1. CEPC Input Coupler Discuss 6th IHEP-KEK SCRF Collaboration Meeting
Ma Q., Huang T.M.

2. Index Requirement of CEPC FPC Concept design of 650MHz Coupler
Design of 1.3GHz Coupler

3. Requirements of CEPC FPC
Main ring
Booster
Frequency (GHz)
0.65
1.3
Power (kW)
300 (400 update?) 10
Coupling (Qext)
Variable: 1E5~2E6
Variable: 4E6~4E7
2 K heat load
(dynamic300kW,TW,CW)
1 W
0.3 W
Assembly
Clean assembly of coupler to cavity in class 10 clean room

4. Concept design of 650MHz coupler
The length of coupler in the cryomodule
Variable coupling
Change outer conductor length
Change inner conductor length
Change inner conductor length, Bellow on 1/4 λ shorter port ( LHC Type )
Single window or Double windows

5. Concept design of 650MHz coupler
The length of coupler in the cryomodule
As the inner diameter is 1300, the length of coupler (window and vacuum coax ) is less than 460.
The short vacuum coax line leads the difficulty of heat- load controling.
If use the rectangular module, the length of coupler is not a problem. Maybe it's a another choice.
FPC
coupler port
Beam Pipe
cryomodule inner surface

6. Variable coupling
Usually,Changing the penetration depth of the antenna tip to adjust the Qext.
Calculation shows the length of change is about 30mm.

7. Variable coupling Change outer conductor length, like TTF coupler.
TTF-III coupler

8. Variable coupling
Move the window to change the outer conductor length.
Bellow needs special cooling. otherwise the temperature will be over 400K.
Remove the length of window (~120) and bellow(~220), the length of coax line is too short for heat insulation(<120).
This design need fatter cryomodule or rectanglar crymodule.
fixed by WG
window
water cooling bellow
fixed by Cavity
move window 5K
80K
300K

9. Variable coupling
Change inner conductor length, like ATF coupler or KEK-STF coupler .
ATF coupler
STF coupler

10. Variable coupling Add bellow on inner conductor.
Bellow cooling: water or air?
Water cooling: bellow corrosion by water? air: insufficient cooling?
Easier heat load control.
Need more heat simulation.
window
Bellow
coolingpipe
move antenna tip 5K
80K
300K

11. Variable coupling
Change inner conductor length, Bellow on 1/4 λ shorter port ( LHC Type )
The ONLY variable coupler operating above 300kW CW in the world.
LHC Type need rectanglar Cryomodule.
It is a future design or not?
LHC coupler

12. Single window or Double windows
Avoid polution when ceramic was broken.
Expensive.
More complex, more trip rate.
Single window
Maybe 1~3 module were poluted when ceramic was broken. And long period was spent for changing the module.
Cheaper and simpler.

13. Single window or Double windows
transmission line
waveguide
win
Vacuum
transmission line
warm
win
Difficult to cooling in big CW power
cold
win
win
Cavity
Cavity X ?

14. Collabration of 650MHz Coupler
Collabration on concept design and simulation.

15. Design of 1.3GHz Coupler
Finished the RF design and mechanical rough design.
Doing heat simulation now.
RF model of CEPC booster cavity FPC

16. Collabration of 1.3GHz Coupler
Collabration on design and Power test.
Hope to test the coupler in KEK in late 2018.
Prepare the coupler and vacuum connect waveguide( if the connect flange is not same ) (IHEP)
Prepare the power source, low level controller and interlock system (KEK)
The details of test could be discussed later.

17. Thanks