Bunch Separation with RF Deflectors D. Rubin,R.Helms Cornell University

In the event that an injection/extraction kicker with pulse width of 6ns is not practical, then we can increase effective bunch spacing with RF separation injection extraction Transverse RF kicker

ILC Damping Rings Workshop extraction kicker Transverse RF kicker injection David Rubin Cornell University ILC Damping Rings Workshop 5-March-2007

ILC Damping Rings Workshop Separation with transverse RF Timing t = nTRF (t = bunch spacing) N = Trev/TRF t = (m+1/2)TTR (opposite kick for consecutive bunches) Trev/TTR = (M+1/2) (opposite kick for the same bunch on consecutive turns) TTR= [n/(m+1/2)] TRF n=2, m=1 => TTR=(4/3)TRF fRF=650MHz fTR=487.5MHz N=14402 M=10801 David Rubin Cornell University ILC Damping Rings Workshop 5-March-2007

ILC Damping Rings Workshop David Rubin Cornell University ILC Damping Rings Workshop 5-March-2007

ILC Damping Rings Workshop More Timing Train spacing corresponds to bunch spacing in linac (337ns) - Extract damped bunches from the tail of each train (For extraction there are 2t ~6ns for kicker rise time and > 49ns fall time - Inject undamped bunch at head of train (For injected bunch there are > 49ns for kicker rise time and 2t fall time. Bunches near the head of the train are more tolerant of kicker tail) David Rubin Cornell University ILC Damping Rings Workshop 5-March-2007

ILC Damping Rings Workshop Transverse Kick A = 9e-6 m-rad =>Beam size (=25m) = 15mm In order to clear septum > 15mm  Suppose each cavity kick =  0.3mrad Then 3 cavities =>  0.9mrad =>  = 22.5mm David Rubin Cornell University ILC Damping Rings Workshop 5-March-2007

ILC Damping Rings Workshop Deflecting RF KEK B crab cavity (Akai 24-dec-2003) Achieve >21MV/m peak surface field in full scale test => 1.4MV transverse/cell Suitable for 2A LER beam (23kW HOM power) Installed in HER and LER January 2007 Testing began a few weeks ago! (1.4MV -> 1.5MV for super B-factory) At 5GeV beam energy  = 0.3mrad/cell David Rubin Cornell University ILC Damping Rings Workshop 5-March-2007

ILC Damping Rings Workshop KEK-B Crab Cavity K.Oide (19 Jan 2006) 500MHz David Rubin Cornell University ILC Damping Rings Workshop 5-March-2007

ILC Damping Rings Workshop K.Oide (19 Jan 2006) David Rubin Cornell University ILC Damping Rings Workshop 5-March-2007

ILC Damping Rings Workshop Q vs E David Rubin Cornell University ILC Damping Rings Workshop 5-March-2007

ILC Damping Rings Workshop Beam tests began February 2007 David Rubin Cornell University ILC Damping Rings Workshop 5-March-2007

ILC Damping Rings Workshop Summary 4-6 Superconducting RF kickers double bunch spacing Beam tests of crab cavity started in February 2007 Bypass lines must have identical path lengths RF stability for closing the bump TR >> L -> uniform kick over length of bunch Dynamic aperture? Full wave bypass for symmetry? Next step: Implement crabbing RF and separation transfer line in base line lattice and test stability and dynamic aperture with tracking simulation David Rubin Cornell University ILC Damping Rings Workshop 5-March-2007

DR INJECTION/EXTRACTION SCHEMES F. Marcellini,D.Alesini,S.Guiducci,P.Raimondi The length of the DR is properly chosen so that, after one turn, the bunches are 2pi /F (F is the compression factor) out of phase with respect to the RF voltage of the 2nd RF deflector. The residual transverse kick is completely compensated by the 1st RF deflector because the betatron phase advance between the two devices is 180 °. In this way the bunches are progressively recombined. By using the combination of 2 or more frequencies it is possible to increase the ratio /MAX.This means that the needed maximum deflection can be reduced or that the compression factor can be increased. Even if TW RF deflectors are fast devices, a gap in the DR filling pattern has to be introduced to take into account their finite filling time. Minimizing this filling time is important to have the shorter gap possible. If the filling time (F) of the deflectors is less than TDR it is possible to inject or extract the bunches without any gap in the DR filling pattern.  should be  * depending on the ring optics and septum position. Considering a single RF frequency   /MAX=1-cos(2/F)

EXAMPLE OF A TW RF DEFLECTOR DESIGN F. Marcellini, (see TESLA Report 2003-27) Single cell dimensions for 2 possible operating mode considered p/2 p/3 a [mm] 41.8 b [mm] 133 133.5 D [mm] 58.06 38.70 Deflector characterization by simulations mode p/2 (f≈1.3GHz) HFSS MAFIA Series impedance 0.578 0.552 Quality factor 17000 17300 Shunt 16.07 15.95 Attenuation 0.0180 0.0174 Group velocity 0.045*c ns 100 7 . 5 @ MAX » = g F v L mrad GeV t f can be obtained if a 1.5 m long deflector is fed with 9 MW from the RF source The filling time results: