1. Wake-fields simulations and Test Structure
G.De Michele-A.Grudiev BE-RF
G. De Michele

2. G.De Michele-A.Grudiev BE-RF
Outline
Baseline geometry
Material properties
GdfidL simulations
Direct measurements of the transverse long-range wake-fields at FACET facility
G.De Michele-A.Grudiev BE-RF

3. G.De Michele-A.Grudiev BE-RF
Outline
Baseline geometry
Material properties
GdfidL simulations
Direct measurements of the transverse long-range wake-fields at FACET facility
G.De Michele-A.Grudiev BE-RF

4. Baseline structure and HOM damping
Iris radius  2.35mm
WG cross section 11x6.66mm
WG length 90mm
G.De Michele-A.Grudiev BE-RF

5. Baseline structure and HOM damping
SiC cross section  1x1 to 5.6x5.5mm
SiC length  30mm+10mm flat
Distance tip_SiC-structure_axis  50mm
G.De Michele-A.Grudiev BE-RF

6. Baseline structure and HOM damping
Very broad band absorption of the wake-fields
Reflection below -30dB for TE10 mode and below -20dB for TE01 mode
A.Grudiev, W.Wuensch in Linac10 Conference
Design of the CLIC main linac acc. Struct. for CLIC CDR
G.De Michele-A.Grudiev BE-RF

7. Baseline structure and HOM damping
Double-feed coupler cell with a standard X-band WR-90 width
X band, WR-90, 8.2 to 12.4, x inch (22.86x10.16mm)
From 6.66mm to we will need a tapered WG
G.De Michele-A.Grudiev BE-RF
G. De Michele

8. Baseline structure and HOM damping
Coupler similar to the regular cell geometry
Minimum quadrupolar kick from the fundamental mode
Signals back from WG couplers damped on the load if magic-T present
Tapering provides detuning of HOM
G.De Michele-A.Grudiev BE-RF
G. De Michele

9. G.De Michele-A.Grudiev BE-RF
Outline
Baseline geometry
Material properties
GdfidL simulations
Direct measurements of the transverse long-range wake-fields at FACET facility
G.De Michele-A.Grudiev BE-RF

10. EM materials properties (T.Pieloni)
G.De Michele-A.Grudiev BE-RF
G. De Michele

11. G.De Michele-A.Grudiev BE-RF
Waveguide method
High frequency EM characterization:
the intersection of the surfaces with the measured S21 yields the possible solutions. Often one obtains the uniqueness of the solution with only two constrains furnished from the complex S21.
Imaginary S21 at 10.5 GHz
Courtesy C. Zannini, R. Zennaro, T. Pieloni
ESK (Germany)
type
sample shape
(mm) εr
(10.5 GHz HFSS)
(10.5 GHz CST)
(28 GHz CST)
EKASIC F
SiC
L49xW49xH10
11.2+j 1.06
(tanδ=0.095)
11.2+j 1.03
(tanδ=0.092)
11.0+j 0.88
(tanδ=0.080)
G.De Michele-A.Grudiev BE-RF

12. G.De Michele-A.Grudiev BE-RF
Coaxial method
In collaboration with C. Zannini
ESK (Germany)
type
sample shape
(mm) εr
(9 GHz CST)
EKASIC F
SiC
d=1.32
D=4.08
12.0+j 1.08
(tanδ=0.090)
G.De Michele-A.Grudiev BE-RF

13. G.De Michele-A.Grudiev BE-RF
Coax and WG methods
G.De Michele-A.Grudiev BE-RF

14. Cutoff limit and new geometry
New geometry has higher cutoff (around 25GHz)
Easy machining
Series production in order to evaluate chemical treatment and heat treatment
In the ranges where S11<1 has been found a really good match between O.C. and S.C. with TL methods (by taking into account also air-gaps).
G.De Michele-A.Grudiev BE-RF
G. De Michele

15. G.De Michele-A.Grudiev BE-RF
Future work
Machining of the new samples
Measurements (EkasicF, EkasicP, CerasicB1) until 30GHz: HOM-free up to  25GHz
Tolerances study on coaxial/sample variations on scattering parameters.
Investigation of influence of chemical and heating treatments on the properties of materials
G.De Michele-A.Grudiev BE-RF
G. De Michele

16. G.De Michele-A.Grudiev BE-RF
Outline
Baseline geometry
Material properties
GdfidL simulations
Direct measurements of the transverse long-range wake-fields at FACET facility
G.De Michele-A.Grudiev BE-RF

17. G.De Michele-A.Grudiev BE-RF
GdfidL simulations
The electric current source density defined by a Gaussian bunch (6z), moving at the speed of light along the beam line
GdfidL can compute with dispersive dielectrics but does not work very well and is quite CPU-intensive ( W. Bruns, )
A constant value of the effective conductivity is assumed by fixing a frequency and the losses are specified by the loss tangent
G.De Michele-A.Grudiev BE-RF

18. G.De Michele-A.Grudiev BE-RF
GdfidL simulations
A beam with bunch length z =1.2mm is driven along the beam pipe with a transverse offset of 0.5mm
G.De Michele-A.Grudiev BE-RF
G. De Michele

19. G.De Michele-A.Grudiev BE-RF
GdfidL simulations
PEC
PMC y x
Position of the wake
integration path
Source charge
G.De Michele-A.Grudiev BE-RF
G. De Michele

20. G.De Michele-A.Grudiev BE-RF
Future work
New load design if we want to stick to EkasicF
Choose another material with higher tanD: possible candidates could be CerasicB1 or EkasicP. In this case the present geometry will be fine. To be confirmed!
Finally to model wake-fields of the structure with loads (modal sum) and to check if within beam dynamics constraints
G.De Michele-A.Grudiev BE-RF

21. G.De Michele-A.Grudiev BE-RF
Outline
Baseline geometry
Material properties
GdfidL simulations
Direct measurements of the transverse long-range wake-fields at FACET facility
G.De Michele-A.Grudiev BE-RF

22. Facility for Advanced aCcelerator Experiment Test
FACET provide an excellent opportunity to make direct beam-based long-range wake-field measurements of CLIC accelerating structures.
PROPOSED LOCATION
Layout of the ASSET facility
G.De Michele-A.Grudiev BE-RF
G. De Michele

23. Prototype structure for wake-fields measurements
Advantages:
Removable disks
Removable loads
Possibility to put WFM
Pick-ups
Optical ports
Clamped Al cells
Pick-ups
Transition
Simple vacuum tank
WFM
Optical ports
Removable loads
1m
G.De Michele-A.Grudiev BE-RF
G. De Michele

24. Future plans-schedule (W.Wuensch)
Run 1: 16 June to end August
For preparing installation and for being able to do later tests.
Basic check of beam line equipment, for example BPM readout exercises
Arrange a few nighttime checks, adding some known deflections etc., to make sure the optics downstream of the ASSET position is well understood for later experiment
Run 2: Two month run starting in January or February 2012
Positrons will be commissioned at this stage
Redo an H60 wake-field measurement as a practice run. Time can probably found during night shifts
Install structure during summer
Run 3: Starts September-October 2012 to November/December
Installation of our test structure
Test during dedicated runs
G.De Michele-A.Grudiev BE-RF