1. Few Slides from RF Deflector Developments and Applications at SLAC
Juwen Wang
SLAC Accelerator Seminar
April

2. Outline Introduction to RF Deflectors
Basic Theory and Design of RF Deflectors
Deflector Applications (3 Types and 7 Examples)
Manufacture and Characterization
Future Work

3. RF Deflector Applications
Three Types and 7 Examples
- Time-resolved electron bunch diagnostics for the LCLS
- Measurement of bunch time jitter at LCLS
- Bunch longitudinal profile diagnostics at DESY
- Ultra short e- and x-ray beams temporal diagnostics for LCLS
- Drive/witness bunch longitudinal profile diagnostics for PWFA at FACET
- Increase slice energy spread σE as well as measure of slice parameters for Upgrade ECHO-7
- Separator for High Energy Physics Experiments

4. What the RF Deflectors Look Like?
A LOLA-IV
Ready for DESY
Final Assembly
of a 1m X-Band Deflector for LCLS
Two Short X-Band Deflectors for ECHO-7
A Short 13-Cell S-Band LOLA Structure Under Measurement for LCLS Injector

5. Two transverse RF deflectors at LCLS
Paul Emma

6. Bunch Measurement at LCLS
Paul Emma

7. Upgrade ECHO-7 Experiment at NLCTA
Increase Slice Energy Spread and Measurement of Longitudinal Profile
TCAV1 to increase σE
TCAV2 to measure slice parameters
Layout and upgrade of the ECHO-7 experiment
WHY increasing beam slice energy spread?
Echo-7 experiment demonstrated the ability to control the phase space correlations (D. Xiang, et al, PRL, 105, (2010))
The advantage of EEHG over HGHG has not been fully demonstrated because the beam has very small slice energy spread
Scaling to x-ray FEL requires confidence in harmonic generation with the relative beam energy spread on the 10-4 level but NLCTA has σE /E~10-5
HOW: Using a rf deflecting cavity to increase beam slice energy spread to ~10 keV
Dao Xiang

8. Bunch Time Jitter Measurement at LCLS
Paul Emma

9. Regular X-Band Deflector Cups

10. Coupler Design Simulation
Maximum surface magnetic fields ~400 kA/m,
Pulse heating 22 deg. C for 100 ns pulse.
Maximum surface electric fields ~100 MV/m.
Fields Normalized 20 MW of transmitted power, or 21.3 MeV kick for 89 cm structure
V.A. Dolgashev, “Waveguide Coupler for X-band Defectors,” AAC 2008, SALC-WP-084

11. Input/Output Coupler Assemblies
Completed Coupler Assembly
Mechanical Design Model

12. Assembly of the Deflector

13. Maximum Kick 6 and 0.2 MV for ECHO-7 Experiment
Design Example – III
Maximum Kick 6 and 0.2 MV for ECHO-7 Experiment
Name of Structure
D27
D11
Structure Type
2π/3 Backward wave
Aperture 2a
10.00 mm
Cavity Diameter 2b
29.77 mm
Cell Length d mm
Disk Thickness
2.0 mm
Quality Factor Q
6320
Kick Factor k
2.849x1016 V/C/m/m
Transverse Shunt Impedance r┴
41.9 MΩ/m
Group Velocity Vg/c %
Total Flange-Flange Length L
43.6 cm
29.6 cm
Filling Time Tf
26.8 ns
12 ns
Attenuation Factor τ
0.147
0.063
Input Peak RF Power
15 MW
for 6 MV Kick
77 kW
for 0.2 MV Kick
Maximum Electric Field
84 MV/m
6 MV/m
Maximum Magnetic Field
0.29 MA/m
0.02 MA/m

14. A Typical Microwave Measurement Results for 9-Period CellStack
Working 2pi/3 Mode
Desired Horizontal Kick Dipole Modes
Unwanted polarized Mode 80 MHz lower
Vertical Kick Dipole Modes

15. S11 Resonant Modes and Dispersion Curve
for Horizontal Deflecting Modes
Backward Wave 2π/3 horizontal deflecting Mode

16. D27 Amplitude and Cumulated Phase Shift

17. Beam at Maximum Kick Phase In Deflecting Plane of a Short TW RF Deflector
Top: distribution of deflection (V/m/4W)
Bottom: Integrated deflection (V/4W)
There are high electric and magnetic fields in the coupler regions. Due to their standing wave characteristic, the total contribution to the kick is equivalent to 1/2+1/2 cell.
Zhenghai Li

18. Future Application – I
Ultra short electron and x-ray beams temporal diagnostics with X-band deflector
time e- sz
2×1 m bd bs
D  90°
V(t) RF
‘streak’
Dipole
X-band TCAV
energy Dy
High resolution, ~ few fs;
Applicable for all radiation wavelength;
Wide diagnostic range, few fs to few hundred fs;
Profiles, single shot;
No interruption with LCLS operation;
Both e-beam and x-ray.

19. Future Application – II
Plasma Wakefield Acceleration (PWFA) experiments at FACET
Measurement of longitudinal profile for both Drive Beam and Witness Beam
Plasma Wakefield Acceleration (PWFA) experiments at FACET will use unique two-bunch beam.
Acceleration of witness bunch depends strongly on longitudinal profile of the two bunches as well as the inter- bunch spacing.
Will also try non-Gaussian “ramped” driver bunch, which could provide especially high transformer ratio.
Good single-shot measurement of longitudinal profile is essential for interpreting experimental results.
PWFA
(not real data)
Ramped Driver Concept
witness
ramped driver Ez
[1] M.J. Hogan, et al., New J. Phys (2010)
[2] R.J. England, et al., Phys. Rev. Lett (2008)
Mike Litos