1. CLIC_DDS study

2. 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

3. 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

4. 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 = m
∆fmin = 65 MHz
∆tmax =15.38 ns
∆s = 4.61 m
192 cells
8-fold interleaving

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

6. 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

7. 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%

8. CLIC_DDS_A: Dipole properties
24 cells
No interleaving
Qavg ~1700

9. CLIC_DDS_A: 24+2 cells mm

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

11. Profile
accuracy
VDL

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

13. 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

14. Fundamental mode Optimisation CLIC_DDS_HPA

15. Band partitioning: CLIC DDS_A and DDS_HPA

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

17. DDS_HPA

18. 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

19. 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 ?

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

21. 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= (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

22. 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

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

24. 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

25. Cell # 24 :NMr= Damp_r=1.0

26. Accelerating mode
NMr= Damp_r=1
εr= tanδ=0.04

27. 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 ?)

28. 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

29. 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

30. Additional slides

32. 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

33. 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

34. 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

35. 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

36. 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

37. Cell # 1 :NMr= Damp_r=1.0

38. 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