Kicker specifications for Damping Rings CLIC Beam dynamics meeting Kicker specifications for Damping Rings F. Antoniou, M. Barnes, J. Borbourgh, T. Fowler, Y. Papaphilippou February 4th, 2009

Design optimisation for CDR (2010) M. Korostelev, PhD thesis, 2006 Outline CLIC damping rings (DR) layout and parameters DR injection and extraction optics DR septa and kicker parameters Pre-damping rings (PDR) parameters Kicker considerations for PDR Summary CLIC parameter note 2005 CLIC parameter note 2008 Design optimisation for CDR (2010) M. Korostelev, PhD thesis, 2006 04/02/09 YP

CLIC damping ring layout 04/02/09 M. Korostelev, PhD thesis, EPFL 2006

DR bunch structure and timing CLIC DR timing parameters Old (2005) New (2008) Repetition rate [Hz] 150 50 Number of bunches 110 312 Number of trains 4 1 Bunch spacing [ns] 0.533 0.500 Revolution Time [μs] 1.2 >1.2 Machine pulse [ms] 6.67 20 H/V/L damping times [ms] 2.8/2.8/1.4 1.5/1.5/0.76 Reduction of repetition rate from 150 to 50Hz leaves enough time for the emittances to reach their equilibrium Bunch spacing increased almost to same level as for the interleaved train scheme Interleaved train scheme abandoned Extraction kicker rise time relaxed Injection and extraction process simplified 312 bunches with 0.5ns spacing, fill 13% of the rings 4

Kicker and septa optics The angular deflection at the septum is The angular deflection of the kicker is defined as Large beta functions and π/2 phase advance are necessary for minimizing the kicks and small position at the septa The injected beam position at the septum should be Typically, injection and extraction region is dispersion free For lepton rings The thickness of the septum cannot be smaller than 3mm The input emittance can reduce the kick requirements

DR injection/extraction optics Injection and extraction system placed at the same area, upstream of the super-conducting wigglers Kickers placed at maximum beta functions for minimum deflection angle Septa and kickers share the same cell Additional cells to be added in order to increase available space for elements and protection system Phase advance between injection (extraction) septa and kickers of around π/2 M. Korostelev, PhD thesis, EPFL 2006 04/02/09 YP

DR Septa parameters DR septa parameters SEP-1 SEP-2 Effective length [m] 0.4 0.5 Bending angle [mrad] 13 42 Field integral [T.m] 0.11 0.34 Blade thickness [mm] 5 Same parameters for injection/extraction elements due to optics mirror symmetry Septum parameters are scaled from NLC damping rings Two DC modules with blade thickness of 5 and 13mm Effective length can be increased to 2m if additional cells are added Larger septa blade thicknesses and smaller peak field 04/02/09 YP

Kicker stability Kicker jitter is translated in a beam jitter in the IP. Typically a tolerance of σjit ≤0.1σx is needed Translated in a relative deflection stability requirement as For higher positions at the septum (larger injected emittances or lower beta functions) the stability tolerance becomes tighter The tolerance remains typically to the order of 10-4 A similar tolerance can be established for the kicker roll

DR Kicker parameters Rise and fall time significantly increased Effective length can be increased to 2m Smaller peak field Kicker stability refers to field uniformity and pulse-to-pulse stability Tolerance of 0.1σx beam centroid jitter DR kicker parameters Old New Rise and fall time [ns] 25 1000 Flat top [ns] 142 ~160 Repetition rate [Hz] 150 50 Effective length [m] 0.4 0.4-2 Aperture [mm] 20 Kick [mrad] 2.45 3 Field [Gauss] 500 <610 Kicker stability 1.4x10-3 @ inj 1.5x10-4 @ ext Second kicker in transfer line @ phase advance of π for jitter compensation (as in NLC/ATF) Achieved 2.8x10-4 at ATF for shorter rise/fall times and flat top (all of 60ns) Third kicker, delay line and RF deflector are removed Contribution to beam impedance should be addressed (budget of a few MΩ/m in transverse and a few Ω in longitudinal) –external circuit may be important

PDR working parameters F. Antoniou Parameter [unit] Value beam energy [GeV] circumference [m] bunch population [E+09] bunch spacing [ns] bunches per train rms bunch length [mm] rms momentum spread [%] hor. Emittance w/o IBS [nm] no. of arc bends arc-dipole field [T] length of arc dipole [m] number of wigglers wiggler field [T] length of wiggler [m] wiggler period [cm] mom. compaction [10-5] RF frequency [GHz] energy loss/turn [MeV] RF voltage [MV] h/v/l damping times [ms] Revolution time [ns] Repetition rate [Hz] 2.424 260.1 4.5 0.5 312 0.2 0.3 13000 30 1.7 1 20 2 4.7 1.54 16 2.7/2.7/1.35 870 50 312 bunches with 0.5ns spacing, fill 18% of the pre-damping rings Designed for large momentum acceptance and fast damping Large RF voltage, small momentum compaction factor Injected Parameters e- e+ Bunch population [109] 4.4 6.4 Bunch length [mm] 1 5 Energy Spread [%] 0.1 2.7 Hor.,Ver Norm. emittance [nm] 100 x 103 9.3 x 106 PDR Extracted specs Value Bunch length [mm] 10 Energy Spread [%] 0.5 Hor. Norm. emittance [nm] 63000 Ver. Norm. emittance [nm] 1500 10

PDR injection/extraction optics Kickers Septa PDR kicker parameters Value Rise and fall time [ns] 700 Flat top [ns] ~160 Repetition rate [Hz] 50 Effective length [m] ~2 Aperture [mm] ~55 Kick [mrad] ~3 Field [Gauss] ~150 Kicker stability ~3x10-3 @ inj ~7x10-4 @ ext Injection and extraction system placed at symmetric points of the matching area, upstream of the super-conducting wigglers Kickers placed at maximum beta functions with available space of around 2m Phase advance between septa and kickers of around π/2 Kicker stability at extraction quite challenging for positrons 04/02/09 YP

Summary PDR and DR injection and extraction systems Extraction process simplified (1 train) Main issues the kicker stability for both DR and PDR Design should target for low impedance 04/02/09 YP