Investigation into Possible Sources of Tune Jitter in the LHC

The beta function around an accelerator determines the shape and size of the beam. The LHC has demonstrated a beta function control to the 1% level. However as its optics is pushed for increased performance, the measurement techniques are challenged by small perturbations. These measurements can be perturbed by tune jitters that find their origin in power supply ripples and the feed-down effect that stems from the machine’s non-linearities and momentum changes. By extracting machine and orbit data and using accurate models, the effect of these perturbations in recent LHC optics measurements can be evaluated. The factors that contribute to these orbit jitters can also be investigated in order to search for methods to control them. It was found that the feed-down effect in sextupoles caused from orbit jitters is predicted to have a large effect on the tune shift. However the expected results are much more drastic than what is observed so other sources must be affecting the tune. One of the sources of orbit perturbation identified in this thesis is an unwanted activation of the orbit feedback system occurring simultaneously to an AC dipole kick data, potentially generating imprecise corrections.