Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 CLIC_DDS_HPA study

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 CLIC_DDS Study Collaboration Vasim Khan Alessandro D’Elia Roger Jones Alexej Grudiev Germana Riddone Vadim Soldatov Walter Wuensch Riccardo Zennaro University of Manchester and Cockcroft institute, U.K. CERN, Switzerland

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Outlook High Phase Advance (HPA) Structures: Merits and Demerits CLIC_DDS_HPA Future of CLIC_DDS_HPA

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 High Phase Advance Structures 1) Low group velocity → Less power absorbed during breakdown Ref: R.M. Jones, et. al., SLAC-PUB 8887 CLIC

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 NLC: Band partitioning NLC: DS1 a = 4.23 mm ψ acc : 120°→ 150°:Lowest dipole kick factor reduces by ~ 20% Ref: R.M. Jones, et. al., SLAC-PUB 9467

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Fundamental mode Optimisation CLIC_DDS_HPA

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Band partitioning: CLIC DDS_A and DDS_HPA

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 120deg. Γ x = Cell # 1 a=4.0 mm, t=4.0 mm 150deg. Γ x = Cell # 1 a=4.0 mm, t=3.2 mm Dipole mode properties

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 DDS_HPA

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 RF parametersUnitDDS_ADDS_HPA42DDS_HPA32 Phase advance / cellDeg Iris thicknessmm4/ /2.8 Bunch population Q (In / Out)-5020 / /7045 R’ (In / Out)MΩ/m51 / /102.4 vg/c (In / Out)%2.07 / / 0.45 Eacc max (L./UnL.)MV/m105 / / 14390/ 138 P in MW ∆T max sur oKoK51 48 E max sur MV/m S c max W/μm RF-beam efficiency% Comparison: 120 vs 150

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 DDS_HPA: Merits and Demerits  Reduction in dipole bandwidth from 2.1 GHz to 1.8 GHz 1.Necessary to reduce bunch population to satisfy wakefield constrains 2.Luminosity reduction  Reduced input power  Less power absorbed during breakdown  Kick factors reduced  Better dipole coupling  Cost efficient ? MeritsDemerits

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Enhanced damping: Eight manifolds Four regular and four additional manifolds Significant coupling

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Cell parameters a = 4.3 mm t = 2.6 mm R c = 9.0 mm M r = 2.0 mm M c = 15.1 mm Fundamental mode properties Q=7080 R’/Q= (kΩ/m) v g =2.44 (%c) E s /E acc =2.22 H s /E acc =4.3 (mA/m) S c /E acc =5.45 x (W/μm 2 /Eacc 2 ) Dipole mode properties f syn =16.1 GHz Cell # 1

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Cell parameters a = 2.5 mm t = 2.8 mm R c = 8.8 mm M r = 2.0 mm M c = 15.1 mm v g =0.32 (%c) Cell # 24 f syn =17.89 GHz

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Lowest dipole mode properties Δf=2.25 σ=1.78 GHz Δf/f c = 10.5 (%c) Two Cell result Need improvement

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Regular manifold Additional manifold Damping material εr=13 tanδ=0.02 NMr=2.8 Damp_r=1 Eight manifolds and Sic As the coupling in the last cell is poor it is important to enhance coupling by optimising the last cell

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Cell # 24 :NMr=2.8 Damp_r=1.0

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Accelerating mode NM r =2.8 Damp_r=1 ε r =14 tanδ=0.04

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 DDS_HPA_SiC SiC insertion in an 8-manifold cell improves damping The SiC properites and dimensions are optimised for Cell # 24 This optimisation does not improve damping of Cell # 1 Due to SiC losses, multiple avoided crossings are observed Need some modification in circuit model to incorporate additional losses (SiC) (future work ?)

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Closing remarks CLIC_DDS_HPA: 1) Coupling looks promising 2) Need to improve bandwidth To be investigated in detail: 1) Eight manifolds 2) DDS_SiC damping 3) Circuit model modification to incorporate SiC losses

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Acknowledgments We have benefited from discussions with Juwen Wang, Zhengai Li and Toshiyasu Higo on X-band structures Thanks to Igor Syratchev for suggesting to investigate CLIC_DDS_SiC. Thank you

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Additional slides

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Cell # 1 Cell # 24 Cell # 1 Cell parameters a = 4.6 mm t = 2 mm R c = 9.0 mm M r = 2.0 mm M c = 15.1 mm v g = 3.6 (%c) F syn ~15.76 GHz Cell # 24 Cell parameters a = 3.3 mm t = 3 mm R c = 9.0 mm M r = 2.0 mm M c = 15.1 mm v g = 0.95 (%c) F syn ~17 GHz Four manifolds

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Cell # 1 Cell parameters a = 4.6 mm t = 2 mm R c = 9.0 mm M r = 2.0 mm M c = 15.1 mm v g = 3.6 (%c) F syn ~15.77 GHz

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Cell # 24 Cell parameters a = 3.3 mm t = 3 mm R c = 9.0 mm M r = 2.0 mm M c = 15.1 mm v g = 0.95 (%c) F syn ~17 GHz

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Cell # 1 Cell parameters a = 4.6 mm t = 2 mm R c = 9.0 mm M r = 2.0 mm M c = 15.1 mm v g = 3.6 (%c) F syn ~15.77 GHz

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Cell # 24 Cell parameters a = 3.3 mm t = 3 mm R c = 9.0 mm M r = 2.0 mm M c = 15.1 mm v g = 0.95 (%c) F syn ~17 GHz

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Cell # 1 :NMr=2.8 Damp_r=1.0

Vasim Khan X-Band RF Structures, Beam Dynamics and Sources Workshop, Cockcroft Institute /21 Cell # 1 Cell parameters a = 4.6 mm t = 1 mm R c = 9.0 mm M r = 2.0 mm M c = 15.1 mm v g = 4.84 (%c) F syn ~15.65 GHz