Single Side Coupler for input coupler of L
- Slides: 7
Single Side Coupler for input coupler of L 0 -1 Jan 27 -04 Agenda: C. Limborg Tolerances based on maximum emittance growth Review of Blue book analytical computation Zenghai Li Computations with S 3 P of angular kicks from single side input coupler Discussion of geometry define dual coupler geometry to be run by Zenghai Discussion on other studies gun dual feed, gun geometry, wakefields at first iris
Reminder: The 80% emittance is around 0. 9 mm. mrad Tolerance : No more than 1 -2% growth from Head-Tail & Wakefield effects Linear Head-Tail kick at entrance of L 0 -1 No Solenoid, No Wakefield With Solenoid, No Wakefield
First Linac Section Alignment: Wakefield effects Effects of Wakefields (ignoring ): Position : 150 m maximum Angular : 120 rad maximum ~2% increase level • 150 m maximum • Angular Misalignment At end beamline • Position Misalignement ~2% increase level • 120 rad
“PHASE TERM” “AMPLITUDE TERM” In phase with force Fz In quadrature with force Fz Centroid deflection if field on crest Strong Head-to-tail effect if field on crest Without cavity offset : With cavity offset : determined from microwave perturbation measurements , but conditions are not described in blue book
Without Cavity Offset Amplitude term dominant (around crest) With Cavity Offset = Amplitude term corrected but not phase term (which becomes dominant beyond +/- 20 degrees off crest)
Conclusions: Tolerance is 120 rad for a 10 ps bunch (due to wakefields along the structure) Without cavity offset , amplitude term is dominant with a 1. 2 mrad head-to-tail differential kick when cavity operated around crest With the cavity offset, only amplitude term is corrected. The amplitude of the headto-tail is now small enough around crest for a 10 ps bunch, however we want to be able to operate : at least +/- 40 degrees off-crest run ~20 ps bunch l This result is based on the 0. 1% factor measured many years ago (in conditions that we ignore in particular for the field gradient) For all those reasons a numerical computation was needed
