1. Task 2: High-gradient normal-conducting technology development
W. Wuensch
EUCARD2 rf program review
18 July 2011

2. Task 2: Overall objectives
Advance high-gradient, normal-conducting rf technology through development of:
two types of high-gradient CLIC structures - main linac accelerating structures and crab cavities
high-power and beam-based X-band test infrastructure.
Spread X-band and high gradient expertise to many labs – has been concentrated at CERN/KEK/SLAC

3. Rapidly spreading X-band and high-gradient technology
Linear colliders: CLIC
Compact FELs: KVI Groningen, Trieste, Frascati, MaRIE
Compton-scattering light sources: MEGARAY
Medical accelerators: TERA, X-ray sources
Instrumentation: rf based high performance streak cameras

4. Task 2: Activity structure
CLIC main linac accelerating structures with wakefield monitors
CEA
Manchester
PSI
X-band crab cavities
Lancaster
Manchester
STFC
High-power and beam test infrastructure
CEA
PSI
(Valencia)
Overall coordination: CERN

5. 4. CLIC_DDS_A E-field Match-out the full, tapered structure
E-field and S11 shown
Beam
Port11
Port 2
E-field
~198.6mm
Matching cell
Surface E-Field
Axial E-Field
7.5 7
Ez (V/m x104)
Es (V/m x104)
5.0
z (mm)
300
z (mm)
225

6. 2. Work in Progress +Future Plans
CLIC_DDS_A is equipped with mode launchers –aim is to demonstrate ability to sustain HP
CLIC_DDS_B includes full HOM ports
Matching the HOM coupler for CLIC_DDS_B (dipole band ~ 15.9 GHz – 18 GHz)
I/P at
/2=15.9GHz
Construct pair of structures with full damping features
Moving to a high phase advance (HPA) structure allows other parameters to be optimised
5/6 phase advance structure design in progress
In the HPA design further features being explored
Additional manifold (8), add SiC?
Standard
DDS Manifold
Additional
Manifold
Sic
EnhancedCoupling
Sic 6

7. Accelerating structures (fabrication in progress)
Context of the X-band activities at CEA Saclay
CEA entered in the CLIC collaboration with the construction of the Probe Beam Linac CALIFES in CTF3 (in 2005)
Exceptional contribution of France to CERN
CTF3 contributions:
HV modulator and RF components for the CERN klystron test stand and TBL line
Accelerating structures for the Two Beam Test Stand
Period : 2008 – 2012, Budget = 1 M€ - 48 persons-months (p.m.)
HV Modulator
Accelerating structures (fabrication in progress)
RF Components

8. Hybrid HEM modes in the cell generated by an offset beam
Wakefield monitor development for CLIC accelerating structures
Wakefield Monitors = Beam Position Monitors integrated to the accelerating structures
Allows beam-based alignment of structures to remove wakefield effects and emittance growth
Emittance growth very well improved by aligning the structure to an accuracy of 5 µm
GdfidL simulation of TM modes, beam offset dx = 1 mm
18 GHz DX DY
Accelerating Structure features :
TD24 (CERN design) without RF absorbers
100 MV/m accelerating gradient
24 tapered cells with 2/3 phase advance at 12 GHz with mean aperture of 5.5 mm
dipole mode above 16 GHz
WFM features :
WFM = Two coaxial rf pick-ups on the middle cell damping wg
on large side wg for TM-like modes
on small side wg TE-like modes
Hybrid HEM modes in the cell generated by an offset beam

9. CLIC Crab Cavity R&D CLIC-CC R&D: LLRF R&D:
Multi-cell GHz dipole-mode cavity developed.
Various mode damping schemes investigated:
Choke
Waveguide
An optimised 7-cell, waveguide damped design being investigated further.
LLRF R&D:
CLIC-CC and LHC-CC phase control models under development.

10. The 12 GHz Power station project at CEA Saclay
Independant operation to CTF3
Proximity with chemical lab and clean room
Main features:
Modulator HT 430 kV
Klystron 50 MW – 1.5 µs
RF Pulse compressor SLED
LLRF with fast phase modulation
Specifications :
RF Frequency: 12 GHz
Peak power: 120 MW
Pulse length: 300 ns
Repetition rate: 50 Hz
Klystron
Test structure area
RF Pulse compressor
Modulator 10

11. WP tasks Design and fabricate multi-purpose RF Front Ends for WFM.
Should be easily adaptable to different frequencies; 15 GHz, 18 GHz, 24 GHz
Build hard-ware for CTF3 and SwissFEL injector.
Design and fabricate alternative WFM(s) for other structures
(collaboration with CERN).
3. Test and commission the different RFFE and pick-ups with beam at CTF3 and
SwissFEL injector.
Resources:
Hardware: 6 RFFE ~ 120 kE; WFM ~ 80 kE.
Manpower (PSI): Scientist/engineer 6 months, post-doc 2 years, technician ~ 2 years.
+ CERN manpower (?)
Participating laboratories: CERN, PSI
Infra-structures involved: CTF3, SwissFEL Injector

12. CLIC Crab High Power Distribution
Need to understand long term phase stability of the distribution scheme
Requires an experiment to measure phase transients.
Laser interferometer
travelling wave cavity
Dual Output or Magic Tee
Control
12 GHz Oscillator
Main beam outward pick up
Waveguide with micron-level adjustment
Waveguide with micron-level adjustment
LLRF
LLRF
Phase Shifter
From oscillator
12 GHz Pulsed Klystron
( ~ 20 MW )
Pulsed Modulator
Vector modulation
Control
main beam outward pick up

13. Broad range of participants, many activities
Extension of ongoing EUCARD activities
Recent expression of interest also by the University of Valencia

14. CERN request reduced to coordination manpower only
Roughly flattens €/lab/activity to k
Activities are stretched, posts are lost, but primary deliverables are maintained

15. Participation of certain participants in certain activities have been eliminated.
Some deliverables are eliminated
Need to ask the question whether we are below minimum worthwhile level for further participant-activities.