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WG5: HOM Couplers and Beam Line Absorbers

WG5: HOM Couplers and Beam Line Absorbers. T. Higo, KEK M. Liepe, Cornell S. Noguchi, KEK J. Sekutowicz, DESY. General Requirements. Beam spectrum: 3.2 nC, σ z = 0.300 mm, Δ f i,i+1 = 2.967 MHz. 1. 0. f [GHz]. 500. Modes below cut-off, (R/Q) up to 160 Ω /cavity.

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WG5: HOM Couplers and Beam Line Absorbers

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  1. WG5: HOM Couplers and Beam Line Absorbers T. Higo, KEK M. Liepe, Cornell S. Noguchi, KEK J. Sekutowicz, DESY “II-nd ILC Workshop” Snowmass, August 13-27, 2005

  2. General Requirements Beam spectrum: 3.2 nC, σz = 0.300 mm, Δfi,i+1 = 2.967 MHz 1 0 f [GHz] 500 Modes below cut-off, (R/Q) up to 160 Ω/cavity Propagating modes, (R/Q) up to ~5 Ω/cavity ~17 W ~7 W 100 fo 101 102 103 f [GHz] HOM couplers Beam line absorbers “II-nd ILC Workshop” Snowmass, August 13-27, 2005

  3. BCD: HOM couplers and Beam Line Absorbers 2xHOM couplers/cavity (HOMs below cut-off). Transfer function A.U. 1.2 f [GHz] 10.2 1xBLA/cryomodule (HOMs above cut-off). to 70 K beam Lossy ceramic “II-nd ILC Workshop” Snowmass, August 13-27, 2005

  4. BCD HOMs below cut-off The scheme proposed in TESLA TDR based on two coaxial HOM couplers with the recently proposed improvement (mirrored coupler). Propagating HOMs 70 K Beam Line Absorber which is under development for XFEL. pros: This damping scheme was proven at TTF linac and fulfills the spec for major part of non propagating modes. Synergy with scheme proposed for XFEL cons: It makes end-groups expensive “II-nd ILC Workshop” Snowmass, August 13-27, 2005

  5. R&D program for ACD • 1. R&D program towards reducing costs of HOM couplers • Positioning of the HOM coupler output in the plane of the • coupling loop. • Version of HOM coupler without output capacitor. • HOM with one inductance (proposed by KEK). • pros: If works we can lower the cost • cons: Performance must be verified with the beam 2. Beam line coaxial HOM coupler for non propagating modes (see Nikolay Solyak talk). Flange Flange Input couplers (similar to Darmstadt linac) HOM couplers pros: Cavity is cylindrically symmetric and easy for hydroforming cons: Potential problems with tilted field profiles of HOMs “II-nd ILC Workshop” Snowmass, August 13-27, 2005

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