Emittance growth, debunching and integrated luminosity in the LHC with a higher harmonic RF system

Beam dynamics with a double RF system has been considered in several references. Recently the idea of adding a secondary RF system has resurfaced due to heating effects in the beam screens of the LHC that are caused by the high particle densities in the bunch centres with a Gaussian longitudinal profile. It is well known that one can change the longitudinal bunch profile from a Gaussian profile like the pink curve in Figure 1 into a plateau shape like the blue curve in Figure 1 reducing the particle density in the bunch centres. Here we study the evolution of a bunch with such a longitudinal plateau like shape under the influence of IBS in a double RF system and how adding a secondary RF system in the LHC influences debunching losses and integrated luminosity. The simulations presented here are done with the particle tracking code that was used to study IBS effects in the 2010 ion fills. The results of our simulations indicate that installing a secondary higher harmonic RF system in the LHC would significantly reduce debunching losses for both protons and ions. We also observed a significant increase in integrated luminosity for ion beams.