1. Review of rf structure test results
High gradient results
30 GHz
11.4 GHz
For more detailed high gradient results please see:
The first ACE, June 2007
The x-band structure design and testing workshop: June 2007
The High-Gradient workshop, October 2006
Steffen Döbert, ACE,

2. Damage in high field areas
Copper
Tungsten

3. Clamped-Iris Structure Tests in CTF II

4. Accelerating Structure Tests in CTF II
Short, 16 ns rf pulses
New Record for classical accelerating structures !

5. Overview of 30 GHz results
Reached nominal 30 GHz CLIC values :
150 MV/m 70 ns
Molybdenum shows higher gradient but different slope
HDS performs worse than round brazed structure

6. Hybrid Damped Structure (HDS)
CLIC damped and detuned accelerating structure: 30 GHz, 150 MV/m, 70 ns, < 10-6 trip probability

7. Accelerating Structures made out of milled quadrants
HDS60

8. New Materials for High-Gradient
Copper has still the best performance at low break down rate

9. Damage vs aperture or group velocity
HDS60 Large
HDS60 Small
Evidence for correlation between damage and power flow (a,vg,P):
Criteria for optimizing rf designs (P/C):
Px(t1/3)/p/2a < threshold

10. Parameters for 30 GHz test strcutures

11. Recent 30 GHz results
C40vg8_pi/2
HDS4vg2.6_thick_150deg

12. NDS4_vg2.5_thick result

13. Summary of 30 GHz results in 2007
Probing phase advance and P/C theory

14. Summary of 30 GHz results Structure 2a (mm) P (MW) E (MV/m)
All measured data at 70 ns pulse length and 10-3 breakdown rate
Structure
2a (mm)
P (MW)
E (MV/m)
PT1/3/C (wue)
C30vg4.7
3.5
20.2 92
7.5
HDS60vg8.0
3.8
16.1 61
5.6
HDS60vg5.1
3.2
13.3 75
5.5
C40vg7.4_pi/2
4.0
19.2 65
6.2
HDS4vg2.6_thick 67
2.8
NDS4vg2.5_thick
8.6

15. First CLIC x-band structure
One tested at KEK and one tested at SLAC
150 MV/m peak, 125 MV/m avg
150 ns pulse length
No breakdown monitoring

16. Typical NLC/GLC prototype structures
Length: 60 cm
Phase advance: 120 deg
Group velocity: 4 %
a/l: 0.17
Es/Eacc: 2.2
Pin (65 MV/m): 59 MW
Coupler: mode luncher
Preparation: H-brazing, diamond turning

17. Performance of NLC/GLC structures58 60 62 64 66 68 70 72 10 -2 -1
Breakdown rate per hour
Average gradient
FXC3
FXB-006
FXB-007
H60vg4R17
H60vg4S17-1
H60vg4S17-3
FXD1
FXC5
Average trip rate goal

18. Hybrid damped structures (HDX) at x-band Frequency scaling
Scaled structures show very similar performance
HDS-type structures show consistently limited performance

19. A reference structure for CLIC from NLC
Length: 53 cm
Phase advance: 120 deg
Group velocity: 3 %
a/l: 0.13
Es/Eacc: 2.2
Pin (65 MV/m): 41 MW
Coupler: mode luncher
Preparation: H-brazing, diamond turning

20. Tests of old NLC structures at short pulses
T53vg3MC can be used as a first reference for the new CLIC parameters
CLIC goal

21. Pulse Length Dependence

22. Summary of 11 GHz results Structure P (MW) E (MV/m) PT1/3/C (wue)
All data around ~10-6 breakdown rate
Structure
P (MW)
E (MV/m)
PT1/3/C (wue)
T53vg3MC (50ns)
118
110 18
T53vg3MC (100ns)
107
105 20
H75vg3 (150 ns)
155 97 27
HDX11vg5 (70 ns) 59 60 9
First result on power ramping during filling:
100 ns ramp (50%-100%) ns flat top: 97 MV/m at 10-6 BDR

23. Tapered Damped Structure Test in ASSET
Successful experimental verification of strong cell damping and benchmarking of codes
Test results

24. Assembly of a three cell SW structure made by KEK
SLAC/KEK results on short SW accelerating structures
3D model of single cell SW structure
Assembly of a three cell SW structure made by KEK
David Martin
Yasuo Higashi, KEK

25. Breakdown rate vs. accelerating gradient, all breakdowns, flat pulse, a/l~0.21
Time of flat pulse after filling time
Time of flat pulse after filling time
Single Cell SW1
Single Cell SW2
V. Dolgashev, S. Tantawi

26. Conclusions on recent structure tests (some of them preliminary)
Current CLIC design within experimentally demonstrated region
27 wue have been measured (Design used 18)
120 MW input Power for 100 ns into first cell of T53 (the structures showing a promising gradient are not damped)
Hybrid Damped Structures show performance deficit (short phase advance, slots, quadrants and milling)
Copper is still the best material to make accelerating structures (Molybdenum still has some potential, shallow slope seen in previous experiments could be due to iris clamping, slow processing as usual)
Exactly scaled structures seem to perform independent of frequency (therefore 30 GHz test are still meaningful)
Some doubts on P/C theory used to optimize this years structures
Quadrant technology appears not mature
Short phase advance seems not beneficial

27. The end, reserve slides following

28. Post mortem inspection of HDX11cu
High Current Region
Scattered Dark Spots
Input Coupler Iris
Patchy breakdown areas along sides of irises
Areas of Discoloration