HL-LHC,Hilumi,WP4,crab cavities,Accelerators
Crab cavities - How does it work ? (Image: CERN)



Suppression of a beam instability by bringing the beams into collision more quickly


beam,beam instability,beam-beam,WP2,HiLumi,HL-LHC
If the two counter-rotating beams are separated by a transverse offset between one and two rms beam sizes for too long a time, an impedance-induced beam instability can develop due to a loss of transverse Landau damping. (Image: CERN)


Mode-cility of cooupling instablliding beams suppressed by the hourglass effect


e-coupling instability,hourglas effect,colliding beams,WP2,HiLumi,Accelerators
The strong focalization of the beam at the interaction points leads to a deformation of the beam profile due to the hourglass effect, which suppresses the mode-coupling instability between beam-beam and impedance through Landau damping => Please note that the hourglass effect (seen on the right picture) has been amplified to see it more clearly BUT the stabilising effect was observed with the correct HL-LHC parameters. (Image: CERN)