1. CEPC 650MHz High Efficiency Klystron R&D
Zusheng ZHOU(周祖圣)
Beihang Uniersity
Sep. 2, 2016

2. Contents
■Design proposal
■R&D Progress
■Summary

3. Design proposal

4. (top parameters of D. Wang 20160329)
CEPC Main Ring SRF parameters
Parameters
(top parameters of D. Wang ) H
(Pre-CDR) W Z
650 MHz cavity (bulk Nb)
5-cell
2-cell
Cavity number
384
480
160 32
VRF (GeV) 7
3.65
0.82
0.13
Eacc (MV/m)
15.9
16.5
11.1
8.6
2 K
4E10
2E10
Cryomodule number 96 80 16
Max. phase shift of 4+4 trains (deg) /
3.9
7.4
12.9
RF power c.w. / cavity (kW)
276
215
224*
254*
Cavity number per klystron 2
2 / 4
Total klystron number
192
HOM power / cav. (kW)
3.6
0.8
0.4
Total RF power (MW)
106
104
36* 8*
Total cav. wall 4.5 K eq. (kW)
22.2 24

5. (top parameters of D. Wang 20160329)
CEPC Main Ring SRF parameters
Parameters
(top parameters of D. Wang ) H
(Pre-CDR) W Z
650 MHz cavity (bulk Nb)
5-cell
2-cell
Cavity number
384
480
160 32
VRF (GeV) 7
3.65
0.82
0.13
Eacc (MV/m)
15.9
16.5
11.1
8.6
2 K
4E10
2E10
Cryomodule number 96 80 16
Max. phase shift of 4+4 trains (deg) /
3.9
7.4
12.9
RF power c.w. / cavity (kW)
276
215
224*
254*
Cavity number per klystron 2
2 / 4
Total klystron number
192
HOM power / cav. (kW)
3.6
0.8
0.4
Total RF power (MW)
106
104
36* 8*
Total cav. wall 4.5 K eq. (kW)
22.2 24

6. Klystron output power (kW) 1 klystron power 2 cavities
CEPC Main Ring RF Power source
Baseline
Considering klystron lifetime and power redundancy, 2 cavities will be powered with a CW klystron capable to deliver more than 800 kW.
Parameters
Value
Operation frequency
650MHz+/-0.5MHz
RF input power (kW)
280 CW（250）
RF source number
160
Klystron output power (kW)
800 CW
1 klystron power 2 cavities

7. Klystron key design parameters Centre frequency (MHz)
CEPC Main Ring RF Power source
Klystron key design parameters
Parameters
Now
Future
Centre frequency (MHz)
650+/-0.5
Output power (kW)
800
Beam voltage (kV) 80 70
Beam current (A) 16 15
Efficiency (%) 65

8. Klystron key design parameters Centre frequency (MHz)
CEPC Main Ring RF Power source
Klystron key design parameters
Parameters
Now
Future
Centre frequency (MHz)
650+/-0.5
Output power (kW)
800
Beam voltage (kV) 80 70
Beam current (A) 16 15
Efficiency (%) 65
How to do?

9. Klystron key design parameters Centre frequency (MHz)
CEPC Main Ring RF Power source
Klystron key design parameters
Parameters
Now
Future
Centre frequency (MHz)
650+/-0.5
Output power (kW)
800
Beam voltage (kV) 80 70
Beam current (A) 16 15
Efficiency (%) 65
How to do?
There are some R&D work supported by IHEP innovation funds.

10. R&D Progress

11. Klystron Schedule and strategy
Because of klystron efficiency is more than 80%, in order to fulfill this program, there may have following problems:
1) No experience and no related infrastructure on this kind of klystron;
2) Design and simulation are not enough and matured;
3) Let’s start from beam tester, classical design and currently progressed design(higher efficiency design).

