CLIC_DDS study 30.11.2010

CLIC_DDS Study Collaboration University of Manchester and Cockcroft institute, U.K. CERN, Switzerland Vasim Khan Alessandro D’Elia Roger Jones Alexej Grudiev Germana Riddone Vadim Soldatov Walter Wuensch Riccardo Zennaro

Outlook Summary of Optimisation: CLIC_DDS Overview of test structure: CLIC_DDS_A High Phase Advance (HPA) Structures: Merits and Demerits CLIC_DDS_HPA Future of CLIC_DDS_HPA

CLIC_DDS_C ∆f=3.6 σ =2.3 GHz ∆f/fc=13.75% Dipole mode Manifold mode 192 cells 8-fold interleaving Manifold mode Manifold Coupling slot ∆f=3.6 σ =2.3 GHz ∆f/fc=13.75% 24 cells No interleaving ∆fmin = 8.12 MHz ∆tmax =123 ns ∆s = 36.92 m ∆fmin = 65 MHz ∆tmax =15.38 ns ∆s = 4.61 m 192 cells 8-fold interleaving

DDS_C Fails to satisfy rf breakdown constraints! Surface fields DDS_C Fails to satisfy rf breakdown constraints!

CLIC_DDS optimisation summary Circular cell ε=0.82 ε=1.38 Manifold-damped single cell Circular ε=1.38 DDS_E DDS_C DDS_E DDS_C

CLIC_DDS_A: Monopole properties Max. Values Esur=220 MV/m ∆T = 51 K Pin= 70.8 Eacc_UL=131 MV/m Sc=6.75 W/μm2 RF-beam-eff=23.5% ∆T 35*Sc Esur Eacc Pin Dashed curves : Unloaded condition Solid curves: Beam loaded condition CLIC_G Values Esur=240 MV/m ∆T = 51 deg. Pin= 63.8 Eacc_UL=128 MV/m Sc=5.4 W/μm2 RF-beam-eff=27.7%

CLIC_DDS_A: Dipole properties 24 cells No interleaving Qavg ~1700

CLIC_DDS_A: 24+2 cells 198.6326mm

Water pipes for cooling Vacuum flange Power input Power output Tuning holes Cut-view Beam

Profile accuracy VDL

High Phase Advance Structures 1) Low group velocity → Less power absorbed during breakdown Ref: R.M. Jones, et. al., SLAC-PUB 8887 CLIC

NLC: Band partitioning a = 4.23 mm NLC: DS1 ψacc : 120°→ 150°:Lowest dipole kick factor reduces by ~ 20% Ref: R.M. Jones, et. al., SLAC-PUB 9467

Fundamental mode Optimisation CLIC_DDS_HPA

Band partitioning: CLIC DDS_A and DDS_HPA

Dipole mode properties 120deg. Γx = 0.0126 Cell # 1 a=4.0 mm, t=4.0 mm 150deg. Γx = 0.021 Cell # 1 a=4.0 mm, t=3.2 mm

DDS_HPA

Comparison: 120 vs 150 RF parameters Unit DDS_A DDS_HPA42 DDS_HPA32 Phase advance / cell Deg. 120 150 Iris thickness mm 4/1.47 3.2/2.8 Bunch population 109 4.2 3.2 Q (In / Out) - 5020 / 6534 6931/7045 R’ (In / Out) MΩ/m 51 / 118 72.4/102.4 vg/c (In / Out) % 2.07 / 1.0 2.1 / 0.45 Eaccmax (L./UnL.) MV/m 105 / 132 93 .3/ 143 90/ 138 Pin MW 71 68.2 63.6 ∆Tmaxsur oK 51 48 Emaxsur 220 234 225 Scmax W/μm2 6.75 5.9 5.5 RF-beam efficiency 23.5 29 23.3

DDS_HPA: Merits and Demerits Reduced input power Less power absorbed during breakdown Kick factors reduced Better dipole coupling Reduction in dipole bandwidth from 2.1 GHz to 1.8 GHz Necessary to reduce bunch population to satisfy wakefield constrains Luminosity reduction Cost efficient ?

Enhanced damping: Eight manifolds Four regular and four additional manifolds Significant coupling

Cell # 1 Cell parameters Fundamental mode properties fsyn=16.1 GHz Cell parameters a = 4.3 mm t = 2.6 mm Rc = 9.0 mm Mr = 2.0 mm Mc = 15.1 mm Fundamental mode properties Q=7080 R’/Q=10.356 (kΩ/m) vg=2.44 (%c) Es/Eacc=2.22 Hs/Eacc=4.3 (mA/m) Sc/Eacc=5.45 x 10-4 (W/μm2/Eacc2) Dipole mode properties

Cell # 24 Cell parameters a = 2.5 mm t = 2.8 mm Rc = 8.8 mm Mr = 2.0 mm Mc = 15.1 mm vg=0.32 (%c) fsyn=17.89 GHz

Two Cell result Lowest dipole mode properties Need improvement Δf=2.25 σ=1.78 GHz Δf/fc= 10.5 (%c)

Eight manifolds and Sic As the coupling in the last cell is poor it is important to enhance coupling by optimising the last cell Regular manifold Additional manifold Damping material εr=13 tanδ=0.02 NMr=2.8 Damp_r=1

Cell # 24 :NMr=2 .8 Damp_r=1.0

Accelerating mode NMr=2 .8 Damp_r=1 εr=14 tanδ=0.04

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 ?)

Closing remarks CLIC_DDS_A is being fabricated CLIC_DDS_A: High power test by 2011 end 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

Acknowledgments Thank you 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

Additional slides

Four manifolds Cell # 24 Cell # 1 Cell # 1 Cell # 24 Fsyn~15.76 GHz Cell parameters a = 3.3 mm t = 3 mm Rc = 9.0 mm Mr = 2.0 mm Mc = 15.1 mm vg = 0.95 (%c) Fsyn~17 GHz Cell # 1 Cell parameters a = 4.6 mm t = 2 mm Rc = 9.0 mm Mr = 2.0 mm Mc = 15.1 mm vg = 3.6 (%c) Fsyn~15.76 GHz Cell # 1 Cell # 24

Cell # 1 Cell parameters a = 4.6 mm t = 2 mm Rc = 9.0 mm Mr = 2.0 mm Mc = 15.1 mm vg = 3.6 (%c) Fsyn~15.77 GHz

Cell # 24 Cell parameters a = 3.3 mm t = 3 mm Rc = 9.0 mm Mr = 2.0 mm Mc = 15.1 mm vg = 0.95 (%c) Fsyn~17 GHz

Cell # 1 Cell parameters a = 4.6 mm t = 2 mm Rc = 9.0 mm Mr = 2.0 mm Mc = 15.1 mm vg = 3.6 (%c) Fsyn~15.77 GHz

Cell # 24 Cell parameters a = 3.3 mm t = 3 mm Rc = 9.0 mm Mr = 2.0 mm Mc = 15.1 mm vg = 0.95 (%c) Fsyn~17 GHz

Cell # 1 :NMr=2 .8 Damp_r=1.0

Cell # 1 Cell parameters a = 4.6 mm t = 1 mm Rc = 9.0 mm Mr = 2.0 mm Mc = 15.1 mm vg = 4.84 (%c) Fsyn~15.65 GHz