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

Transverse RF injection extraction kicker

David Rubin Cornell University ILC Damping Rings Workshop 26-September-2006 Separation with transverse RF Timing t = nT RF (t = bunch spacing) N = T rev /T RF t = (m+1/2)T TR (opposite kick for consecutive bunches) T rev /T TR = (M+1/2) (opposite kick for the same bunch on consecutive turns) T TR = [n/(m+1/2)] T RF n=2, m=1 => T TR =(4/3)T RF f RF =650MHz f TR =487.5MHz N=14402 M=10801

David Rubin Cornell University ILC Damping Rings Workshop 26-September-2006

David Rubin Cornell University ILC Damping Rings Workshop 26-September-2006 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 26-September-2006 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 26-September-2006 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) For installation 2006 (1.4MV -> 1.5MV for super B-factory) At 5GeV beam energy  = 0.3mrad/cell

David Rubin Cornell University ILC Damping Rings Workshop 26-September-2006 KEK-B Crab Cavity K.Oide (19 Jan 2006 ) 500MHz

David Rubin Cornell University ILC Damping Rings Workshop 26-September-2006 K.Oide (19 Jan 2006)

David Rubin Cornell University ILC Damping Rings Workshop 26-September-2006 Q vs E

David Rubin Cornell University ILC Damping Rings Workshop 26-September-2006 K.Oide (19 Jan 2006) - beam test 2006

David Rubin Cornell University ILC Damping Rings Workshop 26-September-2006 Summary  4-6 Superconducting RF kickers double bunch spacing  SC Cavity beam tests soon?  Bypass lines must have identical path lengths  RF stability for closing the bump TR >>  L -> uniform kick over length of bunch � Full wave bypass for symmetry?

1)If the filling time (  F ) of the deflectors is less than  T DR it is possible to inject or extract the bunches without any gap in the DR filling pattern. 2)  should be   * depending on the ring optics and septum position. Considering a single RF frequency    /  MAX =1-cos(2  /F) 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. DR INJECTION/EXTRACTION SCHEMES F. Marcellini,D.Alesini,S.Guiducci,P.Raimondi 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.

EXAMPLE OF A TW RF DEFLECTOR DESIGN F. Marcellini, (see TESLA Report ) /2/3 a [mm]41.8 b [mm] D [mm] mode /2 (f≈1.3GHz) HFSSMAFIA Series impedance Quality factor Shunt impedance Attenuation Group velocity0.045 * c Single cell dimensions for 2 possible operating mode considered Deflector characterization by simulations ns MAX   g F v L mradGeV   can be obtained if a 1.5 m long deflector is fed with 9 MW from the RF source The filling time results: