HL-LHC Wakefield Simulations: 7TeV STABLE conditions

PyHEADTAIL macro-particle simulations (http://github.com/PyCOMPLETE/PyHEADTAIL) of single bunch stability in the High Luminosity LHC at top energy lead to the present data. Head-tail instabilities driven by the machine impedance can seriously degrade the beam quality and even lead to machine protection issues.

Here we simulate with smooth approximation optics and recent versions of the complete HL-LHC impedance model at flat-top conditions at an energy of 7TeV. The influence of the different wake terms (dipolar, dipolar + cross-terms, dipolar + cross-terms + quadrupolar), the longitudinal distribution (thermal and q=3/5-Gaussian) and the different impedance scenarios (without MoGr coated TCTs yet) are compared. For each case, we scan the linear chromaticity. The transverse feedback is taken into account with an ideal damper model at 50 turns. Longitudinal non-linear synchrotron motion is employed. Lattice non-linearities (such as detuning with amplitude from octupoles) are not considered.

Here we consider STABLE conditions, i.e. the impedance model for fully squeezed beta*=15cm at IP1 and IP5.