one of the single-bunch instabilities observed in 2012 and a comparison with the HEADTAIL and NHTVS codes.

Instabilities observed on 2^nd April 2012 during the collimator's "loss maps"

 

 

Comparison between the octupole current during the measurements and the threshold from HEADTAIL and NHTVS.