C-AD Accelerator Physics Seminar

"The Large Hadron Collider (LHC) at CERN is a high-energy circular hadron collider designed to provide a maximum center of mass energy of 14 TeV and a peak luminosity of L = 1e34-1e35 cmâˆ'2 sâˆ'1 . The LHC 2012 RUN has shown strong coherent transverse instabilities developing at top energy (4TeV) which where causing large particle losses and in many cases also beam dumps. Coherent modes driven by the machine impedance are normally Landau damped by the use of octupole magnets which are regularly powered to ensure enough detuning with amplitude. Also beam-beam effects contribute to the detuning with amplitude and they could therefore increase or decrease the Landau damping range of frequencies depending on the spread obtained from the octupoles. The interplay between impedance, Landau octupoles and beam-beam interactions defines the stability limits of the accelerator that can be evaluated by the so called stability diagrams. In the tune spread analysis there is no information on possible mechanisms which modify the particle distribution, second fundamental ingredient of the Landau damping. Therefore it is fundamental to explore experimentally, through Beam Transfer Function measurements, and with simulations the effects of different distributions to the stability diagrams. The High Luminosity Large Hadron Collider (HL-LHC) projects aims to extend the LHC discovery potential and it is designed to operate with beams of much higher brightness resulting in much stronger beam-beam interactions. Landau damping properties for this scenario are also presented."