12. Short term Schedule

13. Klystron Schedule and strategy(2)
Merits
Saving the money
Saving the time
Possible to try 2 or 3 designs
(1) Beam tester
(2) #1 prototype
(3) #2 prototype

14. Simulation Results using DGUN
Triode gun（anode modulated）with f10 hole
DGUN simulation result :
Beam Diameter=17.8mm
Current=15.12 A
Perveance= 1.43 μA/V3/2
Vc =-81.5kV
VMA=-48.0kV
1.77 kV/mm
on Anode
3.94 kV/mm
on BFE
2.51 kV/mm
on M.Anode
54 mm
35.6 mm ０ 4 2 6 5 10 15 25 30 35
Cathode R(mm)
Current Density
(mA/mm2) 20

15. Simulation Results using EGUN
Triode gun （anode modulated）with f10 hole
EGUN simulation result :
Beam Diameter=17.7mm
Current=14.88 A
Perveance= 1.41 μA/V3/2

16. Simulation Results using CST
CST simulation result :
Beam Diameter=17.7mm
Current=14.88 A
Perveance= 1.41 μA/V3/2

17. Simulation Results Comparison
Electron Gun
Vc =-81.5kV, VMA=-48.0kV
Type
DGUN
EGUN
CST
Current(A)
15.12
14.88
Beam DIA(mm)
17.8
17.7
Perveance(μA/V3/2)
1.43
1.41

18. Simulation Results Comparison
Magnet field
Amplitude of magnetic field Bz on axis

19. Ripple rate = 8.0%

20. Beam Optics for Collector

21. Gun assembly with Drift Tube and Collector
500
1000
1500
2000
2500
4000
3500
3000
Z (mm)
Solenoid

22. HV Gun Envelop for Electron Gun

23. Collector Design and Simulation
Collector shape and beam dissipation optimization
J collector optimization using universal beam spread curve
collector optimization using EGUN code
Analytic design
Numerical design
Collector Length
2147mm
1912mm
Collector radius
210mm
Total Beam power
1231kW
1230kW
Capability of power density in collector
150W/cm2
Max power density in collector
197W/cm2
207W/cm2
Crosscheck of beam trajectory with EGUN and MAGIC

24. Collector Design and Simulation(2)
Groove dimensions optimization
Groove number
Groove dimensions(a:b)
Total water flow rate
Water pressure loss for ideal smooth surface
180
1:2
1400kg/min
2.34E+4 Pa
Contour of temperature and water pressure loss

25. Collector Design and Simulation(3)
Collector Thermal analysis
Groove structure for 2 meter tapered collector in Ansys-CFX
contour of temperature on inner surface of copper domain
contour of temperature of water domain

26. Collector Design and Simulation(4)
Collector geometry of tapered part
2030mm A B C D E
Geometry of collector tapered part
Section A B C D E
groove number
180
150
120 60 40

27. RF Section Design and Simulation
The results of 1D code AJDISK indicate that the efficiency is 73% and the 1dB bandwidth is more than 2 MHz .

28. RF Section Design and Simulation(2)
All six cavities have been designed and optimized using CST and HFSS.
Input and output cavities electromagnetic field

29. RF Section Design and Simulation(3)
The simulation results of two-cavity klystron in 1D-code AJDISK and 3D-code CST are in good agreement, which indicate that 3D simulation in CST is feasible.
The results of two cavity klystron in CST

30. Current Status -Beam tester
Concept
Simulation
Gun
HV Seal
Collector
Drawing
Gun HV Seal
Drawing

31. Current Status -Beam tester
The drawing has almost completed!
It’s ready for manufacturing!!

32. Summary
The design of the electron gun and collector has been completed;
RF Section for classical design klystron is almost completed;
Mechanical design for beam tester is also completed;
Pushing procurement and manufacture for beam tester as soon as possible;
Mechanical design for classical design klystron is about to begin.
RF Section for high efficiency design klystron is about to begin.

33. Thanks for your attention!