Update on design of final TALs in the CLIC Drive Beam
R. Apsimon, J. Esberg
Optimisation techniques
• Local optimisation– Each cell optimised separately• Easy to tune• Poor energy acceptance
– Sextupoles don’t help a lot
• Global optimisation– Match all sextupoles and quadrupoles• Very good energy acceptance• Very weak sextupoles needed
• 20 sextupoles used– 4 sextupoles per arc cell– Maximum pole-tip field ~0.018 T
Locally optimised solution
Globally optimised solution
Dispersion energy dependence
R56 energy dependence
Emittance growth vs sextupole strength: PLACET tracking
Emittance growth vs sextupole strength: PLACET tracking
Emittance growth vs sextupole strength: PLACET tracking
Emittance growth vs sextupole strength: MADX-PTC tracking
HorizontalVertical
Longitudinal
PLACET tracking: longitudinal phase space: no synchrotron radiation
Emittance growth vs sextupole strength: PLACET tracking
HorizontalVertical
Longitudinal
PTC tracking emittance growth
Horizontal Vertical LongitudinalLocal optimisation 138 μm.Rad 2.2 μm.Rad 1.8 μm.GeV
Global optimisation 3.0 μm.Rad 2.0 μm.Rad -0.0012 μm.GeV
PLACET 0.67 s.f. 3.0 μm.Rad 0.85 μm.Rad 0.0 μm.GeV